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Old August 14th, 2005, 05:57 AM   #1
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total noob here doing research on 35 adaptors, wherever i look it feels like im always coming in on the middle of the action.

no more dummy questions after this, i swear!

what will happen if i attach a 35mm lens by itself?

why all the stuff in between?
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Old August 14th, 2005, 07:35 AM   #2
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If you attatch a 35mm lens straight to the cam you wont get any DOF. it will just be like zooming in your dv cam. It has to do with the 'target size' projecting the image onto a big 35mm frame is what gives the DOF effect, without the 'inbetween stuff' like ground glass, it will be projecting straight onto the tiny ccd without the DOF.

Im sure someone will be along to explain this properly.

Wayne.
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Old August 14th, 2005, 07:41 AM   #3
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Not sure how much you understand about optics, so I'll try and keep this simple.

When you say "35mm lens" - I am assuming you mean a lens from a 35mm SLR or a lens meant for a 35mm Cine camera... correct? Not, specifically a 35mm focal length lens?

The target for a 35mm slr or Cine camera, is much larger than your ccd's on your video camera. Simply attaching them directly to your XL2, means that the part of the focused image that they project onto your ccd is MUCH smaller than intended... you are, in effect ENLARGING the power of the lens. That's why they have a different effective value when attached directly to your xl2. A 'wide angle' lens on your 35mm EOS for instance, will still be a telephoto when directly mounted on your xl2. This is not a problem if what you want is high quality, long lenses for sports and nature shooting.

The point of 'everything in between' is to capture an image that more closely resembles that of a 35mm film camera. Specifically, the shallow depth of field that comes with a larger imaging area, the better optics and even a 'simulated' grain effect.

This is achieved by focusing the image created by the lens ONTO a 'screen' of some sort of translucent material. Typically ground glass, but people are experimenting on this board with polished plastic.

THEN the image projected onto this optical surface is re-photographed by the video camera's optics... so that the shallow depth of field is re-created when captured on tape.

In addition, the optical material can be vibrated, or rotated at high speed. The reason to do this is so that the 'ground glass' or roughed up surface that 'captures' the shallow depth of field image, more closely resembles the optical qualitites of shifting grain patterns that we have come to unconciously expect while watching cinema. It's one of the subtle cues that differentiates 'film' from 'video'. It's one of the reasons that video looks so sharp.

SO - To answer your question. Yes, you can attach a 35mm lens dirrectly to your xl2 in order to get higher resolution and greater focal power, but it won't make it look more 'film like'.

To do that, you need to 'project' the image onto a surface that captures the full cine-like aspects of grain and shallow Depth of Field, and rephotograph it.

Clear as mud?
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Old August 14th, 2005, 08:24 AM   #4
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Quote:
Originally Posted by Richard Alvarez
In addition, the optical material can be vibrated, or rotated at high speed. The reason to do this is so that the 'ground glass' or roughed up surface that 'captures' the shallow depth of field image, more closely resembles the optical qualitites of shifting grain patterns that we have come to unconciously expect while watching cinema.
Actually, the reason to vibrate or spin the ground glass is not to simulate the grain effect of film, but to make the grain pattern of the ground glass dissappear alltogether. Depending how fast it is vibrated or spinning, you may get this effect, but it is not the intention of moving the ground glass, the intention of doing this is only to make the grain invisible to the camera.

If you want a film grain its best to add it in post.

Wayne.
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Old August 14th, 2005, 09:06 AM   #5
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Wayne,

I've heard it described both ways... that because its' spinning so fast, it's 'invisible' and because it's spinning so fast... 'it's more like film'. Clearly, it's better than SEEING the static grain of a non-moving ground glass. Most people don't 'see' grain when they watch a movie, just like most people don't 'see' how dirty their windshield is when they look through it. But it's there.
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Old August 14th, 2005, 09:28 AM   #6
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thanks for the informative and prompt response guys,

yes i meant 35mm slr type, and thanks a million for clearing all that out. :)

what i've picked up thus far is a static adaptor (my interest in this version for its stealth) is more perceptible to grain but after having had a look at this guys pics http://www.enormousapparatus.com/35adapter.htm i am left awestruck! where can i buy something like that? i would be hopeless at diy.
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Old August 14th, 2005, 10:34 AM   #7
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Richard,
I was just clearing things up there. It sounded like you meant that the moving ground glass was designed to simulate film grain, as if that was the intention of the design, which it wasn't. But as you say it could give that effect, especially if you higher the shutter speed then it becomes more visable.

Wayne.
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Old August 14th, 2005, 11:34 AM   #8
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Right Wayne, we're on the same page.
Owen, that link is for a 'satic' work-around. You see in the blow-up where the ground glass (marked as 'gg') is in place in FRONT of the MACRO lenses, that allow the camera lens to focus on the ground glass in front of it. The stills illustrate the shallow depth of field possible with such a work around.

Typically, in a solution like this, the problem that occurs is SEEING the ground glass, as Wayne and I point out. "Hotspots" can occur because of the focal distance - this shows up as a brighter center to to the image, with a kind of 'falling off' vignette towards the image. And of course, when you stack all those macros, ground glass and lenses in FRONT of your normal video lens, you tend to loose exposure range and image quality. But, you get what you pay for...
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Old August 14th, 2005, 11:39 AM   #9
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Finally!

Richard,

Thanks very much for the detailed reply earlier. Being new to this, I had read well over a hundred posts on this forum, searched the web and other forums, and could never find an explaination of what the purpose of the GG addition was. Now I know.

And now that I see how it is used, I think that the reason to vibrate it or spin it, is to eliminate see any imperfection in the screen and just have it look clean. It can have inconsistant grind marks and scratches on it, but they will not be visable if in motion.

Thanks

Mike
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Old August 14th, 2005, 11:53 AM   #10
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I found after reading all the post, nothing compared to going out and doing it, and then re-reading the posts, and then doing it again and getting help here.
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Old August 14th, 2005, 01:25 PM   #11
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Mike,

Like my comment to Wayne earlier. It's not that the mottled specks, or tiny scratches become "invisible"... they become less visible, like the blades of a helicopter. Your mind still sees them, but like the actual grain of filmstock, they are in motion constantly, and this is what adds to the 'fluid' or 'organic' look of the image. If you look closely at the images in the link that Owen posted, you can see the 'mottled' appearance on the out of focus background images. Some people don't mind this, and find it an acceptable trade off in the cost, simplicity and convenience over the moving gg solution.


It's a subjective call, but in my book, the elements that add up to "Film Like" images are 24p, grain, and DOF- And of course all of the 'professional' elements of lighting/composition/acting.

Some people would drop grain out, or put it after D.O.F, but 24p and grain are ALWAYS a part of a cinema image. Shallow depth of field isn't necessarily so. Some DP's and Directors chose to shoot with really deep D.O.F.

But like I said, it's a subjective call, and there's a couple of long threads that argue the various merits. No point in re-hashing them on this thread.
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Old August 14th, 2005, 05:39 PM   #12
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Quote:
Originally Posted by Richard Alvarez
Some people would drop grain out, or put it after D.O.F, but 24p and grain are ALWAYS a part of a cinema image.
That really depends. I mean, if you look at a film on a DVD, The Matrix for example, you dont see any grain from the image, or any that i can see. I think its all down to personal taste of a certain aesthetic, an aesthetic look that suits the style and mood of the story your trying to tell. I have created very different looks via after effects, one that uses every possible filter and effect to remove any sign of grain, another that adds grain for effect. As long as it fits the look of the story.

Wayne.
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Old August 14th, 2005, 09:10 PM   #13
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Not to get into film look, but just try upping the contrast and boom, you've got more film-like video. Gamma and color control are really important. You don't see grain in half the films anyway, I don't think it's worth the bother other than to cover up the sharpness of DV.

Also, having video at 24p versus 30p is nearly indistinguishable. I've shown many clips between those frame rates and many people have said they like 30p better.

That's the last I'll say on film look, I swear. lol.
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Old August 14th, 2005, 09:23 PM   #14
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Something else confusing to newcomers is that most people around here seem to use the term "DOF" incorrectly. For example, above someone stated "If you attatch a 35mm lens straight to the cam you wont get any DOF." That's totally backward and maybe misleading to a newbie. What that person meant was that you'd get LOTS of DOF, and that is not what you want. You are after a shallow depth of field, meaning shallow field of focus, not a deep field of focus.
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Old August 15th, 2005, 05:57 AM   #15
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Quote:
Originally Posted by Bill Porter
Something else confusing to newcomers is that most people around here seem to use the term "DOF" incorrectly. For example, above someone stated "If you attatch a 35mm lens straight to the cam you wont get any DOF." That's totally backward and maybe misleading to a newbie. What that person meant was that you'd get LOTS of DOF, and that is not what you want. You are after a shallow depth of field, meaning shallow field of focus, not a deep field of focus.
Very true, sorry I think that was me. I guess what i meant to say was, you wont get any 'change' in the DOF, without the ground glass.

Thanks for pointing out my mistake.

Wayne.
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