Re: X-Rite Passport Inaccuracies
Re: X-Rite Passport Inaccuracies
- Subject: Re: X-Rite Passport Inaccuracies
- From: Thomas Lianza <email@hidden>
- Date: Fri, 20 Sep 2013 16:53:47 +0000
- Thread-topic: X-Rite Passport Inaccuracies
"For example, I want the colors in the photo taken with ambient/artificial
mixed light to match with those taken under CFL's at night."
If that is what you truly want to do, then this product is not for you. A
DNG profile is incapable of correcting for lighting that has very poor
Color Rendering Index. This has little to do with inaccuracy of the
target or software. You are just asking for something that can't be done
with a DNG profile. The color checker passport target has a set of colors
which closely align with the hue/saturation/luminance adjustments in
Lightroom. They were put there just for situations that you are
describing. That is where you make the adjustments that are needed when
dealing with a light source that has poor rendering characteristics. It
is not even clear to me that an ICC profile can be built to do what you
are trying to do.
I would be interested in seeing the results of actually using the target
correctly. Go out in the early morning with your two cameras and
photograph the Passport. Create the profile and compare the results from
the two cameras after you apply the corrected profile. Don't compare the
camera data to the reference values on the web site. Compare the camera
data between the two cameras. Now you are testing the target with a
reasonable light source that is rendering the scene very warm. Note that
if you white balance the scene you will completely eliminate the warm
appearance of the original scene.
In your case, I would take up x-rite on their offer to refund your money.
I don't think that you can utilize it for the task you mentioned.
Regards,
Tom Lianza
On 9/20/13 12:18 PM, "Justin Krug" <email@hidden> wrote:
>I was directed here by a helpful photographer whom I contacted regarding
>my issues with the X-rite Passport. My primary purpose for using it is
>to get accurate and consistent colors across different ambient and
>artificial light sources for architectural photography. For example, I
>want the colors in the photo taken with ambient/artificial mixed light to
>match with those taken under CFL's at night. Also, I wanted
>to use it to match color between cameras. On both counts, it has
>failed, and when I subjected it to a test using the reference values
>available on X-rite's website, it did not perform well. I would like to
> get some feedback from experienced members here regarding my findings
>and the response I received from X-rite after sending them details of my
> testing.
>
>Here is an outline of my test:
>1) I took the photo
>of the X-rite Passport under overcast daylight (no artificial light)
>with two cameras, the Canon 5d and Canon 60d.
>2) Then I created custom profiles from each photo using the X-rite
>Passport software.
>3) Next, I applied the custom profile to each photo of the Passport
>4) White balance was corrected in ACR by clicking the WB on the square
>two over from black (#22)
>5)
> Both photos were loaded into Photoshop and color sampler points were
>applied to the blue, green, red, and yellow squares (#'s 13,14,15,16)
>6) The image was converted to Lab color and the a and b values were
>compared against the reference values on X-rite's website.
>7) The same process was repeated for the photo from each camera using the
>Adobe Standard profile
>
>
>What
> I discovered was that the color was just as accurate if not more
>accurate in the Adobe Standard profile. Also, the colors did not match
>between the Canon 60d and 5d after applying the X-rite profiles.
>A couple sample points from the Canon 5d (again, a,b values):
>Daylight
> overcast test-- X-rite: red a,b= 69,41; Adobe Std: red a,b= 61,37;
>Reference (rounded to nearest whole number): red a,b=53,28.
>X-rite: green a,b=-51,39; Adobe Std: green a,b=-47,36 Reference: green
>a,b= -38,31
>
>I
> did the same test under artificial light (CFL I think) and the results
>were a little closer between the Adobe Standard and the X-rite, but for
>$100 and promises of accurate color, I was very disappointed.
>
>After
> contacting X-rite, and sending over my findings and photos, I waited
>over a month to hear back, after their engineers were going to review my
> results. The response I received was surprising. X-rite said "To make
> a long story short, your standards for performance and data analysis
>would not be well suited to use ColorChecker Passport and its DNG
>profiles." And also "ColorChecker Passport software was designed to be a
> simple camera profiling solution for casual and non-professional
>photographers..." The recommendation was that I use an ICC profile as
>opposed to a DNG profile. They also offered me a refund on the
>Passport.
>
>What do you think of my test and X-rite's response?
>Have you conducted your own objective testing? I don't need perfect
>color, but I do want consistent and accurate looking color. Thanks in
>advance.
>
>-Justin Krug
>
>
>
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