Homemade 35mm Adapter

[Matthew Kent]

Hey guys... ya, I'm definately using the lens that curves out on one side. It's DIA is 60mm, and FL is 83mm.

I've just posted my most recent video using it: Telegraph

It's hard to really see the distortion at low res, and I've also noticed there's still a little bit of vignetting, but it may have been my fault (not completely centered maybe). One possible issue I also discovered with the lens today is that it has some of the same cons of a static GG. If there is ANY dust on it whatsoever, it shows up... my lens also has a couple tiny bubles in it :'( , which show up in some of my shots sometimes. I'm going to attempt to get it replaced, but in the meantime, tell me what you guys think...

The two shots where the distortion seem to show most is just after the first cut in the out of focus tie die shirt past the tea pots, and the last shot before the fade out. Do you think I need to get a more curved, or less curved lens? Is the distortion different with different 35mm lenses (As in different brands, and also focal legnths)? Also, since the distortion is comming from the lens, and being projected onto the CD, can a correction after the projection even take place? I don't really undertsnad optics that well, but my first assumption was that the PCX would go between the CD and Lens, until I saw all the posts talking about it going between the GG and camera (which after more reading does make sense now)

Just FYI... my current setup looks like this:
Lens - GG - (| Condenser - +5 Macro - Camcroder

Thanks...

P.S. You may notice flickering in the video... the batteries for my CD motor were going dead :P

[Matthew Kent]

Ok... it may be a little early to celebrate, but I think I fixed my distortion issues. I just received my Canon FD 50mm lens yesterday, and while messing around with my setup came across Mandy's thread about a homemade achromat lens. I played around with my macros, trying to see if I could get better results, and then starting playing around with my PCX lens... I turned it around so the curved portion faces the ground glass, and even though it looked REALLY distorted to my eyes, when I placed my camcorder in front of it, everything looked normal.

So far, I don't see any kind of distortion, so this may be what I've been needing to do from the beginning. Sorry Jonathon if I misunderstood your instructions.

Anyways, I've made another DOF test at this link (same as before) called DOF_Test_4.mov.

I'm hoping this solves my distortion issues... I'm going to go out and shoot some more with it in the next couple days, and will make an update on how it looks...

Thanks everyone!

[Dan Diaconu]

Mathew, the image is gorgeous. No vigneting (that I could tell) and as crisp as possible (for the frame size ;...spider web in 720/480....? That is as good as it gets). I think I will make myself one!!! (I was planning anyway, but this time I got inspired) hehehe. You still have to do another one for that right corner spot, but that's nothing! The pic is good. Get the footage in a retail store and watch it on a lage screen, let us know how it looked.What is the frame size?

Bravo!!!

[Matthew Kent]

Thanks Dan,

So far I'm pretty happy with it... for those of you who can view H.264, I've posted a full resolution clip of the video there (720x405).

Can anyone tell me how to use Brett's chart with a 50mm lens? His instructions say to fill the screen with the 24mm x 18mm printout, but even with macro lenses I can't seem to get close enough. Should I print it larger?

Thanks

P.S. it seems heavy traffic knocks the link to my files down every so often... sorry. Anyone got space/bandwidth to spare?

[Eric Ohman]

I do have space to share.
Drop me an e-mail at eric-ohmanATtelia.com and we continue from there...

AT = @

// eric

[Leo Mandy]

Matthew,

Do you have a picture of your setup? Congrats on getting so far so soon! I has taken me a good 6-7 months and I am nowhere near you as far as quality!

What are you using for a condenser and where did you purchase it? Are you still using the Macro lens - or did you get an achromat?

[Andresh Vazquez]

hi
first. english dont's my born language. excuseme
i'm making a 35mm-dv converter with static groundglass
i have a problem. on the GG apear a circle more lighting. do how can resolve it.
i think to use a old +4 filter used however condenser lens. it's ok?
* the cam lenses take focus on GG without close-up lenses. it's ok?
* the cam record the images inverted. do i rotate 180d after?
thank you

saludos

[Josh Harlan]

Yes Mathew! You have done an amazing job. I'm in the process of building a spinner, but yours takes the cake. Would you please let us know your design and what gg, condensor, etc. you used? I'm very impressed!

[Bob Hart]

A bit of an update on the AGUS35 plumber's version.

After the Cunderdin Airshow debacle when the heat softened the glue and the appliance fell off the front of the camera like a melted candle, I finally got around to fitting another glass groundglass for two student single scene shoots.

I am also getting in some more prisms, this time with coatings on the reflective surfaces. In the meantime, I found I could just get the image through past the chips in the damaged prism if I positioned it the right way.

I had rejected this particular glass disk because it ran out and shook the camera too much and had forgotten it still existed.

This time, I took the time and trouble to remake the front lens mount cap and bring it closer to camera lens centreline and to set the backfocus sharp across the whole frame.

This is apparently very important for the wide angle lenses 28mm or similar. Whilst these have a greater depth of field than a zoom, it seems they are less tolerant of backfocus being off.

The results in bright daylight with the prime lenses are better. In poor light, there still is softness in the image. The glass gg does not flicker.

Despite being a f4 to f6.3 aperture, the Sigma 50 - 500mm zoom lens confers a satisfactory image via the groundglass in good lighting. The 2x doubler is a little softer. This lens must be supported otherwise it will pull the lens mount out of a plastic pipe cap.

[Wayne Kinney]

Bob,
Thats great to hear you have a spinning glass adapter.

Could we possibly have some pictures? How was the disk created and centred?

[Rob Lyons]

I only read the first 50 pages of this thread so excuse me if this is a re post. I'm wondering about the setup they used for www.marlathemovie.com. It's a static ground glass setup. Well actually it's not even ground glass I believe it's a focusing screen of some kind for a slr. I assume you'd still get the 35mm dof with this setup. If you had a good enough screen grain probably wouldn't be a factor. No noise, no moving parts. alot smaller, and if built correctly you wouldn't have to mount the dv camera at a 90 degree angle to the slr body. If anyone is familiar with the adapter they used on that movie could you please explain why this adapter is undesirable. It seems to me that it should work perfectly, I must be missing something.

[Wayne Kinney]

Originally Posted by Rob Lyons

If you had a good enough screen grain probably wouldn't be a factor

That is usually the factor!

Most peope following this type of design have had luck from the 'Nikon D' screens or the more expensive 'Beatie Screens'

[Leo Mandy]

Bob has had a spinning glass unit for a couple of years now, if I am not mistaken - it isn't anything new for him.

[Ben Winter]

Rob,
I experimented heavily early on with using the Nikon D static screen. This setup is undesireable because as soon as you start closing the iris of the lens (no matter how fast it is) the grain becomes alarmingly apparent. If you have a 1.2 of 1.4 lens you would certainly want to close the aperture somewhat at certain times because the DOF will be almost too shallow. If you have a static setup, however, closing the iris instantly creates serious grain problems. I'm sure that if you talked to the creator(s) of Marla they'd confirm that they never closed the iris. If you want aperture control, you need to go either wax or moving gg, bottom line.

Also, having your $2,000+ camera mounted vertically into a 35mm SLR camera on a spraypainted wooden board is simply unprofessional and awkward. Who would want to steadicam that thing?

Finally, I encourage you to look at the stills of the movie on the site www.marlathemovie.com. Even when the aperture seems to be wide open, the "translucent waviness" characteristic of a static adapter is always there in areas of shots that are out of focus. To many of us (including lazy old me) that's simply unacceptable. Also it looks like they didn't flip the image the right way (the name tags and letters in the stills are backwards?) Anyway, look at the media on that website and ask yourself if you could really live with the results of that adapter. I should add that they had to go through each individual frame of that movie and manually remove the grain from each shot.

[Michael Maier]

Well, with all that, it still looks great and is a very entertaining movie. The artifacts kinda contributed to the look and style of the movie.