Series of uncropped shots taken at 2:1 and focus stacked of a fairly high contrast situation of a dark dead fly on a light background.
I was using styrofoam packing sheet for the diffusion where 3 layers gives a 1 stop light loss from the flash gun.
The non diffused shot actually had a deeper focus stack so the rear of the abdomen is more in focus.

Brian V.

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the nine layer is definitely the best.

and that would be 3 stops!

is that right?

Originally Posted by stevehapp the nine layer is definitely the best. and that would be 3 stops! is that right?

Think in this slightly rigged high contrast situation then the high level of diffusion is best. Yes it would give 3 stops light loss - a bit high but not necesarily a killer- on my rig this would give good light on 1/8th flash power in manual at this magnification, so still the potential for multiple fast shooting without waiting for the flash to recycle. I'm actually going to try the 6 layer for a while- I had been using 3 layers but 6 layers gives the same light loss as kitchen paper towel gives which I used for a couple of years quite happily.

In case you are wondering I measure the light loss by shooting with the flash in manual at a series of flash times and see where they equate.

Brian V.

Thanks for that explanation, brian.

imho, the biggest factor is the colour/brightness of the subject...

Black subjects suck up the light like a sponge, and lighter subjects just bounce off like crazy..

I know this is basic light theory but it took me a while to get it. !

But i think it is the major factor.. afaik...

You almost need different lighting setups for light and dark subjects..

?????????

Originally Posted by stevehapp Thanks for that explanation, brian. imho, the biggest factor is the colour/brightness of the subject... Black subjects suck up the light like a sponge, and lighter subjects just bounce off like crazy.. I know this is basic light theory but it took me a while to get it. ! But i think it is the major factor.. afaik... You almost need different lighting setups for light and dark subjects.. ?????????

Yes light or dark or hairy/ smooth subjects do have different lighting properties but you can often adjust a bit for that with FEC when in TTL mode on the flash.
IMO the main point of a diffuser for flash photography is to stop blown highlights/ specular highlights and to make the apparent size of the light source appear larger.These effects will will make the lighting appear more even across the subject. However they also mean a loss in contrast and also in apparent detail (high contrast detail always shows more).
So from that line of reasoning it would be useful to have variable diffusion depending on whether you are likely to get bright reflections from the subject and also whether you are dealing with a low or high contrast subject/ background matter. As is usual you just have to pick some sort of balance for the lighting you prefer.

Anyway , it's interesting to play with flash diffusion :).

Brian V.

Thanks again, brian, for that further explanation.
I am slowly starting to get it..

doh!