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View Full Version : Experiment - Light Meter/Stofen Diffuser/Translucent Umbrella


bigdazzler
30-07-2010, 2:49pm
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)
http://i445.photobucket.com/albums/qq176/DarrenGrayPhotography/f16.jpg

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)
http://i445.photobucket.com/albums/qq176/DarrenGrayPhotography/f11.jpg

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 !!
http://i445.photobucket.com/albums/qq176/DarrenGrayPhotography/f71.jpg

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 :D
bigdazzler
30-07-2010, 3:24pm
ahh shit ... just realised the whole thing is flawed anyway .. must have bumped my shutter speed without realising it. 1 shot is at 1/125 and the other 2 are at 1/100 .... oops :lol:

Good thing I was only doing it out of boredom anyway ... :D
Remorhaz
30-07-2010, 9:05pm
I'm just wondering if you could do the same sequence but instead lock the camera on a fixed shutter speed & aperture & ISO (so we get the same DoF, etc) and adjust the flash power output to compensate to get a better feel for the differences in the quality of light?
MarkChap
30-07-2010, 9:48pm
I'm just wondering if you could do the same sequence but instead lock the camera on a fixed shutter speed & aperture & ISO (so we get the same DoF, etc) and adjust the flash power output to compensate to get a better feel for the differences in the quality of light?

Shutter speed shouldn't be playing a big part in these any way Darren.

Good results and good examples
bigdazzler
31-07-2010, 7:47am
Shutter speed shouldn't be playing a big part in these any way Darren.

Good results and good examples

no probably not in the overall scheme of things, it was pretty much lit entirely with flash, and the ambient didnt really come into play at all. The variation in SS was only very small anyway, 1/3 stop. But for the sake of accuracy, and given that I had 125th punched into the meter, it would have been good if I didnt stuff that part up nonetheless :D
bigdazzler
31-07-2010, 7:48am
I'm just wondering if you could do the same sequence but instead lock the camera on a fixed shutter speed & aperture & ISO (so we get the same DoF, etc) and adjust the flash power output to compensate to get a better feel for the differences in the quality of light?

Yep .. absolutely. Will do that one next time I got nothing to do :) This was really only about taking a closer look at the effect the umbrella and stofen had on the metering and light output, not so much the quality.
bigdazzler
31-07-2010, 7:56am
Another thing I thought interesting here was the reflections of the specular highlights in the foreground, coming from the door of the car.

They are much harsher and starker in #2, the shot with the stofen on the flash, than they are in #1 when the flash was bare.