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Thread: LCC method

  1. #1
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    LCC method

    I am finally going to take this seriously, but need some instruction.

    my process:

    1. with a diffuser over the lens, take a shot in the same sort of lighting as the image to be corrected. Adjust exposure to center the histogram (maybe a stop or two more, done with the shutter speed)
    2. repeat this for various amounts of shift, cataloging the images.
    3. here is the part i am unsure of: when the LCC shots come into Phocus, do I apply any corrections to them, such as white balance or exposure, before applying them as a scene calibration? Typically, my H39 back produces as shot images that are way our of white balance into the magenta, even though the back is set to daylight.

    my thinking is that Phocus looks at the LCC file, figures out what and where corrections need to be made to get it all neutral, then applies those corrections, whether the entire image is way magenta or not, it will correct local cast and overall WB in one go


    thx
    jm
    Last edited by jlm; 2nd August 2011 at 09:28.

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    Re: LCC method

    John,

    I am using the back of an H4D50 camera on a view camera and process the captures in Phocus as well.

    Your first process step for LCC is okay. Usually I add 2 EV (shutter speed) for the calibration shot. By the way I am using a white IKEA plastic chopping board as a diffuser

    Once your captures have been imported to Phocus do not yet apply any corrections, neither to the real capture nor to the calibration shot. Just open the calibration shot and activate the scene calibration. Here create a calibration file, name it accordingly and save it. Then go back and open the real capture. Activate scene calibration again and open the calibration file you just created in the step before. Take care that the the calibration and / or vignetting button are checked, i.e. make sure they are active.

    Now you are ready to take any other actions like exposure corrections, white balancing, etc.

    One other thing, make sure both shots, i.e. real capture and LCC capture are taken with the same fixed white balance setting.

    This process works perfectly for me. Good luck.

    Regards,
    Udo

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    Re: LCC method

    thx;

    i got it to work

    jm

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    Senior Member Thierry's Avatar
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    Re: LCC method

    John,

    Just think of the LCC as a subtraction of the color cast in your image. The white shading file you have taken is nothing else than the same camera setting, with the same light and same f-stop used for the image shot. Which means that this white shading shot does produce and have the exact same color cast as the image. Now the software will take this amount of cast present in the white file and subtract it from your image.

    WB is something else, and can be done when the image is corrected.

    Thierry

    Quote Originally Posted by jlm View Post
    thx;

    i got it to work

    jm
    Thierry Hagenauer
    [email protected]

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    Re: LCC method

    Not sure about phocus, but generally you can also use the LCC to subtract dust spots - escape the dust bunnies - if you shoot one along with your actual shot. Conversely if you build a catalog of LCCs then you need to ensure there are no dust bunnies.

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    Re: LCC method

    Quote Originally Posted by jlm View Post
    with a diffuser over the lens, take a shot in the same sort of lighting as the image to be corrected
    I am using a square opaque white plate (15cmx15cm)(6"*6") that I'm holding at 10cm distance of the lens for making the lcc shot. Not easy. Depending on the shift, this card is sometimes not correctly positionned. And depending on the light, a shade from the camera itself can be projected over the card.

    So it took me some time to wake-up :sleep006: and understand that you guys are using a translucent card placed directly over the lens (not at a certain distance) to make those lcc correction shots. Am I completely awake (right) ?

    Still wondering if an lcc correction shot taken when the sun is at your back f.i. can also work perfectly for correctling another shot when the sun is 45 at your right f.i. (supposing same lens, focus distance, aperture and shift) ??

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    Re: LCC method

    Yes, you are fully awake now - the LCC card is placed directly over the lens.

    It is always best to expose an LCC frame for every shot if you make any changes (camera settings, position). Each unique exposure should have a unique LCC frame. However, having a library of LCC frames can work SOME-of-the-time and has helped me in some instances when I was caught shooting not fully awake!

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    Sr. Administrator Jack's Avatar
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    Re: LCC method

    John,

    Here is my .02, but from the perspective of using it in C1, not Phocus. Having a library of LCC files is fine, but I find having the exact correct LCC right after the string of images taken with the same settings makes for very convenient processing. Hence, my procedure is as follows:

    1) Set exposure, focus and desired composition.

    2) Wait for light as needed, take as many exposures as desired.

    3) When done, take the LCC frame.

    4) Repeat for each new composition.

    Step 3 takes about 5 seconds tops as all I have to do is open the shutter 1 or 2, hold the plate over the front of the lens and snap. Done. Now when I process, all my required LCC's are in that session or album, all with the exact same lens settings as the image(s) and all in proper order for the frames I've shot, so no need to hunt them down or import from another library/session/album. Here is my main point: The little extra time I spend and slight inconvenience generating the LCC are significantly less that the time and inconvenience spent hunting down the proper LCC from a library -- moreover, there is no need for me to write down shift, rise, tilt angle and aperture settings for each frame, unless I want them for some reason, like using the Alpa lens distortion tool.

    Hope that makes sense,
    Jack
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    Re: LCC method

    Same here
    I find it easier to photograph them instead of creating a library and having to make note on lens movement and aperture values.
    The downside is increased processing time and using up space for those files
    I am wondering 2 things:
    - when will C1 finally implement batch processing of LCC files and
    - if everybody is actually keeping LCC files since the necessary data after applying resides elsewhere outside the session folder anyway in some preference folder if I am not mistaken.
    Do you guys keep those LCC shots or just the generated adjustment file?
    I noticed when moving a capture folder to a different computer those adjustments files have to be copied manually

    Any thoughts on this?


    Quote Originally Posted by Jack View Post
    John,

    Here is my .02, but from the perspective of using it in C1, not Phocus. Having a library of LCC files is fine, but I find having the exact correct LCC right after the string of images taken with the same settings makes for very convenient processing. Hence, my procedure is as follows:

    1) Set exposure, focus and desired composition.

    2) Wait for light as needed, take as many exposures as desired.

    3) When done, take the LCC frame.

    4) Repeat for each new composition.

    Step 3 takes about 5 seconds tops as all I have to do is open the shutter 1 or 2, hold the plate over the front of the lens and snap. Done. Now when I process, all my required LCC's are in that session or album, all with the exact same lens settings as the image(s) and all in proper order for the frames I've shot, so no need to hunt them down or import from another library/session/album. Here is my main point: The little extra time I spend and slight inconvenience generating the LCC are significantly less that the time and inconvenience spent hunting down the proper LCC from a library -- moreover, there is no need for me to write down shift, rise, tilt angle and aperture settings for each frame, unless I want them for some reason, like using the Alpa lens distortion tool.

    Hope that makes sense,

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    Subscriber & Workshop Member GrahamWelland's Avatar
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    Re: LCC method

    I find it better to keep the LCC images unless you have a separate untouched archive of your raw captures. You never know when you might need to go back and reprocess files, say for example when Phase One added the tech-wide option for LCC processing.
    Remember: adventure before dementia!

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    Re: LCC method

    Quote Originally Posted by rupho View Post
    I am wondering 2 things:
    - when will C1 finally implement batch processing of LCC files and
    We hear you... Real Soon Now(TM).

    Quote Originally Posted by rupho View Post
    Do you guys keep those LCC shots or just the generated adjustment file?
    I strongly recommend saving the original image file. That said, we do support LCC files created back to (and including) by Capture One 3.x, even if they were created on a PowerPC. If we does not work for you, file a bug.

    Quote Originally Posted by GrahamWelland View Post
    I find it better to keep the LCC images unless you have a separate untouched archive of your raw captures. You never know when you might need to go back and reprocess files, say for example when Phase One added the tech-wide option for LCC processing.
    I would follow this recommendation.

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