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Old February 15th, 2005, 12:51 PM   #16
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Yep, those have been used :)

They provided decent results for static designs I believe. They still show grain of course.
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Old February 15th, 2005, 01:20 PM   #17
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I knew that others had tried them, but I could never figure out which grit they used. I read where some people were planning to _buy_ the 1500, but then I never heard a follow-up. Do you know who actually bought one? I'll search a bit more and see if I can dig it up...

I think (not sure) that Mandy's making a static design -- so this might be a good direction.
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Old February 15th, 2005, 05:01 PM   #18
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No, I am using the CD motor - spinning CD. Static might end up being a viable option depending on how well I can make the end product look - but I have to try this way first because I have come too far now.
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Old February 15th, 2005, 05:14 PM   #19
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Ah -- okay, my bad. You'll be much happier with the spinner (I was), and in that case the THOR products won't help you unless you move things elliptically.
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Old February 15th, 2005, 05:19 PM   #20
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What Thor products? Have you finished your design? Do you have a url for it, would love to check it or even some video/pics that you have taken with it.
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Old February 15th, 2005, 05:22 PM   #21
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THOR Labs -- they sell pre-made laser-etched fine-grained diffusors (i.e. ground glass).

Yeah - there's some not-very-finished stuff on my website:

http://www.aqua-web.com in the film section.
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Old February 15th, 2005, 05:43 PM   #22
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Jonathon, great looking site! I see you went with the project box design - can you tell me how the heck you manage to calibrate the Focal Length AND got it to stay in the project box? I have been racking my brain over this one since I start this project - aside from having a hard time get the right focal lenght for my Sigma Zoom II, attaching into the project box has become sort of a mystery on how you got it in, screwed it into place AND then calibrated everything!?!?!?

AND what is the frosted CD? I am thinking that it is homemade?

The footage looks great for a VHS-C - colours are sharp as well. Great job!
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Old February 15th, 2005, 06:03 PM   #23
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Yeah the camcorder is certainly the weak link :-( Someday I'll upgrade, and I'm sure I'll have to improve the adapter at that point. It's just a 'hobby' after all for me.

I mounted the CD motor into a square piece of plywood. This is attached by four bolts to another piece of plywood which is affixed to the back of my project box. There are 'spacer' bolts in between the two pieces of plywood... I used a focus chart at a precisely measured distance at the lowest end of my SLR lens and focused the lens to this. Then... I adjusted those four spacer nuts and moved the plywood holding the cd motor until I had a focused image, according to my view of the GG through a loupe.

Theoretically this would allow precise focusing and also allow for correction of slight off-axis 'warble' to the disc. This is a big issue which is hard to pick up on... if your disc is not spinning completely flat, the GG is actually moving in and out slightly -- which causes softness in the focus.

In reality, it was a pain in the ass, and it ended up slightly off anyway. In my _next_ adapter :) I'm going to make the focal flange adjustment and lockdown something that can easily be done from outside the box. My idea worked, but it's not great. I'd advise you to think of other alternatives.

Do realize that you have a small margin of error here... and what you trade off for that error is one end or the other of your focal length and accuracy of the marks. In other words, if you're off by a bit in your flange distance, it will likely still work, but when you're lens says you're in focus at 5m, you may actually be in focus at 7m.

On my GG -- I used a piece of single-ply mylar architectural film glued to the cd. With my low-res cam, it worked fine, and saved tons of time. A sheet of this stuff is like $2 at any architectural/blueprint supply shop. It will need improvement once I have a higher-res camcorder, but for now it works great... plus, once you move the GG - your problem is less one of grain, and more one of flicker and oscillation error (as mentioned above).

Hope this helps...

Another tip: look on ebay for viewfinders for older pro-cameras. I have an Ikegami viewfinder which I bought for $9. It has a beautifully sharp CRT image (albeit b/w which I prefer) and I can flip the whole thing upside down to fix the image rotation problem if need be... or maybe mount it to a helmet (!) for a steady-cam-like project I'm working on. I had to dig a little to get a pinout to hook it up, but it's a good solution for image rotation.
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Old February 15th, 2005, 06:25 PM   #24
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Jonathon,

My own personal steady-cam is on hiatus right now. I started building it in the summer - got the gimbal and yoke finished, but stalled on the arm (the really tough part).

Ok, back to the DOF machine.

I have done it exactly the same way, except ( and a big one ) I don't have a focus chart for this lens. I got it at a charity shop, so nothing with it to help me out - just a Sigma Zoom II, 35-105mm (done the search on Google and that was no help). So I have had to adjust it by eyeing it - and it is an absolute chore because of the lack-luster macro lens I set up in series with a magnifying lens. What I tried to do was set the Mark to Inifinity and then the lens at 105mm so it was as close as it could go - then I made the adjustments - but getting it right is so darn hard!

Also, figuring out where to drill the hole in the plastic so it is lined up with the GG and the SLR is lined up as well is a nightmare! The Project boxes are only $10.00, but I don't like to waste money! How did you get over this hurdle?


I use the magnet trick to fix the upside down image, so that doesn't really bother me.

I love the footage you had - the colours were soooo bright and sharp, but having said this, I did notice the wobbling in the upper left hand corner. But it did not detract from the nice image at all.

BTW, what does "according to my view of the GG through a loupe" mean?
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Old February 15th, 2005, 06:42 PM   #25
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A loupe is a little magnifier. large-format photographers use them on a ground glass for those big cameras to check focus. I used (and got) mine while I was a typesetter. I magnified printed materials to check the halftoning, etc. Anyways...

If possible, take the macro out while setting the focal flange length. It just complicates things. In other words, take the camcorder off, and the macro out, and try to look directly at the ground glass with nothing else but your naked eye (or a loupe if you have one). You don't really need a focus chart, but do find something with lots of fine detail... you can open up a book with small type -- that works well. A focus chart is just easier to use (there's plenty for download/print online... such as: http://www.creativevideo.co.uk/refra...back_focus.htm) The idea behind the star is as you focus, the center will blur and sharpen. You focus until the sharpness extends the farthest into the center.

It's _much_ easier to focus to the short end than to inifinity. I don't know much about your Sigma lens... but crank it down to the nearest focal setting and place the book at exactly that distance (measure it with a tape measure) from the front of the SLR lens. Lock all of this down if you can :) Then look directly at the ground glass from behind (as if you were the camcorder) and adjust the focal flange distance until the words on the page of the book are as sharp as they can get. I found it helped to put plenty of light on the book, but to have the rest of the room (particular back where I was) much darker.

The way I handled the hole drilling: I figured it out on paper -- and used Adobe Illustrator to make and print myself out an exactly measured template, with the hole exactly where I wanted it. I taped this right onto my project box and drilled right through the paper template. It worked well - got it in the right spot on the first try.

Ideally, (another TODO for my next adapter), you'd have x-y translation on your GG as well, so you could make slight left right up down adjustments after everything was in there...
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Old February 15th, 2005, 06:58 PM   #26
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One other comment -- my notes earlier about the 'leeway' you have on your focal flange depth don't apply if you're using a zoom. For a prime, you can usually find a spot which is in focus but may not line up with the marks. But for a zoom - if your focal flange distance is wrong, than you'll find that the lens will be in focus on one end of the zoom and out of focus on the other. If your FFL distance is correct, this won't happen - and you're best approach to focusing will be to zoom in, focus, then zoom back out. Worthless unless your focal flange distance is exactly right. :)
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Old February 15th, 2005, 07:04 PM   #27
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Jonathon,

Thanks for the information - that will help out alot. I am going to try to do that adjustment tonight. An X-Y adjustment would be a great idea as well - because even though it is a small area, once you drill those holes in the housing, there is no going back - so adjusting the GG up or down would be boon!

The loupe, could this be substituted with a magnifying glass?

Do you think your CD wobbles because it is not optically true or do you think it is the motor or the casing or a combination? I don't seem to have the same problem, but then again, I don't get the nice colours you get as well.

As far as focusing down on the closest point - I am used to working in a TV studio, and we would always zoom in and focus to infinity, and then zoom out to make sure that everything was in focus - so that is new to me.

I am going to try the book/fine print thing tonight - to infinity and see what happens and then I will try the close (as you suggested) and see what happens.
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Old February 15th, 2005, 07:20 PM   #28
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Nope - my 'wobble' comes from my mounting being slightly out of whack... such is the crude mechanism I have for adjustment. The sure sign... with the 'lid' off, I turn on my CD and as it spins if I edge a piece of paper up to it ever so slowly, rather than a steady HIIISSSSSSS, I get PHHT PHHHT PHHT PPHHHT as the 'high point' of the CD (from my mount) makes contact. Not good. The next one'll be better (and the one after that, and the...)
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Old February 15th, 2005, 07:21 PM   #29
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And yes, a magnifying glass would be fine for a loupe -- better probably, because a loupe is really supposed to rest against the surface it magnifies. Not good for a spinning disc!
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Old February 15th, 2005, 07:45 PM   #30
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With the magnifying glass, it is still very difficult to make out anything clearly. With the DV (I know, I know - I will try without it tomorrow during the day when I have light) I found this out, interestingly enough...

When I pull my zoom out to 105mm, on infinity - the 'STAR' (pdf from the link) picture was out of focus, even though at 35mm at infinity, it looked good. If I turn the rubberized barrel to 12 (# in beige on the barrel) inbetween the 3 and 4 (#'s in green), it comes into focus. So does that mean :

1) that is needs to be recalibrated to make sure it focuses on infinity instead of on 12 (in between the 3 & 4 on the rubberized barrel)
2) That the target is not far enough away (it is about 3 meters at present).

I think it might be the former (1) because when I moved the camera back, the STAR still did not come into focus, but I could be wrong.

I wonder how your mounting went out of whack?
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