Thanks. The color shift is actually the coloration of the lens. The Pentax 67's coating is not optically neutral in color tone. POC makes diffusers, great, I'll look into them. I was just thinking I'd use a Beattie. POC is proof of concept but I'm probably misusing my TLA's (three letter acronyms).

Oh, right - proof of concept.

POC (Physical Optics Corp) manufactures 'beam-shaping diffusers' which could incorporate both GG and field lenses into one - you could have it shape the beam and redirect it towards your relay lens. Then you would see a DOF advantage without ridiculously fast relay optics.

However, POC isn't really interested in dealing with individual customers. You can get their diffusers at Edmund Optics, but they're expensive (to the tune of $300 for a reasonably sized one). And for the truly custom stuff I imagine you'd have to be a rather large customer.

I still haven't received my 'engineer's sample' that I requested about a year ago. I guess the company's reorganizing, spinning the diffuser portion off into its own company... I don't know. It's a mess and they haven't been very helpful. So I hope I didn't accidentally steer you wrong with that one.

I have a POC20 Edmund Optics holographic diffuser you speak of for sale if you want it to test it out. $50 takes it. Absolutely fantastic diffusion and light transmission, but too much grain for my homemade design.

Ben I need a diffuser that's about 40x70. How big is the one you're offloading?