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Questions about making 8X10 video camera

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LatFab
(@latfab)
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Some years ago I did an experiment similar to DIY large format digital camera in latest DIY Perks video. https://wp.me/p2bcWy-l8  Because of the video I was inspired to re-create it with some quallity of life improvements.

Already started to order parts, but I have some technical questions, that I couldn’t find anywere:

  1. Does the focusing mechanism needs to move both camera and lens side to avoid focus breathing? I know that by only moving the lens the focus breathing is quite noticeable.
  2. How close does the front fernel lens, need to match focal lengh of camera lens, to achieve best results(I will use Industar-37, 300mm f/4.5)
  3. What is the finest grain medium do diffuse projection? Diffusion paper, sandblasted glass, or chemically etched glass?

And the last question:

   4.  Isn’t it theoretically possible to focus the rear frenel directly to sensor of recording camera?

 
Posted : 10/08/2022 4:41 pm
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DIY Perks
(@diyperks)
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Cool to hear you're having a go on this! You'll be happy to hear that I'm actually working on an improved version with the exact same lens that you have, so you're in luck.

This should answer some of your questions:

1) The focusing system needs to move only the lens, and increase its distance to the diffusion screen to focus closer. If you want to eliminate focus breathing, mount the first fresnel (the one that makes the light rays straight) at a distance from the lens that matches its focal length, and have it move in and out with the lens. So for example, place a 300mm fresnel at exactly 300mm behind the middle point of the lens, and have it move with the lens when focussing. It will eliminate focus breathing because the rays of light will be made parallel, but you will get significant chromatic abberation when focusing at close objects, so it's a bit of a trade off.

I guess you could devise a way to have the camera move out too but relying on its autofocus to remain locked to the diffusion screen might be a bit hit and miss. Best to crop and pan in post if you want to avoid it cleanly, I'd say.

 

2) Fresnel lenses are difficult to find at exact focal lengths. Ideally you want it just under the focal length of the lens, so for a 300mm lens a 280mm fresnel would be ideal. They aren't available however, so 300mm fresnels are the only option, and honestly they perform the same pretty much - you won't really notice a difference. Just make sure you use the centre of the lens as the measurement point, rather than its rear.

 

3) Tricky. Chemically etched glass is probably the finest, but doing that DIY is inconsistent. Sandblasted glass I don't have much experience with - my guess is that the 'sand' would have to be extremely fine.

 

4) I thought that, honestly, but I couldn't get it to work well from my tests. It was very distorted.

 

 
Posted : 10/08/2022 4:53 pm
LatFab
(@latfab)
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Topic starter
 

Thanks for quick reply.

 One idea about simplifying focusing mechanism I am thinking about: Instead of making geared mechanism with two screws  - A single bidirectional leadscrew should do the trick. 

 

 

Waiting your video.

 
Posted : 10/08/2022 7:27 pm
DIY Perks
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Yep, that's the plan with the second version too. The original was so heavy that it was necessary to keep the tripod plate centred.

 
Posted : 11/08/2022 9:37 am
wallpaperviking
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Hello, new member here...  Just wanted to say congratulations on the Episcope camera build, is amazing!  I have also tried to recreate an 8 x 10 DOF camera in the past, with fairly limited success unfortunately..  

 

Was just wondering when the download link will become available?  Is this for Patreon members only?  If so, what do I need to do? Am really looking forward to it, in particular the information on the diffusion screen used and also some more information on the fresnel lenses..

You noted that the total build was $190 including the lens.  How is this possible?  The single fresnel lens you linked to in a previous post is 135 pounds?

With regards to shooting the image with "bounced" light, you mention that the image would be "noiser".  Is this just because the image is darker and therefore when shooting video, you would need to crank the ISO quite high?  How many stops darker would you estimate this approach is to your "diffusion" approach?

Am really looking forward to your upcoming 8 x 10 build, should be a lot easier to manage.  Also, I believe you get enough of a different look with 8 x 10 to differentiate it from smaller formats..  Especially with a fast lens like the Industar 300mm 4.5.

One last note, would love to see an option for some creative movements with the 8 x 10 build (front tilt/swing), should this be possible without messing with the optics/fresnel science of it all?

Thanks again, congrats again on a great project!  🙂

 
Posted : 15/08/2022 7:57 am
DIY Perks
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Welcome to the forum! I'm actually still working on the download link as I'm taking some time to re-design it to make it much simpler and easier to put together (and cheaper). It should easily hit the $190 budget because it utilises some fresnel lenses from China instead (they're ironically better quality too, despite being cheaper).

 

That's correct about the bounced light 'noise' - it's a camera sensor thing. It's pretty dim - I'd say maybe 3 stops darker than the rear-view approach, which is in itself about 3 stops darker than direct to sensor (very roughly from memory).

 

Tilt shift is possible, but it will mean you'd have to redesign the frame to accommodate moves like that. I don't think it would mess with too much and would probably be a lot of fun!

 
Posted : 15/08/2022 9:06 am
wallpaperviking
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Posted by: @diyperks

Welcome to the forum! I'm actually still working on the download link as I'm taking some time to re-design it to make it much simpler and easier to put together (and cheaper). It should easily hit the $190 budget because it utilises some fresnel lenses from China instead (they're ironically better quality too, despite being cheaper).

 

That's correct about the bounced light 'noise' - it's a camera sensor thing. It's pretty dim - I'd say maybe 3 stops darker than the rear-view approach, which is in itself about 3 stops darker than direct to sensor (very roughly from memory).

 

Tilt shift is possible, but it will mean you'd have to redesign the frame to accommodate moves like that. I don't think it would mess with too much and would probably be a lot of fun!

Wow, thanks so much for the quick reply, much appreciated!  Having been playing around with the "reflective" approach and have had much better results than my original approach with a DOF camera.  Light loss and the ability to focus is a big issue though, so am really looking forward to your 8 x 10 design!   I have both 300mm and 360mm lenses for the 8 x 10 format, would the one fresnel setup ( 2 x fresnel either side ) cover both of these focal lengths?  Also, what digital taking lens is suggested for the rear for the 8 x 10 format if shooting roughly a "standard" lens (300mm/360mm) on the front?   Thanks again!  Look forward to more! 🙂

 
Posted : 15/08/2022 12:18 pm
DIY Perks
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Yes, I think you can get away with a 360mm lens with this new one. It won't be perfect in regards to vignetting because of the slight fresnel mismatch, but it won't be too bad.

 

As for the camera you actually take the photo with, anything will do really - though a fast lens will result in lower a lower ISO and less noise as a result. A 24mm equiv prime would probably work nicely.

 
Posted : 15/08/2022 4:24 pm
wallpaperviking
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Posted by: @diyperks

Yes, I think you can get away with a 360mm lens with this new one. It won't be perfect in regards to vignetting because of the slight fresnel mismatch, but it won't be too bad.

 

As for the camera you actually take the photo with, anything will do really - though a fast lens will result in lower a lower ISO and less noise as a result. A 24mm equiv prime would probably work nicely.

Thanks again for the quick reply, much appreciated!  If possible, can you please include a couple of stills in your next build/video?  I will be looking to use such a build exclusively for stills and am wondering if the vignetting is any worse with stills than with video (as you are using less of the extreme corners with video)?  

Am already thinking of a build that somehow incorporates drop in fresnels lenses for different 8x10 focal lengths.  From your research, do the Fresnel lenses from China that you mention come in similar "thickness"?  ie can you get a 200mm and a 500mm that are the same thickness?  

Any chance of posting a link to the Chinese Fresnel supplier so I can have a look?  No worries at all if you would rather wait for everything to be delivered at once..

 

On that note, any idea of an ETA of the 8 x 10 build?  😉

Thanks again, really looking forward to see more soon!  

 
Posted : 16/08/2022 1:25 am
DIY Perks
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Should be ready next week! The fresnels are all either 2mm thick and 3mm thick from what I can see. I bought mine from Aliexpress but as I've not technically tested image quality yet I won't link to them until the final build is ready.

 
Posted : 16/08/2022 8:52 am
wallpaperviking
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Posted by: @diyperks

Should be ready next week! The fresnels are all either 2mm thick and 3mm thick from what I can see. I bought mine from Aliexpress but as I've not technically tested image quality yet I won't link to them until the final build is ready.

To say I am excited is a massive understatement! 🙂

Looking forward to it, hope the Chinese Fresnel lenses meet expectations!  

This is probably a dumb question but the Fresnel should cover all lenses of a similar focal length right?  I have a Goerz Dagor 305mm 6.8 and this should work based off the fact that you are using an Industar 300mm 4.5 for your build?  Possible a bit slow but should work otherwise?

Would love to see a sample of a still image that shows the whole 8 x 10 imaging area.  The video section is really just using the centre portion right?  Do you think the whole 8 x 10 area should be usable?  

Thanks again! 🙂

 
Posted : 17/08/2022 4:14 am
LatFab
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About quallity and focal length of fresnel lenses. I haven’t tested it myself, but in theory using having mismatched camera lens and fresnel should result in slightly less brightness, but I doubt it’s very mutch.

As for image resolving quality - a finer groove fresnel should result in better image resolving, but less light transmition(92-97% between fine and course fresnel).

How much of the whole 8x10 frame you can effitiently use: If you are using photographic 8x10 lens - it should be able to resolve hundreds of megapixels and sharpness throughout the whole 8x10 frame. What I found is that the bottleneck is matted surface the image is projected on.

ps.

35mm equivalent crop factor for 8x10 is X0.13. So 305mm f/6.8 should be quivalent to 39,65mm f/0,884

 
Posted : 21/08/2022 9:46 am
wallpaperviking
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Posted by: @latfab

About quallity and focal length of fresnel lenses. I haven’t tested it myself, but in theory using having mismatched camera lens and fresnel should result in slightly less brightness, but I doubt it’s very mutch.

As for image resolving quality - a finer groove fresnel should result in better image resolving, but less light transmition(92-97% between fine and course fresnel).

How much of the whole 8x10 frame you can effitiently use: If you are using photographic 8x10 lens - it should be able to resolve hundreds of megapixels and sharpness throughout the whole 8x10 frame. What I found is that the bottleneck is matted surface the image is projected on.

ps.

35mm equivalent crop factor for 8x10 is X0.13. So 305mm f/6.8 should be quivalent to 39,65mm f/0,884

Good One, thanks for the info!  To be honest, a lot of this is out of my league unfortunately..  Not very scientific and/or handy.  Am really hoping that the new 8 x 10 build comes out this week with detailed instructions and I can pair up with somebody locally who is better at this stuff than me 🙂

 

I agree that the key seems to be the transmissive material and fresnel combination.  Without that working, you really have nothing.  I have tried shooting on glass before and it looked like you were taking a photo of an image on glass.  The video footage of the original Episcope camera looks really good to my eyes..  

Fingers crossed that the Fresnels from China are up to the task and the 810 version looks just as good! 🙂

 
Posted : 22/08/2022 8:17 am
LatFab
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Most of things about fresnel lenses I learned from this video:

Projector is basically a reversed camera. 😀

Some things about transmissive material:

I just recently tried spray frosting for glass. Shooting 4k on 8X10 frame you can see the texture, that looks like light grain(can be removed with light noise reduction). Next I will try sand blasted and chemicaly etched glass.

I too am waiting, fingers crossed, fresnels from China. 2 months of waiting now 😩

This post was modified 1 month ago by LatFab
 
Posted : 22/08/2022 7:29 pm
wallpaperviking
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Posted by: @diyperks

Should be ready next week! The fresnels are all either 2mm thick and 3mm thick from what I can see. I bought mine from Aliexpress but as I've not technically tested image quality yet I won't link to them until the final build is ready.

I just remembered that I have two 8 x 10 Fresnels lying about somewhere.. 🙂  I also think I have some of that "foil" lying about.  Can I just sandwich this foil between the two fresnel lenses, without needing to make a frame?  Should work right, as long as I can keep it flat?

Also, when using a Fresnel in combination with a Ground Glass in a large format camera, how come there is never mention of the "focal length" of the Fresnel?  These somehow seem designed to fit a wide range of focal lengths...  How is this achieved?

 

Thanks again, hope you are having success with your new build!  🙂

 

 

 
Posted : 24/08/2022 1:59 pm
LatFab
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Posted by: @wallpaperviking

Also, when using a Fresnel in combination with a Ground Glass in a large format camera, how come there is never mention of the "focal length" of the Fresnel?  These somehow seem designed to fit a wide range of focal lengths...  How is this achieved?

Projector camera has two fresnels to atchieve maximum brightness.

Large format cameras have only one fresnel, that focuses light from ground glass to eye. This is why focal length isn’t crucial. You can always move your head to get into the best viewing position and it doesn’t effect quality of the final image, so why bother with focal length… 😉

 

This post was modified 1 month ago by LatFab
 
Posted : 26/08/2022 3:49 am
wallpaperviking
(@wallpaperviking)
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@latfab 

 

Gotcha!  Thanks for that information!  

 

I tried the same technique as DIY Perks many years ago and went and purchased a really expensive "Maxwell" screen and two Fresnel lenses for it.. 

I was using a Goerz Dagor 12 inch, so I assume the Fresnels were a similar focal length..The results were not great unfortunately.. 

 

The results from the Episcope footage encouraged me to try again.  I still have those items but they are 1-2mm too wide to fit directly into my Cambo SC 810 🙁  

Any ideas to shim glass and plastic down?  It is just missing from fitting..

 

I have had much better results using the "reflective" method of capturing an 810 image but as pointed out earlier, light loss is Huge! 

 

Looking at the fresnels, am not even sure what side to place them on.  I do not even see any really difference between the two sides, they both just look like they have quite course circular patterns throughout...

 

Any ideas?

 

Hope the upcoming video can sort it all out! 🙂

 
Posted : 26/08/2022 5:18 am
LatFab
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Any ideas to shim glass and plastic down?  It is just missing from fitting..?

Cut it!

 

I have had much better results using the "reflective" method of capturing an 810 image but as pointed out earlier, light loss is Huge! 

I was first inspired making 8x10 camera by this video:

Altough this method isn’t very efitient unless you have full frame camera with tilt shift lens.

 

…am not even sure what side to place them on.  I do not even see any really difference between the two sides...

 Go outside and try focusing sunlight to burn something 😀 You will find the direction real quick.

 
Posted : 27/08/2022 8:38 am
wallpaperviking
(@wallpaperviking)
Posts: 10
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Posted by: @latfab

Any ideas to shim glass and plastic down?  It is just missing from fitting..?

Cut it!

 

I have had much better results using the "reflective" method of capturing an 810 image but as pointed out earlier, light loss is Huge! 

I was first inspired making 8x10 camera by this video:

Altough this method isn’t very efitient unless you have full frame camera with tilt shift lens.

 

…am not even sure what side to place them on.  I do not even see any really difference between the two sides...

 Go outside and try focusing sunlight to burn something 😀 You will find the direction real quick.

I managed to cut the glass I found and trim down the fresnel lenses I had, so they could fit in my Cambo SC...  Hmmm, not sure to be honest..  I tried a fresnel in front and behind the Ground Glass but I could generally "see" the lines of the fresnel, which renders the whole thing useless really..  

You mentioned that you lose more light (92%) with a finer groove fresnel, any links you could share where I could possibly see such a fine groove fresnel?

 

The best result I found is using the Ground Glass itself (Maxwell Screen) which is a couple of stops better than a standard Ground Glass but then this is only a bit better than the "reflective" method, which has the benefit of being a smaller more compact setup..  

I also used Zev Hoover's method as my original attempt... Works pretty well but you do lose a serious amount of light, which makes it tricky and why I was hopeful for DIY Perks version...

I will wait for the video from DIY Perks to go any further, as I really believe that the key is in the Fresnel + Photo Foil combination.  If he ends up using a super fine fresnel, where you cannot see the circular lines, then this could really work... Otherwise, will stick with the reflective method..

Am wondering what issues he is having with his 8 x 10 design?  I thought his video would be out by now... 

 
Posted : 01/09/2022 5:23 am
LatFab
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…I tried a fresnel in front and behind the Ground Glass but I could generally "see" the lines of the fresnel, which renders the whole thing useless really…

This is where I will talk out of my arse, untill I get my hands on fresnels I ordered: I think the second fresnel should solve it, because projectors don’t have problem with those lines.

Also, did you put a gap between fresnel and ground glass?

 

…You mentioned that you lose more light (92%) with a finer groove fresnel, any links you could share where I could possibly see such a fine groove fresnel?

The finest ones I was able to find are around 0.2mm and thick ones from 1mm.

 
Posted : 05/09/2022 3:03 pm
wallpaperviking
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Posted by: @latfab

…I tried a fresnel in front and behind the Ground Glass but I could generally "see" the lines of the fresnel, which renders the whole thing useless really…

This is where I will talk out of my arse, untill I get my hands on fresnels I ordered: I think the second fresnel should solve it, because projectors don’t have problem with those lines.

Also, did you put a gap between fresnel and ground glass?

 

…You mentioned that you lose more light (92%) with a finer groove fresnel, any links you could share where I could possibly see such a fine groove fresnel?

The finest ones I was able to find are around 0.2mm and thick ones from 1mm.

Am confused by the placement unfortunately...   It is hard to tell where he is placing them in the video.  Are they moving away from each other when the bellows are moved?

 

I did not leave a gap in between mine and it is quite hard with my setup, as I am using the existing space of where the original Cambo SC Ground Glass sat.   I will probably not try any further until the next video is released, hope that is soon..

 

Do you have a link by any chance of where I can purchase the very fine (0.2mm) fresnel?  Thanks!  🙂

 
Posted : 06/09/2022 7:28 am
LatFab
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Am confused by the placement unfortunately...   It is hard to tell where he is placing them in the video.  Are they moving away from each other when the bellows are moved?

Watch the diy projector video. It shows how to find the distance between ground glass and frsenel.

Do you have a link by any chance of where I can purchase the very fine (0.2mm) fresnel?

Boght mine here:  https://m.aliexpress.com/item/32833111557.html

The finest groove fresnel, with my required size/focal length, was 0,3mm.

 
Posted : 07/09/2022 2:34 pm
wallpaperviking
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Posted by: @latfab

Am confused by the placement unfortunately...   It is hard to tell where he is placing them in the video.  Are they moving away from each other when the bellows are moved?

Watch the diy projector video. It shows how to find the distance between ground glass and frsenel.

Do you have a link by any chance of where I can purchase the very fine (0.2mm) fresnel?

Boght mine here:  https://m.aliexpress.com/item/32833111557.html

The finest groove fresnel, with my required size/focal length, was 0,3mm.

Thanks for the links, much appreciated!  Have you had any luck with your build?   

It has been close to two months since the original video was published on YouTube and no follow up, so I am sorta losing faith to be honest..  

It could just be a matter of the Fresnels he ordered not being up to the task..  I hope it is that and not some bigger, personal issue in his life..

 

Thanks! 🙂

 

 
Posted : 27/09/2022 7:17 am