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Old December 19th, 2003, 07:15 AM   #256
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cosmin rotaru says in a early post to agus that he should use a fresnel lens in order to get rid of the hot spot on the GG. Another user posted a link to an american store who sells fresnells, i live in europe and i have not been able to get a fresnel to eliminate the hot spot on my agus35. does anyone know where they're sold in europe? or perhaps another device where they can be taken out?

thanks

Thomas
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Old December 19th, 2003, 08:09 AM   #257
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Use a dove prism to flip the image.

http://www.doveprism.com/
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Old December 19th, 2003, 01:43 PM   #258
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Quote:
I've used a 25 cd spindle box, and a 50mm lens. But when I have the lens focus all the way in, I need the ground glass to be as far from the lens inside the spindle box as it can to focus on anything thats about 2-3 metres away. Anything closer than that and I can't focus.

Any ideas?

Thanks
I experienced something similar, and it's one of the trials of experimentaion. If you look at Agus's design, you'll note that there's an extender between the front of the adapter and the back of his 50mm lens -- bringing the rear of his 50mm lens about a half to three-quarters-inch away from the adapter's surface.

Likewise, his motor is mounted at the front of the adapter, with the spindle facing back toward the DV camera -- with the CD mounted at the tip of the motor's spindle, placed very close to his macro lens.

I did a quick-n-dirty mockup last night with a 9v battery hooked up to an on/off button and my motor and ran tests with the GG within a half-inch of my 50mm lens, and then as far away as I could get it inside of the CD case -- in order to get focus on the GG, your film lens must be placed 3-4 inches away. Maybe slightly more. Experimentation will find your answer.

- jim
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Old December 19th, 2003, 03:31 PM   #259
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Jim, about the distance from the lens to the GG

I measured my SLR camera from the front of the body where the lens mounts to the film plane, the distance came out 46mm, I adjusted my box so the distance matched to the GG. I still haven't tried any video yet, I haven't made mine light tight yet, too much to do and never enough time!

Tom
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Old December 19th, 2003, 09:00 PM   #260
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Quote:
Has anyone made one of these sucessfully for the gl1? If so which macro filter are you using and what are the distances between the macro filter and the gg and the fresenel lense and the 35mm lense?
I can answer your questions with partial confidence, as I'm about 85% done my GL1 adapter.

The macro power should be +7 or greater -- this allows you to move your camera in close enough to the surface of the GG and still zoom in to avoid vignetting.

I've got probably a half inch between the surface of my Century Optics +7 macro ("achromatic diopter") and the GG. I'm working on having about two inches between the GG and the rear of my 50mm lens.

If you've got a macro, you'll likely not need a fresnel.

However, and this goes back to my comment about partial confidence:

I put together a mock-up of my final adapter design last night and I couldn't pull focus accurately. I'm making an educated guess that this is because of the distance between the 50mm lens and the GG, which I figure was too short. I'm now extending the distance with a rubber ring between the F-mount and the front of the adapter.

Also -- I haven't actually shot anything yet, only looked through the viewfinder while holding my adapter up to the camera. No telling if my guesses, educated or ingorant, will prove to make for a functional adapter.

I will be done tomorrow, and plan to have footage up by Sunday. Check for it at http://ideaspora.net then...

- jim
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Old December 19th, 2003, 09:08 PM   #261
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I don't know whether anyone has already posted this link to a diagram and explanation of the Agus35 CD + spindle concept.

Quote:
And after we have all this crap put into a box strapped to the camera, we finally have a picture that's more blurry, darker, and harder to focus and zoom. But that's what we want, because it will fool people into thinking you're filming on film instead of video. Isn't photography wonderful?
Not exactly a rave endorsement; nice schematic though. And check out the Fresnel link while you're there.
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Old December 19th, 2003, 10:03 PM   #262
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here is a new video made with a beta version of the adapter
like you can see.. there is no vigneting.

http://altoque.tv/35mmAdapter/35mmtestBETA.wmv

Now we are working on fliping the image for perfect control and making all the pieces to look pretty and profesional, as well as making a pro rod system and baseplate. as well as a matte box.
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Old December 19th, 2003, 10:11 PM   #263
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Quote:
Not exactly a rave endorsement; nice schematic though. And check out the Fresnel link while you're there.
Of course it's not a rave endorsement. The footage still isn't perfect because the device is still in development. But even if it were done like the Mini35, it's still harder to focus, blurry (because the background is in focus), darker (this adapter doesn't create light, you know), and we're doing it to try to make it look more like film.

Of course, I meant that ending line rather tongue-in-cheek anyway (yes, you linked to my website. Thanks. :) ). When I have the time, I want to make one of these adapters myself. And thanks about the schematic. I haven't put the macro lens nor any flipping scheme into it yet. Actually. I'll do that now.

Edit: Wow. Agus, that footage looks amazing. I had some doubts after some of your earlier footage, but that last clip really does look wonderful.

Edit 2: Near the 3:30 mark on that footage and onward, I could start to make out the edge of the hotspot on the edges of the frame. I assume this was because the sun was setting so you didn't have the same light, but how bright was it at the time, and how much light should we expect to have to work with as you have your adapter right now?
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Old December 19th, 2003, 10:26 PM   #264
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I promised I wouldn't contribute anymore to this already gigantor thread, but after reading about someone else (Jim Lafferty) building their own mini-50mm for a GL1, I had to post a question!

Ever since the beginning of this thread several weeks ago I was under the impression that the fresnel between the SLR lens and the GG was solely there to focus the image onto the GG - even in my own "beta" version of the mini-50mm the fresnel performed this action. Jim , I noticed you said "If you've got a macro, you'll likely not need a fresnel." I must be missing something here, or maybe your adapter is built a little differently than mine - but I can't see why you wouldn't benefit from having both a fresnel lens to focus your image onto the GG and having a macro to allow you film something up close. Can you shed some light on this? Also...

You said you use a century optics +7 achromatic diopter. If I had the cash to squander, you'd be certain that'd be my "macro" lens of choice. However, I'm a cheap college student on a tight budget. I remember reading that the century achromatic diopters allow for zoom thru to a certain extent. Regular macros don't pull that off as well, correct? So in essence if you fail to get a powerful enough macro lens to get you close enough to the GG to fill the frame and avoid "vignetting," you wouldn't be able to zoom in and pull sharp focus would you? I guess in this case it's better to overkill and get a +10 macro lens - better to be closer than further?

Anyways, Jim I'm very interested in seeing how your set up looks/works as a fellow GL1 owner. Unfortunately my cam is in the shop for a faulty LCD and so I haven't gotten a chance to test things out, so I'm living vicariously through this thread!
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Old December 19th, 2003, 11:00 PM   #265
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Lovely pre-sanded GG (from CD spindle)

I have followed this thread from the beginning, and was thrilled to rush into buliding mine. I collected all the materials, except lens, and was worried to find that I could not locate a clear CD. All of the ones I had were already frosted. I went through about 5 or 6 of them until I finally found a clear one, I was quite relieved. I should have just tried the frosted to see if it would work, now I'm glad to see that they are preferred. (I hope I didn't throw those frosted ones away...) As far as where to get them from I'm not sure. I know that most of them came from 100 pack spindles, gotten for free after rebate (boy was that a hassle) on the day after Thanksgiving. I don't know if its a feature of the higher count spindles or what. The Discs are old ones, so I'm not certain, but I think there is a decent chance they came from KHypermedia or Memorex. I'm not sure on this, but if your desperately against grinding the CD yourself, it could give you a start.

I am loving this thread! This is the funnest little project to work on, and impress your friends with. My following of this post here has been kind of sparratic, I just got to previewing Aguss's newest beta posting. BEAUTIFUL! I'm about 90% done on mine, 90% as far as consturuction goes. I think I'll have a lot of tweaking to do, so maybe only 30% as far as complete finalization. I've got to run to the local pawn shop and see if I can't find me a 35 mm now...
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Old December 19th, 2003, 11:07 PM   #266
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Chris,

Please, please, please extract pertinent information and post to an Agus35 information thread. I think that would help us all! It would definite help me, because I can't find anything when I need it...

...on that note...I have completed stage one and wanted to offer what I have done and ask a question.

For connecting the box to the camera, I bought a UV filter, drilled a hole that size and super-glued it in. That way, you just screw the box onto the camera (just make sure you have it so when screwed all the way on it is straight! I didn't...learn from my mistake!) Also, you can then screw the macro right into the front of the filter due to their similar thread size! I have been using super-glue with good results...I got hot glue and super glue and decided to use super glue. It has worked great so far. The lens cap that goes on the back was used for the front to connect the lens. Thank you to whomever posted about that idea!

I have recorded footage without the fresnel lens (by the way, thanks Ryan for confirming that the fresnel lens is the same as a reading magnifier...I bought one in hopes that it was) or the spinning glass and it just seems to be darker. I haven't tried it in the day yet or on close ups. I also didn't notice a huge difference in the DOF as compared to footage without the Agus35 on. I hope (and know someone has stated it before, am too busy to read through 450 posts - another reason Chris!) that someone can tell me that the GG and fresnel will give me the DOF Agus is getting??? Please tell me this is what is missing for the DOF! If so, that's what tomorrow will be...a quest for DOF. Sorry for the long post. Thanks in advance from my fellow Agus35er's.

Clay
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Old December 20th, 2003, 03:30 AM   #267
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Hey, I've been following this thread and im scheming out my own little project...

We're mostly all using 35mm SLR lenses right? There should then be no need to put a fresnel in between that lens and the GG, as long as the GG is the same distance away as the film plane for that lens (there was a post on this maybe two or three pages back). If anything, I would think the fresnel would be just like the macro lens (but cheaper)...

Im not sure if I missed something, but what is the order of elements in your device, Agus? Seems like you've got the vignetting problem mostly solved. Does any vingetting become visible when the 35mm lens is stopped down, or filming in low light?

Another thing... Im worried that the box and the relatively heavy lens will pull down slightly, warping the image. Or the whole thing move as I'm filming...
Is there any place I can go to find out how to make a rail mount system, or where I can find specs/dementions of the real ones?
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Old December 20th, 2003, 08:53 AM   #268
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Flange Focal Distance / Depth / Length; Support Rods

Here is a link that gives FFDs for various lens mounts.
http://www.gregssandbox.com/gtech/filmfacts/flange.htm
There are also tables in the likes of the American Cinematographer's Manual and David Samuelson's Hands On manual - but these are biased towards movie camera mounts.

The FFD is the distance between the mating surface of the body/lens (not the bayonet lugs, screw thread or whatever) and the image plane.

One inch is 25.40 mm.

If your lens isn't there do a search: just use 'flange focal minolta' or whatever because of the various names used for this.

If you want an upscale alternative to using a rear lens cap as your mount, look around for second-hand bellows adaptors. These are the mounts made for using lenses on bellows for close-up work. Try http://www.srbfilm.co.uk/ They also make custom parts very cheaply compared to movie industry places. They export.

Standard 'lightweight' Arri support rods (also used by everyone else for DV cameras) are 15 mm diameter, 60 mm centre to centre. These dimensions have to be very accurate for some standard equipment to fit. The rod axis is 85 mm vertically below the lens axis and the rods are equidistant from the lens axis (at least they are on my Petroff matte box). Some adjustment is usually possible for the exact lens axis / rod axis alignment. Plenty of people offer rod adapters as standard items. They aren't terribly expensive even when custom made.

Best,
Helen
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Old December 20th, 2003, 09:47 AM   #269
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To Chris: The condensing of the thread. Good idea. Soon enough we will be beginning to see thread deja-vu otherwise.

To All: A useless and unproductive curiosity question?

Has anyone added controlled lighting onto the groundglass to achieve an effect similar to that of pre-fogging motion film. It might be interesting in situations where the contrast exceeds the workable range of the DV camera. It might be interesting creatively if different colours were used, even more so if a known colour temperature offset was used and the lighting then adjusted back in post., ie., an effect perhaps similar to using an 81EF filter at sundown with tungsten balanced film.
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Old December 20th, 2003, 10:19 AM   #270
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Quote:
I must be missing something here, or maybe your adapter is built a little differently than mine - but I can't see why you wouldn't benefit from having both a fresnel lens to focus your image onto the GG and having a macro to allow you film something up close. Can you shed some light on this?
Devin,

Well, maybe you're right -- I thought I'd read something in one of the earlier posts where Agus discarded his fresnel after installing the macro. Now I see, going over the old threads that this wasn't necessarily the case. My mistake, sorry. And so I have to ask -- is everyone using a fresnel and are they helpful?

Agus -- is the fresnel in your latest version of the adapter?

Quote:
So in essence if you fail to get a powerful enough macro lens to get you close enough to the GG to fill the frame and avoid "vignetting," you wouldn't be able to zoom in and pull sharp focus would you? I guess in this case it's better to overkill and get a +10 macro lens - better to be closer than further?
I think this is all correct. I'd go with a more powerful macro either way you slice it.

I'll definitely keep you posted,

- jim
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