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Old April 20th, 2007, 04:16 PM   #46
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Marty,

At the heart of the design in most 35mm adapters are 35mm SLR-sized ground glasses. Since the targeted market is for most who cannot afford high end adapters and for those who already owns 35mm SLR lenses, the ground glasses are made to work in that way, i.e. the image area is 36mm x 24mm.

Actual usable image area is debatable since it depends on which adapter, on which camera and on which lenses. These are the vignetting or edge to edge sharpness issues that are well documented in these forums. DOF characteristics for the SLR lenses are still the same regardless of how much image area you use.

Compare that to 35mm motion picture film. The Super35 format has an image area of 25mm x 19mm. Usable area here depends on which aspect ratio you shoot at. DOF characteristics for the format remains the same throughout all aspect ratios.

So as far as your concerns for adapters being shallower than 35mm motion picture film....I highly doubt it. My only concern with these adapters is the use of cine lenses on a 36x24 ground glass.

But that's for another topic another day. Now back to the topic!

Great images with the letus! May I ask which Letus are you using with the A1? The LetusA or FE? Best shots for me were at 0:35 and 1:05!!!! There is a story to those shots! I definitely agree that your kids have the best photographic childhood anyone can get!
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Old April 20th, 2007, 04:55 PM   #47
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Quote:
Originally Posted by Marty Hudzik View Post
On the bright side, if you can use the iris inside the camera to set your exposure properly and you have enough light then you should be able to use just about any fstop you desire with the external lens. In other word, iris on it would simply be used for setting DOF and not necesarrily for exposure. right?
Not only iris, but shutter speed and gain, too !
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Old April 20th, 2007, 04:58 PM   #48
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Originally Posted by Steven Dempsey View Post
:)


Thanks for all the input everyone. There's never a dull moment in my threads :)
Can we look forward to topic next Friday ? :)
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Old April 20th, 2007, 05:48 PM   #49
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Not only iris, but shutter speed and gain, too !
You said the G word!
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Old April 20th, 2007, 05:55 PM   #50
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I understand that the cropping of the image doesn't affect the DOF. I was talking about if the image size projected from the "front" lens was different....caused by distance perhaps. Say light enters through the lens and projects onto a 35mm print. Then say that same lens is mounted on a 50mm print camera and the distance between the lens and the sureface area of the film is increased. At the same settings wouldn't the depth of field be far shallower on the 50mm print?

I am assuming this based on working with a photographer who does amazing portrait work and he used large format film to accomplish great DOF effects. He described to me that this is a byproduct of the film size and not just the lens.

If that is true, then a 35mm adapter that projected the image onto a larger area of the ground glass (potentially furhter away?) should affect the DOF also.

Zooming or not zooming into the ground glass by the camera would not affect this...that would essentially be like cropping the image.

Either way it is a moot point! Just some BS theory!



Quote:
Originally Posted by Zulkifli Yusof View Post
Marty,

At the heart of the design in most 35mm adapters are 35mm SLR-sized ground glasses. Since the targeted market is for most who cannot afford high end adapters and for those who already owns 35mm SLR lenses, the ground glasses are made to work in that way, i.e. the image area is 36mm x 24mm.

Actual usable image area is debatable since it depends on which adapter, on which camera and on which lenses. These are the vignetting or edge to edge sharpness issues that are well documented in these forums. DOF characteristics for the SLR lenses are still the same regardless of how much image area you use.

Compare that to 35mm motion picture film. The Super35 format has an image area of 25mm x 19mm. Usable area here depends on which aspect ratio you shoot at. DOF characteristics for the format remains the same throughout all aspect ratios.

So as far as your concerns for adapters being shallower than 35mm motion picture film....I highly doubt it. My only concern with these adapters is the use of cine lenses on a 36x24 ground glass.

But that's for another topic another day. Now back to the topic!

Great images with the letus! May I ask which Letus are you using with the A1? The LetusA or FE? Best shots for me were at 0:35 and 1:05!!!! There is a story to those shots! I definitely agree that your kids have the best photographic childhood anyone can get!
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Old April 20th, 2007, 06:10 PM   #51
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Originally Posted by Marty Hudzik View Post
You said the G word!
OOPS... and I forgot to mention NDs too...
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Old April 20th, 2007, 06:16 PM   #52
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Originally Posted by Marty Hudzik View Post

If that is true, then a 35mm adapter that projected the image onto a larger area of the ground glass (potentially furhter away?) should affect the DOF also.
Would not affect depth of field, but the farther way you get a 35mm from lens from the GG, the less ability you will have to focus to infinity. In other words, one of issues with any adapter is it set up with the right distance to the GG so the lens has the proper focus range. Too close to the GG, and the lens focuses past infinity, to far away, and you don't get focus at infinity, but you start getting macro focus capability.

Now there are those who are trying larger format, cameras that throw a larger image. I've gotta Kowa Six Ive threatened to do that with, but I think depth of field will be even shalower in those cases, as a normal lens is 85mm, wide is 55. One of these days I'll try the 55 in a makeshift way on my DIY adapter, but I am not expecting much.
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Old April 20th, 2007, 10:18 PM   #53
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Chris I think that you are getting the idea of how it works.

There are two kinds of 35mm that are being talked about as one.

First there is the 35mm Film camera and then there is the 35mm still camera.

The still is about 2 and change times larger than the film. Therefore the 35mm adaptor that uses 35mm still lenses have a shallower DOF because the film plane is twice as big as a 35mm film. That is why a film camera's regular lens is about 20mm and an still camera is about 50mm.

That is what someone meant when they said that the image area of an adaptor is bigger than a 35mm. Meaning that it is larger than a 35mm film plane.

Another thing, by analyzing the still picture you can tell that the focus is behind the eyes.

Most lenses are sharper when closed 2 f stops from fully open. This specially true on under $10,000 video cameras. 35mm still lenses are no exception. You can't expect a $400 lens to be as sharp at full open as it would be by stopping it down a couple of stops.

To achieve a sharper image on a 50mm f1.4 you have to stop down to f2.8 while on a 28mm f2.8 you would have to stop down to f5,6.

Someone did a comparison of some of the 35mm adaptor (sorry I can't remember his name. An English fellow I think) and he came to the conclusion that they all looked better with the lens stopped down from fully open.

Another thing to consider when it comes to digital camera is that it introduces electronic sharpness on the blacks to make the image look sharper.

A more contrasty lighting help the perception of sharpness. In the case of Steven's daughter a harsher lighting wouldn’t have help sharpness because the young girls face is silky smooth. Instead an old wrinkled person with harsher/contrasty lighting would have the image appear sharper.

Sorry about the long rant but I am still at Vegas Airport. I have another 5 hrs before I get in the plane for a 6.5 hour red eye flight ;D
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Old April 21st, 2007, 08:20 AM   #54
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Douglas,
Thanks for the info. I knew somewhere, someone had mentioned something about 35mm lenses being something else or something.....

:)

Seriously I think you hit it. It was that a 35mm still camera is larger than the area of a 35mm film camera. That has to be what I was thinking of......I think.

So potentially some of the perception of sharpness can be caused by the Nikon lenses that Stephen is using. IF he were to stop down it could do 3 things. Expand the "in focus" area of the image, potentially having all of his subject in focus and increase perceived sharpness too.

I do know that my 16x manual lens for the H1 I can see a serious kick in the sharpness pants when I can film at f5.6 vs. f1.6. So I guess optics are optics and I should expect to live by these same rules for 35mm glass too.

Thanks.
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Old April 21st, 2007, 09:05 AM   #55
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Douglas, many thanks for your insight. This has been an education :)
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Old April 21st, 2007, 01:39 PM   #56
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From what I understand, what Doug was saying is that 35mm for a film in production, the width of the image is measured inside of a strip of 35mm film if held vertically, whereas, if we were shooting 35mm film in a still camera, the height of the image is that same measurement, and width is about 2.5 times that height. Do I have that right ?

Not ever having seen a 35 mm film camera up close, this makes sense to me.
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Old April 21st, 2007, 03:16 PM   #57
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That is exactly right, a 35 still shoots +- 36 mm wide while motion film is +- 24 mm wide.
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Old April 22nd, 2007, 07:02 PM   #58
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2.35:1 aspect ratio

Steven -- I understand you apply a matte in post to achieve this aspect ratio, but when you shoot, do you have some sort of markers that remind you where your frame is? How do you frame for this aspect ratio? Put tape marks on your LCD??

Thanks.
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Old April 22nd, 2007, 07:16 PM   #59
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Steven -- I understand you apply a matte in post to achieve this aspect ratio, but when you shoot, do you have some sort of markers that remind you where your frame is? How do you frame for this aspect ratio? Put tape marks on your LCD??

Thanks.
the XHA1 has a 2.35:1 guide bars
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Old April 22nd, 2007, 07:22 PM   #60
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Well I'll be danged, so it does. Thanks, Marlon. Had glanced through the book, didn't find it, but there it is as a menu item...
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