What are general rules for ISO settings when using a flash?

Question

I am trying to stop using the auto mode. I think I sort of understand the following ISO rules:

• Use an ISO of 100 or 200 when taking photographs outside in sunny conditions.
• If the sky is overcast or it is evening time, then use an ISO within the range of 400 to 800.
• Night time or in cases of low light you might need to set your digital camera ISO to 1600.

Should I follow the same rules when using a flash (direct/bounce mode)?
Thanks!

Answer 1

When you use flash outside in sunny conditions to fill shadows you should set it to a low value. When you use flash in low light and you want to illuminate just your model, it's better to use low iso values. If you want to illuminate the model and the scene you should use a higher iso value like 400 and up (the value depends on light and model of camera). For more information, have a look at: http://neilvn.com/tangents/flash-photography-tip-find-your-background/

Answer 2

I would say "no, do not use the same rules" - but that's because I wouldn't use your rules when not using flash. In most circumstances, I think you should start by selecting the shutter speed and/or aperture that you want, and then use the lowest ISO which allows you to expose the scene correctly. I can't think of many circumstances where I would choose the ISO before choosing other things.

Answer 3

flash is, imo, a lot trickier to set a rule around. it really is dependant on how you want the shot to turn out.

in low light, if you set to iso 100, 1/50 sec, flash on, the background scene will be dark/near black. there is a certain look some ppl like about the way that is shot but be wary of blowing out your subject unless you have a diffuser.

in low light, my preference with flash is to iso 100, 1/15, f1.8. this opens the shutter longer allowing the flash to freeze my subject while allowing the slow shutter to show up in a nicely lit ambient mood. as you move to iso 200++, this allows your shutter to be set faster without motion blur if your subject moves while still pulling up the ambiance. But that is entirely up to you as the slower shutter opens up some veryy creative motion blur with flash photography.

flash photography isnt as easy to "can" in respect to settings so while my rule may work for me, you may find it is inappropriate to your stylr or taste.