Basic info for someone new to flash photography

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Revet

Senior Member
I am just starting to learn flash photography so I am a little confused on how the camera with flash is working together to get a good exposure.

I tried some practice TTL shots using manual camera mode (i.e. I am setting F stop and shutter speed while watching the meter on the camera). With my flash turned off, I adjusted my aperture and shutter speed until I got the needle in the middle on the viewfinder and took the shot. Then I turned my flash on and repeated the process. It took the exact same settings to get the needle in the middle (correct exposure according to camera). So in both cases the needle was in the middle (correct exposure) but the result was an underexposed shot without the flash (can be normal for my camera) and a better one with it. I don't get this.

What is going on with the metering process in this example (with and without flash)? Also why is it able to meter with the flash on before you even push the shutter release down so that pre-flashes are fired?? Also, when I take the picture, I don't see pre-flashes. Are these so close to the primary flash that you can't detect them?

I'm using an SB-700 on a D3100. I like to know how things work, not just trust that they will.
 
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FastGlass

Senior Member
If shooting in TTL. The meter in camera has nothing to do with flash. Only ambient light. So if setting the cameras meter for proper exposure for ambient light and then turning on flash. The flash most likely will not contribute much to the exposure. Well it will add a little fill but thats about it. The flash will fire preflash which you can't really see happening and it will adjust according. If you're scene has good lighting than the output on the flash will be dramaticly reduced because it feels it doesn't need it. But at the same time while stopping down the ambient to underexpose the background. You're in camera meter will try and tell you you're underexposed which is o'k but you're flash will fire and light up what ever you're metering and focusing on. When in TTL mode the camera is metering the light output from the flash through the lense until it sees a good exposure and then shuts down the flash. For the most part it works pretty good. Alot of times I need to tell the flash to give or subtract a little power.
 
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FastGlass

Senior Member
By the way there's so much more to understanding flash and it's differant modes. It's hard to explain everything in a quick reply. There is so much information on youtube or the internet readings. I actually baught a course that Mark Wallace put out on speed lights. Pretty in depth couse that explains and shows you how. Worth looking into. For some people it's hard to learn something so in depth such as flash from reading manuals than seeing someone do it and explain what their doing and why.
 
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Revet

Senior Member
Thanks, Fastglass. I will look into that. My problem is I need to do a large group indoor photo in less than a week (amateur, not paid luckily). So as I read what your saying, if I set my F stop, ISO, and shutter speed around where I want them, I should not worry about what the meter says??? What I want to do I think, is set my camera and shoot the shot and then tweak the flash output from there. Does this sound right??
 
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Mfrankfort

Senior Member
Change your settings on the camera (shutter speed/aperture) to get the ambient (background) light correct. Then change the flash output to get your subject(s) light correct. If you slow down the shutter... change the aperture... it won't effect flash on TTL. Your flash fires at about 1/10,000 of a second. So in complete darkness, you can use a shutter speed of 30 seconds, and still get a theoretical shutter speed of about 1/10,000.
 
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Revet

Senior Member
I think I got this now. I am going to be shooting a large group indoors using 3 speedlights. Thus, I should first set my camera's f-stop (to the lowest value that keeps the whole group in focus), ISO (400, maybe 800) and shutter speed (1/60 to 1/125) to what I want. After that it is all about changing the flash output or position of flashes (bounce vs direct, further back, etc) to get the correct exposure. Does that sound correct?? Than along the same lines, if I have reached the limits of my flashes in TTL for lighting this large group, will they be firing at 100% power (In other words, increasing the output with flash compensation would not help. Correct?)
 
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Revet

Senior Member
Thanks Mike, sounds perfect for me. I am somewhere between clueless and competent at this stage (As I become more educated and competent with some things, more questions arise and bring out the clueless side).
 
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