Cinemascope for DVX

S

Shaw

Veteran
hey guys,

I've been working on a small project in my spare time. I'm getting clos(er) to buying some parts for my project so I thought I would share the idea and see what others think.

I've been working on an anamorphic adapter for these homebuilt mini35 systems. I'm currently working on a mini35 with a wax intermediate rather than GG but that's a different story.

Anyway, it hit me one day that there is no reason that you couldn't build a *rear* anamorphic adapter. This has numerous benefits over any front mounted system.

1) Any 35mm lens can be mounted to it regardless of its front lens diameter
2) It's smaller than a front adapter
3) It would allow the use of any 35mm lenses you already own rather than having to go out and purchase multiple adapters (I'm not sure they even make 'em for 35mm lenses). Definitely a plus!

Would anyone be interested in this sort of system? I may make a few extras if the initial test works out that I could sell for a rather cheap price since I'm not really in need of profit - it's being done merely out of interest on my behalf.

I'll post some screenshots as soon as I can.

I'm just very excited about the possibilities of full res 2.35 footage. Especially if you were to stretch it out with photozoom before importing! The possibility exists for some sweet footage!
 
Re: Cinemascope for DVX

I brought up this exact idea earlier this year so do a search on the subject for all the tech details but basically your going to need whats known as achromat cylindrical lens with a horizontal power of 1.78. This is a strange number I know but it will bring a 2.35 image down to the aspect ratio of your CCD. Either put it right next to the GG and have it removeable so you can shoot 2.35 with the option of full screen or simply turn the plano side of the lens into your GG and make it a dedicated 2.35 adapter.
 
Re: Cinemascope for DVX

Really? Wow, guess I should search on these things!

Yeah I'm aware of what I will need (mostly). I'm still finalizing the design but I've had access to some excellent lens design software so I'm pretty much set in that regard. It's just a matter of tweaking the design for maximum light transmittance and abberation control while still working with readily available parts. It's easy enough to design a great lens with custom glass but that's far more expensive than I want to approach!

I'm not entirely sure why I would want to shrink the image down to the size of my CCD. Since it is an adapter for a mini35 I won't need to fit the image directly onto the CCD (want to keep that nice 35mm DOF!).

Using the plano side as a GG is a very interesting idea... I'm just not sure that would work with a wax disk rather than a ground filter.
 
Re: Cinemascope for DVX

Shaw, sounds like a great idea, but I would be more interested in just a 1.85 rear anamorphic adapter, that would allow the same compatability with 35mm lenses. Are you planning on making this rear adapter switchable, allowing both aspect ratios?
 
Re: Cinemascope for DVX

Hi scharky,

I hadn't thought about that but I certainly could add that functionality easily enough. In fact I could probably split the adapter into several elements: 1 main element and a second element that you attach which dictates the final compression ratio. I'm not sure how practical this would be. I'd have to look into it. If worst came to worst adapting the design for a different compression ratio is easy. Just plug in the numbers and let the computer spit out the adjustments. I can at the very least provide you with plans for such a piece.

In fact, for those who don't have a mini35 type system I could probably add a little relay lens which would allow you to connect the thing straight to the DVX's threads. You wouldn't retain the 35mm depth of field but you would get the use of 35mm lenses, the full field of view, and the anamorphic compression. Would anyone be interested in this? If anyone is I'll make up some plans to give out for free. If there is enough demand I could make a few myself I suppose.

In any case I'll willingly pass out plans to any of these ideas or variations thereon free.
 
Re: Cinemascope for DVX

Cool! I'll keep you guys updated as I progress. I have quite a bit of spare time now that finals are over (thank goodness) so I should be able to work quickly!

As an aside: I think some worry about how to utilize a 2.35 video source as it doesn't conform to the DV spec. Footage captured this way is actually quite easy to use. You just have to stretch the footage out to 2.35 and then import it into a 16:9 timeline. Should work perfectly. I know it works in Vegas at least. Still have to try Premiere. This stretch to 2.35 could also benefit from Photozoom Pro! While not being upressed the footage is being reinterpreted by photozoom so it will pass on a bit of that sharpness it seems to produce.

Having all your pixels put into a 2.35 image instead of cropping would do wonders, I believe, for viewing on HD or widescreen TVs. You're cramming all these pixels into a smaller percentage of the HD screen so your footage isn't nearly as spread out.
 
Re: Cinemascope for DVX

You wouldn't notice better quality on an HD set though, because your source would be re-shrunk to an anamorphic, letterboxed image. You'd lose any extra resolution that you originally had gained, because it will become just 16:9 footage with letterboxed bars.

You'd likely get nice artifacts though, the horizontal lens flares and such typically associated with cinemascope films, and THAT would be a pretty nice aspect!

But for resolution, you'd be just as well off (if not better off) shooting with the 16:9 adaptor and letterboxing the footage to 2.35:1
 
Re: Cinemascope for DVX

I think you misunderstood. What I was talking about gives you 35mm DOF and 2.35 anamorphic. Basically imagine a miniture version of the Panasonic anamorphic lens (about 24mm x 36mm) placed either right before or right after the GG in any given Mini35 adapter. It allows the image you record on the GG to be anamorphically squeezed while still maintaining the DOF.

Now if DONT want 35mm DOF but a lens just like the Panasonic anamorphic that does 2.35 instead what you need is a much larger lens than the one above. It will have to anamorphically squeezes the image by a factor of 1.78. While they are rare they do exist. Check ebay and google for "anamorphic" and "1.78". I found the toughest issue when trying to make one of these was finding a lens that had a large enough rear exit element for the DVX to look thru. If not try Edmunds. They have cylindrical lenses but they arent achromats.

This is a tough project. What software are you using for your optical design? I've never gotten that technical so maybe you could use it to make one thats sure to be fully zoom thru. Thats way beyond my knowledge. If so you would have something very marketable and I'd buy one for sure. Let us know how things progress.
 
Re: Cinemascope for DVX

Brett,

I have access to software known as OSLO
http://www.lambdares.com/products/oslo/index.phtml

I'm not sure that adding a small adapter with the same design as the Panasonic a-focal version would work for a rear adapter. As far as I know the panasonic uses (in its most basic form) two cylindrical lenses. This of course gives you all sorts of interesting focus problems (as we know!).

If you were to put this immediately behind or in front of the GG you would end up with an image much smaller than the full 35mm frame size. You would also get a lot of vignetting as you would suddenly be acquiring a much wider field of view.

A rear adapter would bypass all of these constraints but with one downside: you loose one full stop. Whether this is enough to make any design useless on a mini35 has yet to be seen. Haven't you worked with a mini35 before Brett? Has anyone else? How many stops would you say you loose through these systems (typically) - 1 or 2 stops? An adapter that was 1.85 would loose slightly less light.

It works in essence like this:

ANAMORPH.GIF


What it does is expand the vertical axis by whatever magnification you wish to have. You loose part of the image (as it extends beyond the 35mm size) and thus some light but you get a squeezed anamorphic image. This also cuts the field of view down slightly in the vertical axis. Nothing very bad though.
 
Re: Cinemascope for DVX

I completely understand what your saying and see whats happening in the picture. Thats basically a plano concaved cylindrical lens. What I was recomending was the opposite - a plano convex cylindrical lens. If your looking down on the two elements put this on next to the ground glass
like this: || |)
Not like yours: || )|

By doing so you dont loose any light because its not streched out. Instead its squeezed in. This makes the image slightly BRIGHTER. The other issue of vignetting doesnt occur either because having a PCX cylindrical lens right next to the GG doesnt widen the FOV like a typical anamorphic lens. What its doing is taking that 24mm X 36mm image on the GG and squeezing it down to something like 24mm X 20mm. You frame up 20mm X 13.5mm with the DVX lens.

Anyways you can see why I dropped this idea. While it will work the image you end up shooting is just too small. Your idea is better in that sense but has a light loss problem. So theres a trade off.

The other idea is putting a anamorphic lens in front of the 35mm lens but it would be nearly impossible to make it work with all of the lenses someone would want to use.
 
Re: Cinemascope for DVX

Mmm, ok, I see what you are saying now! That's a very interesting idea. It's just too bad that the image size is so small. If we could find a grainless GG then this wouldn't be nearly as much of a problem. Though, we might get more distortion from the necessary high magnification macro lens (higher powered than a normal mini35 system that is to say).

So much hinges on the darn GG! There has to be something out there which is grainless. There just has to be. I wonder if one could use semi-rigid polyurethane for this? Hmmm....

Thanks for the comments Brett. It's great fun to have others to discuss this sort of thing with!
 
Re: Cinemascope for DVX

Same goes for you. One work around this small image size is to use medium format lenses. They project a image much larger on the GG so after you anamorphically squeeze it you still are working with a large image. In fact its still much larger than 24mm X 36mm. Check it out.

-Brett
 
Re: Cinemascope for DVX

That does seem like an excellent idea brett! It would allow me to use a rear anamorphic adapter (your version would be the choice in this case) and a mini35 without sacrificing so much light (the major downside to the whole project of course).

I just don't have any medium format lenses at the moment which will make experimentation hard ;). Do you know of any place to find some fast, cheap, medium format lenses to purchase? I checked ebay but there is a very, very limited selection (at the moment).

Out of curiosity, are MF lenses generally slower than 35mm? Also are wide angle lenses much more expensive? I've looked around but can't seem to find anything wider than about 30mm (though what would this equate to in 35mm terms?).
 
Re: Cinemascope for DVX

Shaw,

without getting into small details one could say that you could divide the focal length of the medium format lens (assuming a 60mm wide image for the medium format lens and cropping the 35mm SLR image to achieve a 1.33 aspect ratio instead of the original 1.5) by two, making the 30mm medium format lens roughly equivalent to a 15mm 35mm SLR lens.

Medium format lenses are neither fast nor cheap. F2.8-F4 is normal with the shorter focal lengths tending to be slower. There are a few F2 lenses but they are rare and very pricey.

Browse the medium format lens section of a site like B&H to see what is available.

One other thing, more and more digital and 35mm SLR lenses have no iris control ring, so the iris cannot be set manually (Canon EOS and Nikon Digital lenses for example).

Bill Turner
Century Division
Schnieder Optics
 
Re: Cinemascope for DVX

Thanks for the info Bill. I was afraid that would be the case :-/

Ah well, you get what you pay for I suppose! Now I just need to run some calculations and see how much light I would actually get through a whole setup like this with an f2.8 medium format lens (with a compressed image).
 
Re: Cinemascope for DVX

Something else just occured to me:

In still photography people have been known to take images with the lens cap on. These images (various processes) are then combined to help remove, accurately, thermal noise and noise from dark current. Could something similar work with a ground glass? That would be a _very_ helpful means as we could use just about and GG..
 
Re: Cinemascope for DVX

Shaw,

Interesting idea, if I understand it, you are suggesting the possibility of using a computer program of some kind to remove the "grain" caused by the ground glass. The grain size limits the resolution so even if you removed the "grain" the resolution wouldn't improve unless you also did a computer enhancement of the image.

I know from talking to Nancy Schreiber that taking the DV movie "November" and bumping it up to HD for Sundance (a process which includes enhancing the image) cost about $75,000 if my memory serves me.

My point being that it seems the goal is trying to find a "cheap" Mini 35 solution and my guess is that frame by frame ehancement runs counter to that goal. If I am missing something here, please set me straight.

Bill Turner
Century Division
Schneider Optics
 
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