Depth of Field Adapter on Steroids

Matt over at DIY Perks on YouTube has made a "next-level" camera rig. It's awesome and is very much in the spirit of this forum. Someone posted about it here yesterday but perhaps because the video contained sponsored content the post/link was removed; so instead of linking directly I'll have to let you search for yourself (but maybe DPR will feature it on their own soon given how rad it is)!

He took a giant barrel lens from an old episcope (a Ross 17" / 432mm f/5 - I bet Bosun Higgs has one of these somewhere), and fabricated a housing with focusing capabilities and a focusing screen coupled with Fresnel lenses that you then record / image with a normal camera/lens. The resulting image in terms of depth of field and field of view is like shooting with a 37.4mm f/0.43 lens on full frame, which is of course unheard of. His sample videos and images are stunning! They're not pixel-perfect, but they're certainly very cinematic and more than good enough for pleasing-looking 4K captures.

I've experimented with this kind of thing before , although on a smaller scale with nowhere near as much elegance/completeness and with results that pale in comparison. There are also a couple of niche products that have since been discontinued that work in the same way (one such product is Redrock Micro's M2 Depth of Field Adapter Kit).

I feel like the Fresnel lenses and diffusion material involved will limit resolution, so the bigger the imaging area is, the better it may perform. But as the rig gets hilariously large, it would start to get unwieldy pretty quickly hehe. Maybe Matt has already found the sweet spot.

I'm inspired to build a rig like his, but the exact lens he used doesn't look easy to find. Whether I'm scaling the rig up or down, what other lenses would be good candidates for this kind of rig that are cheap and/or readily available?

Yeah I had a thought that using such a gigantic screen would dwarf any texture pattern seen in people's previous attempts. I would be curious to see a video which continually shrinks the lens image circle used until the texture became noticeable...

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!

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!

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.

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 (BTW, shouldn't he have replaced the plastic with the Fresnels rather than added them?) really are not very visible.

Eggplantt wrote:

Yeah I had a thought that using such a gigantic screen would dwarf any texture pattern seen in people's previous attempts. I would be curious to see a video which continually shrinks the lens image circle used until the texture became noticeable...

Those were my thoughts as well. Given that ProfHankD's 4x5" pinhole version of this linked below and my 6x9cm version of this both had visible texture issues, going that small is maybe not looking promising.

But maybe Matt's choice of diffusion material was also a significant step up.  When he makes the parts list available I'd at least like to get my hands on some of it and compare it to various grits of ground glass (or ground acrylic).

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.

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.

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.

(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?

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?

fferreres 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's a lovely video. No wonder the person has so many followers. The idea of shooting with a lens with a big image circle is something that I've been looking forward for a long time. I had not noticed the idea of a double fresnel lens to get most all the light. That was a mayor roadblock. Of course, the resolution will be low but the larger the screen, the higher the resolution of the capture if the fresnel is high quality.

Yup it seems like going big is the right idea.

These very fast projector for large venues are ideal,as they'd give looks for impossibly fast lenses. Position closer to the camera and the DOF is useless. But position far away, and they are another thing.

Most large format lenses I have would not look as ultra fast lenses. For example, something 6.8 covering 8x10, say a 12" dagor 6.8 will look like 50mm f1.2, and these are usually shot at f11 to f64. An f4 with 8x10 is more interesting, if DOF is the thing, with a look of about f0.7.An f2.5 will look f0.44 and f2 like f0.35. But one needs a long FL. As I said, 300mm is a normal lens.

I'll have to whip up a spreadsheet to plug in specs for potential lens choices.  I'm very unfamiliar with the large format lens scene.  Rattle off a few if you think of any!  The ultra fast look is really the main draw for Matt's rig (where else would you get it?), so yeah the Dagors might not be compelling enough when one can just slap a fast fifty on a full frame camera and take it anywhere with ease.

Nikon's Apo-Nikkor lineup is slower than Matt's Ross 17" but some of them have some massive image circles, so a similar f-stop equivalent could be had, but the rig would be just too dang big.

I have a Kodak Aero Ektar 178/2.5 on one of my shelves that could be a candidate for a smaller rig, but screen grain might be an issue on the 4.5" x 4.5" plane it was designed to cover (48mm f/0.7-ish equiv.).  Close-ups have more coverage, good enough for 8x10" from what I can gather (24mm f/0.33-ish equiv. - could be interesting for life-size headshots?).

I really like this very simple camera. No movement, motorized, the idea of double fresnell and a housing to host the camera as well. This is likely viable even if eccentric, and could be made relatively lightweight. Can be a fun camera an equiv. f0.4 lens.

Thanks for sharing.

The project is a culmination of so many things I find fun - 3D-prints, tinkering, basic electronics, adapted lenses, photography... had to share!

ProfHankD wrote:

Tons o Glass 0 Class wrote:

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.

I can't quite wrap my head around what the light rays involved are doing and what they need to do. He explains some stuff half way through the video right after the sponsored content and illustrates it to a degree, but not enough for me to say "I get it." I'm going to continue grabbing at straws here hehe.

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?

Matt also built a DIY projector and that's where he got the idea to use the Fresnel lenses, so the rear-projection TV angle checks out hehe! I'll wait for his supply list, but yeah, his budget might not be able to be matched by anyone.

I'm playing with an online ray-tracing simulator to try to visualize things better and set up components like he describes:

A rough ray diagram of Matt's system for light rays that pass through the diffusion screen?

So... this diagram only illustrates rays that aren't dispersed by the diffusion material? And light focused on the diffusion screen could be seen by the lens+camera observer without the Fresnel lenses... So... if the Fresnel lenses are used in this manner, does the rig even need a focusing screen? If not, could you just use one Fresnel that is about half the focal length of the current two, placed right where the focusing screen was?

The whole system isn't doesn't quite behave like that of a system with a focal reducer as the observer's lens would never have an aperture wide enough to focus all the rays pointed at it - I feel like my lens+camera observer is problematic in this diagram...

I feel like I'm missing something (everything?)...

https://www.dpreview.com/news/2691266174/video-diy-perks-creates-a-massive-35mm-f0-4-equivalent-lens

Those are some solid ideas! I was thinking about maybe making some giant bellows instead of the aluminum panels, and I was also thinking of adding some tilt shift, but I didn't even think about how the Fresnel lenses may make movements a no-go.

Was I right in thinking you have one of those exact Ross 17" lenses laying around?

You happened to post about these epidiascopes just a couple months ago! I missed it until yesterday while deep in a google rabbit hole for this project.