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Old December 12th, 2003, 09:07 AM   #181
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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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Old December 12th, 2003, 10:30 AM   #182
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So is the fresnel a good replacement for a macro adapter? Which would be better?

Thanks
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Old December 12th, 2003, 01:28 PM   #183
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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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Old December 12th, 2003, 02:36 PM   #184
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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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Old December 12th, 2003, 04:02 PM   #185
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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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Old December 12th, 2003, 06:15 PM   #186
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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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Old December 12th, 2003, 08:07 PM   #187
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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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Old December 12th, 2003, 09:34 PM   #188
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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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Old December 12th, 2003, 09:44 PM   #189
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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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Old December 12th, 2003, 10:09 PM   #190
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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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Old December 13th, 2003, 12:56 PM   #191
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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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Old December 13th, 2003, 10:15 PM   #192
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<<<-- Originally posted by Peter Sciretta : 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 -->>>

Hey man, that looks really cool, BTW i am upgrading my Agus35 using all the tips that everybody have posted here. I am making a support skeleton using aluminiun rods, also i am making a matte box which can be attached to the whole thing.

I will post some footage soon and also the plans, which seens not necesary ... :-) but still will make them...

for all the newbiews here is some footage.

http://altoque.tv/maserati.wmv

http://altoque.tv/35mmAdapter/kartfilm.mov
http://altoque.tv/35mmAdapter/moto35mmfilmtest2v4.mov
http://altoque.tv/35mmAdapter/spotAdapter35mm2.wmv

http://altoque.tv/35mmAdapter/Agus35maseratitest.wmv

Some pics

http://altoque.tv/35mmAdapter/35mm7_0004.jpg
http://altoque.tv/35mmAdapter/35mm7_0005.jpg
http://altoque.tv/35mmAdapter/35mm8_0001.jpg
http://altoque.tv/35mmAdapter/35mm8_0003.jpg
http://altoque.tv/35mmAdapter/35mm8_0008.jpg

http://altoque.tv/35mmAdapter/moto01.jpg
http://altoque.tv/35mmAdapter/moto02.jpg
http://altoque.tv/35mmAdapter/moto03.jpg
http://altoque.tv/35mmAdapter/moto04.jpg
http://altoque.tv/35mmAdapter/moto05.jpg

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Old December 14th, 2003, 12:24 AM   #193
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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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Old December 14th, 2003, 12:58 AM   #194
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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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Old December 14th, 2003, 01:07 AM   #195
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what do you mean fake cds?
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