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Old March 1st, 2005, 01:07 AM   #16
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Hey Brett thanks for the advive on the powder coating...
I have another question, do you have the Flange Focal Distance chart for
35mm lenses cause I found your post with the helpfull links and specifically this link "http://www.gregssandbox.com/gtech/filmfacts/flange.htm" that has the chart is dead.

Thanks,

Gev
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Old March 1st, 2005, 02:26 AM   #17
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Oh damn. No I dont. And I didnt back up that page. Anyone else? You can figure it out by setting your lens to wide open and to the infinity focus mark. Point the lens at the far horizon and inch in your focusing screen. This will give you a pretty good idea what the flange focal length is. To find it exactly you need to now set the lens at the minimum focal distance thats marked on the lens. Set up a object at the same distance in front of the lens. This measurement should be from the object to the GG. Where the image appears to be perfectly in focus is your exact flange focal length for that lens mount. Measure carefully or make your adapter adjustable for back focus.
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Old March 1st, 2005, 02:33 AM   #18
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back focus distance

I think with Nikon lenses, it's about 48 mm
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Old March 1st, 2005, 03:45 AM   #19
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Gev Babit: what did you use for holding the shafts ??? Some bearings, or some shaft sleeve or what ? I stick in this, do not know what to use for smooth movement of shafts in the plates...
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Old March 1st, 2005, 11:53 AM   #20
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internet is largeeeeeeeeeeeeeee:)

Camera mounts & registers:
http://www.a1.nl/phomepag/markerink/mounts.htm
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Old March 1st, 2005, 12:29 PM   #21
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FWIW, you can also buy do it yourself powder coating and aluminum anodizing kits from the internet. They aren't prohibitively expensive either. Do a google search and you'll find plenty of info.

Having seen your fine machining work Gev, I think these options would be well within your skill level.

-gb-
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Old March 3rd, 2005, 03:38 AM   #22
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Thanks Dogus & Greg!

Daves- I used ball bearings for the shafts and sandwiched the bearings between two plates. If you hammer in the bearings into the plate you might not be able to take them out or adjust them and they will get damaged, thats why I sandwiched them together between two plates. I am happy with this method, I can take the bearings out and adjust them whenever I wan't. The diameter of the bearing holes on the thin plates are 1mm less than the bearing, you tighten the three plates with small screws and nuts. Look at the pictures you can see how all the parts work. BTW I used two bearings for each shaft on the non-moving plate.

Gev
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Old March 3rd, 2005, 03:47 AM   #23
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<<<-- Originally posted by Gev Babit : Thanks Dogus & Greg!

Daves- I used ball bearings for the shafts and sandwiched the bearings between two plates. If you hammer in the bearings into the plate you might not be able to take them out or adjust them and they will get damaged, thats why I sandwiched them together between two plates. I am happy with this method, I can take the bearings out and adjust them whenever I wan't. The diameter of the bearing holes on the thin plates are 1mm less than the bearing, you tighten the three plates with small screws and nuts. Look at the pictures you can see how all the parts work. BTW I used two bearings for each shaft on the non-moving plate.

Gev -->>>

Thank you, I understand how it works, but I did not know that baerings can be so small... I'm building racing car, so I know just much bigger bearings :))) We are bulding SteadyCam, so we used the same technique in the arms... But had no idea about these small bearings... Going to build it next week... Thanks...
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Old March 3rd, 2005, 02:34 PM   #24
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Gev,
Here is a tip for aligning and testing your device without a camera: Use a laser pointer and bounce it off the ground glass at an angle. Run the device, and view the spot the laser makes on a wall several feet away. The spot should not move around at all. If it is moving you will have image shake when you use it with a video camera.
Before you get too far into mounting a lens, etc, you might want to try this.
-Les
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Old March 4th, 2005, 03:32 AM   #25
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laser drift...

les,

although a good way to pick up misalignment, wouldnt that method exagerate the error that might not be as evident to a simple relay lens??
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Old March 4th, 2005, 05:05 AM   #26
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Re: laser drift...

Not really. Your eyes are very good at seeing image shake, and you really don't want any image shake at all. When the ground glass is moving, it should look motionless to the eye, unless you see the edges of the glass which are obviously seen to be moving. The shiny side of the GG should look like a static mirror. Trust me, I've had several attempts that 'looked' like it would work, but looked like crap with the video camera.
I finally got a version that works, which I plan on offering as a sub $500 kit, as I mentioned in another thread. I test with a HDV camera to make sure it will work on DV as well..

The laser test saves time, you don't end up wasting a bunch of time mounting up optics to a GG that is flapping around
-Les


<<<-- Originally posted by Sarena Valilis : les,

although a good way to pick up misalignment, wouldnt that method exagerate the error that might not be as evident to a simple relay lens?? -->>>
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Old March 6th, 2005, 12:04 PM   #27
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Re: Re: laser drift...

I finally got a version that works, which I plan on offering as a sub $500 kit, as I mentioned in another thread. I test with a HDV camera to make sure it will work on DV as well..


I don't want to cross-post, and you aren't having direct e-mail, so I'll just ask here that you make contact with me as someone truly interested in acquiring your kit when you're ready to make it available. I've seen in other threads that you're not too concerned with directly setting up for an XL. I wish you were, and I understand your disdain for SD resolution. HD is where it is all heading, I just wish the standards wars would conclude. I would be happy now if only I could have controlled DOF in shots, an artistic tool that I believe is the common desire drawing most of the people to all these Alternate Imaging Threads.
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Old March 9th, 2005, 01:48 AM   #28
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So Gev, How did it look when the video was shot through the device ?
-Les
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Old March 9th, 2005, 02:14 AM   #29
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I did a really messy setup and taped it to a peice of wood. There was no image shake, it worked great....only problem is that the ground glass at 1500 grit is no good, resolution and projection wise. The mechinism works great the only thing is the optics that are not so good like the condensor and achromats. There are no hotspots or anything but it looks low res, maybe its my lens I dunno. But the mechnism works really well! I don't have any footage cause the ground glass has all these lines and spots, from touching it I guess, so I'm gonna get a new one and then see what happens!
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Old March 9th, 2005, 02:39 AM   #30
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In my experience a fairly ordinary groundglass works pretty good. The motion of the groundglass hides any defects unless they are really big. Did the image look sharp without the condenser, just having the video camera shoot the ground glass directly? That would tell you if the condenser is blurring the image.
-Les
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