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35mm DoF sans the film grain?


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#1 darrin p nim

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Posted 27 December 2006 - 11:06 PM

as cinematographers im sure we have all considered it. Certain productions can call for the clean look of HD and some times film is the "look" that may be necessary. What if the production calls for the Depth of Field and a grainless clean image? but because everyone wants the film look this has never been mentioned, atleast not with the hvx (as far as i know). So is it possible?

Ive only really brought the idea to a few and ive heard mixed replies but follow me here. If you were to take the P+S adapter and some how remove the ground glass, would you still be able to attain an image? i think that if you have your zoom and your focus set (to where the ground glass should be) that you will. I do understand that you have to have the ground glass to set the zoom and most of all the focus. But theoretically speaking, it should work.

Aside from that idea, is there another way to achieve the DoF without the grain?

Thanks.
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#2 David Mullen ASC

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Posted 28 December 2006 - 12:28 AM

The lens image is set to focus on the film plane, which in this case, is the groundglass. So you sort of defeat the whole point of the P&S Technik if you remove the groundglass, which is to capture the field of view / depth of field of that lens as if it were on a 35mm camera. Without the groundglass, the field of view becomes more much telephoto for a small imager, assuming you can even get the lens to focus onto the prism block/CCD.

You might as well just use the HD zoom lens if what you want is more depth of field.

But sure, if you want a grainless image with a lot of depth of field, an HD camera with a 2/3" CCD or smaller would be one method. Or shoot in 35mm on slower-speed film and a s---load of light!
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#3 Mike Panczenko

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Posted 28 December 2006 - 12:49 AM

I think what he means is to remove the actual ground glass, but leave the optics set up to focus where the ground glass would have been, so you'd lose the grain of the glass, but still be able to focus on the rays. I've wondered sometimes about a similar situation, and while I suspect removing the ground glass would open up all sorts of other problems, from a physics standpoint I'm curious as well as to whether a ground glass is needed in this setup. It seems like it would work, but I've never been able to get an answer.
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#4 darrin p nim

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Posted 28 December 2006 - 05:14 AM

yes, what mike says is what im questioning. my question is mainly in regards to the HVX and the P+S. I understand i could use other methods to essential get the end result but that would defeat the purpose of this idea.

yeah i could use the factory leica lens on the hvx and zoom in but that wouldn't give me true (or close to exact) FoV nor DoF. I guess what im saying is the ground glass in the P+S is only there for a couple important reasons:

-to give the image the film like appearance
-to give the focus point for the connecting camera

"magically" remove the ground glass and the image should theoretically be grainless and in focus. correct?

i guess im trying to spark the development of a grainless 35mm lens adapter, if at all possible.
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#5 darrin p nim

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Posted 28 December 2006 - 05:14 AM

double post...

Edited by Darrin P Nim, 28 December 2006 - 05:14 AM.

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#6 olan

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Posted 28 December 2006 - 09:23 AM

double post...



Hello,

You can?t remove the ground glass and keep the DOF. David is right the effect without the ground glass would be a kind of field of view more much telephoto. Believe me I already tried with my homemade adapter it doesn?t work. If you want to have the DOF and no grain you can use the movietube adapter, the ground glass is in wax and there is almost no grain. You can find all the info you need on http://www.movietube.com

Cheers

olan & olivier
director/dp/editor/colorist
brussels. belgium
www.theblacksheep.be
http://dp.theblacksheep.be
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#7 David Mullen ASC

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Posted 28 December 2006 - 11:34 AM

If you could remove the groundglass and make these adaptors work better don't you think they would have done that???
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#8 Mike Panczenko

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Posted 28 December 2006 - 12:03 PM

If you could remove the groundglass and make these adaptors work better don't you think they would have done that???


Well that's what I was saying, it would open up a whole new can of worms, I was curious more from a physics/optics perspective.

Continuing on that topic, why would the image be larger if the ground glass was removed, but the focal plane remained the same?
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#9 David Mullen ASC

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Posted 28 December 2006 - 12:17 PM

Well that's what I was saying, it would open up a whole new can of worms, I was curious more from a physics/optics perspective.

Continuing on that topic, why would the image be larger if the ground glass was removed, but the focal plane remained the same?


I meant if you thought you could use it as a simpler adaptor to put a 35mm lens onto a 1/3" CCD prosumer HD camcorder.

What you guys are describing sounds like the principles of an aerial image optical printer, a concept that I never could fathom either, how to focus onto an image formed in midair with no surface to project onto.
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#10 Daniel Sheehy

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Posted 28 December 2006 - 02:27 PM

I meant if you thought you could use it as a simpler adaptor to put a 35mm lens onto a 1/3" CCD prosumer HD camcorder.

What you guys are describing sounds like the principles of an aerial image optical printer, a concept that I never could fathom either, how to focus onto an image formed in midair with no surface to project onto.


I was reading about that idea in Kris Malkiewicz's 'Cinematography'.
It obviously works, so in theory it must be possible to adapt the principle for the lens adaptor. I don't think it would affect the apparent DoF, as that is decided be the lens, not the projection surface.

But David has a point, if it is really that simple, why hasn't it been done yet?
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#11 Mitch Gross

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Posted 28 December 2006 - 03:11 PM

In theory it could work, but in practice never. To focus an image arially, you must maintain a precise relationship between the optically surfaces. That's impossible when you're removing the lenses on the front of one of these adapters and removing the camera from these adapters. It would be a mightmare to realign and they would lose optical reference every time the camera was powered down.

Try the MOVIEtube if you don't want the "grain" from the Mini35 groundglass.
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#12 Mike Panczenko

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Posted 28 December 2006 - 03:20 PM

It's a quirk of our brains that we can only see virtual images and not real images. The rays must enter our eyes, but it seems that our brains filter out real images. I once asked an optometrist why that is, and he suggested that because real images are upside down and backwards as opposed to how they really are, our brains filter them out so that we would not be confused to the true orientation of things.

The purpose of the ground glass in a film camera is to have a textured surface for our eyes to focus on. Because it is ground and textured our eyes are able to focus on that surface and see the image.

But regardless of whether or not the screen is there, the rays are still refracting in the same way. The rays would still meet and the focal plane regardless of the film or the ground glass being in the optical path. And once it gets past the ground glass, they diverge.

In many ways it's identical to the actual object the that is being filmed. The photons are emitted in all directions from one point. The lens then brings them back to a point at the focal plane. After they converge at the focal plane, they diverge again. So coming from the actual object, the rays start at a point and diverge. Coming from the focal plane, the rays start at a point and diverge, so either way, a lens can be used to focus those rays, regardless of whether a material object is in the optical path.

And I don't think he wants to affect the depth of field, but rather get rid of the "grain" the 35mm adapters have on the ground glass.

I think they reason that the adapters use the ground glass is because it is mechanically easier to troubleshoot. If the ground glass is out of place, it is easier to fix in some ways because you know where it should go, or at least the general vicinity, whereas if there was no ground glass, if the focus was off, it would make fixing it much more difficult as there is no place where the image actually can be seen. You would have to spatially measure the elements of the optical system. I can't think of any other reason than that. I'd be curious to see if anyone has other ideas.


Edit:
Beat me to it Mitch. Thanks for the explanation!

Edited by Mike Panczenko, 28 December 2006 - 03:21 PM.

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#13 darrin p nim

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Posted 29 December 2006 - 01:20 AM

But David has a point, if it is really that simple, why hasn't it been done yet?


my answer for that is: the industry is so preoccupied in recreating the film-look that the idea has been either over-looked or unrealized.

correct me if im wrong but my understanding of the P+S's ground glass is that it is just a perferated piece of plastic (or something of the nature, is it actually glass?) that sits, to put it simply, inbetween the camera lense and the 35mm lens on the adapter. The image is never captured from the ground glass itself, moreso from an image reflecting inbetween the 35mm lens and the ground glass, on a mirror i believe. does that sound right?

now taking into consideration what you guys have said, my question is if it necessary to have a plain at the point of the ground glass, what if the ground glass was replaced with a clean piece of glass that didnt oscilate? would the system still work and give the desired look?
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#14 David Mullen ASC

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Posted 29 December 2006 - 02:07 AM

Yes, the image is rephotographed off of the groundglass, hence why it has to vibrate or shake to hide the granularity in the groundglass surface, the granularity that allows the image to appear on the surface of the groundglass in the first place.

There are a half-dozen competing technologies to the P&S Technik and do you really think they all overlooked the idea of using clear glass??? With so many people working in their basements to invent some variation on the P&S Technik adaptor, don't you think it odd that not one of them has done what you are suggesting? A clear glass that didn't have to vibrate or shake would have made the P&S Technik simpler & cheaper to build, so why didn't they do that rather than deal with a groundglass?

What do you think you'd see in a movie camera viewfinder if the groundglass was replaced by clear glass? A sharper, better image of what the lens was seeing?
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#15 darrin p nim

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Posted 29 December 2006 - 04:40 AM

Well i hope im not offending you David, I guess i just was unclear, my knowledge on the internals of the P+S is obviously limited, that is really the reason i posted this. To ask. I probably am wrong with my theory that it was overlooked, it's just that i do strongly feel everyone is looking for that film-look and the grain just adds to the look, so why bother getting rid of it? you know? Even if i tried to answer any of your questions, Im sure they are rhetorical, so ill save myself the embarassment. Not that it matters, but in my defense, im still learning. I posted this to get some questions answered, had i come off demeaning and arrogant, I apologize but this was just one way i had to learn.
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#16 David Mullen ASC

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Posted 29 December 2006 - 01:09 PM

The granularity from the groundglass screen was not originally intended/invented to add a "film grain look", it's an after-the-fact justification for the artifact of having to rephotograph the projected image off of a groundglass. "Oh, that groundglass texture.... well, don't you think it sort of reminds you of film grain? Maybe? Sort of?"

If the texture of the groundglass was desirable, P&S Technik wouldn't have spent so much time, money, and research trying to find ways of vibrating, shaking the screen to hide it!
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#17 darrin p nim

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Posted 29 December 2006 - 04:27 PM

If the texture of the groundglass was desirable, P&S Technik wouldn't have spent so much time, money, and research trying to find ways of vibrating, shaking the screen to hide it!


i dont feel that its meant to be hidden, i feel that P+S vibrates/shakes it add to the aesthetic of the film appeal. film grain artifaction is never the same for every frame, it is always changing, i think that P+S developed the movement to mimic that. i believe this because other 35mm adapters do not have spinning GGs like the P+S, yet im sure theyre GGs are more finely perferated or something to have less distracting artifacts.
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#18 David Mullen ASC

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Posted 29 December 2006 - 04:50 PM

i dont feel that its meant to be hidden, i feel that P+S vibrates/shakes it add to the aesthetic of the film appeal. film grain artifaction is never the same for every frame, it is always changing, i think that P+S developed the movement to mimic that.


No, they did it to reduce the effect of a static granularity pattern from a groundglass over the image, not to create a film-look effect. The cheaper adaptors basically are living with the inevitable static pattern or are using finer-grained material to make it less objectionable, but P&S Technik's approach of moving the groundglass has nothing to do with adding a film-grain effect. Film grain does not shake or vibrate or spin anyway and the idea is that the movement is meant to remove the groundglass granularity as much as possible.

You're just confused by marketing hype trying to justify a mechanical artifact as an intentional effect.
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#19 Kyle Stueve

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Posted 07 May 2009 - 01:55 PM

No, I would recommend not removing the glass from the adapter. Even if you do screw with it and remove it, you risk realigning it wrong. This could lead to more serious problems later because of that as well. The glass is the purpose of the adapter and is what you use to get the DOP, I would only imagine getting a magnified zoom effect. Bottom line, opening up the adapter is not smart.
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#20 Gabriel Bordas

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Posted 08 May 2009 - 03:41 PM

In reality there are 2 ways of doing real Dof witout a 35mm adaptor. But you simply must change the camera. I now that it´s not the point here.
The first technique is to shot at a very high frame rate with variable-sincro start-stop focus. In post-pro using the fluid motion you make a 24/25 conform based on all the frames in all the focus range. With the same technique it´s posible to do 2 or more exposures in a single take with a special mecanic or electronic toy.
The other technique it was invented by Adobe. It simply a special lens and software. In post you can select the range of dof as you please.


All the best

Gabriel Bordas DP
Terra Vision Pictures - Barcelona - Transilvania
www.terravisionpictures.com
gabriel@terravisionpictures.com

Edited by Gabriel Bordas, 08 May 2009 - 03:44 PM.

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