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12-19-2014, 05:13 PM   #1
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Why is ISO cranked up with flash?

When shooting with built-in flash or top mounted flash (Metz 50 AF-1) in Tav mode (where the camera gets to control the ISO) it decides to crank it up to 3200 (the max I have set). Why is this? It doesn't make sense.

When it's dark I know I can get a bright picture by upping the ISO but then I get noise. I would guess that if the camera knows it will use flash, it would set ISO at 100 or close to it to have no noise and still bright picture due to the flash? There must be something I'm not understanding.

Would appreciate a clarification.

Thanks.

12-19-2014, 05:40 PM   #2
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Check the range you have set the ISO for :
Try setting the ISO range to 100-400 , or even 100-200 or simply a fixed ISO ...
If you have allowed the camera to select an ISO of 3200 , why would it not do so ..


So time to hit the menu , and check those settings ...


Depending on what camera you have ????
You may have a Fn button to press , or a ISO button to press at the back ...
12-19-2014, 05:47 PM   #3
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I have a K50.

The range I currently have it at is 100-3200.

I know I can change the ISO range or simply fix the ISO at whatever I want. However, the purpose of my question was to understand the rationale of why the camera is choosing such a high ISO number given that it knows it will be using flash. Am I explaining myself? I'm just a beginner in this stuff but I want to learn.
12-19-2014, 05:51 PM - 2 Likes   #4
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QuoteOriginally posted by Moropo Quote
the purpose of my question was to understand the rationale of why the camera is choosing such a high ISO number given that it knows it will be using flash
It is quite simple really: the camera is trying to balance ambient light with the output from the flash. However in your case the ambient light levels are extremely low, so the camera is using a High ISO. This is why I prefer to use manual exposure when I'm working with flash. You will never see a studio photographer using AUTO- settings with professional strobes in a studio. Flash is a controllable, reliable light source. So when working with flash, I set my camera in manual mode so can set my exposure exactly how I want it.


Pentax K5IIs - Sigma 180mm f/3.5 - Wireless AF540GFGZ flash with 1/4CTO filter


Last edited by Digitalis; 12-19-2014 at 05:58 PM.
12-19-2014, 05:53 PM   #5
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Tthe camera is trying to make the exposure without flash and then add on,ynfill flash.

Sometimes automation is not a good thing.

You are better to set the camera into manual mode and set the native exposure as you wish and then set the flash . The camera will stil control the flash in P-TTL mode
12-19-2014, 06:01 PM   #6
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TAV can be used so that if necessary, the camera can up the ISO so you still get the shot you want without changing the other two aspects of the exposure triangle. ( Shutter speed and aperture )
That's why in low light the ISO shot up ...


TAV is probably not the best mode to be in ..
Again , set your ISO range to what you want , and your probably better of in Green Mode or maybe manual mode ...
12-19-2014, 06:24 PM   #7
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The program line settings could have something to do with it too.
12-19-2014, 06:51 PM   #8
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QuoteOriginally posted by Moropo Quote
When shooting with built-in flash or top mounted flash (Metz 50 AF-1) in Tav mode (where the camera gets to control the ISO) it decides to crank it up to 3200 (the max I have set). Why is this? It doesn't make sense.
Because you are shooting in TAv mode, it makes perfect sense.

QuoteOriginally posted by Digitalis Quote
It is quite simple really: the camera is trying to balance ambient light with the output from the flash.
What he said. When you use TAv mode with P-TTL, you are basically tying the hands of the camera's automation saying that the only tools available are ISO and flash intensity and that the camera must balance flash against ambient despite whatever strange settings the user might stipulate. It could be worse though. You could be f/8 in Av mode at fixed ISO 100 in a dim room. The body will set the shutter speed way down and ghosting will be the result.


Steve

12-19-2014, 08:06 PM   #9
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Upshot of all the good info above, TAv is probably the worst setting when using PTTL flash. Although TAv can be very helpful in some situations, it is not really the recommended setting for general use.
12-19-2014, 09:27 PM   #10
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QuoteOriginally posted by Digitalis Quote
.... Flash is a controllable, reliable light source. So when working with flash, I set my camera in manual mode so can set my exposure exactly how I want it.
Amen.



12-19-2014, 09:43 PM   #11
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QuoteOriginally posted by Moropo Quote
When shooting with built-in flash or top mounted flash (Metz 50 AF-1) in Tav mode (where the camera gets to control the ISO) it decides to crank it up to 3200 (the max I have set). Why is this? It doesn't make sense.

When it's dark I know I can get a bright picture by upping the ISO but then I get noise. I would guess that if the camera knows it will use flash, it would set ISO at 100 or close to it to have no noise and still bright picture due to the flash? There must be something I'm not understanding.

Would appreciate a clarification.

Thanks.
It is the chicken-and-egg scenario, you think that the camera controls the ISO, however, the camera thinks that the flash should take a read on the camera's setting... is it the failure on the flash (egg) or the camera (chicken)? Neither the camera nor the flash knows how you want the final picture looks like.

Last edited by aleonx3; 12-19-2014 at 10:56 PM.
12-19-2014, 11:05 PM - 1 Like   #12
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I've experienced this myself and its annoying. They really need to program it better. I feel if flash is being used it should know that it doesn't have to boost the ISO otherwise we wouldn't use the flash
12-19-2014, 11:59 PM   #13
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QuoteOriginally posted by Moropo Quote
I have a K50.

The range I currently have it at is 100-3200.

I know I can change the ISO range or simply fix the ISO at whatever I want. However, the purpose of my question was to understand the rationale of why the camera is choosing such a high ISO number given that it knows it will be using flash. Am I explaining myself? I'm just a beginner in this stuff but I want to learn.
TAv mode is probably the least favoured shooting mode if you are using flash. You can use either P, Av, Tv or M mode with fixed ISO. As many posters suggested, best to avoid any auto-shooting mode which do not give you the ability to control how much you want the flash light vs ambient light. Having said that I have seen people using high ISO for flash photos, there is nothing wrong with that - the result often does not have a 'flash' look but still nice and sharp.
12-20-2014, 12:42 AM   #14
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QuoteOriginally posted by shaolen Quote
I've experienced this myself and its annoying. They really need to program it better. I feel if flash is being used it should know that it doesn't have to boost the ISO otherwise we wouldn't use the flash
Think why this can't be so, Shaolen.

You would get a bunch of pictures with a lit subject but everything in the background would be lost - it'd be black.
12-20-2014, 10:23 AM   #15
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I'm still a flash novice but would like to join the "TAv with flash is bad" club. I only use flash with manual ISO. Av mode when ambient light changes frequently, and full Manual when in a more predictable environment.
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