Depth of Field Adapter on Steroids

Tons o Glass 0 Class wrote:

ProfHankD wrote:

Tons o Glass 0 Class wrote:

Thanks Tom; hopefully my explanation is sufficient to now post his video:

https://youtu.be/9cT0jXI7l4E

While I agree that as a mod you're not obligated to watch, I believe you and others here will enjoy it!

That is a beautiful piece of work!

Agreed! As nice as it is though, I think it would look absolutely fabulous if he swapped out the aluminum for some finished mahogany.

He probably could have used 1/8" plywood instead with no significant changes. Basically, I'm talking about stuff like wood paneling.

Fresnel lenses usually do rather visible badness to the IQ, so my answer has been to capture HDR sequences and correct the vignetting as they are merged. I actually did the smart merge in-camera using Canon PowerShots programmed via CHDK. However, I was only using a 4x5" screen -- and an ultrawide pinhole: Digital Pinhole Camera Obscura . There was naturally a lot of vignetting and I got a lot of texture from the screen.

What did you use for the screen? I'm hoping to compare a few different grits of ground acrylic to whatever diffusion material Matt used when he makes the parts list available.

I actually tried a lot of different materials. Best overall is a plastic "paper" I used to use with my E-format inkjet printer, but for the pinhole I wanted something less opaque. I believe it is actually velum art paper in the camera obscura.

It sounds like the material he used wasn't a very good diffuser, but that does help minimize texture and maximize brightness. At the scale he did this, the textures from the screen and Fresnels really are not very visible.

Yeah I had to search for it, barely any texturing was visible.

Yup, his is very effective.

(BTW, shouldn't he have replaced the plastic with the Fresnels rather than added them?)

He had the Fresnel lenses spaced away from the diffusion sandwich (yum) a little bit, and one of the Fresnel lenses looks to be moving with the lens section when he focuses, so at least with the way the rig was built, he still needed the sandwich. He mentioned that the Fresnel lenses' focal lengths should closely match the main lens to work best, maybe the extra spacing was needed to compensate for a slight mismatch?

I don't get that at all.

You don't want the Fresnels up against a plastic sheet because you'll get Newton's rings, but Fresnel lenses shouldn't be needed with a good diffuser... it's just that a good diffuser will make a much darker image. Basically, what he did is a lot like you'd find in the old rear-projection large-screen TVs. In any case, large Fresnel lenses are usually pretty pricey too, so I'm not sure how his budget worked... even ignoring the fact that I haven't seen a comparable lens for less than the total price he's claiming for the lens and all. I guess he's a really good shopper or just got very lucky?