Quick help needed: seamless black background w/ 1 flash

[cruz610]

Hi guys -

I've had a last-minute assignment come up tonight shooting a fashion photo booth and I am not prepared! Ideally I would have had 2 flashes for key + fill, but alas, I will only have one at my disposal. I'll be shooting against a black backdrop, but I want to get the black seamless look going on a la Zac Arias white seamless tutorial. I remember reading something a while back about having a smaller aperture, highest flash sync speed possible, w/ max flash to only capture the first 5 feet or so while not giving enough time to expose for the background.

Any tips or pointers for doing this?

Thanks!

[gonzogolf]

The higher your shutter speed, and lower your iso you will kill the ambient making your background darker. As long as you dont have a lot of spill from your light that falls on the subject it will go black. The big problem with lighting this sort of scene with only one light is people with dark hair will have no background separation.

[steveathome]

If using a black background, then as long as you keep the background more than 4½ times the distance from your light source than the subject (or 4½ stops - same thing) you shouldn't get any problem with light spill.

[Wilt]

If using a black background, then as long as you keep the background more than 4½ times the distance from your light source than the subject (or 4½ stops - same thing) you shouldn't get any problem with light spill.

I'd say that to get -3EV differential (measured with reflected meter), compared to the gray card or incident reading at subject position, is sufficiently dark to call it 'black'. The scaling of the distance is not simply linear, but geometric. n use distances like f/stops.

4' to light-to-subject vs 11' to background... f/4, -3EV is f/11
8' to light-to-subject vs 22' to background...f/8, -3EV is f/22

[Titus213]

At 4 feet from the backdrop, properly lit, what color should a black backdrop be?
I think the bigger problem will be getting separation, as mentioned above.

[Wilt]

Say folks, at 4 feet from the backdrop, properly lit, what color would a black backdrop be?


:D

My post was assuming a 18% gray background and rendering it black. If you are starting with black backdrop, you only need worry about surface sheen, which can be signficant depending upon the material in use.