'aerial image'

[Dan Vance]

Yes, I've seen the cutaway drawing on the data sheet and it's a non-trivial design, to say the least.
I asked Angenieux twice, and the second time I said:

"Thank you for the reply. So does this mean I can use my standard Depth of Field charts for 35mm lenses (American Cinematographer Manual), without any conversion factor?"

And the reply was:

"Yes you can use the 35mm depth of field chart for the focal length of the lens mounted on the adapter."

So it's pretty unambiguous. Still looks like a big undertaking for a home builder, though I'm not giving up yet.

[Brett Erskine]

Okay Im interested.

Looks like it has a internal focus mechanism. 12 elements / 10 groups....Theres got to be a way to simplify this. Perhaps its this complex because they wanted to make it work with all the different back focus lengths they have out there in cine lenses. If thats true then a design thats set up to work with just one type of lens like say Nikon OR Arri's then it may make the optical design much much easier. Hopeful thinking...This ones out of my hands. We need a professional optical designer to look this one over. I am excited though. If we point Angenieux to this and the other threads that have popped up over the internet on the subject it MAY get them interested in applying all that R&D they have already invested to a 1/3" CCD adapter. The demand is record breaking for sure. Now wheres the supply.

-Brett Erskine
www.CinematographerReels.com

[Quincy Alexander]

Gentlemen,

I contacted Angeniux and got a nice response from their US Sales Manager. See response below.




~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Quincy,

My name is Chris Beauparlant. I am the US Sales Manager for Angenieux. I have read the entire discussion on your forum and would love the opportunity to discuss in more detail with you our anyone in your community. I can be reached at (973) 812-4346 (my direct line). Jean-Marc Bouchut is our Technical Support Manager who is an optical engineer and designer with over 15 years experience. He is the "Angenieux rep" that Dan keeps referring to. I can assure you and your community, he knows what he is talking about. You should know that the product that you are referring to is co-designed between Angenieux and Zeiss. It is manufactured by Zeiss and marketed by Angenieux. If you wish to contact me, I may be able to provide another view or explanation that will help your discussions.

Thank you for your contact.

Best Regards,

Chris Beauparlant

[Frank Ladner]

Wow. That's a pretty good response. So I guess it is what they say it is, then.

It would be interesting to actually talk to this guy, but I'm just a country boy and would be intimidated. ;-)


Thanks for the info, Quincy!

[Sebastian Scherrer]

Hi folks!

So - did anyone contact the Angenieux guys? What became of it?

My fellow aldu35-builder has been talking to an engineering prof, and he suggested the just the same principle the other day.

So, interestingly enough, when I checked dvinfo for
"aerial image", this thread pops up!

From what I understand (I am a filmmaker, not an optics engineer), the image could be focussed on the groundglass,
then the groundglass could be taken away and it'd work
just fine.

Someone proposed further up that he'd taken some test images proving it wouldn't work. Would love to see them!

Would be great if we could get it to work - no grain, no groundglass (a real pain to focus though, i bet)

[Wayne Morellini]

This sounds bad, because I was thinking of a way to do an ariel type image, now somebodies beat me to it.

If you want to find out what they are doing look up their patent on it (and other patent references quoted in the patent (if there is any). IBM and the European Union has patent systems on line. I am still to learn more optics, to see if it is possible before I start work on my own. I'm still interested in how they did it, because if it's significantly different I could patent my own.

[Frank Ladner]

In a setup like this, how difficult would it be to keep from only receiving the middle rays from the 35mm lens? (ie. The side rays would spread out and miss the DV camera if they are not 'captured' first at the focal plane, right?)

Any ideas?

[Wayne Morellini]

Wouldn't that give you nearly unlimited focus?

Here's a funny thought that just entered my head, does depth of feild depend on the Aperature relavent to the target size? If this is so, the maxium aperature of a medium format lense (f2.8) might be equivalent to a much smaller aperature (below f1.0) when passed through a condensor onto a 1/2 inch sensor, thus giving a smaller relavent DOF. Is this right, or am I just dreeaming?

Thanks

Wayne.

[Frank Ladner]

I posted this link a while back, but wanted to post it again with emphasis on the quotes below:


http://www.toddvideo.com/film_chain.html


Quote from link:
-------------------------------------
Illustration A shows that without a field lens or a screen at the image plane, only the light coming through the very center of the image gets into the camera lens. The corners are not illuminated. Only a small circular field is visible.

Illustration B shows that when the image is projected onto a rear projection screen, it can be seen by the unassisted eye as well as the video camera, but there is considerable light loss due to the screen's bend angle. Image quality is lost due to grain in the rear projection screen.

Illustration C shows that a field lens located at the aerial image directs light from all parts of the field lens into a small circle. When the camera lens is placed at this circle, the entire field is illuminated. This is the system we use for the highest quality image.
-------------------------------------


You can tell a lot from just reading these, but the pictures on the page will help. As you can see, 'Illustration C' is what we're after.

[Wayne Morellini]

This is not a very good illustration because the projection is flat film (DOF is simulated on 2D film and set). We deal with rays that converge all over the place to give DOF, so normal condensing the image converts the DOF back. Still what about my idea above, because we are opening the aperature we reduce the DOF in sixe? If you close down the aperature more of the off axis light rays can not go through the iris hole that increases DOF, simular to what you were talking about, is it the same?

That link says: "Space to insert AP screen" (or RP screen) between the feild lense, on the image. Seems a bit simular to what I was thinking, but without screen. It sounds exactly like what the 35mm adaptors are currently doing.

It looks like that, the first feild lense straigtens the light to go through the screen, as off axis light is more likely to go sidways, angularly or reflect off, and not be captured by the second feild lense that passes it to the cumilator lense to the camera. The screen is there to stop off axis rays from going out of focus again. But how do we get rid of the screen for good?

[Frank Ladner]

Hrrmmmm...

Wayne: I'm not sure. I'll let the experts tackle that one. The whole concept is very interesting, but I know very little.

[Brett Erskine]

Sorry to bust your bubble guys but the Zeiss/Ang. format converter talked about above only maintains the FOV but not the DOF of 35mm cine lenses. It does however increase the light getting to the CCD and this means good news for you Wayne. IF a similar system existed that was designed to maintain the FOV of medium format lenses you would see a HUGE difference in brightness (apparent f stop). Use the law of squares to determine how many stops brighter it would be between medium format and a 1/3 inch CCD. The concept can be seen in practice on telescopes that use large mirror to gather the light. The larger the mirror the more light it can gather. Same idea but in the situation you are using lenses to focus the light down to a smaller spot not unlike a magnifying lens and a ant.

Also the idea of removing the GG and trying to focus on a aerial image wont maintain the DOF either.

Sorry guys.

-Brett Erskine

[Wayne Morellini]

Brett, I have in the past. I had an thread on it last year, all you need is a dual lense condensor (not any of this stuff). But people have claimed that Ang claims (via email) it does maintain DOF aswell. I know it should be possible, but the illustration I was talking about is little more than our existing 35mm adaptors (still some screeen).

But I have noticed that as you open an Iris the DOF gets shallower, so wouldn't a medium format lense through a condensor just be a bigger Iris in the converted format, and thus get shallower DOF? Can anybody experiment measuring DOF normally and DOF with a very fast MF hrough a condensor. It probably won't be as much as a normal MF, but as long as it is better than without an adaptor, then at least we have some improvement.


Thanks

Wayne.

[Brett Erskine]

1)Post examples if you have them but I must insist that while you may be able to see thru the film lens you wont be able to see the benifits of the shallower DOF.

2)Yes given that the field of view and f/stop stays the same between a 35mm lens and Medium format lens - the dof will be shallower on the medium format lens. You still need to have some form of GG to see the DOF though.

-Brett Erskine

[Wayne Morellini]

1) I am saying that others are saying it can, so I would like to see some examples of DOF being matained myself.

2) you didn't get my drift.