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Aspect Ratio - Lens Relation


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#1 Dominik Muench

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Posted 07 April 2006 - 07:26 AM

Hi,

im just starting to gain as much knowledge with 35mm as possible.

what i havent understood yet (apart form a lot of other things, but one step at a time;) )...are there certain lenses needed to achieve a certain aspect ratio ? i mean, obviously for an anamorphic picture you need an anamorphic lens, but what if i wanna shoot in 1,85 or 2,4, how is that achieved ? do i need special lenses for certain formats or is there just the groundglas with the different framing guides and i frame for whatever i wanna shoot and the rest is done during the printing process or gets masked accodingly ?

sorry if thats a stupid question, this thing just doesnt wanna get into my head :(
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#2 Alex Haspel

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Posted 07 April 2006 - 08:59 AM

as far as i know from my photography background, i'd say you simply need a lens with a big enough "bildkreis" to cover your desired format without vignetting.
unfortunately i don't know what "bildkreis" is called in english, but it's the size of the image projected by the lens on film plane level.

Edited by haspel, 07 April 2006 - 08:59 AM.

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#3 Dominik Muench

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Posted 07 April 2006 - 09:06 AM

i know what you mean :)

so the final projection format gets masked out in print then ?

i see your from vienna, a good friend of mine opened up a gallery there a few weeks ago, have you heard of: http://401rush.com/ ?
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#4 Max Jacoby

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Posted 07 April 2006 - 09:10 AM

Simply speaking you have two kinds of lenses:

- Anamorphic lenses give a Cinemascope aspect ratio (2.40).

- Spherical lenses cover the full height of the negative (1.33), but one can mask (letterbox) them to any aspect ratio that one wants. The most common ones are 1.66, 1.85 and 2.40.
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#5 Alex Haspel

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Posted 07 April 2006 - 09:25 AM

i see your from vienna, a good friend of mine opened up a gallery there a few weeks ago, have you heard of: http://401rush.com/ ?


no, never heard of it. but it says it's located in the lindengasse, just a few houses away from where a good friend of mine lives... i might stop by there before i'll visit him next time...

jaja, die welt ist ein dorf..
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#6 Dominik Muench

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Posted 07 April 2006 - 09:37 AM

Simply speaking you have two kinds of lenses:

- Anamorphic lenses give a Cinemascope aspect ratio (2.40).

- Spherical lenses cover the full height of the negative (1.33), but one can mask (letterbox) them to any aspect ratio that one wants. The most common ones are 1.66, 1.85 and 2.40.



cool thanks, now i got it.
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#7 John Pytlak RIP

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Posted 07 April 2006 - 11:04 AM

Standard SMPTE 59 specifies the image areas for 35mm camera apertures. Standard SMPTE 195 specifies the projectable image areas for 35mm prints. Standard SMPTE 96M specifies the scanned area for all 35mm and 16mm formats.

Once you know the image area on the film, you can choose the lens with the appropriate focal length and coverage.

http://www.smpte.org...tore/standards/
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#8 Dominik Muench

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Posted 07 April 2006 - 11:10 AM

thanks john, it really is time that i learn all these technical details :/
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#9 Laurent Andrieux

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Posted 09 April 2006 - 08:10 PM

so the final projection format gets masked out in print then ?


No, usually it's done "in camera". It's the gate's size that determines what frame the image will be shot with

And yes, there is also a mask in print, but only so that the positive interimage is dark, accordingly to the desired format, that should be the negative format, that is slightly smaller that the neg image as to insure a tolerance.

In some cases, the gate is not at the desired format and the image neg is wider, so there is a mask in print that cutts off the image a bit, but that's not too common.
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#10 Dominic Case

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Posted 09 April 2006 - 10:12 PM

Except for anamorphic (different lenses as you say), you use standard spherical (flat) lenses for all aspect ratios. They are all designed to cover the full width of the 35mm frame (and therefore the full height) and most cameras are masked so that the full Academy area is exposed. That's an aspect ratio of 1.37:1, which isn't normally projected anywhere. The extra image at the top and bottom of the frame that is on the negative, and on the print, is masked out by a mask in the projector. This is cut to give the 1.85:1 or possibly 1.66:1 ratio that you shot for, and which is indicated by the rulings on your groundglass.

If you are using a Super35 process, then the full width of the negative (perf to perf) is exposed instead of the narrower Academy width (which allows room for optical soundtrack on the print). A number of regular (not super35) cameras expose this extra width on the negative as well, although it's not used in the projected image. (The only difference is that for super 35, the lens is centred on the film, for regular 35 it's centred slightly to one side).

Some lenses will show slight vignetting in the corners if they are not designed for the super35 format. Someone else may have information about which lenses this applies to.
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#11 Dominik Muench

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Posted 10 April 2006 - 06:00 AM

thank you guys, the ASC manual couldnt have explained it better :)
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#12 Laurent Andrieux

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Posted 10 April 2006 - 07:58 PM

most cameras are masked so that the full Academy area is exposed. That's an aspect ratio of 1.37:1, which isn't normally projected anywhere. The extra image at the top and bottom of the frame that is on the negative, and on the print, is masked out by a mask in the projector.


Well, may be that depends on countries. I don't say it doesn't happen here, but most of the time we ask and shoot with the gate at the desired format.

Also, we don't trust projectionist operators, so at least the print should be at the desired format so he doesn't project 1.85 if shot 1.66 or the other way round...
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#13 John Pytlak RIP

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Posted 11 April 2006 - 09:51 AM

Well, may be that depends on countries. I don't say it doesn't happen here, but most of the time we ask and shoot with the gate at the desired format.

Also, we don't trust projectionist operators, so at least the print should be at the desired format so he doesn't project 1.85 if shot 1.66 or the other way round...


Standard SMPTE 195 specifically recommends shooting with the full frame 1.37:1 "Style A" camera aperture, and introducing any "hard matte" during printing, and NOT in the camera. The "hard matte" should have an image height of at least 0.505 inches (12.83 mm).
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