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Old April 23rd, 2008, 01:32 PM   #1
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35mm DOF adapter help please

I'm trying to build a static 35mm DoF adapter and I need some help. Basically I have all the parts except the focus screen (and macro), but I do have a piece of plastic that will suffice (I think, maybe I'm wrong) for while I'm building this.

Because I have some Canon FD lenses, I chose to build my adapter around them. I'm starting with a 50mm f1.8 attached to an FD/EOS adapter which in turn attaches to the "Asian" EOS extension tubes.

Because of the FD/EOS adapter, I'm uncertain as to placement of the rest of the parts. When I place my temporary focus screen behind the lens assembly (about 1cm using 2 #1 bits of tube), I can focus the image on the screen using the Canon lens focus adjustment. The image is not all that bright (probably because it is "open", but that's not what I'm concerned with.

Not only do I see the image I'm wanting, but I see a round bright area. Also, the image is rather large, almost filling the entire 55mm of the temporary screen.

I have read Daniel's tutorial on the vibrating DoF adapter and was curious what I could make with what I had.
The FD/EOS adapter came with a lens element installed that is designed to allow focus to infinity when attached to a Camera. I before I removed this, the image I saw was smaller and brighter, but so was the round "second" image.

Please forgive my ignorance of photography and lenses, but could someone please explain what I'm seeing and if this is what I should be seeing prior to attaching the whole thing to my camcorder?

Here are three images:

http://i120.photobucket.com/albums/o.../35mmtest1.jpg
http://i120.photobucket.com/albums/o.../35mmtest2.jpg
http://i120.photobucket.com/albums/o.../35mmtest3.jpg

Last edited by Paul Nixon; April 23rd, 2008 at 03:49 PM. Reason: additional information
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Old April 23rd, 2008, 05:37 PM   #2
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Hi Paul, a mod might move your thread over to Alternative Imaging.

... from one amateur to another ...

The bright region depends on how big an opening you have on the lens (aperture). You're supposed to zoom in with your camcorder to get the dark edges out and maximize the 'bright area' assuming your aperture at its widest (1.8 in your case) ... well for artistic purposes you might not want all the dark portions out. The dark area effect is called 'vignette'. You could get that if your 'ground glass' doesn't have a PCX condenser in front of it (brightens the picture up some more). Also check your lens and make sure the action from f1.8 (brightest) and up (darker) is working. I bought a used lens once and the iris stuck. You fix the zoom from your camcorder, fix the focus, then adjust your 35mm to the aperture setting that suits you. It takes experimentation.

Hope that helps.
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Old April 23rd, 2008, 06:01 PM   #3
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Hi Mike,

Thanks for the reply. I know enough about some of this stuff to get myself into trouble.

I have no PCX lens - I just read about that on wiki.

I think I'm also going to need a macro lens.

Do you know how transparent the ground glass should be? Daniel at jetsetmodels has a tutorial for making a "GG" from wax sandwiched between two slides which is what I had originally thought about (though I have two 55mm UV filters that I'm planning to use - if the wax will stand up to our summertime heat during normal use)

The first temporary "GG" I experimented with is a thin, grayish, translucent piece of plastic. It is what I used to shoot some test footage (and where the screen captures came from).

The second temporary "GG" I experimented with was a simple piece of printer paper. It yielded very dark image but did not produce the center hot-spot. Maybe this is because it simply blocked out so much light?

My current temporary "GG" is a round piece of CD case (similar to Tupperware) that is almost transparent. I can see a stunningly clear image of my monitor through it (when looking through it directly rather than connected to the camcorder), but then there's the actual opening of the lens also visible (see http://i120.photobucket.com/albums/o.../35mmtest3.jpg for an idea).

I just get the feeling that my "GG" is a fundamental issue, but I don't know for sure.

As for "the action" - this is indeed working. In fact my FD-to-EOS adapter has a neat feature (neat to me at least): a lock. I can lock the aperture open (which, I think, is what I will want ultimately).

Again, thanks for the reply
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Old April 23rd, 2008, 06:27 PM   #4
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Paul,

It should be translucent ... usually a frosted white. I haven't tried the wax technique myself. I'm using the focus screen from a Nikon F3 Type D which has the PCX built in. It has a fine frosted glass look ... like a dirty block of ice. My tests with the Maxell CD yielded a not so bright image like yours. BTW, what is bright to our eyes isn't so for the camcorder. For the HV20 you need to lock it down to 1.8 if you can. You'll definitely need a macro lens for the HV20, it can't focus that well unless you have one.

Focus Screen vs Maxel CD
http://yousillyman.blogspot.com/2007...-just-yet.html

Early test with the CD ground glass:
http://yousillyman.blogspot.com/2007...eed-macro.html

Early test with Nikon F3 Type D.
http://yousillyman.blogspot.com/2007...th-static.html

Here's what my ground glass looks like from the matte side:
http://yousillyman.blogspot.com/2007...oundglass.html

From the PCX side:
http://yousillyman.blogspot.com/2007...und-glass.html
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Old April 23rd, 2008, 07:35 PM   #5
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Thanks Mike,

So the screens I'm experimenting with should be okay for the time being - my main goal is to get the distances of the optics sorted out, and that seems to be an issue at the moment (of course).

I read where someone used the objective lens from a pair of binoculars as a macro (achromat), I happened to have an old set of binoculars and cannibalized one of its objectives. I've got it mounted but I don't think it's in the right place - it's not doing anything as far as I can tell.

I'm using http://www.jetsetmodels.info/pics/konzept1.jpg as a guide except I'm not using the vibrating part and I'm using the "Asian" EOS entension tubes rather than empty filter rings.
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Old April 23rd, 2008, 11:22 PM   #6
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I made a different gg - this one using wax. The results are better than before but still a long way off from being great. Seems a big issue is the light loss (which I read about), so perhaps my results are not as good as they would be in bright light.

Anyway, here are the results:

http://i120.photobucket.com/albums/o...test2_wax1.jpg
http://i120.photobucket.com/albums/o...test2_wax2.jpg
http://i120.photobucket.com/albums/o...test2_wax3.jpg
http://i120.photobucket.com/albums/o...test2_wax4.jpg
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Old April 24th, 2008, 06:59 PM   #7
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The recent pics look better. But it looks like you'll benefit from a condenser too. Then after that have to figure out how to manage the static grain. In lower light the grain shows up a lot. Also I noticed the CMOS grain in one of your outdoor pics are you using cinemode?

I suggest you also try a a canon ee-a focus screen for reference. If you order it from canon parts its significantly cheaper than from a camera store ($5+6 shipping --no retail packaging, just the tiny screen in a plastic ziplock).
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Old April 24th, 2008, 10:14 PM   #8
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I ve made a few adapters to shoot with the HV20. Most recently, I built a Nikon tube set up, and bought the vibrating gg holder from Daniel, then used the $ 7.00 achromat from Surplus Shed. The results are pretty nice. You do have to use parts of a second extension tube set to get enough set back from the ground glass to allow zooming inside the vignetting area. Total length of my set up is about 5 inches.

I also had decent luck with a wax gg I made per Daniel, but the EE-a screen is much superior, and I believe it has a bit of condensing built in, as it seems to even out the image issues.

In my opinion, a vibrating gg is the only way you are going to get your images to acceptable standards. Is tough enough with them to have a decent image without worrying about the dust, hairs and grain that will show up with a static adapter.

Daniel's vibrating gg holder is cool, but I manage to break it at installation, and there went $90 down the drain. I converted it to a Letus like vibrating systems, as a result.
I did buy the Letus 35a about a year ago. I had to actually add a Cinevate achromat behind the original one to get decent zoom capability. But as the cost of image sharpness. Recently, I dropped the Letus achromat out of that set up, attaching the Cinevate achromat only in its place, and image is much nicer- actually beating the Daniel contraption.
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