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December 12th, 2003, 09:07 AM
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#181 |
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Major Player
Join Date: Sep 2003
Location: Colorado
Posts: 316
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John,
Thanks for the answers. I am going to try to get started this weekend. Is the fresnel lens used so that you don't have to zoom in so far? And, how much does it help the problem of not having enough light? Thanks again... Clay
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I understand everything about nothing. |
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December 12th, 2003, 10:30 AM
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#182 |
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Regular Crew
Join Date: Feb 2003
Location: UK
Posts: 130
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So is the fresnel a good replacement for a macro adapter? Which would be better?
Thanks |
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December 12th, 2003, 01:28 PM
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#183 |
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Regular Crew
Join Date: Jun 2003
Location: Akron, Ohio
Posts: 65
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Fresnel and Macro
The way I see it, the fresnel is placed between the SLR lens and the GG to focus the light more directly onto the GG.
1..2.3....4..5.6.7......... [| < |==== | [|[|CCD 1.SLR lens 2.Unfocused light rays from SLR lens 3.Fresnel Lens (about 1/4 inch from the GG) 4.Redirected Light Rays (reduced vigneting) 5.GG 6.Macro Lens attatched to Video Camera's lens to allow it to focus on the 35 mm negative sized image on the GG while zoomed in. 7.Video Camera Hope this helps some ppl out...excuse my terrible ascii art skills, Spencer
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www.par-t-com.net > C'mon, you know you wanna click it. |
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December 12th, 2003, 02:36 PM
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#184 |
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Regular Crew
Join Date: Jun 2003
Location: Akron, Ohio
Posts: 65
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Re: Re: Fresnel and Macro
<<<-- Originally posted by Agus Casse :
Have you even tried that ? cause i believe it wont work, the fresnel have to be after the GG and before the Camera. -->>> I've tried it and its the only way i belive it will work. Also take a look at John Gaspain's design: http://www.imagestation.com/picture/...c/fa531009.jpg I don't think the fresnel is accomplishing anything optically if you place it after the GG. By then all is done in terms of vignetting on the GG, nothing you can do to change it from the Camera side besides zooming past it. Anyone else try out a fresnel? Spencer
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www.par-t-com.net > C'mon, you know you wanna click it. |
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December 12th, 2003, 04:02 PM
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#185 |
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Regular Crew
Join Date: Nov 2003
Posts: 72
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I am experiencing a high flicker... anyone have any idea why?
here are two pics (after film look post) from video i did today http://www.orfilms.com/luke1.jpg http://www.orfilms.com/luke2.jpg |
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December 12th, 2003, 06:15 PM
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#186 |
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Major Player
Join Date: Sep 2003
Location: Colorado
Posts: 316
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Agus, John, and anyone else who has made one,
How do you know where to cut the holes? Obviously, one hole has to be bigger than the other. Do you just guess as to where they should be? Is a fresnel lens the same thing as a magnifying glass? I went to Walgreens and got a bausch and lomb "magna-thin" magnifier as it is the closest thing they had that resembled what John used. Is this it? John, I bought the bigger box (8X6X3) and the GG clears it fine...just a little more bulky. I have all the stuff ready to go, but don't want to mess anything up and have to start over. Also, John, how did you connect the camera to the box? Ok, can't wait to get started. Thanks in advance for the advice! Clay
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I understand everything about nothing. |
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December 12th, 2003, 08:07 PM
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#187 |
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Inner Circle
Join Date: Dec 2003
Location: PERTH. W.A. AUSTRALIA.
Posts: 4,477
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To Peter Sciretta.
High flicker. My guess is you are getting an intensity strobe effect which might be related to variations in density or texture of your groundglass surface and the disk rpm coming close to the frame rate of your camera which means that although the texture of the surface will be moving fast enough past the frame to average out all the small defects, larger patches of say quarter to half a disk size will phase in and out of your frame. The scratches on your groundglass disk - are there some which go straight across the disk or uniformly circular in an even finish? Your 35mm lens centreline axis is also bent off-centre to the left in your second frame so I guess you are at very early prototype stage yet. |
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December 12th, 2003, 09:34 PM
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#188 |
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New Boot
Join Date: Dec 2003
Location: Vietnam
Posts: 23
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According to this link from what i understand: http://www.camerascreens.com/PDF/Ins...ew_Cameras.pdf
You put the fresnel lens between the gg and the lens. Here's a difinition from B&H photo: A fresnel lens is an accessory for a groundglass focusing screen. It helps "even-out" the brightness of the groundglass image and make the image appear brighter. The effect is more noticeable with wide angle lenses. Fresnel lenses are essential when using reflex housings. I haven't tried this out, but i'm going to assume it should be place between the gg and lens. Clay just know the size of your SLR lens and Camcorder lens, then get a hole saw or a mill and drill the holes. You need to convert the millimeter sizes to inches e.g. 37mm = 1 1/2 inches 52mm = 2 1/8 inches, 58mm = 2 3/8 inches Friendly advise from a fellow Texan Peace Peter |
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December 12th, 2003, 09:44 PM
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#189 |
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New Boot
Join Date: Dec 2003
Location: Vietnam
Posts: 23
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My bad
My bad Clay you asked where to put the holes. You have to be careful aligning the lens hole and camera hole. I goofed once and had the lens hole lower than the camera by 1/4 inch. So one side of the film can became useless. Just measure and mark each placement of your holes including your motor and thay should lessen the degree of the vignetting.
More friendly advise from a fellow Texan |
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December 12th, 2003, 10:09 PM
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#190 |
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Major Player
Join Date: Sep 2003
Location: Colorado
Posts: 316
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Hey Peter,
Thanks for the advice. I got out the ol' trusty tape measure and got the inch readings. I hope to find center of both and somehow line them up and get them centered. I just didn't know if anyone else had any tried and true methods. I am still wondering about where to drill the holes on the box (CD spindle)??? I guess that's what makes this so great...fly by the seat of your pants! Well, we'll see what I come up with if I don't hear from anyone else... Clay
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I understand everything about nothing. |
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December 13th, 2003, 12:56 PM
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#191 |
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Regular Crew
Join Date: Feb 2003
Location: UK
Posts: 130
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Just tested my frosted CD with the lens, was surprised it looked very good and it wasn't even in a casing. Will try and get this done over the next week and post some footage.
I put the scratched cd directly infront of my GL2 and it went into macro mode and focussed on the cd, would I still need a fresnel lens or a macro adapter? I'll test some more when I have a casing. |
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December 14th, 2003, 12:24 AM
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#193 |
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Major Player
Join Date: Dec 2003
Location: Brooklyn, NY
Posts: 636
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Alright, some questions on tightening up the design...
I put mine together tonight, after having received my macro zoom yesterday, and it's functional, but there is a noticable haze around everything. I used 600 grit sandpaper, and did my best to put down an even surface. I've got my apertures wide open, and setting the 35mm lens to an infinite focal plane, I've set my DV camera's manual focus. So: how do I remove the haze, or cut it down significantly? Agus -- in your experience, was haze a problem? If so, do I need to up the speed of my motor? (I'm using a CD motor, but have a Radio Shack 18,000rpm motor at hand...) Jesus this needs light :) - jim |
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December 14th, 2003, 12:58 AM
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#194 |
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Major Player
Join Date: Jul 2003
Location: Guatemala
Posts: 322
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Dunno what is haze ....
BTW.. tip for all, i found a little teasure... look for fake cds what are already translucent... they are 100% perfect GG !!!!! I found 2, and i have a 20% image improvement... |
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December 14th, 2003, 01:07 AM
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#195 |
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Regular Crew
Join Date: Dec 2003
Location: Rowland Heights, CA
Posts: 62
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what do you mean fake cds?
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