Author Topic: Flash Compensation  (Read 7361 times)

Offline Kirk Baker

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Re: Flash Compensation
« Reply #15 on: April 28, 2011, 09:18:49 AM »
Hayo,

Hi Kirk, the new beta gives me +0.0 instead of e.g., -1.0 (the previous beta didn't give me anything, so this is an improvement). This is with a raw file from a D3.

Can you get me a sample file and also tell me what the expected flash compensation value should be?

Thanks,

-Kirk

Offline Hayo Baan

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Re: Flash Compensation
« Reply #16 on: April 29, 2011, 12:15:34 AM »
Hi Kirk, I've attached a small jpg saved with Capture NX2 from the raw file. All exif/maker note info is intact and this is what exif tool has to say about it:
Flash                           : On, Return detected
Flash Setting                   : Normal
Flash Type                      : Optional,TTL
External Flash Exposure Comp    : -1
Flash Mode                      : Fired, External
Pre Flash Return Strength       : 74
Flash Sync Speed                : 1/250 s (auto FP)
Flash Shutter Speed             : 1/60 s
Auto Bracket Set                : AE & Flash
Auto Bracket Mode M             : Flash/Speed
Modeling Flash                  : On
Internal Flash                  : TTL
Flash Info Version              : 0103
Flash Source                    : External
External Flash Firmware         : 5.02 (SB-900)
External Flash Flags            : Fired, [1], Dome Diffuser
Flash Commander Mode            : Off
Flash Control Mode              : iTTL-BL
Flash Compensation              : -1
Flash Focal Length              : 12 mm
Flash GN Distance               : Unknown (128)
Flash Color Filter              : None


Incidentally, Nikon Capture NX2 lists the flash compensation as -0.7, but I'm quite certain they take the exposure compensation of 0.3 into account there (if I recall correctly, I was indeed shooting at -1); I see similar discrepancies with other files.

Cheers,
    Hayo

[attachment deleted by admin]
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Web: www.hayobaan.nl

Offline dennis

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Re: Flash Compensation
« Reply #17 on: April 29, 2011, 07:39:25 PM »
Hey Hayo,

Thanks for your help with this flash comp issue!  For some reason this has always worked for me in the past using my equipment, but after additional testing it appears that there is both a formatting issue with new Nikon tags, and a realization that the regular flash comp and the external flash comp are tied to each other.

Essentially the body has a flash comp setting, and there is an additional external flash comp. Nikon adds these two together to produce a final "flash compensation" value.

So if your body's flash comp is at +0.3 and your SB flash is set to -2.0 then the effective flash comp is -1.7.  I should know this of course but I spend too much time using a keyboard instead of a camera.  ;)

IOW the two compensation values need to be combined by addition (of log).  Previously they were overriding each other and what I suspect you would get is a bogus value (like +0.0) when the external flash wasn't being interpreted correctly.

I'll see about a new build for you to test.

Thanks.

--dennis

Offline Hayo Baan

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Re: Flash Compensation
« Reply #18 on: April 30, 2011, 01:24:33 AM »
Hi Dennis, you're welcome :)

It is true both the compensation set on the camera and the compensation set on the flash work additively. This is why in my workshops I always tell people to only set it on one of the two (the flash) to prevent confusion.

Note that on cameras that don't have a built-in flash (eg. a D3), you can only set the external flash compensation anyway. Perhaps this is why until now haven't really seen the problem? Heck, this post actually triggered me to check for my self…

I will be happy to test a new version for you.

Cheers,
    Hayo Baan
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Offline dennis

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Re: Flash Compensation
« Reply #19 on: May 01, 2011, 04:24:29 PM »
Hayo,

I'm not the fortunate owner of a D3 or D3s.  But I suspect these cameras will still be affected by the same issue?  Does the D3/D3s have a "body" flash comp setting?

At least this exercise certainly illustrates the need to zero the camera flash comp unless you need to adjust this universally.

I look forward to the results of your testing.  Special build coming your way.

Regards,

--dennis

Offline Hayo Baan

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Re: Flash Compensation
« Reply #20 on: May 02, 2011, 02:22:17 AM »
Hi Dennis,

Typing on an iPod made my reply a bit terse and cryptic, but what I tried to say was that if your Nikon camera body does not have a built-in flash, you can only set the flash exposure compensation on the flash itself. If the body has a built-in flash, you can also set it on the camera, in this case both settings are taken into account. To prevent confusion I strongly suggest people to only use one way to set the flash exposure compensation.

Anyway, as the D3 (or D3s or D3x) does not have a built-in flash, there is only the flash exposure compensation as set on the flash, so no potential for confusion in this case  :)

Cheers,
    Hayo

PS I've sent you a personal message with feedback on the test version you provided.
Hayo Baan - Photography
Web: www.hayobaan.nl

Offline dennis

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Re: Flash Compensation
« Reply #21 on: May 02, 2011, 06:22:36 PM »
...if your Nikon camera body does not have a built-in flash, you can only set the flash exposure compensation on the flash itself. If the body has a built-in flash, you can also set it on the camera, in this case both settings are taken into account.

Hayo,

This was the confirmation I needed and the next beta should have this fixed (finally we can put this issue away?)!

Thanks as always for your detailed help,

--dennis

Offline Kirk Baker

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Re: Flash Compensation
« Reply #22 on: May 05, 2011, 04:56:38 PM »
The beta that addresses this issue can be found here:

http://forums.camerabits.com/index.php?topic=6368.0

-Kirk