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  #1  
Old September 23rd, 2010, 06:08 PM
Doug Kerr Doug Kerr is online now
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Default The Datacolor SpyderCheckr

Datacolor, whom we mostly know as the manufacturer of the Spyder series of monitor and (more recently) printer colorimetric calibration gear, has introduced a camera calibration package, the SpyderCheckr system, comparable in general purpose to the X-Rite Passport system described a while ago in this forum section. It was introduced at this year's Phototokina.

The DPR article on the product is here:

http://www.dpreview.com/news/1009/10...pdercheckr.asp

The centerpiece is a folding color target, comprising 48 color patches (8 of them neutral). The patch panels are reversible and replaceable, and have a gray target (and gray patch row) on the reverse side.

A clever touch is an indicator on the front of one of the panels that is presumably sensitive to ultraviolet light, and changes color to advise when the accumulated UV exposure on your panels is such that they might be expected to have faded enough that the panels should be replaced.

There is also a software package that runs as a plug-in to Photoshop, Photoshop Elements, and Lightroom.

The drill is that we take a shot of the target, and then open the raw file. We manually crop the image to the general span of the target, white-balance color correct it (using one of the neutral patches in the target), and make white- and black-point adjustments based on the black and white patches.

The we ask the primary app to send the image for editing to the SpyderCheckr plugin.

There, we can help the app find the centers of the 48 patches if it hasn't figured that out quite correctly by itself. We then ask it to analyze the file and develop a camera calibration (and Datacolor seems to carefully not call it a profile - well, not often).

It evidently does this in terms corresponding to the slider settings in the "HSL mode" color adjustment panel in Photoshop and related applications.

This suite of settings is apparently then saved as a Photoshop "preset" (that is, settings file) so it can be called up and invoked on actual subject shots.

A video showing the use of the system is here:

http://www.youtube.com/watch?v=KV7k5_f3eM8w

Best regards,

Doug
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  #2  
Old September 23rd, 2010, 06:17 PM
Andrew Rodney Andrew Rodney is offline
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Quote:
Originally Posted by Doug Kerr View Post
A clever touch is an indicator on the front of one of the panels that is presumably sensitive to ultraviolet light, and changes color to advise when the accumulated UV exposure on your panels is such that they might be expected to have faded enough that the panels should be replaced.
The question is, does it work, is it representative of the fading of the patches and are the patches well made in terms of the colorimetry, consistency and ability not to fade?

Quote:
It evidently does this in terms corresponding to the slider settings in the "HSL mode" color adjustment panel in Photoshop and related applications.
Instead of building a DNG profile OR updating the Calibration tab. The HLS controls are quite different, in the processing order in Adobe app’s. Is this a good idea? Should not “calibration” in terms of raw processing in Adobe app’s happen either with the calibration tab (going way back to the Bruce Fraser article that lead to a number of scripts to do this) or using a DNG profile?

That DataColor’s last two product releases appear to be (IMHO) rip-off’s of existing products rubs me the wrong way. Innovation doesn’t seem to be on their radar.
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  #3  
Old September 23rd, 2010, 06:43 PM
Doug Kerr Doug Kerr is online now
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Hi, Andrew,
Quote:
Originally Posted by Andrew Rodney View Post
Instead of building a DNG profile OR updating the Calibration tab. The HLS controls are quite different, in the processing order in Adobe app’s. Is this a good idea? Should not “calibration” in terms of raw processing in Adobe app’s happen either with the calibration tab (going way back to the Bruce Fraser article that lead to a number of scripts to do this) or using a DNG profile?
I suppose that the attraction of the "HSL" approach is that it has 24 degrees of freedom vs. the 7 degrees of freedom in the camera calibration paradigm.

Quote:
That DataColor’s last two product releases appear to be (IMHO) rip-off’s of existing products rubs me the wrong way. Innovation doesn’t seem to be on their radar.
Looks that way here as well.

Best regards,

Doug
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  #4  
Old September 23rd, 2010, 06:46 PM
Andrew Rodney Andrew Rodney is offline
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Originally Posted by Doug Kerr View Post
Hi, Andrew,
I suppose that the attraction of the "HSL" approach is that it has 24 degrees of freedom vs. the 7 degrees of freedom in the camera calibration paradigm.
You’d have that anyway (its not like those controls disappear). The question is, WHERE in the processing chain should a so called “calibration” take place? Bruce Fraser and others, prior to DNG profiles, did this in the Calibration tab. DNG profiles do this in a similar area in the processing chain. My understanding is, calibration and DNG profiles take place prior to any of the sliders above. If this is a design decision on the part of Adobe, it begs the question, why is this new product setting the HSL controls?
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Old September 23rd, 2010, 07:01 PM
Doug Kerr Doug Kerr is online now
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Hi, Andrew,

Quote:
Originally Posted by Andrew Rodney View Post
You’d have that anyway (its not like those controls disappear). The question is, WHERE in the processing chain should a so called “calibration” take place? Bruce Fraser and others, prior to DNG profiles, did this in the Calibration tab. DNG profiles do this in a similar area in the processing chain. My understanding is, calibration and DNG profiles take place prior to any of the sliders above. If this is a design decision on the part of Adobe, it begs the question, why is this new product setting the HSL controls?
Well, doing the camera calibration with the "HSL faucets" rather than the "camera calibration faucets" allows tweaking of saturation, hue, and quasi-luminance, at 8 hue values rather than control of hue and saturation only, at 3 hue values

Perhaps this is felt to give a more refined adjustment of the camera colorimetric behavior over the color space.

Of course the DNG profile paradigm gives the potential of an even more refined adjustment.

Best regards,

Doug
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  #6  
Old September 23rd, 2010, 07:18 PM
Andrew Rodney Andrew Rodney is offline
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Quote:
Originally Posted by Doug Kerr View Post
Well, doing the camera calibration with the "HSL faucets" rather than the "camera calibration faucets" allows tweaking of saturation, hue, and quasi-luminance, at 8 hue values rather than control of hue and saturation only, at 3 hue values.
Its more about “more sliders are better” its about where the calibration should take place! I’ve asked in the DNG and LR Adobe forums, hoping Eric Chan will comment.

Quote:
Perhaps this is felt to give a more refined adjustment of the camera colorimetric behavior over the color space.
Where they feel (based on whatever science or knowledge they have about the raw processing engine) and where it should be set is the question I’m asking. My understanding is this process should not be taking place where they are affecting the processing.
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  #7  
Old September 23rd, 2010, 08:36 PM
Doug Kerr Doug Kerr is online now
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Hi, Andrew,
Quote:
Originally Posted by Andrew Rodney View Post
Its more about “more sliders are better” its about where the calibration should take place! I’ve asked in the DNG and LR Adobe forums, hoping Eric Chan will comment.
Well, in basic raw development (such as takes place inside a Canon EOS camera), the camera calibration (fixed) is rolled into the white balance color correction vector and applied as essentially the first step of raw processing.

Best regards,

Doug
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  #8  
Old September 24th, 2010, 09:03 AM
Doug Kerr Doug Kerr is online now
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By way of elaborating on my comment about camera calibration-

In my EOS 40D (in its current state of mind), if the WB is set to "daylight", then as near as I know, the digitized outputs of the four sensor "channels" (R, G1, G2, and B) are multiplied by:

2131, 1024, 1024, and 1247

respectively, and then presumably divided by some appropriate scaling constant (likely about 1024).

Thus that four-value vector can be regarded as the camera calibration vector for "daylight" illumination.

Realize that there is no such concept as a camera calibration vector not predicated on any particular illumination. The closest we could have to a "fundamental" calibration vector would be one predicted on illuminant "E", which has equal spectral power density (inexplicably usually called "energy") across the visible spectrum. And it of course is still predicated on a specific illumination.

Some would prefer that any given four-value vector be considered to be a "fundamental" camera calibration vector already combined with a color correction vector for the chosen assumed illumination, but this is an artifice. That color correction vector in fact would have to be predicated on the difference between the assumed illumination and the illumination that defines the white point of the output image file (and we are not at this point in the process working with such a representation - we are still dealing with "scaled" raw values).

So, circling back, we must consider any of the stored vectors to describe the "four-channel" calibration of the camera (at the sensor) assuming a certain illumination - in general, not one of the standardized CIE illuminants, but rather an illumination chosen by the camera designers as representative of a "named situation" (such as "daylight").

It would seem that, were we to wish to apply a "custom" calibration of the camera (perhaps one defined separately for different regions of the object reflective color space, and of course predicated on a certain illumination), it would be desirable to do it at this stage of the processing (right after digitization).

The ACR camera calibration panel

I do not know if the "camera calibration" sliders in ACR work at this stage in the process.

They of course, in any case, do not provide for different adjustments for different portions of the object color space on a generalized basis, but probably work "by channel type" (by which I mean not distinguishing between the G1 and G2 channels). But I am not sure of their behavior.

If we use a PNG-style profile

Now, when a "PNG" style profile is used, we have the following situations:

• The profile is applied after conversion of the raw data (using whatever algorithm is used in the raw development software being used) to a certain RGB color space, and thence to an HSV color space.
• The profile table can potentially provide for distinct adjustments in as many separate regions of the color space as we wish, shifting either H, S, and or V as required to new values.
• The result is then converted to whatever color space we have ordained for the output image.

Best regards,

Doug
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  #9  
Old September 26th, 2010, 06:20 AM
Andrew Rodney Andrew Rodney is offline
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Got this from Jeff Schewe on the Lightroom forum:

Quote:
I'm not Eric (not sure he would want to respond to this question) but I'll take a stab...first off, let me state that I haven't personally tested either the SyderCHECKR PRO color target or the software. I've only watched the video and read the user manual. But I do have some issues regarding usability and the "practical implications" of using the HSL Sliders vs a DNG profile.

There is one major implication–the SpyderCheckr produces a preset using the HSL adjustments rather than a DNG profile. I have no understanding (and haven't heard the rational) why Datacolor chose a Lightroom or Camera Raw preset instead of a DNG profile. But the first problem with creating "presets" is Lightroom and Camera Raw don't share "presets". So, unlike a DNG profile which will work in both Lightroom AND Camera Raw, the Spyder solution is application specific. The other major issue is that presets are not easily transportable compared to DNG profiles which actually get imbedded in a raw file. I have no reason to suspect that the HSL adjustments of Lightroom and Camera Raw CAN'T handle the color corrections needed for calibration, but the fact that the calibration depends on a "presets" limits its usefulness.

What is also not mentioned in the videos nor the manual is what the user is supposed to do regarding the starting DNG profile. Does Datacolor suggest using Adobe Standard or some other DNG profile? I ask because the HSL calibration applied as a preset depends upon the DNG profile used to create the color sample file and adding a calibration on top of an existing DNG profile seems to complicate the whole calibration process. When using DNG profiles, it's pretty straightforward what the DNG profile creation is actually doing. Adding an HSL adjustment on top of an existing DNG profile adds complexity to the process and reduces the portability of the camera calibration.

The documentation seems to imply that both DNG Profile Editor and X-Rite's Passport solution somehow limits the end user's ability to make further adjustments. I think this is false...while you can't currently edit the resulting Passport generated DNG profile in X-Rite's software, you can indeed edit the resulting Passport generated DNG profile in Adobe's free DNG Profile Editor. You can edit the preset that SpyderCheckr creates in either Lightroom or Camera Raw, but you are editing an absolute preset that applies HSL adjustments requiring the saving out of a new subset of HSL adjustments-and again presets are not interchangeable between Lightroom and Camera Raw. I see this as a very limiting factor.

In principal, I encourage the development of more and better solutions for both Lightroom and Camera Raw. Whether or not the HSL calibration approach is superior to the DNG profile calibration approach, I really wonder whether or not HSL is a better solution than the DNG profile approach. It seems to me that Adobe (and Thomas Knoll and Eric Chan) have spent a lot of time and effort to develop an open solution to camera calibration that the SpyderCHECKR approach is ignoring. Personally, I would have encouraged the option to create either a DNG profile _OR_ an HSL calibration preset. I think it's a mistake to ignore the DNG profile approach.
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  #10  
Old September 26th, 2010, 02:51 PM
Michael Tapes Michael Tapes is offline
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To amplify or maybe clarify Jeff's statements (not that he needs me for that :>), One cannot use the HSL Preset Calibration at will. They HAVE to have the proper DNG profile in place in order for the HSL "profile" to be meaningful. Said another way, a DNG profile is absolute and the HSL "profile" is relative. That could get you into a lot of trouble. Also if you want to use the HSL panel for its intended use, you now have no 0 (zero) reference as the new reference is the values of the "profile". A real PITA if you ask me. Also a DNG profile can be set automatically to be used each time for the camera it was made for by simply setting it as part of the camera default" settings. I do not recall that a Preset could be applied on an automatic basis, so this again is a hit and miss process if you have more than 1 camera model.

So putting aside any technical implications, simply from an ease of use situation, the DataColor solution is not elegant at all imo.
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  #11  
Old September 26th, 2010, 07:47 PM
Doug Kerr Doug Kerr is online now
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Hi, Andrew,

Is it likely that application of a DNG profile is the next thing that happens after demosaicing (white balance color correction happening before or in the course of demosaicing)?

Best regards,

Doug
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Old September 28th, 2010, 03:28 PM
Asher Kelman Asher Kelman is offline
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Andrew, there's an interesting revelation in your quote.

Quote:
Originally Posted by Andrew Rodney View Post
Got this from Jeff Schewe on the Lightroom forum:
"The documentation seems to imply that both DNG Profile Editor and X-Rite's Passport solution somehow limits the end user's ability to make further adjustments. I think this is false...while you can't currently edit the resulting Passport generated DNG profile in X-Rite's software, you can indeed edit the resulting Passport generated DNG profile in Adobe's free DNG Profile Editor."

So, is the free DNG editor capable of allowing us to use the Xrite Passport DNG calibration from Adobe Camera Raw, (or Lightroom for that matter), in other non-Adobe applications such as, but not limited to, Capture One?

If so, how is this done in practice. I'd like to be able to apply the Xrite's "profile" based on it's Passport color Checker, so it travels with the DNG file in a form that other software packages can now recognize.

Asher
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Old September 28th, 2010, 03:30 PM
Andrew Rodney Andrew Rodney is offline
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Quote:
Originally Posted by Asher Kelman View Post
So, is the free DNG editor capable of allowing us to use the Xrite Passport DNG calibration from Adobe Camera Raw, (or Lightroom for that matter), in other non-Adobe applications such as, but not limited to, Capture One?
IF the other packages support DNG profiles of course.
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Old September 28th, 2010, 03:33 PM
Asher Kelman Asher Kelman is offline
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Quote:
Originally Posted by Andrew Rodney View Post
IF the other packages support DNG profiles of course.
As far as I understand, Xrite only works at present with Adobe products. I was thinking that the Adobe DNG editor might be able to put the Xrite profile where other software packages expect to find it. Can you shed light on what the block is?

Asher
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  #15  
Old September 28th, 2010, 03:37 PM
Andrew Rodney Andrew Rodney is offline
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To build the X-Rite DNG profiles, you have to use either the X-Rite stand-alone software or the Lightroom plug-in. What other raw converters support DNG profiles? I don’t know. Its an open spec. The editor takes any DNG profiles (those made by the Adobe DNG profile creator, X-Rite or anyone else who would write DNG profiles to spec) and allow you to edit them. A DNG profile is like an ICC profile in that there’s a spec in how to make em. Who uses them thereafter is the question. Who other than Adobe is implementing DNG profiles to be used in their raw converters?
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Old September 28th, 2010, 05:21 PM
Doug Kerr Doug Kerr is online now
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Hi, Asher,

Quote:
Originally Posted by Asher Kelman View Post

So, is the free DNG editor capable of allowing us to use the Xrite Passport DNG calibration from Adobe Camera Raw, (or Lightroom for that matter), in other non-Adobe applications such as, but not limited to, Capture One?
No, the profile editor is just that: it allows one the take an existing DNG profile and change some of its properties - not to convert it to some other kind of profile (what ever kind that might be).

For example, you can select a part of the color space (by clicking on a specimen in a sample DNG image) and then change the "corrections" (in terms of Hue shift and Saturation and Lightness scaling - in the HSL color space sense - in the profile that will apply in that general region of the color space.

You can also make a DNG profile in the Editor. You must start with a DNG image of a 24-patch ColorChecker target.

You can also set a white balance color correction vector that will travel with the profile, and change the "color matrix", which is a camera chromaticity calibration scheme that works by "channel" (not by location in the color space) - organized like the camera calibration panel in Photoshop. We can also change the global "tonal curve" to be used in development.

But if we are interested in an application that cannot utilize DNG profiles, having the editor doesn't change that.

Best regards,

Doug
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  #17  
Old October 2nd, 2010, 10:22 AM
Andrew Rodney Andrew Rodney is offline
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Quote:
Originally Posted by Andrew Rodney View Post
Its more about “more sliders are better” its about where the calibration should take place! I’ve asked in the DNG and LR Adobe forums, hoping Eric Chan will comment.
Just got this from Eric on the Adobe forum.

Quote:
Andrew, the approach to use HSL controls to perform color adjustments based on a measured target is fine, but has some limitations. For example, if you have your own HSL presets that you prefer to use (for creative effect), then it's hard to use those along with this approach (since this approach relies on setting the HSL sliders to certain values). There are also fewer degrees of freedom using the HSL controls. That is, there are some things that the DNG color profile model can accomplish via its lookup tables that cannot be accomplished by the HSL controls -- e.g., saturation-dependent effects, such as making less-saturated reds a little warmer, and making more-saturated reds a little cooler.
The bit about lookup tables is most interesting.
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Old October 2nd, 2010, 10:44 AM
Doug Kerr Doug Kerr is online now
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Hi, Andrew,

Quote:
Originally Posted by Andrew Rodney View Post
Just got this from Eric on the Adobe forum.

Quote:
That is, there are some things that the DNG color profile model can accomplish via its lookup tables that cannot be accomplished by the HSL controls -- e.g., saturation-dependent effects, such as making less-saturated reds a little warmer, and making more-saturated reds a little cooler.
The bit about lookup tables is most interesting.
Indeed. In the DNG profile, the camera calibration table is (potentially) organized along three axes, H, S, and V, under some form of the HSV color model.

For any pixel, the table is entered with its (current) H, S, and V coordinates, and the table then delivers (potentially):

• A shift in H (hue)
• A scaling of S ("saturation", in one reasonable definition)
• A scaling of V ("value", something like luminance)

to be applied to the original HSV values to give an "corrected" set for the pixel.

This then allows for exactly the subtlety Eric speaks of, with the adjustments potentially different for each spot in the color space.

Of course, presumably not all profile-generating facilities will fully exploit this potential three-dimensionality of the table, or may do it very "coarsely" along one or more of the input axes.

Thanks for the follow-up.

Best regards,

Doug
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