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Old June 17th, 2007, 10:46 AM   #1
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DIY 35mm Adapter Query

hi, im new here, but have been browsing for a lil while

i have a question

i want to build my own adapter,

but, i want the camera to sit on it at an angle, in the same way the movietube does

http://berlinfcp.de/BLOG/images01IBC...15movietub.jpg

now, im at a crossroads here.

can i just place the acromat at a slight angle, then the image would be bent directly on the cameras lens? (light reflected through the glass?)

or would i need to place some kind of mirror or something to reflect the image onto the lens?

thanks
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Old June 17th, 2007, 11:19 AM   #2
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David

Do you have a prism that corrects the image from the ground glass?
Because thats why the movietube is built that way.

Otherwise, its best to have a straight path from camera lens to gg to 35 lens.

This lessens the variables in aligning your st up.

Ted
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Old June 17th, 2007, 11:35 AM   #3
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nah, no prism

i just thought it looked better like that instead of being straight

where would i get the prism from though?

is it expensive and does it have an disadvantages, like loss of light, quality etc?
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Old June 17th, 2007, 11:54 AM   #4
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A prism is expensive to cutom build for an adapter.

Using those on 35mm cameras is too narrow for this purpose.

Your next option would be to use mirrors. I found a guy using it in either this forum or the other. Try to look in this thread by doing a search.

My advice though is try to keep a straight path to avoid, mis alignment, light loss, and less sharpness.

capturing an image on a moving gg is already sacrificing a certain amount of light depending on your GG. adding several elements in between aggravates the matter unless you have high quality mirrors.
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Old June 17th, 2007, 12:49 PM   #5
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i see, thanks

that brings me to another question

are the static or vibrating GG's better than spinning ones?

as in allowing more light, less noise etc.

thanks
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Old June 17th, 2007, 01:01 PM   #6
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the advantages vary,

The vibrating tends to give a samll circular pattern of grain caused by the small movement axis( Vibration moment) which becomes obvious under high shuuter speeds on your cam, whereas the spinner shows abig "wiper" like pattern under hight cam shutter speed.

The vibrating will give you a much smaller housing due to the small size of the moving parts, the spinner needs to placed in a bigger, usually box like, container to house the rotating disk.
The vibrating unit can be placed in a tube like container that can be threaded directly to your cam's filter thread, whereas the spinner needs to be mounted on a rod like support or somthing similar.

There is no straight answer to this, both have their pros and cons. what matters are the kind of resources that are available to you.

In my opinion, the key elementsbefore you undertake this are, the groundglass(gg) or focusing screen that is available to you and the other, if your using a cam with a filter thread higher than 52mm is an achromat which will allow you to "zoom in" on the GG image without edge distortion and CA (chromatic abberation).

Ted
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Old June 17th, 2007, 01:03 PM   #7
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David,

Static, vibrating or spinning GG does not effect the amount of light loss. This is down to the type of GG material and its diffusion properties. The method of movement does not affect lightloss, it only affects how effective it is at hiding grain.
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Thanks,
Wayne.
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Old June 17th, 2007, 01:28 PM   #8
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thanks both of you

actually Wayne i was planning to buy the sgpro acromat to use in the diy box

but im unsure on where to aquire the groundglass.

i read in some places, some people use cd cases cut into a circle, but i would assume some clarity is lost with that method.

whats the best option for a very tight budget?
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Old June 17th, 2007, 01:45 PM   #9
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David,

Its not the CD case but a frosted CD, the dummy CD you find at the top and bottom of a spindle of CDs when you buy them in bulk, say 25 or 50 pcs per spindle, actually I used this in mine. I think it came from a maxell.

Heres a grab from an 80mm lens at f1.9 to show you what a frosted cd can do.

But of course I wont discourage you from getting wayne's sgpro which is among the best adapters out there together with the Brevis and M2.
Attached Thumbnails
DIY 35mm Adapter Query-maggie80mm.jpg  
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Old June 17th, 2007, 02:57 PM   #10
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oh

i would have dont it so wrong lol.

that pic looks good

is that a frame grab from raw footage or corrected?

what cam was used, u shoot in hd or sd?

thanks
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Old June 17th, 2007, 11:47 PM   #11
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Its from raw test footage, uncorrected, just flipped in post.
Shot in 24p with jvc hd100.
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