Flash diffuser material comparison

[LordV]

Awful weather today so I played with some different diffuser materials on my coke can.
The amount of diffusion not suprisingly seemed directly related to the light loss. The light loss was estimated by looking at a series of shots taken with the flash in manual (ie 1/64,1/32,1/16,1/8) but the comparison shots are all ETTL.

click on pic for larger size

Brian V.

http://farm4.static.flickr.com/3020/2991229609_074a5f61bc_b.jpg (http://farm4.static.flickr.com/3020/2991229609_bb9953f04a_o.jpg)

[racketman]

Kleenex possibly gives the least harsh reflections. I wonder how a Gary Fong would compare.

[LordV]

Kleenex possibly gives the least harsh reflections. I wonder how a Gary Fong would compare.

Not sure about the gary phong - I was mainly interested in working out a simple test system including light loss - will obviously try some different materials and perhaps multiples. I actually tried this with just the raisin first and got virtually no differences between anything :)
Brian V.

[Dalantech]

I actually tried this with just the raisin first and got virtually no differences between anything :)
Brian V.

I've noticed that as well -some subjects don't work well when testing out new diffusers. I usually get a couple of my son's Hot Wheels cars -lots of odd angles and different colors to shoot against.

Excellent test Brian! How did the red channel look with different diffusers -notice any difference there?

[macro junkie]

I've noticed that as well -some subjects don't work well when testing out new diffusers. I usually get a couple of my son's Hot Wheels cars -lots of odd angles and different colors to shoot against.

?
i usually get a mantis out thats willing to sit still for ages.not all of us are lucky enough to have mantids lying around tho for subjects ;) :D

[LordV]

I've noticed that as well -some subjects don't work well when testing out new diffusers. I usually get a couple of my son's Hot Wheels cars -lots of odd angles and different colors to shoot against.

Excellent test Brian! How did the red channel look with different diffusers -notice any difference there?

Thanks John -
a quick look indicates some red channel suppression in all the paper based diffusers even though I adjusted the colour temp of all the shots to the same value.

Brian V.

[Dalantech]

Thanks John -
a quick look indicates some red channel suppression in all the paper based diffusers even though I adjusted the colour temp of all the shots to the same value.

Brian V.

8-)

Oddly enough I'm getting the warmth I want and at the same time not blowing the reds by using a 1/8 CTO gel. Removing the front plastic from a set of Sto-Fens and replacing it with some diffuser material from a Bogen diffuser kit also helped ;)

[LordV]

Some more tests together with red channel histograms. Oddly this time I don't think the red channels changed significantly between tests. The shots were all taken with manual flash power. The wide angle flash diffuser gives a somewhat odd result. Think I'll try the 3-layer styrofoam packing for a while and see how it does.

Brian V.

Click on pic for larger version go full screen and click again

http://farm4.static.flickr.com/3230/2994009715_f09bef7056_b.jpg (http://farm4.static.flickr.com/3230/2994009715_f8c6c12080_o.jpg)

[Dalantech]

Look at the spikes in the red histogram on the far right Brian in the last three images -the higher the flash duration the more the red channel is blown. I'm seeing the same thing with the MT-24EX with some diffusion materials, although I think the problem is a lot more severe than with a standard flash. There's no way I could afford to lose two stops with the MT-24EX...

IMHO it's best to keep your light loss to one stop or less -the tricky part is finding something that will diffuse the light more than block it. I couldn't find a household material that would give me the diffusion to loss ratio that I was looking for, and everything that I tried also shifted the color temperature of the light, and that's why I broke down and bought that diffusion kit from Bogen (about 24 USD + shipping). I haven't tested the light loss yet (would be a PITA since I use a two stage diffusion with the first stage hot glued directly to the flash head) but I'm sure it's low -I can hear the flash making a short popping sound every time it goes off and I'm not even close to blowing the red channel. It's not perfect -still needs a lot of fine tuning. But the light quality I'm getting now is the best I've ever managed from the twin flash. Maybe there's a local camera shop with some diffusion material you could try -something that won't block a lot of light or change the color temperature of the flash. Keep in mind that if you do use a plastic that's designed to diffuse a flash that the light will be daylight balanced and you're probably use to a warmer light source (due to the kitchen towel). I've added a 1/8 CTO gel to my setup so I don't have to adjust the white balance in post and it gives me light that's a little on the warm side but it's subtle. I tried a 1/4 CTO and it looked too warm.

[LordV]

John - think the spiking in those pics is due to slight overexposure as a whole- the large peak to the left of those is slightly shifted in comparison to the control with no diffuser. You may be right about diffuser materials - I'm just playing with what I have available. The only "professional" diffuser I have is 3 feet diameter :) but will see If I can do a test with it. Just useful to have a slighlty standardised test for comparing these things.

Brian V.