supplierdeeply

DNG calibration, again (was Re: pixls.us wants your raw samples)

  • 23 Replies
  • 470 Views
*

Offline philmoz

  • *****
  • 2999
    • Photos
  • Publish
    Re: DNG calibration, again (was Re: pixls.us wants your raw samples)
    « Reply #20 on: 16 / July / 2017, 19:18:13 »
    Advertisements
    One option might be to try and create a collection of proper colour profiles for cameras without native RAW and host them somewhere.
    Should I assume by this you mean that color profiles created with a color card and standard tools are not easy to translate back into exif CAM_COLORMATRIX info for DNG headers?


    It's easy enough to extract the matrices out of a profile created with a colour card; but the results may not be what you expect.
    There is a lot of other stuff in the profile that is used to create the final rendering, the colour matrices are only the starting point.


    For example, the profile I created for the IXUS 310 gives very good results in Lightroom (where the whole profile is used).
    But if I use the matrices from this profile in CHDK, and then don't use my custom profile in Lightroom, the results are actually a bit worse than the C&P matrix in the current CHDK build  :(
    Most of the colours are good, except for the blues which come out too dark and saturated.
    Same happened with the SX40 - that's why I was trying to understand DNG4PS2.


    Quote
    Frankly, the whole idea of getting DNG  exif calibration data for Powershots that support RAW natively is pretty much a redundant exercise, isn't it?   The real fun of CHDK is getting RAW support for the low end P&S cams that would not have it otherwise.  And that needs the color profiles you mention - or the ability to convert those back into DNG CAM_COLORMATRIX values.

    Unless you also think that CHDK DNG gives us something that Canon native CR2 does not?

    Failing the ability to get those into the DNG header somewhat accurately  with CHDK,  a repo of color profiles would make sense. Except for the punters having to pay $70+ for a color card ($25 for a cheap ebay knock-off from china) to calibrate a five year old+ Powershot bought off eBay fo $15 ..

    To quote Gilda Radner "If it's not one thing, it's another".


    Yep - trying to avoid opening too big a can of worms here as well.

    The CHDK DNG does have some use when trying to analyse the raw data (e.g. without this the G1X issue with cooked images would have been hard to identify). But generally for cameras with native RAW it doesn't provide much.

    Phil.
    CHDK ports:
      sx30is (1.00c, 1.00h, 1.00l, 1.00n & 1.00p)
      g12 (1.00c, 1.00e, 1.00f & 1.00g)
      sx130is (1.01d & 1.01f)
      ixus310hs (1.00a & 1.01a)
      sx40hs (1.00d, 1.00g & 1.00i)
      g1x (1.00e, 1.00f & 1.00g)

    *

    Offline reyalp

    • ******
    • 10668
  • Publish
    Re: DNG calibration, again (was Re: pixls.us wants your raw samples)
    « Reply #21 on: 16 / July / 2017, 19:49:39 »
    If anyone ever got DNG4PS2 to work creating a colour matrix, I'd be interested in hearing how.
    I think D10 was the last camera I got it work on. (edit: or not, see below)

    I tried with elph130 and the process always failed.

    Both are CCD (and elph130 using the c&p'd D10 matrix seems fairly usable in raw therapee)

    From what I remember I basically followed the process on http://chdk.wikia.com/wiki/DNG4PS-2/Calibration

    One thing I've wondered about but never really investigated is whether the greater distortion and vignetting on modern cameras causes problems.
    « Last Edit: 16 / July / 2017, 20:42:20 by reyalp »
    Don't forget what the H stands for.

    *

    Offline philmoz

    • *****
    • 2999
      • Photos
  • Publish
    Re: DNG calibration, again (was Re: pixls.us wants your raw samples)
    « Reply #22 on: 16 / July / 2017, 19:57:35 »
    If anyone ever got DNG4PS2 to work creating a colour matrix, I'd be interested in hearing how.
    I think D10 was the last camera I got it work on.


    Any chance you still have the image files?


    Phil.

    CHDK ports:
      sx30is (1.00c, 1.00h, 1.00l, 1.00n & 1.00p)
      g12 (1.00c, 1.00e, 1.00f & 1.00g)
      sx130is (1.01d & 1.01f)
      ixus310hs (1.00a & 1.01a)
      sx40hs (1.00d, 1.00g & 1.00i)
      g1x (1.00e, 1.00f & 1.00g)

    *

    Offline reyalp

    • ******
    • 10668
  • Publish
    Re: DNG calibration, again (was Re: pixls.us wants your raw samples)
    « Reply #23 on: 16 / July / 2017, 20:40:12 »
    Any chance you still have the image files?
    Hmmm. Looks like I was mistaken. The D10 matrix actually came from another user: https://chdk.setepontos.com/index.php?topic=5252.msg54433#msg54433

    I *thought* I remembered doing it successfully for some camera  :-[
    Don't forget what the H stands for.