Thanks useful information: 
Im a little bit bored today so thought I would do a little experiment with a couple of different cheap and easy light softening techniques/tools and take note the differences/effect on exposure.
I set the car up on my computer desk and took three exposures, one with a bare flash, one with a stofen type speedlight diffuser, and one with a small translucent umbrella.
Base exposure was manual mode, ISO100, 1/125th, and I metered the aperture with a Sekonic meter. The flash was at full power, zoomed to 50mm, and the distance flash > subject was the same for all three shots.
My umbrella is supposedly a one-stop shoot through ... but Ive long thought that it sucked out a little more light than that, and it seems im right. (Never got around to testing it properly before now)
1. bare flash , Aperture f16 (the meter read f11.9 so close enough)
2. flash with stofen on the flashhead , Aperture f11 (meter was bang on f11.0 Seems this reduces light by a full stop .. I wouldnt have thought so)
3. flash with "one-stop" shoot through brolly ... mmmmm. Aperture f5.6.6 (which in 1/3rd stops gets you to a shoot ap of f7.1) Thats a whole 2 1/3 stops difference in exposure from the bare flash at f16 !!
I took these with my 85 1.4 at close to MFD, so the DOF and overall sharpness has suffered in the last one with the brolly. Something to be wary of with longer lenses and smaller apertures, even with flash.
The point ?? Not much really, except to demonstrate the effect even the smallest diffusers can have on your exposures and light output. It also shows how a cheap umbrella can give you a really nice feather light. You can see that when comparing the shadows and the specular highlights.
.... and .....
I was bored
Reply With Quote
Add To Bookmarks
