Thread: RED ONE Lense Shading?

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  1. #1 RED ONE Lense Shading? 
    Hi RED Team,

    are there any aims of implementing a lense shading system with RED ONE?

    As now the RED ONE is aware of an individual lense, based on the latest firmware builds and a functional /i system, its at least thinkable and potentially practicable to implement a lense shading system.

    The camera could detect the lense meta data, especially on fixed primes, but with /i in theory even with a zoom - but then way more complicated to measure. Depending on the optics a tyical lense fall-off may be visible by a more or less detectable "vignette" effect.

    To be clear:

    Its not at all necessary to do the typical correction processing inside the camera. Instead it would be possible to apply the correction in the post production, preferably inside RED CINE or similar tools, so that RAW is multiplied with a correction bitmap to equalize shading per pixel.

    I know, this may sound very obsolete to some around, but for making the perfect camera this is typically required.

    I was recently at a camera rental shop and they did measure many professional HD cameras such as the F23, F35 and Panasonic on their large Ulbricht sphere to generate required correction data to compensate for lense errors.

    There are also plugins for certain apps to apply such corrections to images in the post production.

    My point is that we need a typical measurement method, an Ulbricht sphere as uniform radiation source, and an algorythm inside the camera to capture the data. The latter is practically simple, its shooting RAW images on several exposure levels (or at 50% gray at least) to make shading non-uniformity visible. But I guess the specialists at RED don't need any explaination on this :) They know that for sure.

    So my goal would be to see a lense correction being implemented inside the RAW processing (RED CINE etc.), as this is the best step to do it - quality wise.

    Even without /i it would be possible to make a lense correction file per lense and select it manually in the post. /i makes it easier, as it could automatically find the file (or ask for it if required) to apply the correction.

    One more thing to say:

    I do in NO WAY say that any lenses out there are bad and need the correction, especially not the RED lenses. But lense shading is *normal* and even the best lenses can show small artefacts in that way. And as RED ONE is the Indy camera of choice now, its just *normal* as well that lenses of minor quality are used in productions, such as old lenses, photo lenses, special purpose lenses etc. Often lenses that do not exactly match the field of view of the RED ONE sensor in the particular case. And exactly for this situations a lense shading correction could result in better images, reducing vignetting artefacts to a minimum.

    So RED users who feel their need for lense shading correction could go to a service center (rental houses for instance) and measure their camera / lense combination with an Ulbricht sphere in a "standardized measuring environment". As a result they get the files for their lenses to be perfectly corrected.

    Cheers,
    Axel
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  2. #2  
    Senior Member NateWeaver's Avatar
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    Sometimes we like to choose our lenses based on their imperfections...
    Nate Weaver
    Director/D.P., Los Angeles
    www.nateweaver.net


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  3. #3  
    Yep, Nate, you are right :)

    But sometimes poeple can't afford the perfect lense and use the one on hand.
    Lense shading is not a myst, but making it easy and right sometimes is one.

    Axel
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  4. #4  
    Ah,

    and you can technically convolute the different lense shading correction bitmaps to make a perfect lense look like the imperfect one. And that in post...

    Puts just another option into play.

    Axel
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  5. #5  
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    I think it would be far simpler to develop a set of lens files for your post system with preset "corrections." Then just take some decent Script Supervisor notes or even mark it on the slate or camera report. It's not like FX houses haven't been doing exactly this sort of thing for years.
    Mitch Gross
    Applications Specialist
    AbelCine

    mitch@abelcine.com
    212-462-0100
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  6. #6  
    Hi Mitch,

    in general I'd agree with you, but - as an owner of a post house - I am interested in optimizing workflows.

    Your argument is likely the same as if I would say people have used film for years, so where is the need for a RED? I am interested in improving things and making them easier, and with less errors. But you are right, we can continue doing it the old way for the time being.

    Just sayin :)
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