Re: X-Rite Passport Inaccuracies
Re: X-Rite Passport Inaccuracies
- Subject: Re: X-Rite Passport Inaccuracies
- From: Matthew Ward <email@hidden>
- Date: Sun, 22 Sep 2013 10:24:03 +0100
Hi
where are you getting your Lab values from if you are using Lightroom?
Best
Matthew Ward
On 20 Sep 2013, at 20:43, Justin Krug <email@hidden> wrote:
> I had sent this to Tom without CC'ing the list.....not sure what the protocol is in this case, but I thought I'd send it along in case someone else wanted to chime in as well. Thank you for all the input thus far.
>
> Tom
>
> Thank you very much for the detailed response. If I'm not mistaken there are two issues at play.
> 1)
> First, there is the problem of matching color across different light
> sources (including 100% CFL's), for which I understand you to say that's
> outside of the capabilities of the Passport and other DNG profiles.
> I'm better off using the HSL sliders to get the color right there. To
> do that I would probably set some color sampler points on swatches and
> get the RGB values close between different shots of a color checker
> under each light source. However, it seems like Lab would be a better
> color space, so I could look at color only, and that's not available in
> Lightroom. Otherwise I'm not sure of a reliable way to do that.
>
> 2)
> Then there is my test, which I first conducted in daylight (overcast)
> with the 60d and 5d. In that case the Passport proved to be no better
> than the Adobe Standard Profile in correcting colors or matching colors
> between cameras. Am I mistaken in thinking this is basically the test
> you were suggesting I do? Or is there something special about warm
> daylight?
> Here is the data from my test--
>
> The color values after correction with the Passport (given in a,b values of Lab):
> 5d: green= -51,39 red= 69,41 yellow= 4,86 blue= 27,-65
> 60d: green=-42,34 red= 60,39 yellow = 4,79 blue= 25,-53
> The color values prior to correction with the Passport, using Adobe Std (given in a,b values of Lab):
> 5d: green= -47,36 red= 61,37 yellow= 1,87 blue= 18,-59
> 60d: green= -38,31 red= 56,33 yellow= 2,78 blue= 16,-46
>
> I cannot discern any appreciable change in the difference between the color values of the 5d and 60d using the Passport.
>
> Thanks,
>
> Justin Krug
>
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