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#1 Krstic Zoran

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Posted 26 October 2008 - 01:23 PM

Last few days I tried to find an answer about DigiPrime's MTF.I understood that for HD video most important area is around 56 cy/mm and DigiPrimes have MTF 90% at 56 cy/mm.How MTF looks at 200 cy/mm for DigiPrimes?Is it same like a UltraPrime's MTF,which have 5-10% at 200 cy/mm.

I found on www.cinematography.net this sentence :"A high definition 24P CCD sensor is 1920 pixels or 960 line pairs, the limiting resolution of the sensor is 100 Lp/mm".
Is it means that all spatial frequencies above 100 cy/mm (Lp/mm) are not "captured" with CCD?

What happen with resulting MTF,when we have 2/3" F900+Pro35+35mm lens?Is it less than 100 cy/mm?

In the case of RED ONE camera,we have CMOS with 4520 X 2540 pixels.If we look last quote,we have calculation: 4520 pixels or 2260 line pairs, limiting resolution is less than 100 Lp/mm!?What is resluting MTF for RED ONE with 35mm lenses?Is it limited on less than 100 cy/mm?

Thank you in advance!!!
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#2 David Mullen ASC

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Posted 26 October 2008 - 02:43 PM

You also have to factor in the Optical Low Pass filter in digital cameras, without which you'd get aliasing (moire). Generally you actually don't want to get the maximum line resolution that the sensor and recorder offers because of this problem.

So looking at the lens and sensor resolution and the recording specs are not enough to determine the MTF of the system. Plus there is the additional factor of the display technology that will be used.

Ultimately, I'm not sure getting down to this level of technical detail matters a whole lot for the cinematographer compared to just shooting tests and picking what lens, camera, etc. gives you the degree of detail you want. There are SO many factors that affect sharpness in the chain of events leading to what the viewer eventually sees that trying to quantify it seems like an exercise in frustration because of the variables.
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#3 John Brawley

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Posted 26 October 2008 - 03:16 PM

Last few days I tried to find an answer about DigiPrime's MTF.I understood that for HD video most important area is around 56 cy/mm and DigiPrimes have MTF 90% at 56 cy/mm.How MTF looks at 200 cy/mm for DigiPrimes?Is it same like a UltraPrime's MTF,which have 5-10% at 200 cy/mm.


Thank you in advance!!!



You know I tuned off reading your post after the first sentence.

While it's great to know all the *tech* stuff you can, I find i really want to know how it looks to the eye, how it handles flare, how it handles on the camera.

I try to learn only what i need to know in the uber geek department and then leave it to wire-benders and propeller heads to argue the finer points

There's nothing better than shooting your OWN tests and comparing them in the conditions YOU want to shot in.

jb
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#4 DJ Joofa

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Posted 29 October 2008 - 08:08 PM

I found on www.cinematography.net this sentence :"A high definition 24P CCD sensor is 1920 pixels or 960 line pairs, the limiting resolution of the sensor is 100 Lp/mm".
Is it means that all spatial frequencies above 100 cy/mm (Lp/mm) are not "captured" with CCD?

In the case of RED ONE camera,we have CMOS with 4520 X 2540 pixels.If we look last quote,we have calculation: 4520 pixels or 2260 line pairs, limiting resolution is less than 100 Lp/mm!?What is resluting MTF for RED ONE with 35mm lenses?Is it limited on less than 100 cy/mm?


You need to divide 2260 line pairs with the width of the sensor also to get lp/mm. Can't seem to remember Red's width, however, using 24 mm, it comes out to be 2260/24 = 94 lp/mm.
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