Film-Tech Forum ARCHIVE: DLP, turrets and 35mm lenses

This is topic DLP, turrets and 35mm lenses in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=007772

Posted by Brian Guckian (Member # 1678) on 01-23-2006, 08:14 PM:

The present arrangement for many of the new DLP setups, where Scope is shown flat inside the 2K imager area (with a typical aspect ratio of 1.79:1) seems a compromise too far to me.

I understand from another thread and from industry sources that the cost of an anamorphic attachment is prohibitive, which made me wonder if 35mm standard lenses and turrets could be used instead.

I don't know enough about lens optics to know whether the entrance pupil of standard 35mm lenses could "see" a 2K DLP imager adequately. Are the areas of a 35mm frame and a 2K DLP imager roughly similar? Or is there a lens adapter that could be employed without sacrificing too much quality?

If you could fit standard off the shelf 35mm lenses and say a 3-lens turret to a DLP projector, you could really go places! Although I guess the speed of the lenses must be an issue as well.

Any thoughts on this?

Posted by Steve Guttag (Member # 268) on 01-23-2006, 09:57 PM:

Thus far, the DLP lenses are nothing like the standard cinema lens in size so I would suspect that adapting a standard cinema lens to a DCinema projector would not work or work easily.

Anamorphic lenses are indeed avaiable for the DCinema projectors. In fact, a requirement for the DCI spec is that the anamorphic lens change must be automatic.

The anamorphic lenses for the DLPs are expensive, more so than the film varieties due to their emence size and current low production. I want to say they are under $8K. It may sound like a lot but as a percentage of the projector, they are less than their film counterparts.

Posted by John Pytlak (Member # 331) on 01-23-2006, 09:58 PM:

I recall that since three separate chips are used with a prism system, a special telecentric lens design must be used.

Posted by Amanda Mundin (Member # 3386) on 01-25-2006, 01:47 PM:

As a potential recipient of a Christie CP2000 as part of the new Digital Screen Network in the UK I would be interested to know if there is a noticeable drop in quality when projecting Scope films without an Anamorphic lens as anyone getting a CP2000 through the DSN scheme won't be getting an Anamorpic lens as part of the standard package offered?

Posted by Steve Guttag (Member # 268) on 01-25-2006, 04:50 PM:

It is a trade off. Without the anamorphic lens, you will not be using as many pixels as possible. If you zoom the primary lens to fill your scope screen (presuming you have side movable masking) then you will notice a drop off in light and decrease in perceived image quality.

The anamorphic lens will allow Scope films to retain as much light as possible for side-movable masking theatres but you do pay a little "hit" for use of the anamorphic lens. All one has to do to prove it to themselves is to project a test pattern that outputs down the the pixel (Barco has a nice one in their "focus" test pattern). Even when focused, the anamorphic lens softens the image a bit.

Remember that the source material is going to be 2K for your projector (or less) so to use the anamorphic lens, you are scaling up the image vertically to work with the anamorphic lens...you don't get something for nothing here.

Now if they recorded the "scope" movies using anamorphic lenses like with film (not counting the dreadful super-35 format) then the resolution of Scope DCinema movies would be better with the anamorphic lens, hands down.

Posted by Brian Guckian (Member # 1678) on 01-25-2006, 05:58 PM:

Steve, John

Many thanks for your comments. Of course I'd forgotten that in cinema-grade DLP you're dealing with 3-chip systems. I'd be very interested in finding out more about telecentric lens designs.

Good point too re. the cost of the anamorphic as a proportion of the overall spend and that blowing up the image certainly isn't best practice.

It's also a concern, from reading the above, that even if you have the anamorphic the material has to be scaled - I thought it could be supplied in "squeezed" format, like anamorphic 16x9 for TV or DVD.

Posted by Steve Guttag (Member # 268) on 01-25-2006, 06:59 PM:

If the source material is only 2K...then somewhere it HAS to be scaled to fill the imager...UNLESS an anamorphic lens is used while shooting the movie.

Now as features move to 4K and beyond then the source could be downscaled to fill a 2K imager in preparation for anamorphic projection.

Given a typical cinema with side-adjustable masking...I would use the anamorphic everytime...it is the best trade off. With movable vertical masking...I'd skip the anamorphic. You are dealing with both light and resolution issues. Scaling progressive to progressive is not all that bad...certainly to be avoided if possible though. In life one often isn't presented with the "ideal" everything and one has to make choices.

BTW...my anamorphic estimate was LOW...once you add in the motorized mechanism to a typical DCinema DLP. Barco's LIST price for the whole contraption (motor and all) for the DP100 is $14,136.00. Bulk of that is in the lens, I'm sure. For the 1.3K DLPs, the Anamorphic lenses had a LIST price of $10,098.00 When you deal with low-volume lenses...they are quite pricey. The list price for say a Schneider lens for 8/70 projection can be upwards of $19,000. And that is for a straight lens!