My flash compensation not working?


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LBL2009

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Jul 9, 2009
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#1
I tried some test shots with TTL build-in flash and find the flash compensation not showing any effect on the pics.

The settings -

Subject - A chair, a table and some posters on the wall in a room.
Camera - Nikon D40
In A mode, with aperture set to F8, shutter speed is 1/4 sec under ambient light.

When the built-in flash is activated, camera set the shutter speed to 1/60 sec. This is the default setting by the camera when TTL built-in flash is used.

I took 3 pics, at 0, -1 and -3 flash compensation at 1/60 sec and F8.

The 3 pics are similar in brightness. The histograms are also not showing much difference. I expected darker pic at -1 and darkest at -3.

I tried M mode. With similiar settings, I shot another 3 pics. Same results.

The flash compensation didn't seem to show any effect whether at 0, -1 or -3 in both A and M modes.

Next, I tried manual flash instead of TTL and repeated the test.

Same results.

I am at a loss. What is the problem? Is my camera flash compensation not working or I have a wrong understanding of flash compensation application?
 

madmartian

Senior Member
May 2, 2009
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Outer Space
#2
I'll try to help you.

I assume you are using the onboard flash. It should work because I just tried it. I follow your setting and I got 3 different exposures.

Go to the flash compensation part and select -1, then press ok. I think you did not press ok that's why it did not work.

On your camera lcd, the -1 will be displayed at the flash compensation window.

Hope this helps.:)
 

catchlights

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Sep 27, 2004
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#3
you try to open your lens aperture to f4
or cut the distance from camera to subject in half,
or set your ISO to 800 or higher

do the same test and let us know the results.
 

LBL2009

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Jul 9, 2009
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#4
you try to open your lens aperture to f4
or cut the distance from camera to subject in half,
or set your ISO to 800 or higher

do the same test and let us know the results.
OK it works. Either at f4 keeping the same distance or at f8 at closer distance, the results were obvious. haha. Happy. No problem with my camera. :bsmilie:

Thanks a lot.

So I am the problem. :embrass:

Previous pics were shot at f8 at 20 fts from subject. So this is the problem.

Can you explain why at far distance or smaller f number, the flash compensation fails to make a difference?
 

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madmartian

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#6
Makes no difference. I tried again at your original settings and stand 20ft and 30ft away shooting the same subject, I still get 3 different exposures.

So it got nothing to do with the distance or aperture.

It's the flash compensating factor that's doing the job, it did not fail.
 

madmartian

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#7
That's right also. It does not have enough juice to hit that distance.
 

LBL2009

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Jul 9, 2009
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Seletar Estate, Singapore
#8
Makes no difference. I tried again at your original settings and stand 20ft and 30ft away shooting the same subject, I still get 3 different exposures.

So it got nothing to do with the distance or aperture.

It's the flash compensating factor that's doing the job, it did not fail.
To put things in perspective, it is working but the results were not noticeable at my original settings and I was looking at the camera LCD. At f4 or closer distance, the results are obvious. Good learning for me.

Wonder whether ambient light plays a part too.

By the way, what camera are you using?
 

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madmartian

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#9
I'm using D60. Lets say at your given settings and your subject is 10ft away, with the different flash compensation settings, you should get 3 different exposure.

Of course if you move away like 20 or 30 ft away, the onboard flash will not hit your subject, unless you use a much higher iso without adjusting the aperture, and still, you'll get 3 diff exposures.

At 1/60s and f8, ambient light is not significant at long distance. You'll still get real under exposed shot.

I'm basing the situation at 10ft. Any further, you got to do adjustments on your camera settings but the flash compensation part still stays.
 

madmartian

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May 2, 2009
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#11
Yup, thats right, guide no is like 12 or 15. But not if you up the ISO and shoot wide open. (I mean the aperture, not your legs, haha :sticktong)

Its good to own a strobe
 

Feb 16, 2008
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the blue planet
#12
...

So it got nothing to do with the distance or aperture.

It's the flash compensating factor that's doing the job...
really?
if the subject gets twice the distance from light source (flash in this case), you'll need 4 times more flash power..or you increase (widen) the aperture by 2 stops..
TS' original exposure setting might have exceeded the cam's flash power so the results of + or - flash compensations were not obvious..
that's why catchlights let the TS to cut the distance, as well as increase the aperture (& ISO)..
 

madmartian

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May 2, 2009
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#13
what catchlight is saying is correct. When shooting at a given distance, say 10 ft, you'll get the normal 3 exposures that TS wanted. When i said it has got nothing to do with the distance and aperture, i meant if you move back 20ft, you'll still get 3 different exposure but real bad ones. But if you move back, then you have to change the ISO or aperture accordingly, and change the flash compensation, you'll still get 3 different exposures.
 

Feb 16, 2008
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the blue planet
#14
what catchlight is saying is correct. When shooting at a given distance, say 10 ft, you'll get the normal 3 exposures that TS wanted. When i said it has got nothing to do with the distance and aperture, i meant if you move back 20ft, you'll still get 3 different exposure but real bad ones. But if you move back, then you have to change the ISO or aperture accordingly, and change the flash compensation, you'll still get 3 different exposures.
oh..sorry for my confusion of your previous statement..
i thought you were saying different to what i understood..:)
my bad..
 

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