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Old March 9th, 2004, 01:06 PM   #511
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Corrected image

First off, I know using an inverted external monitor is an option but I would rather save myself the time and effort of fixing orientation in post. I think a correctly oriented image is doable. Saying this,I must point out that I am not an optical engineer. In fact, I've learned almost everything I know about this subject from you all and the articles you've posted here in this and the Agus35 thread. Experts, please chime in.
Frank, I don't think you're crazy! I gave your idea about projecting onto a reflective surface with a mirror some serious thought. We Southern Boys must think alike! I didn;t throw the projection idea out completely but I do have a few concerns about it.
1. We would be talking about a front projected image, right? Well, you would have an issue with left to right orientation when compared to a rear projected image (GG) A front projected image is really a reflected image just like a mirror so left to right orientation would be reversed while vertical would remain the same. I bet that is why SLR cameras use a GG element the viewfinder assembly instead of simply focusing on a projected image.

2. I haven't come up with a simple way to orient all of the elements to make using a projected image practical

Here's my stab at a simple correct oriented image. Sorry for the poor diagrams.

Basicall, I'm proposing an optic quality mirror mounted at 45 degrees to the light path from the slr lens. The GG and condenser lens are mounted above the mirror. (which comes first GG or CL is still under debate) The video camera is mounted vertically and is focused on the GG. I have a nice short camera 9.5" from lens tip to battery pack, so the vertically mounted camera wouldn't be too awkward. My adapter wouldn't need to use a round GG or round tubing either as I would house the whole thing in a compact, lightproof black box. In a nutshell, this is identical to a top view viewfinder on a med. format camera. In fact, you could use a med. format camera body and just add your own GG and condenser. Watcha Think? Joe

_________
' '
' '
' DV '
' Camera '
' '
'--------------'
/____\

CL (___)
GG ====
' /
' /
[ SLR ] ---------'/ 45 degree mirror
Lens /
/




_______
| | |
| | |
| | |
|____ | |
/___\ | |
--------------| |
I | |
I CL (___) | |
I GG==== | |
________ I / | |
_ _ \ | SLR Lens I / | |
/ |________I / | |
______I_/_______ | |
|__________Mount_ __|
[ ]
/ / \ \
/ / \ \
/ / \ \
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Old March 9th, 2004, 01:21 PM   #512
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YIKES!!! Well, I guess my ASCI art leaves a lot to be desired. Never tried it before. Sorry. Guess my written description will have to do. Joe
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Old March 9th, 2004, 02:05 PM   #513
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LOL
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Old March 9th, 2004, 02:07 PM   #514
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Actually, Olivier and Sebastien used that same idea for their first prototype and the video turned out great. They posted pictures of that setup at http://www.originalversion.net/temp/makingof01.jpg. Also, you can check out their movie thread at http://www.dvinfo.net/conf/showthrea...threadid=21567. If you haven't already seen "Marla," its very worth the download.
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Old March 9th, 2004, 02:14 PM   #515
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to Frank Ladner

frank,

you just "stoled" my idea, he, he...
i was thinking about the same thing, but never tested it in practice.
some time ago i saw slide portable projector, and i was inspired from it. the original device looks like this:

PLEASE, IGNORE THE DOTS! i was unable to "draw" it wihtout...


.....................\
......................\ <----- your eye
.......................\
........................\ big frosted GG
.........................\
..........................
small ...\.......
mirror ... \...... <------ ray () <------!! <----- lamp
..............\.................... lens.......slide

small mirror is parallel to big GG.

so if i'm right - you can use certain flat grainless surface instead of big GG. and use "system" like this...


.....................\
......................\
camera POV.......\
----------> ........\ grainless opaque surface
...........................\
..........................
small ...\.......
mirror ... \...... <--------- ()
.............\.................35mm lens



what do you think?

filip
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Old March 9th, 2004, 02:14 PM   #516
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Joe: Ha ha! Yeah, that ASCII art is quite difficult to pull off. I do understand what you're saying, though. That sounds pretty good to me, but I'm not an expert. I like the idea of using box/square stuff, because it's easier to line parts up correctly whan they're not circular.

Filip: Whew....I feel better now that some of you guys didn't laugh at my idea. What you are illustrating is exactly what I'm thinking about. Actually, it's better, because I was adding a few too many mirrors to the equation while envisioning it. :-)
That looks doable! Nice!

,Frank
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Old March 9th, 2004, 02:16 PM   #517
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he, he i was designing the whole asci drawing during yours replies...
nice to see that everyone is thinking here!
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Old March 9th, 2004, 02:21 PM   #518
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So my next question is......are mirrors just mirrors? ie. Are there certain mirrors that are better than others as far as quality? How are they rated?
Thanks!
,Frank
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Old March 9th, 2004, 02:31 PM   #519
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mirrors

in my opinion (i'm not a mirrorist :),

the mirrors used must have reflecting surface on the TOP ...

(so called venetian mirrors, hm, well at least in poland)

... surface, not the bottom.

in that case you do not have reflection distorted by glass itself.

just a thought.
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Old March 9th, 2004, 03:56 PM   #520
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since projecting the image on a solid white surface seems a good idea, i am afraid that the loss of light in such process would be too big.
What about projecting the picture on a surface mirror ?
I am not sur that in that case we get the same result than with the gg, but in theory, the picture would be build the same as on the GG and in the same time reflected (and inverted) so we get the economy of several parts.
We could use the mirror of the SLR body that is just the right size.
the only problem i see with using mirror before the gg is that we could create a light path that could exceed the about 46mm that is required to focus properly.
On the other hand we usually have plenty of useless space after the GG due to the requirement needed by the macro lens.
So using here a kind of zig-zag path could be usefull to build a compact adapter.
My best guess would be to have the light comin out of the SLR lens to a 45 deg surface mirror (inverting picture) to an horizontal plano convex lens with the flat side acting as GG.
This still require to have the camera mounted vertically and the picture inverted a 2nd time.
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Old March 10th, 2004, 01:31 AM   #521
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I hate to be the bringer of bad new this time but Filip your design wont do what you want it to do. In fact it ends up having the same effect as if you had done nothing at all. Do a test with a mirror, 35mm lens a white piece of paper. In fact even if it did you still would have a problem with having the whole image in focus top to bottom. You would have to have your camera at 45 degrees so that that image plane is flat to the camera's CCD.

The rest of the last few designs ideas only do a partial correction -leaving you rendering your footage in the end anyways.

One front projection idea I had was to use a 35mm lens > forward slainted 45 degree two way mirror > white grainless projection surface > directly below the first two way mirror theres another mirror. This one is a regular one way mirror mounted at a 45mm rearward slating position > video camera.

It has two problems though. It doesnt flip the image L to R and wastes too much light. It does however makes alot of other things possible (flips the image right side up, doesnt need a condenser or ground glass, is grainless, possibly no need for a diopter either)

Personally Im still going the GG/Condenser route and simply rotating the monitor and render in post. The reasons: making my adapter much shorter, Im shooting with anamorphics, easier for steadicam work, etc.

-Brett Erskine
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Old March 10th, 2004, 05:44 AM   #522
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<<<-- Originally posted by Brett Erskine:
In fact even if it did you still would have a problem with having the whole image in focus top to bottom. -->>>

i don't understand this. why image will be out of focus? isn't it just a periscope system? if two mirrors are parrarel to each other, in my opinion (i'm not a periscopist:))) the image will be in focus all the time. i will of course make a test with a mirror and white surface, but as i remember my games with a periscope, there is no need to correct anything, everything is in focus...

oupsss...

ok. now i can see what you wroted... you are talking that the image IN THE CAMERA will not be in focus if camera itself is looking on 45 angle white screen. you are right. i just thought about the first part - mirror--->white screen parallel system. sorry, i was too fast...

<<<-You would have to have your camera at 45 degrees so that that image plane is flat to the camera's CCD. ->>>

correct.

<<<- One front projection idea I had was to use a 35mm lens > forward slainted 45 degree two way mirror > white grainless projection surface > directly below the first two way mirror theres another mirror. This one is a regular one way mirror mounted at a 45mm rearward slating position > video camera. ->>>

can you ascii this? i have problems with understanding the whole construction.

THANK YOU
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Old March 10th, 2004, 11:07 AM   #523
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I just receive my roller bearing.
the hole is 50mm dia and the external ring is just 65mm dia.
the thickness is 7mm
I will use a 50mm dia. condenser lens mounted inside with the flat side grounded with 1000 grit alu. oxide (still waiting for it) so i should not need an additional GG.
Then i got the choice to rotate it or not.
the roller bearing cost 30$, so it doesn't add to much to the price of it.
I think i will make a flange on the roller in Delrin (kind of white plastic , easy to use, very used in mechanics)
The flange will be a kind of ring, to accept inside the gg-lens and outside the way have the motor rotating it (probably a simple plastic belt)
Ideally everything clips together so there should be no need for soldering or glueing anything
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Old March 10th, 2004, 12:15 PM   #524
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Francois,

is it possible to pass somehow (somewhere) some jpgs of your roller bearing etc.
it will be nice to see that!

thanks

filip
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Old March 10th, 2004, 02:12 PM   #525
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I've been following this and the agus topics very closely for past few weeks. And you may have noticed I'm new here. One major questions for you guys is, do any of you( and mainly to those of you that live in the UK) know where to buy aluminium oxide grit in the UK? I can only seem to find it attached to paper, and even then, it's not 1000. It's only about 250, which from what I have read , would be far to coarse.
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