Digital Photography Tips and Techniques

Smart Optical Slave Flash Trigger, II

picmax — Fri, 05 Mar 2010 14:20:21 +0000

If you haven’t seen it, here is the original post about the Smart Optical Slave Flash Trigger (SOSFT) prototype built on an Arduino platform. Since I need to free up the Arduino Duemilanove board for other purposes and want to test the trigger in more practical situations, I decided to build it on a small perfboard I found in RadioShack.

Here is the final result.

The changes from the original design are minimal. ATMEGA168 is used as the micro controller. I simply programmed the Arduino bootloader and the trigger hex code on the Duemilanove then plugged the chip in the socket on the circuit board. The power supply circuit is added (LM7805C and two capacitors) to supply the 5 volts needed. The unit is powered by a 9 volt battery. To make it easy to connect and disconnect a flash, I used a 3-pin TTL socket I took off a Nikon AS-E900 on the board and the AS-E900 on the flash.

The following is the schematic.

I haven’t found a box yet to put it in but it is robust enough to allow some further testing. The sensitivity is adequate for typical indoor applications. It is surprising since I didn’t use any amplifier. I did see a potential issue. Since the code doesn’t examine the validity of the pulses it detects, the trigger can misfire when the distance from the camera or the commander unit is too far away. The reason is that the detected pulses may not all be above the pre-set threshold. Using the high sensitivity mode helps to extend the distance.

Smart Optical Slave Flash Trigger

picmax — Mon, 01 Mar 2010 07:10:26 +0000

Optical slave trigger is the easiest way of getting the flash off camera without wires. However, most of the optical slave triggers are quite dumb. They trigger the flash as soon as a light pulse is detected. This works fine if all of your flashes are in manual mode. If you want to use a dumb flash in TTL flash system, or wireless flash system such as Nikon’s Advance Wireless Lighting (AWL), you will run into trouble. The flash will be triggered prematurely when the TTL metering pulse or wireless communication pulses are emitted.

There are some smarter flash triggers that can work around the problem. Here are some examples I found.

A Programmable Optical Slave Flash Trigger for Digital Cameras with Processor PIC 12F675 – This one has a programming mode that allows the trigger to learn new flash patterns.
Slave Flash Trigger Kit, Optical with PIC Controller, Ver.III – This one uses the same PIC chip but the circuit is slightly different. It is targeted for point-and-shoot cameras but it was reported to work with Canon EX Flashes.
Slave Flash Trigger using AVR micro controller – This is a simple pulse counter that triggers on 1st, 2nd, 3rd, or 4th flash.

All of the above is based on the assumption that the flash synchronization (or main flash) pulse is the last one. This is true in most cases. The problem is uncertain number of pulses before the last one. If the camera emits fixed number of pulses before the main flash, it is easier to handle. But for the complicated system such as Nikon’s Advanced Wireless Lighting system, the light pulses can have virtually unlimited variations. I have previous post a series article on the communication details of the Nikon system. Interested readers may refer to the 1st article and all the articles in the Related Posts section.

After studying the details, I discovered some characteristic patterns in the pulses and came up with a optical slash flash trigger that can work in Nikon AWL setup as well as normal TTL flash setup. The trigger is built upon the Arduino prototyping platform with some limited and inexpensive parts. Most of the trick is done by the software.

The hardware

The following is the schematic.

A photodiode (BPW34) connected in photo-conductive mode is used to detect the flash pulses. The signal is filtered through a RC network (C1, R2) to remove the ambient light component. The signal goes to an analog pin on the Arduino Duemilanove board. Built-in analog-to-digital conversion (ADC) unit converts the analog signal to digital value representing the signal intensity. A custom software code analyze the pulses and determine when to trigger the flash.

S1 is a simple button switch for test firing the flash. S2 is a 2-bit DIP switch for configuration purposes. The first bit controls the trigger mode. The default is the “smart” mode. The other mode is the dumb mode. The second bit controls the sensitivity of the trigger. Only two sensitivity levels are available: low (default) and high.

An optocoupler (MOC3041M) is used to trigger the flash. Sync voltage lower than 400V is safe based on the datasheet. Other variants of MOC30XX may also work. I simply used the parts I already have.

The software

The software is the heart and soul of the smart trigger, and it is not overly complicated. No attempt was made to fully decode the pulse communication of Nikon’s AWL although it may be possible. So how exactly does the software figure out when to trigger the attached flash?

The communication protocol of Nikon’s AWL is quite compact. It sends out unmodulated pulses that are normally ~70 microsecond long. The pulses follow simple binary format except for the channel indicator bits. Between groups of pulses, there are delays of various lengths. It turns out that the longest delay between the pulse groups is before the final sync pulse or main flush. That’s when the camera raises the mirror and fully opens the shutter. So if a pulse comes after a specially long delay time (more than ~40ms) of a previous pulse, it is most likely the sync or final flash pulse. There are exceptions but it can be handled by examining the characteristics (number of pulses) of the previous pulse groups preceding a pulse.

For anyone who is interested in testing it out, here is the code for Arduino IDE. Arduino source code

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// Defines for setting and clearing register bits
#ifndef cbi
#define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit))
#endif
#ifndef sbi
#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))
#endif

// Arduino pins
#define PHOTODIODE 0
#define MODE 3
#define SENSITIVITY 4
#define XSYNC 7
#define BUTTON 8

// 4 microsecond precision timing using 16MHz Arduino
extern volatile unsigned long timer0_overflow_count;
// For timeing measurements
volatile unsigned long prev_pulse, time_passed;

int ar0; // Photodiode input
int threshold; // Pulse height threshold. DIP #2 off: 10, on: 5
int mode; // DIP #1 off: 1st pulse, on: first pulse.
int pulse_count; // Pulse count
int prev_pulse_count; // Pulses in previous pulse groups

// Each tick is 4 microsecond
unsigned long hpticks (void)
{
return (timer0_overflow_count < < 8) + TCNT0;
}

// Fire the flash with a 15 microsecond pulse on the xsync terminal
void fire() {
digitalWrite(XSYNC, HIGH);
delayMicroseconds(15);
digitalWrite(XSYNC, LOW);
}

void dip_config(int info) {
// DIP switch #1
if(digitalRead(MODE) == HIGH)
mode = 1; // Switch Off: smart mode
else
mode = 0; // Switch On: dumb mode

// DIP switch #2
if(digitalRead(SENSITIVITY) == HIGH)
threshold = 50; // Switch off: low sensitivity
else
threshold = 15; // Switch on: high sensitivity

if(info == 1) {
Serial.print("Mode: ");
Serial.print(mode);
Serial.print(", Sensitivity: ");
Serial.println(threshold);
}
}

void setup() {
int start;
Serial.begin(57600) ;

// Use internal reference voltage of 1.2v for ADC
analogReference(INTERNAL);

// Set prescale to 8 for much faster analog read.
// 16MHz/8 = 2MHz ADC clock speed. Each ADC conversion takes 13 cycles.
// So 2MHz/13 = 154KHz sampling rate.
// With other overhead considered, each analogRead takes ~10 microseconds.
cbi(ADCSRA,ADPS2) ;
sbi(ADCSRA,ADPS1) ;
sbi(ADCSRA,ADPS0) ;

pinMode(PHOTODIODE, INPUT);
pinMode(MODE, INPUT);
digitalWrite(MODE, HIGH); // Use the internal pull-up register
pinMode(SENSITIVITY, INPUT);
digitalWrite(SENSITIVITY, HIGH); // Use the internal pull-up register
pinMode(XSYNC, OUTPUT);
pinMode(BUTTON, INPUT);

// I don't why. The first analog read always return 1023 so a dummy read is added
analogRead(PHOTODIODE);
ar0 = analogRead(PHOTODIODE);

dip_config(1);
Serial.println("Trigger Ready.");
}

void loop() {
int new_ar, delta;
unsigned long now;

new_ar = analogRead(PHOTODIODE);
delta = new_ar - ar0;

now = hpticks();
time_passed = now - prev_pulse;

// Pulses come in bundles. The minimal seperation seems to be around 4000 microseconds
if(pulse_count > 0 && time_passed > 1000) {
prev_pulse_count = pulse_count;
pulse_count = 0;
}

// Reset if > 125000*4 = 500ms.
if (time_passed > 125000) {
pulse_count = 0;
prev_pulse_count = 0;
prev_pulse = now;
dip_config(0); // Check the DIP switches. No serial xfer to save time.
}

if(delta > threshold) {
if(mode == 0) { // Dumb mode. Fires upon seeing any light pulse
fire();
}
else { // Smart mode
// If the delay since the previous pulse is longer than 10000*4 microseconds (40ms)...
// Checking the previous pulse group is needed to avoid mis-fire.
if((time_passed > 10000) && (prev_pulse_count == 1 || prev_pulse_count > 5)) {
// Fire the flash now!
fire();
// Reset the pulse counter
pulse_count = 0;
prev_pulse_count = 0;
}
else {
// Get to the end of the pulse. Some pulses are specially wide.
while(analogRead(PHOTODIODE) > threshold);
// Increase the pulse count
pulse_count++;
// Keep track of the time a pulse is detected
prev_pulse = now;
}
}
}
else {
// Background. It should be zero most of the time.
ar0 = new_ar;
}

// Read the button status.
if (digitalRead(BUTTON) == HIGH) {
fire();
pulse_count = 0;
prev_pulse_count = 0;
dip_config(1);
delay(300); // Avoid button contact problem so delay 300ms
}
}

Sensitivity and distance

The sensitivity is quite good thanks to the large sensing area of the photodiode. Since my current setup is still on a messy breadboard, I was not able to test the trigger distance. But it doesn’t require line-of-sight to work. Reflected flashes from walls can trigger it from at least 15 ft away.

Limitations

It works in TTL mode and in wireless mode (only tested with Nikon D200). Front curtain sync seems to work in all cases but rear curtain only works when the shutter speed is faster than 1/2 second. This limitation needs a complex fix to overcome. It will probably be included in future releases.

Future plans

I will be refining the software for the near term to make it work in all situations, hopefully. Another plan is to design a circuit with minimal number of parts. Using the Arduino board is ok for prototyping purposes but it is a overkill for the application. I welcome any feedbacks, suggestions, and feature requests.

Update

Check out the part II. I have put it on a perfboard so I can use the Arduino Duemilanove board for something else. New schematics is available. Code is unchanged.

Photography Hacks and DIY Projects Using Arduino

picmax — Thu, 04 Feb 2010 06:17:16 +0000

People love photography related hacks and DIY projects. The most popular ones are related to photography lighting such as light modifiers, special lighting equipments, etc. If you want to sample just some of the things you can do, DIYPhotography.net has a pretty good list of things you can try.

Here are the couple of things I have been playing with lately. If you have noticed reduced posting frequency on this blog, that’s part of the reasons.

TTL flash output controller

If you read our post about the duration of flash you will know the amount of the flash output is controlled by the duration of the flash. When the flash such as the Nikon SB-600 is mounted on a camera’s hot shoe and the system is set to operate in TTL mode, the camera tells the flash how much light it emits via electrical signal communication between the camera and flash. The communication protocol is proprietary information. To maintain backward compatibility though, the flash in TTL mode can also work in a simple way: Just like you turn on a light, wait for a while, then switch it off. Obviously we need a circuit to do this in a much faster way.

If you look at the flash shoe on a Nikon DSLR camera, you will see something like this (image credit photo.net):

The flash starts to fire when the sync contact (X) is shorted to the ground and stops the flash when the quench contact (Q) is shorted to ground. The simple DIY circuit below does just that. An Arduino Duemilanove I/O board is used to control the flash duration. The precision of the flash duration is about 1 microsecond or 1/1000000s.

Nikon wireless flash controller

Nikon Creative Lighting System (CLS) supports Advanced Wireless Lighting (AWL). I was able to decode most of the communication protocol by recording the light pulses using a photodiode connected to a computer sound card (Part I, II, III, IV, V). What the simple setup below does is quite simple: it records the light pulses from the wireless flash commander then replays the signal via a LED when a button is pushed. The signal from the LED is very weak so the effective distance is only about an inch!

Smart optical trigger

If you try to use a flash with a simple optical flash trigger mixed with Nikon flashes in AWL setup, you will run into trouble because the flash will fire upon seeing the first light pulse from the pre-flashes. The setup below is an optical trigger that cannot be fooled by the monitor pre-flashes sent from wireless commander. It also works in non-wireless TTL mode where the flash on camera still emits pre-flash for metering purpose.

Where are the details?

I will be publishing details of the hacks in the coming days. Stay tuned (if you are interested).

Flash Duration

picmax — Wed, 27 Jan 2010 06:23:26 +0000

Camera flash pulses are typically very fast. It is fast enough to freeze motion even if you use a very slow shutter speed as long as the light from flash dominates the exposure.

Most camera flashes have xenon flashtubes. It lights up when the charge stored in a capacitor is discharged through xenon gas. The xenon gas is not very conductive in its normal state but its resistance can be greatly reduced when the xenon gas molecules are ionized, ignited by a high voltage pulse. The charges stored in the capacitor start to flow through the tube, giving out a very bright light. As the charge stored in capacitor discharges, the light intensity decreases.

The light intensity during a flash pulse isn’t constant. The light intensity emitted from the flash tube rises to a maximum quickly then fall off. If the charges stored in the capacitor are allowed to completely discharge, the light intensity will show a graduate reduction tail. Since we don’t want full power flash for each shot but rather just the right amount of light for proper exposure, the flash unit cuts off the discharge circuit at different times to control the amount of light emitted. Lower flash output power means shorter flash duration.

If you look at typical discharge curves (for example Sigma EF-500 curves or Canon 430EZ), 1/1 output power shows a long tail, 1/2 and other partial discharges show a very steep light fall-off traces. How exactly is the flash duration defined? According to this article, the flash duration is typically defined as the time during which the flash intensity exceeds 50% of its peak value.

For Nikon SB-800 autofocus speedlight flash, the following are the flash duration at different manual (M) output levels.

M 1/1 output: 1/1050s
M 1/2 output: 1/1100s
M 1/4 output: 1/2700s
M 1/8 output: 1/5900s
M 1/16 output: 1/10900s
M 1/32 output: 1/17800s
M 1/64 output: 1/32300s
M 1/128 output: 1/41600s

Nikon SB-600 Minimal Flash Output Level

picmax — Thu, 21 Jan 2010 06:33:25 +0000

The flash output level of a Nikon SB-600 Speedlight Flash can only be set to the minimal of 1/64 in manual mode. That leads many people to speculate the minimal output from the flash is 1/64. If you have used the Nikon Creative Lighting System (CLS) Advanced Wireless Lighting (AWL), you will know that you can use 1/128 output setting on the wireless commander unit. The wireless commander can be the built-in flash of your camera, or SU-800 commander, or SB-800/SB-900 Speedlight flashes. The question is what happens when the remote flash is a SB-600. Will it actually output 1/64 or 1/128 of light when the commander tells it to do 1/128?

To answer this question, I ran a test with a flash light meter to measure the output of the SB-600.

The setup

I used a Nikon D200 to wirelessly control the output the SB-600. The built-in flash was setup as commander, with built-in flash output set to “–” and group A set to M mode. The SB-600 was setup as a remote flash in Group A. The zoom head was left at 24mm. If you are familiar with Nikon’s AWL, you will know that the built-in flash will emit a series of so-called “monitor pre-flashes” (Nikon term) to setup remote flashes, communicate flash output level data to remote flashes, and trigger the remote flash when the shutter is open. The “pre-flashes” can cause a light meter to incorrectly measure the flash output. To avoid this problem, I used the Nikon SG-31R IR Panel for Built-in Flash to block the visible pre-flashes. Infrared signals can still pass through and trigger the flash but the light meter can no longer be fooled. The light meter I used was Polaris SPD100 Digital Exposure Meter. I used ISO 100 and sync speed of 1/200s on the light meter. The distance between the flash and the light meter was one meter.

The results

The flash meter gives a reading accurate to 1/10 of a stop. The measurements are given as aperture value + over exposure value. For example, “f/2 + 1/10″ means camera setting of f/2 at ISO 100 will over expose by 1/10 stop with the light coming out of that flash.

At each output level, the measurement was repeat three times. There are some variations but mostly within 2/10 of a stop.

Conclusion

By using the SB-600 as a wireless flash unit, you can get manual flash output level less than 1/64. As one of our readers, Russ, noted in the comment section below, it is possible to get even less flash output in TTL mode.

Reversing the Nikkor 35mm f/1.8G for Macro Photography

picmax — Tue, 19 Jan 2010 03:20:52 +0000

Before I got my first true Macro lens, a Sigma 105mm f/2.8 EX DG, I had a cheap way of getting macro shots: Mounting a Nikkor 50mm f/1.8D AF reversed using a reverse ring (Nikon BR-2A or the cheaper clone). The picture of that setup and sample image can be found here. Basically it worked OK. On my D200, the camera maintains auto-exposure but no more auto-focus. The images are quite sharp. The magnification is not high through.

Recently I acquired the 35mm f/1.8G AF-S DX, which is a nice prime lens for DX format Nikkon DSLR cameras that gives you a “normal” field of view. When I stumbled across the reverse adapter ring I purchased long time ago on a dusty shelf, I decided to try it with the Nikkor AF-S 35mm f/1.8G lens.

The immediate problem I had was aperture control. Being a G-lens means there is no aperture ring. The aperture gets stuck at the minimal open when the lens is reverse-mounted on the camera. The viewfinder becomes extremely dark, making composition and focusing almost impossible. I overcame this problem by operating the aperture lever by hand. Opening it all the way to compose and focus then let is snap back to the smallest setting (f/22) to take the shot. A SB-600 in remote mode was triggered using the built-in flash on my D200 as wireless commander. Occasionally, I tried to hold the aperture somewhere between the largest and the smallest by hand. Auto exposure, even TTL flash exposure, works on a D200 with a reversed lens. The same isn’t true for D40, D80, D90, etc, which needs manual exposure control.

So how well did it work?

Magnification

The ruler below shows mm/cm scale. Based on the sensor size of 23.6 x 15.8mm on D200. The magnification is 23.6/13.5 = 1.75X! In comparison, revered 50mm f/1.8D gives me only ~0.7X magnification. Most macro lenses give maximum 1X magnification. Besides cost, the magnification is probably the most compelling reason to use the reversed Nikkor 35mm lens as a macro lens.

Image quality

It is decent. A few sample shots can be found below. All images are shown scaled down from the original size of 3872 X 2592 but without cropping. It is a little soft at f/22.

Practical aspects

Exposure – Auto exposure (including TTL flash) is available on high end Nikon bodies. Otherwise the correct exposure can be obtained by trial and error with the help of histogram. Without an aperture ring, it is not very convenient to get an aperture that is not the largest or smallest of the lens. However with practice, you can manipulate the aperture lever with one hand while pressing the shutter release with another.
Focus – No auto focus. It has to be focused manually. It is not possible to focus at infinity. Basically you need to move the camera and lens closer to the subject until the desired focus is achieved. It is not very usable on a tripod without a macro slider or focusing rails. I found it easier to just handhold the camera. With light from flash freezing the motion, the blur caused by camera shake can be reduced to insignificant level. However you still need to be as steady as possible since the depth of field (DOF) is super thin.
Working distance – You have about 50mm or two inches from the lens to the subject. It is very usable.
Magnification – Unlike a true macro lens that allows you to choose different magnification factors by simply changing the subject to camera distance, there is only one magnification using the reversed lens. For a larger subject, the field of view will be too narrow to cover it completely.
Dust particles – The rear of the lens is left unprotected so don’t use it in dusty environment.

Kodak Sues Apple, RIM Over Digital Camera Patents

picmax — Sat, 16 Jan 2010 23:35:12 +0000

Kodak had its glorious Kodak Moment days but now it is struggling to survive. Obviously that means it will go after any possible revenue source. Even though Kodak falls behind in today’s digital camera market, it did invest quite a lot in digital photography technology and accumulated a large portfolio of more than 1000 patents, which is generating hundreds of million dollars royalties annually.

One of the patents at the center of the dispute covers the function that almost all digital cameras have: a real time preview of the scene before the shutter is pressed (US patent 6,292,218). Apparently many other companies have paid Kodak to use the technology but Apple and RIM refused.

Kodak probably isn’t one of the hated patent trolls. The patent seems obvious now but it most likely wasn’t when Kodak started to develop digital photography technology. First digital camera was invented by Steven Sasson of Kodak in 1975, which looked more like a toaster than a modern digital camera.

Kodak sues Apple and RIM over camera tech – ZDNet UK
Kodak sues Apple, RIM over digital camera patents – Yahoo! News

Adorama Introduces The APPOS™ – Photo App Awards and Photo Contest for the iPhone

picmax — Thu, 14 Jan 2010 14:15:00 +0000

Photography is about image quality but not just pixel quality. The quality of the image content is also important. The camera on the iPhone doesn’t produce noise-free images like a PRO DSLR camera but it still offers endless ways of creative photography, especially with the help of more than two thousand photography-related Apps you can find in the App Store.

If you are an aspiring iPhone photographer, this contest offered by Adorama is a great opportunity to display your talent and win some cool prizes. It is easy to get started, just follow the simple steps:

Take a photo with your iPhone
Use the apps of your choice to edit your photo
Submit your photo here, or email it to adorama@strutta.com
Describe how you created your photos and what apps were used, and earn a chance at winning one of many exciting prizes!

A panel of celebrity judges (big names in photography such as Scott Kelby, Joe McNally, Syl Arena, Moose Peterson, etc) will pick the winners but it is you who will select the best iPhone Apps.

Check out the details at contest.adorama.com.

Source: PRWeb

Fotobabble: Photos That Talk

picmax — Wed, 13 Jan 2010 05:32:50 +0000

This is definitely a new comer in the crowed photo sharing site circle but it offers something nobody else seems to have: Photo that talks!

The new site (currently in beta) lets you upload a photo and then record your voice directly through your computer to create a Fotobabble. You can then share it by e-mail, Facebook, Twitter or embed it into a blog or website. There is nothing to download or install. Just a quick registration for a free account.

On almost every other sites, you upload the photo, add title or caption, description, notes, tags. That’s all fine but there just isn’t enough personal touch.

You can do quite a lot with the photo that talks: from simply narrating and describing your photos, sending talking greetings to grandma, telling great stories behind the photo, to marketing or advertising something you sell… the possibilities seem to be endless.

According to the site, they have big plans for the future. Here are just a few examples:

The ability to easily create Fotobabbles from photos on sites like Flickr, Picasa Web and PhotoBucket.
Integration with your favorite social networking sites like Facebook and Twitter to make it easier to share.
The ability to create and share Fotobabbles from anywhere with your iPhone or Android phone.

Check it out

Off Camera Flash Meets Light Painting

picmax — Tue, 12 Jan 2010 06:05:41 +0000

The technique is simple but the result is amazing!

How it was done

Set the camera to 30s exposure and open the shutter
Fire the flash (pre-set the flash power)
Paint the background while the model is holding still

More about it

Flickr discussion thread

The Nabisco Go-Paks DIY Flash Diffuser

picmax — Tue, 12 Jan 2010 05:42:47 +0000

It is amazing how creative people can be when it comes to DIY photography lighting equipment. This Gary Fong style flash diffuser costs only a few dollars to make: just a piece of plastic food packaging (where the name comes from) and an elastic band. We don’t know how well it performs against the real deal that costs ~$50 and the durability may be questionable but the results aren’t bad at all.

How to Add a PC Sync Port to Camera or Flash

picmax — Sat, 09 Jan 2010 07:33:52 +0000

Running coaxial PC cable between PC sync ports is a common way of synchronizing flash with the shutter curtain of a camera. However more and more cameras and flashes come without PC sync port. The PC sync port now appears to be a legacy thing left for only the high end cameras. D200 and D300 have it but D40, D60, D80, and D90 do not.

The PC sync port can be very useful for some special cases. For example, this Nikon shooter wanted to use an iTTL flash on camera while still being able to fire his radio slaves.

This can certainly be done. I have talked about it in my earlier post titled Mixing Flash Modes. What he need is a hot shoe adapter that has all the required electrical connections to pass through the signals while adding a PC sync port. If you don’t need to maintain iTTL functionality, this device should work. Otherwise you need something just a few wires more sophisticated. The following is what I found for a little over $12 from eBay.

This particular model (TF-322) is made by PIXEL ENTERPRISE LIMITED for Nikon cameras and flashes. There are different models for other camera brands but the TTL compatibility is not provided for all brands.

The device is small and light but it very well made. On the top is a Nikon compatible socket with all 4 contacts and the locking hole for securing the flash. The bottom shoe is made of metal with plastic insert where the contact pins are. The pins are spring-loaded to ensure good contacts to your camera’s accessory shoe. It features a thumb wheel lock that also drives a lock pin down when fastened.

The PC sync port is on the front side of the hot shoe converter. Any other location would interfere with the operation of the camera. The PC sync port has screw lock but it works ok with male PC sync plug that doesn’t have screw lock. The connect can be a little loose.

It works as expected. I am able to fire my SB-600 in TTL mode while triggering my remote flash via a pair of transmitter/receiver (more about it here). It also works fine with a 15ft straight PC sync cord connection.

With it mounted on the camera, the flash is raised about 1 inch. This may help to prevent red eye problems.

If you don’t need to have it on camera, you can leave it on flash to add a PC sync port if the flash doesn’t have one built-in. The image below shows how it looks with the Pixel Hot Shoe Converter mounted on a Nikon SB-600. The other way to do it is to open it up and drill a hole on the side for a PC sync port.

Image gallery

CES 2010 Daily – January 7, 2010

picmax — Fri, 08 Jan 2010 06:04:12 +0000

Here is a list of new photography related gadgets from CES 2010 since yesterday.

Updated Exilim P&S – Make your DLSR touting friends envy with 40 shots per second for still images, and up to 1,000 fps video recording.
Casio’s Digital Art Frame – This Wi-Fi connected picture frame has built-in photo effects to unleash your creativity.
Samsung TL210 and TL205 DualView P&S – We covered the DualView camera from Samsung in the past. It makes self-portrait shooting easy and fun. It will perhaps also make your cheese-hating baby smile with the Child Mode. The new models have image stabilization, better video shooting and better lens.
Samsung CL80 – This super thin P&S packs Wi-Fi, Bluetooth, 3.7″ AMOLED touch screen, and 14MP sensor.
New LUMIX P&S from Panasonic – 7 different models…
48GB and 64GB SDXC cards from Panasonic – Great for video shooters. Prices are shockers though: $449.95 and $599.95 respectively.
Sony Cyber-shot P&S comes with GPS+Compass – I am sure it won’t do turn-by-turn like a Garmin.
9 new P&S from Olympus – My first and second digital cameras were Olympus. They were good but there were something much better.
Canon Wireless File Transmitter for latest high end DSLRs – WFT-E4 II A for EOS 5D Mark II and WFT-E5A for EOS 7D.
Polaroid announces new OneStep film and instant digital cameras – If that doesn’t seem interesting, how about Polaroid brand TVs? There was also the news about Lady Gaga being named as the creative director of Polaroid. For people who is getting tired of Flickr or Picasa Web Album, there is the Polaroid Studio (www.polaroidstudio.com) that is supposed to be the “new photo and video sharing service that offers the most extensive features for creating unique, highly customizable online photo albums and keepsakes.”

Nikon Capture NX 2 Seminar Coming to Atlanta, GA on Saturday February 6, 2010

picmax — Thu, 07 Jan 2010 05:31:26 +0000

Nikon School is bring a Capture NX 2 seminar to Atlanta, GA on Saturday February 6, 2010. If you just haven’t got a handle on Capture NX 2 even after reading all the tutorials I have collected for you, this four and half hour butt-numbing sit-and-listen seminar may finally untangle the mess in your brain. According to the announcement, Nikon Technical Sales Representative, Terrence Campbell, will teach you everything from the tools and basic operation of the program to advanced photographic editing. You will learn how to turn your good shots into incredible ones. All for just $79.

For details, check out the following:

CES 2010 Daily – January 6, 2010

picmax — Wed, 06 Jan 2010 14:12:06 +0000

We are now seeing a flood of new electronics being announced at CES 2010 and I have decided to pull the list of photography related gadgets announced at CES or just happened around the same time from Engadget. So here we go…

Pandigital Photo Mail LED frame lets you email snaps over AT&T’s wireless network – You can email your photos to the frame using AT&T’s wireless network. The frame gets own email address. First 300 photos are free but additional emails will cost an undisclosed amount. Cool idea! Just don’t let spammers get their hands on the email address. 4:3 aspect ratio, 800×600 resolution, and 1GB built-in memory.
Rollei rolls out Flexline 100 inTouch digital camera – How does 30 frames per second sound to you?
Canon’s EOS-1D Mark IV gets unboxed, high ISO modes tested – How does it compare against the new Nikon 3Ds? Find our yourself.
Kodak deals Slice touchscreen camera, Pulse digiframe and Playsport camcorder – Kodak’s first tough screen P&S, a Wi-Fi connected digital frame, and the latest pocket camcorder.
Canon debuts A3100 IS, A3000 IS, A495 and A490 low-end shooters – Low end P&S cameras.
Samsung flirts coyly with 7-inch AMOLED Digital Photo Frame – 1 million to 1 contrast ratio, 4GB built-in memory, Bluetooth.
Omnivision illuminates the dark side with new 14.6 megapixel CMOS sensor – Back side illumination is the future of CMOS sensors. The light illuminates the sensor pixel from the backside of the Si substrate, avoiding the front side interconnect layers, which means higher sensitivity and larger effective sensing area.

Source: Engadget

Replace Broken Flash Bulb Without Getting Yourself Killed

picmax — Wed, 06 Jan 2010 06:21:17 +0000

Do you have a Nikon flash that is dead because of a broken flash bulb? One obvious path to resurrect it is to send it in for service. If you are handy and really understand how to follow safety procedures, you can save some expensive repair charges by doing it yourself.

It doesn’t appear very difficult.

One guy ordered a replacement bulb for ~$20 (including shipping) directly from Nikon and fixed his Nikon SB-80DX. Another guy fixed his SB-600 with a $8.52 replacement bulb. If you are motivated enough to try it yourself, be really careful! Some safety tips on camera flash capacitor probably help.

Contact Nikon Parts Department

Phone: 1-310-414-8107
Fax: 1-310-322-6979
Hours: 7am – 3pm PST Mon – Fri

Next Gen Eye-Fi Pro X2 Announced at CES 2010

picmax — Tue, 05 Jan 2010 14:24:07 +0000

Eye-Fi announced the next generation Wi-Fi enabled SD memory card at the 2010 Consumer Electronics Show (CES) in Las Vegas, NV. The new class-6 card has 8GB memory and is capable of 802.11n Wi-Fi connection. One interesting new feature is the so-called Endless Memory Mode, which automatically deletes photos and videos as they’re uploaded. Basically it means you have virtually unlimited storage if you have a wireless connection. It also comes with a new Eye-Fi Center software for viewing and sharing management. The new card is bundked with unlimited geotagging.

The great features of the “Pro” line of Eye-Fi cards are: 1) RAW format support, 2) Ad-hoc networking support so you can wirelessly transfer photos and videos to your laptop computer directly without a Wi-Fi access point. You can even setup auto slideshow using Adobe Lightroom2.

Availability

Amazon pre-order: Eye-Fi 8GB Pro X2 SDHC Class 6 Wireless Flash Memory Card EYE-FI-8PC

Mixing Flash Modes

picmax — Mon, 04 Jan 2010 14:20:23 +0000

The question got asked quite often on the internet lately. Is it possible to mix TTL Flashes with non-TTL manual power flashes or strobes so they sync together? For example, one guy wanted to fire two SB-900s in wireless TTL mode while also triggering an Alien Bee studio strobe at the same time.

The answer is Yes. Since I have only Nikon DSLR and Nikon Speedlight flashes (D200, SB-800, and SB-600), I can only describe what’s possible for people in similar situation. For your particular Camera/Flash brands you will need to decide if this method works for you.

In full manual flash modes, simple optical slaves would work. But Nikon TTL flashes use so-called monitor pre-flashes to determine flash exposure and to communicate with remote flash units. These light pulses will confuse the optical slaves and cause pre-mature firing of the remote flashes. There are also various RF wireless triggers but most transmit only the sync signal unless you spend some hefty amount on TTL-over-RF type wireless triggers.

To make it work, we need to deliver the sync signal to the non-TTL flashes. It is easy if the camera and flash have PC sync ports. Running a PC sync cable between the two is the easiest way. This could be a hassle for many who hates wires. In that case, a cheap set of eBay trigger such as the iShoot PT-04 CN can be used. Just hook up the transmitter to the camera via PC sync cable, then connect the non-TTL flash to the receiver.

However one thing about the Nikon DSLR camera is very strange. If you are thinking about firing the TTL flashes using the built-in flash as a commander unit, forget about it. It won’t work! The reason is that there is no sync signal when the built-in flash is popped up! It has to be down. To work around this problem, you can use a SU-800 commander unit or use one of the Nikon CLS compatible flash as a commander unit. If you need all flashes off the camera, you will need to wire one Nikon CLS compatible flash via a TTL sync cord (SC-28 or SC-29) as a commander and also contributing to exposure.

What about the cameras that do not have a PC sync port, such as D40, D40x, D50, D60, D70, D70S , D80, D90, D3000, D5000? You will need to add a PC sync port to the camera. If you are brave enough, you can probably achieve this by opening up the camera and drilling a hole somewhere. But you can also try to get the so-called TF-322 Nikon i-TTL Flash Hot Shoe to PC Sync Socket Convert Adapter (available on eBay). This little device basically passes all electrical signal of the flash hotshoe through and adds a PC sync port. A regular hotshoe to PC adapter such as the Nikon AS15 Synch Terminal Adapter will not work because it takes away the hotshoe.

What does mixed TTL and non-TTL flash mode offer compared to the all-manual flash setup that can be easily accomplished using cheap eBay triggers? For people who like to use TTL, this helps them to use additional lights that are not compatible with TTL. The TTL flash should also handle mobile subjects much better because the distance between subject and lights are not constant. In those cases, the TTL flash can provide the main source of lights while the non-TTL flashes can be used for background.

Moon and Clouds

picmax — Sun, 03 Jan 2010 06:14:09 +0000

Shooting the mysterious Moon is a frequently discussed photography topic. For a Moon in a cloudless sky, the shooting pretty much is a matter of trivial exercise in term of exposure determination. We have some general tips for moon shooting. The following is the Moon shot with 1/640s f/8 and ISO 200.

It becomes challenging when you want to photograph the Moon behind the veil of the clouds. The reason? At night the Moon is so much brighter than the clouds, a proper exposure of the clouds will pretty much gurantee a blown-out Moon, just like the title image of this post, which was shot with 1/3s f/3.5 at ISO 200 -0.7EV. (It may be a good practice if you want to count the exposure differences between the two shots in stops or EV.)

Are there ways to preserve the details of the Moon surface while properly exposing the clouds?

Not a chance with single exposure but there are some tricks you can play.

Two exposures + HDR. Take one photo properly exposed for the Moon and another photo properly exposed for the clouds then blend them together using HDR method (tone mapping). The key is to make sure the Moon or the clouds haven’t moved significantly in the two photos.
Two exposures + Copy/Clone in image editors such as Adobe Photoshop. The two exposures do not have to be taken in the same day. You can merge a Moon shot taken in a cloudless day with a shot taken during a cloudy night.
Shoot the Moon during the day time when the brightness difference between the Moon and clouds isn’t great.

If you have other ideas please share with us using the comment box.

–

What inspired this post: Another “Moon shot” question – A discussion thread on flickr.

Happy New Year!

picmax — Sat, 02 Jan 2010 06:48:50 +0000

Happy New Year to all DPTnT readers! My deepest appreciation goes to all the visitors of this site that have made the last year’s blogging journey a great joy for me. You can expect great new stuff to come in the New Year of 2010. One of my new year’s resolutions is to grow this site by 5x in terms of page views and visitors. I know this cannot happen without better contents and your continued support.

If you’d like to offer any suggestions on how best I can help you to help me, please kindly use the comment area below or use the contact form.

Thank you and have a joyful and productive New Year!

Balancing Flash and Ambient Exposure

picmax — Fri, 01 Jan 2010 23:31:12 +0000

In the previous post about front-curtain and rear-curtain sync modes, I used a two-exposure model to describe the final image created by the contribution of both ambient and flash lights. In this post, I will go into details about the shooting parameters that affect both exposures and the most effective techniques of balancing flash and ambient exposure. I will mostly speak in Nikon terms since that’s the only brand of DSLR camera I have access to.

Four parameters

The four camera parameters that affect the final exposure are: ISO, aperture, shutter speed, and flash output amount. If the camera and flash are in full manual mode, all four parameters can be freely adjusted by the photographer. In the chart below, a check mark is used to indicate that the particular camera or flash parameter affects ambient or flash exposure. “–” means it does’t. An important assumption is made here: Flash duration is so short compared to shutter speed that shutter speed does not affect flash exposure. This excludes the FP high speed sync flash mode from our discussion to avoid complications.

Clearly, if you want to adjust the amount of the ambient exposure and flash exposure independently, the straight forward approach is to adjust the ambient exposure using shutter speed and adjust flash exposure using flash output amount. However the adjustments need to be within the confinement of the total exposure, which should be the proper exposure for the photo.

Total exposure = Ambient Exposure + Flash Exposure

Obviously, if either one of the ambient exposure or flash exposure equals or exceeds the amount of proper exposure, an overexposed photo will be produced.

If you are after a certain ratio between ambient and flash exposure, you may hit limiting factors such as maximum output amount from your flash or maximum sync speed of the camera. In these cases, the ISO and aperture settings need to be adjusted to bring shutter speed and flash output amount to a workable range. These two parameters affect both the ambient and flash exposure to the same degree so the ratio of ambient and flash exposures is maintained.

The all-manual mode is quite easy to understand. It offers the most degrees of freedom for exposure control. However not all shooting situations permit extensive adjustments that do need time to complete. The most frequently used settings are auto exposure modes and auto flash output via TTL flash system. The chart below outlines the four common exposure modes and who (user or camera) decides ISO, aperture, shutter speed, and flash output amount.

When camera is in control of a camera setting, it follows a pre-programmed logic and parameter range for the setting. The following discussions look at how Nikon DSLR camera behaves in P/S/A/M exposure modes and TTL flash mode.

P: Programmed Auto

In the P exposure mode, the camera picks both aperture and shutter speed automatically to obtain a proper level of exposure.

For example, one reading in a dim light gives me 1/13s f/1.8 at ISO 400. When a Speedlight flash is mounted on the hotshoe or the built-in flash is popped up, the shutter speed is automatically changed to the flash shutter speed (typically 1/60s but can be changed via Custom Settings Menu). What happens to the aperture? It goes from f/1.8 to f/4. From 1/13s to 1/60s is 2 and 1/3 stop under exposure and from f/1.8 to f/4 is another 2 and 1/3 reduction in exposure. In total, the camera decided to underexpose the ambient by 4 and 2/3 stops. The flash is expected to make up the difference to bring a proper exposure to the main subject.

In another example, the camera meter reading was 1/125s f/5.6 at ISO400. When the built-in flash is popped up, the exposure changes to 1/250s f/4. There is no change to ambient exposure.

S: Shutter-priority Auto

In the S exposure mode, the user selects the shutter speed and the camera picks an aperture based on meter reading. What happens to the aperture when an external flash is mounted on the hotshoe or the built-in flash is popped up? Nothing, unless the shutter speed is too high (but still slower than the sync speed) that a proper exposure could not be obtained (you will see “lo” in viewfinder), in which cases the largest aperture of the lens will be used. This leads to under exposed ambient. If the user selected shutter speed exceeds the sync speed of the camera, the camera will jump to the sync speed and the aperture will be increased automatically to compensate so the ambient exposure is maintained. Therefore in the shutter-priority exposure mode, the camera does not intentionally under-expose the ambient but the user can choose to under expose the ambient by using a faster shutter speed when the aperture is at its maximum.

A: Aperture-priority Auto

In the A (aperture priority) exposure mode, the user selects the aperture and the camera selects the shutter speed.

For example, the camera meter decides 1/4s f/4 at ISO 400 is the correct exposure. When the flash is added, the shutter speed jumps to 1/60s (flash shutter speed, changeable via Custom Settings). In this case, the ambient is under-exposed by 4 stops. In another example, the meter shows 1/160s f/5 at ISO400 is the correct exposure for the ambient. Adding the flash doesn’t change it.

M: Manual

In the M (manual) exposure mode, both aperture and shutter speed are selected by user. User has complete control of the ambient exposure. Mounting a Speedlight flash or enabling on the built-in flash does not cause the camera to change either aperture or shutter speed.

Summary

In P/S/A exposure modes, it is not straight forward to control the ambient exposure without affecting the flash exposure. You have no direct control of at least one of aperture and shutter speed.

In P or A modes, if the ambient exposure reading indicates a shutter speed slower than the Flash Shutter Speed, the camera underexposes the ambient automatically with the underexposure amount depending on the difference between the metered ambient shutter speed and the Flash Shutter Speed. If the ambient exposure reading indicates a shutter speed faster than the Flash Shutter Speed, the ambient will be exposed as is, no ambient underexposure happens.

In S mode, no such intentional underexposure will occur but user has the option to underexposed the ambient by using a faster shutter speed after pushing the aperture to the largest possible on the lens.

One very important factor to consider: On Nikon DLSR cameras, Exposure Compensation dial affects both the ambient and flash exposure. It is convoluted.

In M exposure mode, it is easy to control both ambient and flash exposure without affecting each other because the user has complete control over the ambient exposure via aperture and shutter speed adjustments and flash exposure via Flash Exposure Compensation dial.

Auto ISO: When Is It Useful?

picmax — Wed, 30 Dec 2009 07:24:30 +0000

Many new digital SLR cameras now come with a feature called Auto ISO, which automatically adjusts the ISO sensitivity of the camera based on pre-programed algorithms and user preferences such as maximum allowed ISO and minimum shutter speed.

Is this feature useful?

The typical support argument for the Auto ISO feature goes like this: Camera lenses have the maximum aperture limitation. At a given ISO, the required shutter speed to achieve proper exposure may be too slow to stop motion or avoid camera shake even when the aperture is at its maximum setting. In this case, the ISO setting of the camera needs to be raised until a usable shutter speed can be obtained. This previously human-involved process can be automated by the Auto ISO feature.

Still need to see some more convincing arguments or have some questions answered about the usefulness of the Auto ISO feature? Professional photographer Steve Simon shared his thoughts on the Auto ISO feature in Nikon DSLR camera in two discussion threads on Flickr:

Don’t Try This at Home

picmax — Wed, 30 Dec 2009 02:03:35 +0000

Small flashes such as the Nikon SB-600 can emit quite some energy in a short time, enough to scorch vinyl table top. The story goes like this:

I was shooting tonight with my D90, wirelessly triggering my SB-600. At one point, I left my SB-600 flash tube facing down on a vinyl covered card table. When I released the shutter, the SB-600 obediently fired, probably at full power. A whisp of smoke appeared and a scortch mark 0.25″ by 1.25″ was left in the table top. No damage done to the SB-600, but I was quite surprised at the smoke and burn mark.

Can this be true? I don’t have a vinyl surface anywhere in my house so I tried the following: I set the flash to manual mode, 1/1 (full power) output, covered the flash head with my palm then hit the test button… I felt a sharp burning sensation in my hand that almost made me drop the flash.

Before you actually try something like this, read the title of the post again. That’s your last warning.

Front-curtain Sync vs. Rear-curtain Sync Mode

picmax — Mon, 28 Dec 2009 16:40:21 +0000

In the article titled Understanding Flash Sync Speed, I discussed in details how focal plane shutter works and what maximum sync speed is. What was left out was the two different flash sync modes: front-curtain vs. rear-curtain sync.

In front-curtain sync, the flash fires immediately after the first (front) curtain opens completely; in rear-curtain sync, the flash fires just before the second (rear) curtain starts to close. To understand the differences they make, let’s use a simple two-image model.

The image sensor continuously capture the image formed by the lens on the sensor surface when the shutter is open. There is one image captured by the camera in each exposure but you can imagine the sensor captures two images: one image formed by ambient light and one image formed by the flash. The two images are then superimposed together. In front-curtain sync, the flash image is captured first followed by the image of the ambient light; while in rear-curtain sync, the flash image is captured after the image sensor captures the ambient image.

The flash image is motion-freezing because the typical flash duration is very short: ~1/10000 second to ~/1000 second. But the ambient image may not be depending on the shutter speed and the relative intensity of the ambient light.

When photographing in a completely dark room, there will be no difference no matter which sync mode you choose. In practice, when the light from flash dominates overall exposure, the two flash sync modes do not differ much either. In the two-image model, the final image you get is mostly the flash image.

Things will be different when the ambient light is strong enough and/or the shutter speed is low enough that the ambient image is clearly visible. If the shutter speed is low, the blur caused by camera shake or subject motion can be captured and blended with the flash image. Sometimes the ambient is weak and the shutter speed is not really slow but the subject is fast-moving and it contains bright spots that can still be captured during the time the shutter is open. One example is the head/tail lights from a moving car.

When the shake or motion is completely random, it doesn’t matter (contrary to what some experts said) if you use front-curtain or rear curtain sync mode. The final image is the simple addition of the flash image and ambient image. There is no way to tell which one is on top or bottom. It is different when the shake or motion is not random. A moving car leaves its light streaks behind with rear-curtain sync mode but an unnatural blur in front of the car with front-curtain sync mode.

From what is said here it sounds like it is better to leave it always in rear-curtain sync mode. This may be true if the camera exposure mode is M (manual) or S (shutter speed priority). On Nikon DSLR cameras, selecting the rear-curtain sync mode when the exposure mode is in P (Programmed Auto) or A (Aperture Priority) causes the camera to go automatically into Slow Sync mode, in which the camera will choose a shutter speed that exposes the ambient to a standard level. In Front-curtain sync mode and P/A exposure mode, the shutter speed will be normally between 1/60s (determined by Flash Shutter Speed custom setting) and maximum sync speed of the camera. In typical low light shooting situations, such shutter speed is typically fast enough to make sure the flash exposure dominates when ISO and aperture settings are properly set. In some cases it may cause blur problems. For example when shooting in-doors with available sunlight the shutter speed may be ~1/30s for a proper exposure without flash. So 1/60s shutter speed with flash can leads to fair amount of blur.

Some tips

If you want to freeze all motion, make sure the flash exposure dominates or the shutter speed is high enough. To do that you may have to use manual exposure mode to overcome the tendency of the camera doing things on its own.
If you want to properly capture non-random motion, use rear-curtain sync mode.
Use tripod with slow shutter speed when ambient light is significant to reduce the blur caused by camera shake. However this will not help with motion blur caused by moving subject.