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Flash setting in commander mode

James_Yates

Stokkemarke, DK
3 posts

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James_Yates Registered since 25th Mar 2012
Sun 30-Dec-12 10:44 AM

Is it possible to turn off the built-in flash when using it as a commander for a remote flash?

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elec164

US
2575 posts

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#1. "RE: Flash setting in commander mode" | In response to Reply # 0

elec164 Silver Member Nikonian since 15th Jan 2009
Sun 30-Dec-12 10:21 AM

The built in flash needs to work in order to send the signals to the remote. You can minimize its impact to the exposure by setting it in the menus to "--"; or using the SG-3IR.

Pete

Pete

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Gray_star

US
52 posts

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#2. "RE: Flash setting in commander mode" | In response to Reply # 0

Gray_star Registered since 17th Dec 2012
Sun 30-Dec-12 10:25 AM

Yes and no.

In the Commander, set the built-in to "--". That turns it off. However, the built-in must still send the "fire" command to the remote units, and that occurs just after the shutter opens. So you still get a tiny bit of light. Usually it's not a problem, and the worst you get is a set of catch lights in the subject's eyes. But if you're attempting certain types of product photography, such as shooting wine bottles, then the tiny bit of light from the built-in may cause unwanted reflections.

There are three ways to address this. The first method is free. Set custom setting e1:Flash Shutter Speed to 1/250 AutoFP, and then set a shutter speed of 1/320s to get AutoFP operation. When you shoot with AutoFP flash, the "fire" signal comes before the shutter opens so there's zero contribution.

The second method is to get the Nikon SG-31R IR Panel for built in Flash.

http://www.nikonusa.com/en/Nikon-Products/Product/Flash-Couplers/4905/SG-31R-IR-Panel-for-Built-In-Flash.html

It's just a thin piece of plastic that covers the flash. It's supposed to block visible light while letting IR light through. However I've seen test results where it still lets a tiny bit of visible light through, so it may still be a problem for photographing glass.

The most expensive solution is to get the SU-800 Commander.

http://www.nikonusa.com/en/Nikon-Products/Product/Flashes/4794/SU-800-Wireless-Speedlight-Commander.html

With the Commander you can control up to three groups of lights, and it works more reliably in sunlight. It produces IR only, so there's no visible light at all. It also has AF-Assist lights on it to help focus in low-light situations. It's nice, but pricey...especially when you already have one built into the camera.

km6xz

St Petersburg, RU
3559 posts

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#3. "RE: Flash setting in commander mode" | In response to Reply # 0

km6xz Moderator Awarded for his in-depth knowledge in various areas, including Portraits and Urban Photography Nikonian since 22nd Jan 2009
Sun 30-Dec-12 08:38 PM

The Commander mode setting for the built-in flash will send a series of pulse trains but if the mode is set to "--" no flash will contribute to the exposure. The only problem I have seen is the pre-trigger light pulses can trigger someone's blink reflex.
CLS is a complicated system that requires the camera and all the slaves on each channel to communicate with each other by sending and receiving pulse position coded data by flash.
Pressing the shutter release causes the camera to send out a pulse of light telling all the flashes on Channel A to fire a reference level of light output which is then metered by the camera, and the sequence repeats for each channel. The camera calculates the total light reflected back from the subject.
The camera sends a code by pulse code to each channel separately in sequence that tells each channel how much power to generate. The camera then send a code to fire all the slaves. It the build-in flash is set to TTL while in Commander mode, its power calculation has already been done by the prior measurement command sequence since the camera was able to measure the reflected light from the built in flash every time it was used as the code transmitter. The built-in flash has its power set at the same time, after applying the flash compensation value stored in TTL mode. If the mode is changed from TTL to "--", all the flash sequence is performed by the built-in flash except for the very last one....the one that is fired during the shutter being open.
You can try an experiment to prove that. Remove the external flash but keep the camera flash in Commander mode and set it to "--" and take a photo in a dark room. Black frame even though you see all the pre-flashes, which are so fast that they all appear as one short flash. Change the mode to TTL and dial in flash compensation of your choice (I use it as direct flash as -2-3ev just to get a little catch light) and take a photo of the dark room and you will see an image under exposed by the amount of the flash compensation bias you dialed in.

If you really do not want the flash to go off, the alternative to optical coding is wireless RF flash triggers. Fairly recently manufacturers of wireless triggers have started relaying the coded information so they can be used in a CLS setup.
I designed my own CLS compatible RF flash triggers 4 years ago for my D90 and I did not even know at the time, it was not possible with any commercial product. I never bothered to build it into my D7000 or D800 however.
Stan
St Petersburg Russia

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James_Yates

Stokkemarke, DK
3 posts

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#4. "RE: Flash setting in commander mode" | In response to Reply # 3

James_Yates Registered since 25th Mar 2012
Tue 01-Jan-13 02:19 PM | edited Tue 01-Jan-13 02:24 PM by James_Yates

Thanks for the very thorough explanations. I knew about setting the internal flash to "--", but couldn't understand why the flash kept activating. Great idea about taking a picture without the external flash. The image was almost completely black even though the flash seems to work. To be honest, I thought there was a problem with my camera. Cheers James

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G