making your own mini 35 at DVinfo.net

Zac Stein · May 16th, 2003, 07:43 AM

Heya all,

As a member and contributer i have read a lot about the mini 35 on this site, i am about the start on making my own.

I would like as much advice on getting it right as i can, as i am sure a lot of you are far more knowledgable than i am on the mechanics of lenses and so on.

I am actually taking the easy way out with my design because i don't want a lot of guess work, so i have found and old canon A1 FD 35mm slr. It was broken and i got it for $20.

What i plan to do is open it up and rip and cut out the cage (insides) of where the mount at the front until it hits the ground glass. that way i figure the measurement of distance must be correct. i will remove almost everything else, or cut outwhat i can, so basically i am left with a mount at the front and a piece of ground glass in its place, in a little skeleton holder.

I was then in that exact place of the ground glass going to place a piece of round glass, with a plastic sprocket around it (like a skirting), and put a small electric motor on a 90deg angle onto the sproket to spin it. This then leads to mounting it all into a small metal (aluminium) case and putting a bayonet mount (i own a pd150 for the time being) on the other end.

What i am having trouble is with how far off the ground glass do i place the mount so the distance between the lens of my pd150 and the 35mm projected image of the ground glass are correct.

I did come up with 1 scientific way, and that was to place a 35mm negative on my table and place the pd150 as close to it as i could while keeping it in focus and filling the screen, then measuring that disance and using that as a guide for where to put the mount.

Does this sound feasable at all?? Am i just dreaming or would this actually work?

Also how exactly would i build something to support the weight at the front of the camera so it wouldn't damage it?

Thanks for all your help,

Zac

PS. Chris if i get it working and the results are nice i will write a fully documented article for your site if you wish.

Jeff Donald · May 16th, 2003, 09:33 AM

How are you going to spin the ground glass?

Zac Stein · May 16th, 2003, 09:38 AM

Jeff,
I am kind of copying the way sprockets turn in a clock, but i will put sprockets flush on the end on both sides, and top/bottom, as well as on 90deg angles right near the edge of the sides, so that it can all get held in place without the need to put support dead in the center of it.

I will prob rip out some kind of plastic set of these from a remote control car.

Zac

Jeff Donald · May 16th, 2003, 09:57 AM

OK, assuming you can get it to spin, the ground glass in a 35mm is too course or rough to shot through. It is made course to aid in focusing. It was never meant to be shot through.

Zac Stein · May 16th, 2003, 10:03 AM

Jeff, nah i wasn't going to use the ground glass from a 35mm camera, i was just using its placement as a guide, and also it has mirrors and stuff in it to project the image properly. I found a place here that services and repairs 16mm cameras, going to get a piece off them. I believe it's grading was smack in the middle, and they said if i was to run light through it, you loose around 1/2-1 stop of light.

Zac

Cosmin Rotaru · May 19th, 2003, 04:24 AM

I did some experimenting myself. No spining ground glass, though.... You need a fresnel lens sandwiched with the ground glass so that you have an even ilumination over the ground glass. Than the camcorders lens should be in the focal point of the fresnell lens. Otherwise, you'll have the same vigneting as without the fresnell. The fresnell I tried had a long focal lenght (I gues) so that I had to pull way back the camcorder. So I added a lens (those x5 lens you use in philatelic...) between the camcorder and fresnell and this allowed to move the camcorder closer...
That's all I got till now!

Good luck and get back here with your findings!

Zac Stein · May 19th, 2003, 05:50 AM

Cosmin, where exactly do you need to place the fresnel lens, between the image being projected onto the ground glass and the camera's lens?

Also i wasnt that worried about vigneting as long as it was outside the tv's safe zone, could i steal the fresnel from a slr camera, do they have them in there?

Zac

Cosmin Rotaru · May 19th, 2003, 06:13 AM

The fresnell lens is sandwitched with the ground glass and could be in front or behind the ground glass... There are two theories but i don't know much about. Just try it and see what's working best.
"i wasnt that worried about vigneting as long as it was outside the tv's safe zone" It won't be. You're only goinging to see the image in the centre of the ground glass.
Yes, SLR camera have the fresnell but you'll ned a larger and round one (as you want to spin it).

Zac Stein · May 19th, 2003, 06:22 AM

Can anybody else here comment about the fresnell?
explain how it may be adapted onto it?

Zac

May 16th, 2003, 07:43 AM	#1
Zac Stein Major Player Join Date: Aug 2002 Location: Melbourne, Australia Posts: 730	making your own mini 35 Heya all, As a member and contributer i have read a lot about the mini 35 on this site, i am about the start on making my own. I would like as much advice on getting it right as i can, as i am sure a lot of you are far more knowledgable than i am on the mechanics of lenses and so on. I am actually taking the easy way out with my design because i don't want a lot of guess work, so i have found and old canon A1 FD 35mm slr. It was broken and i got it for $20. What i plan to do is open it up and rip and cut out the cage (insides) of where the mount at the front until it hits the ground glass. that way i figure the measurement of distance must be correct. i will remove almost everything else, or cut outwhat i can, so basically i am left with a mount at the front and a piece of ground glass in its place, in a little skeleton holder. I was then in that exact place of the ground glass going to place a piece of round glass, with a plastic sprocket around it (like a skirting), and put a small electric motor on a 90deg angle onto the sproket to spin it. This then leads to mounting it all into a small metal (aluminium) case and putting a bayonet mount (i own a pd150 for the time being) on the other end. What i am having trouble is with how far off the ground glass do i place the mount so the distance between the lens of my pd150 and the 35mm projected image of the ground glass are correct. I did come up with 1 scientific way, and that was to place a 35mm negative on my table and place the pd150 as close to it as i could while keeping it in focus and filling the screen, then measuring that disance and using that as a guide for where to put the mount. Does this sound feasable at all?? Am i just dreaming or would this actually work? Also how exactly would i build something to support the weight at the front of the camera so it wouldn't damage it? Thanks for all your help, Zac PS. Chris if i get it working and the results are nice i will write a fully documented article for your site if you wish.

May 16th, 2003, 09:33 AM	#2
Jeff Donald Warden Join Date: Mar 2002 Location: Clearwater, FL Posts: 8,287	How are you going to spin the ground glass? __________________ Jeff Donald Carpe Diem Search DVinfo.net for quick answers \| Where to Buy? From the best in the business: DVinfo.net sponsors

May 16th, 2003, 09:57 AM	#4
Jeff Donald Warden Join Date: Mar 2002 Location: Clearwater, FL Posts: 8,287	OK, assuming you can get it to spin, the ground glass in a 35mm is too course or rough to shot through. It is made course to aid in focusing. It was never meant to be shot through. __________________ Jeff Donald Carpe Diem Search DVinfo.net for quick answers \| Where to Buy? From the best in the business: DVinfo.net sponsors

May 16th, 2003, 09:38 AM	#3
Zac Stein Major Player Join Date: Aug 2002 Location: Melbourne, Australia Posts: 730	Jeff, I am kind of copying the way sprockets turn in a clock, but i will put sprockets flush on the end on both sides, and top/bottom, as well as on 90deg angles right near the edge of the sides, so that it can all get held in place without the need to put support dead in the center of it. I will prob rip out some kind of plastic set of these from a remote control car. Zac

May 16th, 2003, 10:03 AM	#5
Zac Stein Major Player Join Date: Aug 2002 Location: Melbourne, Australia Posts: 730	Jeff, nah i wasn't going to use the ground glass from a 35mm camera, i was just using its placement as a guide, and also it has mirrors and stuff in it to project the image properly. I found a place here that services and repairs 16mm cameras, going to get a piece off them. I believe it's grading was smack in the middle, and they said if i was to run light through it, you loose around 1/2-1 stop of light. Zac

May 19th, 2003, 04:24 AM	#6
Cosmin Rotaru Major Player Join Date: Feb 2003 Location: Romania, Timisoara Posts: 453	I did some experimenting myself. No spining ground glass, though.... You need a fresnel lens sandwiched with the ground glass so that you have an even ilumination over the ground glass. Than the camcorders lens should be in the focal point of the fresnell lens. Otherwise, you'll have the same vigneting as without the fresnell. The fresnell I tried had a long focal lenght (I gues) so that I had to pull way back the camcorder. So I added a lens (those x5 lens you use in philatelic...) between the camcorder and fresnell and this allowed to move the camcorder closer... That's all I got till now! Good luck and get back here with your findings!

May 19th, 2003, 05:50 AM	#7
Zac Stein Major Player Join Date: Aug 2002 Location: Melbourne, Australia Posts: 730	Cosmin, where exactly do you need to place the fresnel lens, between the image being projected onto the ground glass and the camera's lens? Also i wasnt that worried about vigneting as long as it was outside the tv's safe zone, could i steal the fresnel from a slr camera, do they have them in there? Zac

May 19th, 2003, 06:13 AM	#8
Cosmin Rotaru Major Player Join Date: Feb 2003 Location: Romania, Timisoara Posts: 453	The fresnell lens is sandwitched with the ground glass and could be in front or behind the ground glass... There are two theories but i don't know much about. Just try it and see what's working best. "i wasnt that worried about vigneting as long as it was outside the tv's safe zone" It won't be. You're only goinging to see the image in the centre of the ground glass. Yes, SLR camera have the fresnell but you'll ned a larger and round one (as you want to spin it).

May 19th, 2003, 06:22 AM	#9
Zac Stein Major Player Join Date: Aug 2002 Location: Melbourne, Australia Posts: 730	Can anybody else here comment about the fresnell? explain how it may be adapted onto it? Zac