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Old Jan 3, 2011, 1:33 AM   #1
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ok so im starting to use manual wireless off camera flash with my d3000 and sb600 im wondering what does changing the shutter speed and aperture do when using the flash ive read that the shutter speed controls the aiembent light behind the subject and aperture controls the exposure of the subject any input on this subject would be really helpful thanks
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Old Jan 3, 2011, 7:01 AM   #2
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Not certain what you mean - shutter speed controls ambient light behind the subject. Ambient light is ambient light. Shutter and aperture are 2 of the 4 or 5 factors that control exposure. The strength and quality of that exposure is what allows ambient light to coexist or be completely overwhelmed.

Generaly speaking, 1/60 @ f8 and 1/30 @ f16 will let the same amount of light in when working with available light, but with flash slightly different. Flash fires 100% of power upwards of 1/1000 sec and is dependent on the shutter being 100% open during that time - thus the maximum shutter sync speed. Using the example above, both would have the same amount of flash output, but f16 would only allow half that flash output in with the 1/30 allowing more available, or ambient, light in to complete the exposure. That's not saying it would be a good exposure as the subject could be underlit from too little flash - just a mathmatical example to put in perspective.

Factors affecting exposure in addition to shutter and aperture include ISO, distance, and lens (or zoom position). In your SB600 manual, the old fashion grid chart on page 27 will give you a good starting point for manual operation. Granted it is the TTL chart and assumes the camera auto setting the shutter around 1/60, it will put you in the ballpark. If you want a headache, go to page 35 for the manual calculation where you even have to include an ISO adjustment factor as it uses a base 100 ISO and I think the camera's lowest is 200.
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Old Jan 3, 2011, 7:44 AM   #3
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ok so im starting to use manual wireless off camera flash with my d3000 and sb600 im wondering what does changing the shutter speed and aperture do when using the flash ive read that the shutter speed controls the aiembent light behind the subject and aperture controls the exposure of the subject any input on this subject would be really helpful thanks
You probably mean the camera is on manual, but the wireless flash remains in Auto...

In which case both the shutter and aperture will affect the ambient light while the flash will keep the exposure constant!
-> The flash exposure is only affected by the flash compensation dial

This is how it works:
1. Check the EV scale in your viewfinder which looks something like this
-2..-1..0..+1..+2
^
2. As you increase the shutter speed or the aperture, the exposure pointer (^)above will move to the left indicating the ambient will get darker. The further left the darker the ambient room light will be, and it'll be the same as the flash if you keep the pointer near the center
3. Meanwhile the flash will always try to expose for the foreground (i.e. subject) right in the center of the above EV scale(0) with the correct exposure
4. To alter the flash exposure you will have to use the flash exposure compensation!

Last edited by NHL; Jan 3, 2011 at 7:56 AM.
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Old Jan 3, 2011, 1:01 PM   #4
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Flash is on full manual also but I've read stuff about sync speeds and using camera shutter speed to control the amibent light behind the subject and aperture to control the exposure of the subject
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Old Jan 3, 2011, 3:13 PM   #5
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Flash is on full manual also but I've read stuff about sync speeds and using camera shutter speed to control the amibent light behind the subject and aperture to control the exposure of the subject
You're on your own here... Or find that link again. Check page 34 of your SB600 manual, but normally all three: shutter, aperture and flash power will determine the exposure.

For practical purpose the shutter can be left on 1/60, but you need to work on both the aperture and the flash ratio:
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Old Jan 3, 2011, 3:46 PM   #6
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Flash is on full manual also but I've read stuff about sync speeds and using camera shutter speed to control the amibent light behind the subject and aperture to control the exposure of the subject
To a large extent, this is correct: for a given flash guide number, you control the subject exposure by the aperture setting (since the flash duration is so much shorter than the shutter speed, only the aperture controls the light).
When you mix flash and ambient, using a longer shutter opening will allow the overall photo to be brighter, but it may also overexpose your subject, so you may need to lower the flash setting. The effect varies, depending on how near your subject is relative to the background, and how much the ambient light differs between subject and background.

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Old Jan 3, 2011, 3:49 PM   #7
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ok i just put up a car pic in a different thread how can i improve it by keeping the car lit with flash but darking the backround
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Old Jan 3, 2011, 7:36 PM   #8
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I have no idea which thread the car pic is, but the alternate way to do what you want is to work with layers in PS, selecting and abjustung the background in on of the layers and blending together. On a flash basis, it gets to trial and error, fine tuning the exposure.

The above is page 34 of the owner manual. That is why I said the TTL chart will get you in the ballpark, manual calculations as explained further will give you a headache. The only way to totally control is to put both the camera and flash on "M". Set the shutter and aperture on the camera and begin with 1/1 (full) flash strength. Review and adjust shutter and flash strength until you get the right combo of subject exposure and background presence.

Over the weekend, I experimented with the "A" setting as I took passport photos of myself. Pre-calculting the exposure would be even more difficult to calculate - but found something interesting. Setup was 2 SB600's shooting through umbrellas, and a 75 watt 6500k background light to eliminate rear shaddow. Both flash on "M 1/1" and camera (D90) flash control was taken off TTL and flash triggered with Cactus triggers. "A" was set to f8.

What I found interesting is that there was some remnant of TTL exposure control. I was expecting the shutter to set at a default of 1/60. Rather, the camera set the shutter at 1/15. That slow shutter also allowed the rear illumination to not be affected. While not obvious with the 6500k bulb, on one set I used a 2700k bulb altering the white balance, casting a yellowish pattern on the muslin backdrop. It set the exposure on the subject, while the slow shutter speed allowed retention of the background.
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Old Jan 3, 2011, 7:39 PM   #9
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its the one labeled my eagle talon
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Old Jan 3, 2011, 7:52 PM   #10
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Try this one...

http://forums.steves-digicams.com/sp...ball-help.html
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