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Old November 9th, 2006, 02:48 PM   #1
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Any advances in adapter flipping???

I cant seem to find a thread detailing info on image flipped adapters. Just curious to know where everyone is towards designing their adapter to flip. I know some of you have already done this. This seems to be the question that all customers ask. Im currently trying to design the DiGi35 so it can flip because it is a pain having to flip in post. I used mirrors but it didnt seem to work properly. Is there any real info about this on dvinfo? If so where cos I cannot find it. Hence the new thread.
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Old November 9th, 2006, 05:08 PM   #2
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Hi tony,

its possible but you need some custom made prisms for a big path of rays and for low quantity their very pricy. I made some designs about image flipping with prisms and mirrors but never posted it because too expensive for DIY.

Daniel
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Old November 9th, 2006, 08:50 PM   #3
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Tony.

Two right-angle or ninety degree prisms, each with the long side facing each other, ninety degrees offset, (rotated a quarter turn) the half hypotenuse face only, of each overlapping the other as in prismatic binoculars will do it for you.

They need to be about 65mm on the hypotenuse face and about 32mm thick across all faces to pass a clean 22mm diameter off the groundglass via a 4+ to 7+ achomatic dioptre to an inbuilt lens camcorder capable of zooming within the range 32mm - 54mm for 16:9 frame.

In $AU they cost about $85 each if you get them in minimum runs of five.

I won't suggest actual dimensions because these have to be chosen to match your adaptor and what you want it to do.

Mirrors are fine but they take more work to build into an adaptor and get correctly aligned. They also must be surface coated.

The conventional rear-coated bathroom mirror cut into small pieces will work for developing an early mirror design but be totally unusable for actual imaging because of internal reflections within the clear glass.

This creates an artifact of parallel lines of decreasing intensity, starting from the edges of the image.

The cut edges of mirrors and the non-reflective (grind finished) faces and corners of the prisms should be flat blacked to reduce stray reflections within the path to help contrast.

I use a pair of prisms, the Letus uses surface coated mirrors, I think the P+S Technik Mini35 uses both in a hybrid arrangement.

This image illustrates one method in very crude terms. As viewed it offsets the camcorder optical centre axis high and leftrelative to incoming optical centre axis.

http://www.dvinfo.net/media/hart/Agusmir1.jpg

This one shows you what you get when you cut up bathroom mirrors.

http://www.dvinfo.net/media/hart/agusmir4.JPG

This one gives you a bit more detail.

http://www.dvinfo.net/media/hart/agusmrcp.JPG

If you want to trawl through an unsystematic bunch of images of my past experiments use the index at.

www.dvinfo.net/media/hart

Any .pdf concept drawings there are obsolete and should not be built to.

Last edited by Bob Hart; November 9th, 2006 at 09:23 PM.
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Old November 14th, 2006, 01:00 AM   #4
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I don't like image flipping idea in adapter at all.
First, You can't avoid additonal lightloss anyhow.
Second, You actually need bigger FV anyway to focus precisely.
So my experiments ended at that point when i got to try external FV first time. Never wanted to make step back from that point.
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Old November 14th, 2006, 02:06 AM   #5
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Most significant advances are the new JVC HD200 and HD250 as those have built in DOF adaptor support and will display and record the image right side up.
I might be wrong but those cams can record 720P 60fps to standard mini DV cassette for one hour, imagine the possibilities there.
Additionally JVC has a Super16 static DOF adaptor for PL lenses (sub $4500) coming out next month. Combine all that with 6 Optar Illumina T1.3 primes (sub $8000 total) and you can get quite a gear for film making already.

Little OT, but most DOF adaptors that can be focused without focus assist and via on-board TFTs are those with Canon EE-S screens by my experience but then again that screen produces unusual lens flare.

Cheers,
T
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Old November 15th, 2006, 10:21 AM   #6
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i find it very easy to focus on my z1 lcd with peaking on. spot on every time...almost!
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Old November 19th, 2006, 05:40 PM   #7
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OK, now I have managed to obtain various clever prisms but I am having trouble getting the 36x24mm clearly on the camcorder, The screen is too small. Now I dont now much about all te optical stuff like you lot, I am still learning. Iwas considering putting a lens between the focusing screen and the prism to make the image larger on the exit side of the prism. Will this work? I mean I know that the lens will have to be of a certain spec but in theory would this work? Or what about macros and diopters or achromats? Still confused as to what they do but would one of these help? I've noticed that on all the adapters the distance of the camcorder from the focusing screen varies, is there a minimum or maximum recommended distance? I see that the sgpro has a tube from the unit to the Sony FX1 and that on the M2 it does'nt, whats difference does it make? Any advice would be great.

Thanks,
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Old November 19th, 2006, 06:17 PM   #8
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the z1 (fx1) does need a space between the achromat and the adaptor. The Sgpro is smaller than the M2, and perhaps the achromat is less powerful? But there is a distance between my achromat and my 2 of about 3 cms or so...the ground glass inside the box is another 1 or 2 cm in
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Old November 19th, 2006, 11:06 PM   #9
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Tony.

I am no expert on optics. For what its worth, the combination of the full 35mm x 24mm groundglass image, into some popular in-built zoom lens camcorders, via a simple prism path might as a compact close-coupled device, be the unattainable grail.

The size of the prisms to create a sufficiently large "tunnel" to pass that image may rrequire distancing the groundglass from the camcorder to physically fit them in. This might require added optics in the path.

Odd sized and shaped prisms rather than an equal pair might help, or the use of a hybrid mirror/prism path which the "real thing", the P+S Technik seems to use.

Some separate developments seem to have shaken down to the 22 - 24mm groundglass image width as being the most practical compromise. The camcorder to GG distance is reasonably short, the device becomes compact, relatively light in weight, the hotspot is avoided rather than corrected with added optics which unless precisely engineered, may not contribute to image sharpness despite recovering a larger area of the projected groundglass image.

A poorly implemented single-condenser arrangement with the condenser between camcorder and GG, might even falsely convey the impression of eliminating the hotspot but instead become a simple magnifier concentrating the camera view on a smaller portion of the GG image, which happens without the condenser anyway.
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Old December 1st, 2006, 06:34 AM   #10
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Got my custom made DiGi35 prism this morning, what a fantastic beautiful piece of craftmanship. see link below:

http://www.geocities.com/anthonyrelph/DSC00507.JPG

Pic not very clear but I wanted to show it flipped against an upright image.

The actual quality of the prism is absolutely amazing.
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Old December 1st, 2006, 06:59 AM   #11
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The great thing about this prism is that image is not displaced unlike the MINI35 where the lens is lower the the exit point (camcorder) or the movieTUBE when the camcorder is angled. With the DiGi35 you will just get a straight beam of light from lens to camcorder.
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Old December 1st, 2006, 07:15 AM   #12
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Sounds promising.
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Old December 1st, 2006, 08:03 AM   #13
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22mm or more clear aperture? Those can get really pricey.

T
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Old December 1st, 2006, 03:29 PM   #14
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How long is the prism (perpendicular to the GG plane)?
If it's short, it could be a universal extension for any 35mm adapter (like an achromat). What'd be really sweet would be a prism/achromat combo. Then you could play with switching out adapter units... or quickchanging adapters (ex. you have two Brevis units with different mounts and/or diffusers).

Thinking out loud here...
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Old December 1st, 2006, 04:15 PM   #15
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The prism is 5cm long. That includes the custom made housing to hold it. The faces of the prism are bigger then the focusing screen meaning I can place it right up against the screen so when you focus the camera its like your just focusing onto the screen, when all enclosed in the housing its like the prism is not there, just a focusing screen. Because its a one piece prism the light loss is great, I will get an accurate measurement I'm just waiting on a spacer to come back from the CNC people, Once Ive got that the unit will be complete (I hope). Now I have designed the prism for the DiGi35 I can get the price on them reduced. Most optical companies make prisms but they do not design them, they need an actual design to build to. This may vary from company to company but this was the case with most of them. I would advise anyone who has a prism custom made to shop around, the prism including the designing cost just under 2,000.
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