Diffusion material for strobe?

I'd like to put something in front of my AB 7" reflector to soften the light a bit. This will be for outdoor shoots where a softbox is impractical.

I won't keep the modeling light on for long, if at all since that gets hot (and won't cast enough light outdoors anyway). Should I just put some white ripstop nylon over the reflector or are there other suggestions? I'd rather not go the $22 AB diffusion filter route (DF6).

-Timothy

TimothyHughes wrote in post #3342594
I'd like to put something in front of my AB 7" reflector to soften the light a bit. This will be for outdoor shoots where a softbox is impractical.

I won't keep the modeling light on for long, if at all since that gets hot (and won't cast enough light outdoors anyway). Should I just put some white ripstop nylon over the reflector or are there other suggestions? I'd rather not go the $22 AB gel route.

-Timothy

Merely putting a sheet of something translucent over the AB's reflector will do absolutely nothing to make the light softer at the subject's plane. All it will do is reduce the amount of light emitted by the flash unit and trap the heat in the reflector (which can be a very bad thing).

In order to make the illumination from a light source softer is to make the effective size of the "source" of the light larger. That requires a reflector, an umbrella, a large softbox, or something similar. If you think about it, putting something translucent over the reflector would do absolutely nothing to the effective size of the light source.

Does this make sense?

SkipD wrote in post #3342677
Merely putting a sheet of something translucent over the AB's reflector will do absolutely nothing to make the light softer at the subject's plane.

Well there is two schools of thought on this one. A scrim or shoot through umbrella is merely a sheet of something semi-transparent in front of the light source. Those absolutely soften the light. Granted the distance is greater from the flash than it would be mounted on the front of a reflector.

A Lowel frost gel according to their website: "Softens and diffuses. Reduces light intensity by approx. 2/3 stop." So perhaps I'd be best off going with that.

Yes Timothy but what Skip pointed out still applies. You can diffuse the light and still have a light source no larger than the AB 7" reflector but to really soften the light for portrait lighting you need to increase the apparent size of the light source. There's no getting around that. That is the science of it, not just opinion or preference.

So if you place your light behind a shoot through umbrella or a diffusion pane of some sort you need to have some distance between the light source and that material. If you had the reflector right up against the material you would not be doing much at all since the size of the light source remains the same.

TimothyHughes wrote in post #3343175
Well there is two schools of thought on this one. A scrim or shoot through umbrella is merely a sheet of something semi-transparent in front of the light source. Those absolutely soften the light. Granted the distance is greater from the flash than it would be mounted on the front of a reflector.

... and the size of the umbrella is MUCH larger than the 7" diameter reflector, making the effective size of the light source much greater. That is what makes the light softer at the subject's plane.

TimothyHughes wrote in post #3343175
A Lowel frost gel according to their website: "Softens and diffuses. Reduces light intensity by approx. 2/3 stop." So perhaps I'd be best off going with that.

The reduction of light intensity is all it will do, in practical terms, unless your subject is within inches of the gel. What the gel (or a piece of rip-stop nylon) would do if mounted right at the front edge of the reflector is merely make light go in various directions instead of in the angle defined by the reflector. The effective size of the light source would be the same as a naked reflector, so when comparing results with the subject 6 feet or so from the flash unit you would have very little difference.

I disagree with absolutely nothing part.

If the bulb is uncovered, then a part of it is acting like just the bulb. So sticking a sheet of paper in front of it turns part of the light from bulb size to 7 inches...

Depending how close it is to the subject, you just might see something.

I just did some self portraits with a single Vivitar 285HV at 10 feet from the subject. I had the flash on automatic so it automatically adjusted for the 1 Fstop light loss when I added several layers of Rosco diffusion material in the filter slot. There was 1/10 of an F stop difference between the image with no diffusion and one with 2 layers of diffusion. I also included a Macbeth Color Chart just to be scientific. After I adjusted the images for the 1/10 F stop difference there was no noticable difference between the 2 images. Also the Macbeth Color Charts in both images gave identical readings in all of the color strips. I think this would also hold true with the AB unit even though it has a 7 inch reflector versus the 2 inch by 3 inch reflector in the Vivitar.

You can argue theories all day long but you can't argue results.

raymushgrush wrote in post #3351102
I just did some self portraits with a single Vivitar 285HV at 10 feet from the subject. I had the flash on automatic so it automatically adjusted for the 1 Fstop light loss when I added several layers of Rosco diffusion material in the filter slot. There was 1/10 of an F stop difference between the image with no diffusion and one with 2 layers of diffusion. I also included a Macbeth Color Chart just to be scientific. After I adjusted the images for the 1/10 F stop difference there was no noticable difference between the 2 images. Also the Macbeth Color Charts in both images gave identical readings in all of the color strips. I think this would also hold true with the AB unit even though it has a 7 inch reflector versus the 2 inch by 3 inch reflector in the Vivitar.

You can argue theories all day long but you can't argue results.

But your test did nothing to confirm or deny Doc's speculation that there is a minimal, but present, difference in the softness of the light output from the flash with no diffusion vs. the flash with diffusion which is merely the original size of the flash lens. You need to perform your test and place some objects in front of the wall a few feet away, and then look closely at the shadow edges on the wall both with and without the diffusion material. (I know the result, even without a test.)

DocFrankenstein wrote in post #3343479
I disagree with absolutely nothing part.

If the bulb is uncovered, then a part of it is acting like just the bulb. So sticking a sheet of paper in front of it turns part of the light from bulb size to 7 inches...

Depending how close it is to the subject, you just might see something.

Wilt wrote in post #3352486
But your test did nothing to confirm or deny Doc's speculation that there is a minimal, but present, difference in the softness of the light output from the flash with no diffusion vs. the flash with diffusion which is merely the original size of the flash lens. You need to perform your test and measure not the exposure, but place some objects in front of the wall a few feet away, and then look closely at the shadow edges on the wall both with and without the diffusion material.

Thanks Doc and Wilt.

Very good points and a greatly misunderstood concept.

I didn't have any proper diffusion material (Rosco) that I could cut down to be the same size as the native lens on my Metz 54MZ, so I improvised with just a piece of printer paper. There is a color shift due to the bond, so I neutralized the color shift via making the images grayscale only.

For my test I focused on a rose colored piece of paper taped to the wall. I set a ruler in front of the wall about 2' away from the wall, casting a shadow on the wall. Since the wall was my point of focus, differences in softness of the shadow edges due to some diffusion vs. native lens would be best observed. I shot from 5' from the ruler (the 'subject')

First is the native lens only, then the printer paper same size as lens...

Hi Wilt,

Clearly, the second image that is being diffused has a much softer shadow line than the image without any diffusion.

TMR Design wrote in post #3352840
Hi Wilt,

Clearly, the second image that is being diffused has a much softer shadow line than the image without any diffusion.

Yes, the lens vs. the paper exhibits just a bit of effect. The native lens is not a true point source, but it also is not a truly diffuse source, either. If you ever notice a small cloud passing in front of the sun, the shadows get a bit softer. Similar effect here. But nowhere as dramatic as even a very tiny on-flash softbox, in the example I added. The Stoffen would be more similar to the paper in front of the lens.

Great examples!! Thanks Wilt. Those images really demonstrate how diffusing and increasing the effective size of the light source soften shadows dramatically.

TMR Design wrote in post #3352924
Great examples!! Thanks Wilt. Those images really demonstrate how diffusing and increasing the effective size of the light source soften shadows dramatically.

And it also shows why I ignore the issue of ceiling bounce, and rely on a small softbox when I shoot weddings. I cannot depend on having a ceiling, or a low enough one, or a neutral colored one, and do not want to use a different solution for each of my shooting circumstances!

That makes good sense Wilt. Do you use the Westcott mini softbox for that?