I have been shooting small birds flying across a three foot gap between a bush and a feeder. In order to freeze the wings, the shutter is set to 1/4000 sec, which then requires an ISO of 4000 in bright sunlight. However, at this time of year, the gap is in shadow at the time when the birds are most actively feeding. So I was hoping I could do something with an SB-700.
According to a review of the SB-700, it has a guide number of 92 at ISO 100 and a flash duration as short as 1/10000 second at a manual setting of 128 and a duration of 1/5000 second somewhere in the middle of the adjustment range.
So far, my cut-and_try efforts have not resulted in the freezing of the wings, which I assume is due to the shutter now limited to 1/200 second (I'm using a D-5100).
Is there any way to calculate where the guide number would go with a change in flash duration and ISO setting?
I might be able to move the flash, but not the camera. It depends if the flash will fire multiple shots while being radio controled. I can't move the camera because these little guys are naturally nervous to begin with. As it is, after I go out on the deck and set up I have to sit pretty much perfectly still for about 15 minutes before they come back. Wouldn't moving the flash closer have the same effect on the birds as increasing the power?
I was hoping to be able to calculate some apperture/ISO settings that would give me a starting point where flash, at 128, would light up the birds but wouldn't allow the ambient light (this is about 3:00 to 5:00 in the afternoon) to show the motion.
>I might be able to move the flash, but not the camera.
THIS IS THE STRATEGY! Move the flash…
* Hi C. Lind Aitken,
If the birds predictably … • come from the same direction • fly at the same hight (+/-), setting up a flash or two slightly higher and behind the bird for one and the other somewhere to brighten up the face of the bird, could be a good solution, radio triggered that is!
The SB-700 has a flash duration of: 1/40000 sec. at M 1/128 power 1/25000 sec. at M 1/64 power 1/18182 sec. at M 1/32 power 1/10000 sec. at M 1/16 power 1/5714 sec. at M 1/8 power
If you want to use the short duration of the flash to freeze the movement of your subject you must set the camera to under expose for the ambient by 3-stops or more. You can do this by dialing in negitive exposure compensation using P, S, or A modes our Manually in Manual exposure mode.
The SB-700 has an exposure calculator built in. When you set it to Manual mode and adjust the power level the "Effective flash output distance" will be shown in the display. 15 feet = 3m That should get you close. You can then tweek the exposure settings or flash power as required.