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Old April 14th, 2004, 01:46 PM   #1
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'aerial image'

A discussion about aerial images was starting in this thread:
http://www.dvinfo.net/conf/showthrea...threadid=24109

...so I thought I would post a new thread on this specific topic.

I have heard aerial imaging mentioned here before. (Used in older printers?) As I understand it, this technique would not require a diffused surface to pick up the image, but the image gets passed through air. The consensus is that aerial imaging is the absolute best way to capture an intermediate image. I'm not sure how that is possible, so I wanted to see what you guys know about it.


Here's some interesting stuff that came up in a search:

One explanation of aerial images
http://groups.yahoo.com/group/DV-List/message/36549

Buhl Mobile Multiplexer
http://www.toddvideo.com/film_chain.html

ATM Lenses
http://astro.umsystem.edu/atm/ARCHIV.../msg00658.html

8mm Transfer
http://www.goaggressive.com/super8fi...er.html#aerial
Quote from page:
-----------------------------
" 'AERIAL IMAGE' TRANSFER - An aerial transfer is a telecine transfer in which the image is projected on a glass surface 5" in front of the film projector. This is more highly recommended for 16mm film, as its larger frame size makes it appear less 'grainy' to begin with. "
-----------------------------

It seems like the term 'aerial image' doesn't necessarily mean 'image suspended in air'. Some people, as in the quote above, are using the term in reference to images that are projected onto a surface.

What are your thoughts?

Thanks!

,Frank
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Old April 18th, 2004, 11:13 AM   #2
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I did experiments with this. My adapter lets me use the condensor without the ground glass - so I did some comparisons. Yuck - the diffused imaging surface is absolutely required for what we're doing. Without the ground glass, the depth of field is exactly the same as my camcorder by itself - just upside down and manual focus :-(

I think the aerial image works for telecine applications, because the 'secondary image' is the first piece of film. The image has already been transferred with whatever DoF characteristics it has to the first piece of film, and the aerial image is the most light-efficient way to exactly replicate it to a digitized format...

I have been meaning to post some comparison pics to demonstrate this, because they absolutely show the difference. Pics are worth thousands of words, as they say...
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Old April 18th, 2004, 11:20 AM   #3
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My comments really apply to telecine transfer - I’ve never seen a discussion of the physics to back up the claim that the image is captured “in the air”, as some folks describe.

The website that describes it as a projection on to a frosted glass plate is certainly not an aerial image, but rather an alternative form of projection screen. It is still better than trying to capture by aiming a video camera at a screen or piece of paper on a wall.

The film transfer devices that bill themselves as aerial image devices still end up focusing the camera on the frame of film by aiming the camera into the transfer device’s lens. Usually this is accomplished by a lens and mirror arrangement to give the proper image orientation. Also, the film is usually back lighted by a low wattage bulb to avoid the problems of aiming a camera at the extremely bright bulbs of the projectors that form the basis of these units.

Even thought the resulting optical device has two adjustable lenses, I see no evidence that the image is being captured in the air.

I've followed the development of the Agus 35 with interest. There is certainly a pack of inventors out there.
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Old April 23rd, 2004, 10:17 PM   #4
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Angenieux 35 HD

Has anyone seen this from Angenieux:
http://www.angenieux.com/pages/index_frame.php?page=301.php
This CLA 35 HD adapter converts PL mount to 2/3". Though it is horribly expensive ($22,000 street price), it implies that the aerial image conversion technique can be made to work, so it ought to be possible to make one for smaller format conversion too. I spoke with the Angenieux rep at NAB, and he assured me that it does use an aerial image. The image is inverted, but that can be dealt with easily enough.
Intriguing.
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Old April 24th, 2004, 10:13 AM   #5
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Great! Now if only someone could design a ghetto version for 1/6" CCDs, I'd by that for a dollar!

Seriously though, there must be a trade-off somewhere.
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Old April 25th, 2004, 01:51 PM   #6
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Hey Dan I believe the deal with that is because its all optical and it reduces the target size you end up getting the same FOV as 35mm but not the same DOF. The DOF would be the same a a 2/3 inch camera in this case. I would want to varify this though. Think of DOF and focus as shaped as a cone coming out of the back of a lens. Generally the smaller the target size the shorter the cone and thus the more in focus. Hope that makes sense. Besides have you seen the internal optics of that adapter?! As I remember there was around a dozen elements in there.

-Brett Erskine
www.CinematographerReels.com
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Old April 25th, 2004, 07:38 PM   #7
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I already post those link on the other thread ,but I got no feedback. I am not shure if this can be usefull , but in the middel of the page they are talking about Telecentric lens systems.
My english are not good enought to understand everything here but that seem's interesting.


http://www.lhup.edu/~dsimanek/3d/illus1.htm#isomet

http://www.lhup.edu/~dsimanek/3d/telecent.htm

http://www.edmundoptics.com/techsup...m?articleid=261
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Old April 25th, 2004, 11:01 PM   #8
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I believe you are right about this being telecentric. That's a lot of glass in there. Angenieux has adapted something designed for lithography or metrology for this purpose. Bravo! It seems though, that it would be cheaper to design 36x24mm CCDs, CMOS, or Foveon, if there is such a demand.
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Old April 25th, 2004, 11:27 PM   #9
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Dalsa's camera shown at the recent NAB has a 36x24mm CCD. From what I've heard, very film-like images.
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Old April 26th, 2004, 02:39 AM   #10
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Yeah the Dalsa is a glimpse of the future. When I shot in doors with it I found the sensor was way too slow (64 ISO - T) but I loved the mechanical shutter, optical viewfinder, 2K X 4K resolution and 35mm cine lenses. They say the next version will be smaller and 400 ISO.

-Brett Erskine
www.CinematographerReels.com
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Old April 26th, 2004, 04:32 AM   #11
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Angenieux DOF

Hmm, the Angenieux rep certainly implied that the DOF was preserved, but if that's so, it's very odd that they don't mention that in their brochure. I'm going to contact Angenieux and get a definitive answer, and I'll post what they say.
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Old April 27th, 2004, 02:08 PM   #12
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Angenieux DOF

Brett, Frank, and other interested parties:
I contacted Angenieux about their 35mm to 2/3" adapter and here's what thay said (emphasis mine):
"The CLA 35 HD is an optical relay, it adapts the 35mm film format to a 2/3" HD format. The advantage is that you keep
the resolution of the 35mm lens and also the field of view AND the DEPTH OF FIELD."
So now I want to know HOW they do it!
And then make my own for 35mm to 1/2" CCD, and 35mm to 1/3" CCD. (For less than $22,000.)
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Old April 27th, 2004, 02:43 PM   #13
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Dan: I hear ya. Without something inbetween there to 'catch' the image, how are they keeping the depth of field? This is mind-boggling to me. This 'aerial/optical' configuration is such an attractive setup with the big advantage being no grain, but it seems to me that someone like P+S Technik would be doing this by now, instead of microcrystalline or whatever, if it was as people say it is.
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Old April 27th, 2004, 05:19 PM   #14
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Mystery

Yeah, it's a bit of a mystery. On the adapter, there is a yellow band around the barrel corresponding to (as the rep explained) the image plane. But it can't be any kind of "surface" if it still retains the resolution of the 35mm lens.
But since everything is "fixed" within the adapter, that is, there is no control of focus from the adapter to the camera, maybe that takes care of any "depth of field" issue of the adapter itself. I wish I'd looked through the one on display! But I'm sure you can see all the way through it (no focusing surface). Maybe some optical engineer will see the posts and 'splain it all to us.
Anyone...? Bueller...?
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Old April 27th, 2004, 08:50 PM   #15
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WOW I hope you were given the right info because I agree with the last few post. Why hasn't P+S done this, etc. I wonder how you phrased your questions to Angenieux. You know how thoughs sales reps are. They often arent techs so if they dont know they'll just tell you what you want to hear. BUT if its true then the reason why we havent seen it show up in the prosumer market could be because of either the cost of the complex element arrangement and/or larger physical size. I believe I remember downloaded the internal optical design drawings. I'll see if I can find it. In the mean time feel free to look for it yourself in the web. Thats where I got it. Even if its true though...the optical system is WAY too complex to hand build for 99% of the people on this thread. Very interesting though.

-Brett Erskine
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