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Old Nov 8, 2009, 6:59 PM   #11
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i agree with TCav. get a feel for it in P, you will see much better results.
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Old Nov 8, 2009, 7:10 PM   #12
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You're trying to expose for ambient light (as if you're not using a flash). So, the flash is contributing very little to the exposure, and you're getting lots of motion blur from the slower shutter speeds and higher ISO speeds being used for those aperture settings. Your meter is telling you the proper settings to use *without* a flash. ;-)

IOW, you're doing the opposite of what's needed to freeze the action (trying to let in too much ambient light).

Turn your ISO speed back down to around ISO 200 for starters and set your shutter speed to around 1/100 second. At the apertures you're using, that means very little ambient light would contribute to the exposure. So, the flash will freeze the action, since your subjects would be dark without the flash, and the flash duration will be very short (usually around 1/1000 to 1/10000 second, depending on the subject distance, aperture, etc.).

Basically, the camera will look at reflected light from the preflash and adjust the exposure accordingly (filling in the light to properly expose your subject, even if the subject would be underexposed without a flash).

If you find that the flash is not providing enough light to illuminate the room when bouncing, increase your ISO speed some (so that you have a bit better flash range) if you want to use those aperture settings (around f/6.3 is what you seem to prefer).

Basically, you want to control the amount of ambient light using ISO speed and shutter speed for a given aperture setting. Shutter speed makes no difference in how much light from the flash the camera is seeing (as long as you're within the camera's x-sync speed limitation, which is 1/250 second with your 40D).

But, you can use it to help vary how much ambient light you let in. So, if you want a bit more ambient light for a given aperture (for example, a further away background outside of the flash range), you can lower your shutter speed and/or increase your ISO speed and/or open up your aperture.

If you want the flash to freeze movement (versus the shutter speed of the camera), just make sure your settings are 2 or 3 stops below the ambient light levels. IOW, if your meter is showing correct exposure at f/6.3, 1/10 second and ISO 800, you would be 3 stops underexposed using 1/10 second, f/6.3 and ISO 100 (or 1/20 second and ISO 200) and could still freeze the action using the flash (despite the slow shutter speeds).

I'd probably go around 1/100 second at lower ISO speeds (although you could go with anything up to around 1/250 second if you want no ambient light contributing), which should be plenty fast at the apertures you're using for that lighting to make sure the flash is providing most of the light (as some of the subjects may be closer to ambient light sources and better lit than you see with the meter).

Then, experiment letting more or less ambient light into the exposure to see what it does. Basically, you can set the camera so that virtually no ambient light contributes (which can be useful if you deliberately want a brighter subject with a darker background), or so that you are letting in more ambient light. But, if you do let in more ambient light, make sure your shutter speeds are not so slow that you're getting motion blur from subject movement.

IOW, I'd suggest setting the camera so that you're exposing a few stops darker than the meter indicates for the ambient light it's measuring (making sure the needle in your viewfinder is well left of center if shooting manual exposure), so that the flash can freeze the action.
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Old Nov 8, 2009, 7:48 PM   #13
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It looks like the meter in the 40D viewfinder is good for + or - 2 stops. So, if you want to use manual exposure, you'd want your exposure so that the needle is all the way left (and then go about a stop darker) to make sure ambient light is not contributing to the exposure when using a flash.

Again, I'd probably start at around ISO 200 and 1/100 second using apertures of around f/6.3 to f/8 and see what you get for those types of group shots. Go ISO 400 if needed to make sure you have enough power for bouncing. In your indoor lighting at night, those settings should let in very little ambient light (so the flash will freeze the action, regardless of any subject movement). Then, experiment with settings to let in more or less ambient light to see what happens if you want to be more creative.
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Old Nov 9, 2009, 7:38 AM   #14
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Judging exposure manually isn't easy, especially if you're just starting out. Use an autoexposure mode if you're going to use flash, and let the camera do all the hard work.
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Old Nov 9, 2009, 7:57 AM   #15
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The camera is doing the work. ;-)

You're only controlling the amount of ambient light when using manual exposure. The camera will automatically throttle the flash output based on your aperture and ISO speed so that your subject is properly exposed, based on reflected light seen from the metering preflash. If you want to change the amount of exposure from the flash, use Flash Exposure Compensation (as your manual exposure settings don't control the flash output).

IOW, you could expose for ambient light in a variety of ways, and still have a properly exposed subject when using manual exposure.

Again, if you want to be safe about it, something like f/6.3, ISO 200 and 1/100 second will make sure that you don't have much ambient light contributing to the exposure (so that the flash will freeze the action) in typical indoor lighting. By default, most cameras use around 1/60 second in non-manual modes with flash in darker conditions.

I rarely use a flash with anything but manual exposure. That allows me to control how much ambient light I want in the scene (from lights in the background, etc.).
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Old Nov 9, 2009, 8:17 AM   #16
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I'm with Jim on this one. Here are my starting point settings for external flash indoors:

ISO 400, f6.3, 1/60

If there's a lot of sunlight then I'll drop the exposure. I'll also alter the exposure if there's a lot of movement (in which point you want to be at -2 exposure) or if there's a strong ambient light source near the subject I want to overpower.

The thing is - the reasons I stated above for when I want to alter the exposure, the camera isn't going to know anything about - so it's not going to get that right either.

My recommendation is to use Manual. Doing so, and experimenting a bit will really help you learn flash photography better. And using the values either Jim or I gave will provide a good starting point. It really isn't that difficult.
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Old Nov 9, 2009, 3:36 PM   #17
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When using flash with TTL it's best to use manual exposure. The camera will adjust the flash output to get the proper exposure.

A and T modes are asking for trouble. P is sometimes okay, but usually not.
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Old Nov 9, 2009, 8:42 PM   #18
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This thread is one of the things that makes this such a great place to learn about photography. Using the manual setting is the LAST place I would have gone to use a flash. I tested a lot of different setting in my home tonight and almost all turned out good. The flash really does do all the work for you.
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Old Nov 11, 2009, 7:30 PM   #19
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Thanks everybody for all your input, I'm looking forward to having a play and see what I can do. unfortunately I have a very busy week ahead so will not be able to try out the suggestions until next week.
I will no doubt be back next week asking for some more pointers,
thanks again!
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