Hi
When shooting the ColorChecker or QPcard, I have hitherto always tried to fill the frame.
And BTW the deep shadows in the black Passport hinges are very useful as an RGB 0 reference, which is something the QP Card doesn't offer.why do you need that for dcp profile building ?
No, but if you're using the Passport on a scene by scene basis in a production situation, it's handy.
For me, the main benefit from making custom profiles is in using different base tone curves.but you do not need to shoot targets to create different base tone curves
Thanks again. Sorry I forgot to specify that I make ICC profiles. They have worked well even with the CC filling the frame, but I am starting on a new round with my workflow, and any possible improvements should be implemented now.
I still don't know just how much of the frame the target should fill, and just how much it should be de-focussed.I doubt that there's a single default answer.
So all in all it does not seem to be very critical.
Iridient Developer, formerly Raw Developer.
> if you will read Iliah Borg (who creates profiles for RPP) you will find out that that it is ...
I can't find anything in that way on the RPP web site. Would you have a link?
> I wrote to the author who said it does support DNG profiles
Oops! That must be of lately, I did not check that. Thanks Andrew.
ID supports the DNG format, to some degree, but not DNG profiles. I see no change to that in the current version 2. What Brian may have meant may have been that ID respects DNG profiles embedded in DNGs?
Good light!
ID supports the DNG format, to some degree, but not DNG profiles. I see no change to that in the current version 2. What Brian may have meant may have been that ID respects DNG profiles embedded in DNGs?
Lighting and Capturing the Target
by Iliah Borg
Properly capturing an evenly illuminated target is the most important aspect of camera profiling. Without a
quality shot of the target, the profiles will be poor - GIGO. The quality of the shot is more important than
having an expensive profiling target. The classic CC24, or ColorChecker Passport, or even a Mini CC is all
that is needed to start.
If you have a studio, you can use Solux 4700K lamps with black-painted backs or HMI lights (Mole-
Richardson is a good source). Broad-spectrum fluorescent lamps (Normlicht or JTI branded) are also a solid
choice. If you are on a budget, any halogen lamps with a stabilized power supply and gelled to reach about
5000K are OK.
For a decent setup, check http://www.imatest.com/docs/lab.html#lighting
You can also use daylight if a studio is out of reach. It is interesting to make different profiles for different
types of the daylight, and with different positions of the Sun.
1. To start, use as simple a lens as possible; a 50mm prime is ideal. You will need a separate profile for your
polarizing filter and also for CC40m and CC30m filters. Some lenses need a different profile, especially old
manual-focus primes. A good deep hood is a must; any reflections or flare will result in a poor profile. Clean
the sensor, the lens, the hood, and, of course, the filters if you are going to use them.
2. Affix the target on a gray card 2-3" larger than the target in each dimension. If the target is not perfectly
flat, the resulting profile will be compromised with shadows, colour casts, and uneven reflection. This is
very important for smaller targets like the Mini ColorChecker.
3. Do not fill the frame with the target. The target should occupy the middle 1/3 of the frame in each
dimension.
4. Cover the target with another gray card and set white balance from it. Remove the covering gray card and
blow away any dust from the profiling target.
5. Shoot at f/5.6 or thereabouts, very slightly out of focus.
6. Take a shot and ensure that readings from the gray card close to the four corners of the target are closely
clustered within a 6-point range. Be sure to cover the viewfinder to prevent the introduction of stray light.
7. Expose so that the whitest patch is in the range of 248-252 (250 is ideal). Take several shots bracketing
with shutter speed to ensure good results.
Vladimirovich,
In the Freelist archive, I see that Iliah Borg makes many contributions. But is there a place where he describes his procedure of profile creation in coherence?
Kind regards - Hening
Here is what Iliah Borg writes about target capture in the RPP user manual, pp. 33 and 34.
Photographing the Targets
Naturally the target to be photographed should be clean and in good condition. Shooting the targets is fairly critical to the success and accuracy of the resulting profile. Once again, the debate among the experts comes into play here. Some experts suggest that all you have to do is set up a studio lighting environment and carefully photograph the targets whereas others suggest that the target must be included in each scene to properly profile how the camera records color. Let’s take the side of the experts who suggest that carefully photographing a camera target in the studio is the key to producing a single camera profile first.
In the studio, the best way to light the target is as evenly as possible to ensure no glare is seen on any of the patches. Placing some white tape to each edge of the target can make it easier to read the numeric values to ensure all four corners are lit as evenly as possible using Photoshop’s info palette. It is a good idea to place a large black sheet or cloth in front of the camera with a hole cut in the center large enough that the target can be seen by the camera. This black sheet of paper, cloth, or foam core will reduce stray light in other areas of the studio from hitting the target. Using black material behind and around the target is also recommended for the same reason. You want to ensure that no stray light bouncing off a colored object can fall onto the target. In such a situation, you can pho- tograph the target with one or two lights so that each corner of the target produces numeric values that are within a point or so as read by Photoshop’s (or a host software) info palette.
Some suggest that a single light be set as close to the lens axis as pos- sible whereas others suggest two lights at a 45-degree angle or what many photographers call “copy lighting.” The advantage to one light is that only one illuminant and color temperature is hitting the target; however, pro- ducing a high degree of even light is more difficult than using two lights. The downside of two lights is that even with electronic flash, finding two units that produce identical color temperatures is difficult. Some users have found that even a few degrees of color temperature difference in the lighting can cause issues with the resulting profile. To digress, I should point out that those users who wish to read the color temperature of either electronic flash or continuous lighting can do so with the Gretag- Macbeth Eye-One Pro Spectrophotometer and the accompanying Eye- One Share software. This can be a useful tool to see if the two lights for shooting the color target is within close specification. If the final studio situation is such that the photographer is photographing artwork and using polarizing filters over the lens or lights, it is important that the camera target photographed this way be measured with a Spectropho- tometer also using a polarizing filter, as this will affect the accuracy of the TDF. A Spectrophotometer, such as the GretagMacbeth Spectrolino allows a polarizing filter to measure a camera target.
Hi Henning,
http://translate.google.com/translate?sl=ru&tl=en&js=n&prev=_t&hl=el&ie=UTF-8&layout=2&eotf=1&u=http%3A%2F%2Fraw-rpp.livejournal.com%2F97552.html
http://translate.google.com/translate?sl=ru&tl=en&js=n&prev=_t&hl=el&ie=UTF-8&eotf=1&u=http%3A%2F%2Fsail2ithaki.livejournal.com%2F129988.html
Apart from the 1/3, it is pretty much what I'm doing.
Here is what Iliah Borg writes about target capture in the RPP user manual, pp. 33 and 34.
How do you do this? Argyll does not seem to support the QP202 card
The QP202 and 203 are supplied with the Lab values for each patch. To make these profiling options available in the profiling dialog in RPP you simply need to make a ".cie" file for the particular target.
I cannot attach the text files so here is the formatted data for the QP203:IT8.7/2
ORIGINATOR "Kirk Thibault"
DESCRIPTOR "QPCard 203"
CREATED "Feb 06 2013"
MANUFACTURER "QPCard AB"
NUMBER_OF_FIELDS 4
BEGIN_DATA_FORMAT
SAMPLE_ID LAB_L LAB_A LAB_B
END_DATA_FORMAT
NUMBER_OF_SETS 35
BEGIN_DATA
A1 86.1 5.2 80.7
A2 81.9 26.1 74.6
A3 72.5 42.0 60.3
A4 85.1 -22.3 -6.0
A5 81.1 -20.7 14.6
A6 85.6 -11.4 33.1
A7 92.3 3.9 41.3
B1 56.1 28.4 -24.4
B2 43.0 51.0 22.5
B3 51.0 -48.7 14.2
B4 43.1 -18.2 -34.3
B5 72.5 -1.9 58.5
B6 54.1 -31.2 -23.4
B7 85.4 20.5 33.2
C1 55.1 35.3 -17.3
C2 44.0 55.1 15.3
C3 54.0 -46.8 25.3
C4 41.1 2.8 -46.4
C5 69.7 -11.9 54.2
C6 57.1 -41.4 -11.3
C7 82.5 24.7 16.1
D1 56.1 38.2 -6.2
D2 43.0 50.1 2.2
D3 52.0 -37.8 31.4
D4 39.1 13.6 -43.3
D5 65.5 -23.5 42.4
D6 55.0 -39.6 -1.1
D7 79.6 17.5 -8.9
E1 95.2 0.3 2.2
E2 85.2 0.3 2.4
E3 70.2 0.2 1.8
E4 59.1 0.2 1.0
E5 44.1 0.1 1.3
E6 34.1 0.1 1.4
E7 29.1 0.1 0.5
END_DATA
Thanks samueljohnchia for the heads up. I'll give the linked values a try (thanks Vladimirovich) as well as the Myers values.
kirk
Hening, will you be testing DCP vs ICC profiles in Irident Developer?
Maybe Andrew Rodney is already doing this as I write this?
I'd like to figure out a ID or any raw converter that supports such profiles can be set to be as agnostic as possible at a stage one loads either type of profile.
You can't even build one until you figure out how to set the raw converter to produce a rendered image to pass to the profiling software.
Opened in ID, displayed through my normal profile, which is linear and everything zero, and WB as shot, the white patch of the ColorChecker reads 124/114/96 in the Digital Color Meter. The WB is displayed as 5200K/+7 (DNG estimate). If I set it to 5000K/0, it gets a little better, 124/114/96. If I adjust the WB so that the RGB curves are adjusted to the same max value (that they end the same place in the right side of the histogram) then the values are 114/113/106. The WB is then displayed as 4407/+7 (DNG).What color space is the file you are reading the values from? The info panel in Photoshop or ACR will give you correct readouts from where your cursor is pointing. Not sure why your white patch values are so low? For ProPhoto RGB, the reference white patch value for the QP203 should be about 234/233/229, the ColorChecker should be about 242/242/238.
The DigitalColorMeter reads the values that the screen displays, so my calibration may be the culprit. But where do I find the values which are actually in the file? ACR and PS CS5 display similar values.
I think you would disable color management in ID to produce the TIF for profile creation.
I'm caught here - if I render an image in the raw convertor to produce a 16 bit ProPhoto RGB tif to feed to the profiling software, wouldn't the raw convertor be using the default camera profile to render the tif in the first place?
AR: Well it is in a way. Your product allows either to be used. So what do we need to do to test this correctly? I've still got software and a group of differing targets I could use to build an ICC camera profile.
I kind of, sort of, allow for either to be used though I think for a truly fair comparison you'd want to use the full abilities of the latest DNG v1.4 spec which includes color table based profiles that I do not support. I think DNG fans would definitely cry foul if you were to limit the DNG profiles to color matrix data only? I recommend limiting the ICC profiles to matrix only as well so still may be an interesting comparison and not really a total mismatch. In both cases I think the color matrix bit is the core part and color tables just allow for more creative tweaking...
The tricky thing with most commercial ICC profilers (been a very long time since I've used them) is that they generally are expecting to get a standard image format for profiling (like a TIFF or JPG). I remember so just could not handle 16 bits/channel or linear RAW data at all. They'd just totally fail.
So probably wisest in RAW developer to setup a camera tone curve that calibrates color chart grayscale to gamma 2.2. Definitely white balance prior to profiling especially if the camera white balance is off. Use either a gray card or with the CC chart the 2nd or 3rd patches from the left are most neutral. With the basic color checker generally the RGB reference data is given in sRGB I believe so just set up a simple tone curve in Iridient Developer that matches the reference values along the gray scale and you've basically got approx 2.2 gamma output.
ArgyllCMS will support linear data and does support 16 bits/channel. Mostly I'll linearize the camera tone curve but many cameras are quite linear already and I'll just do a quick tweaking of the white point to get the levels up to normal exposure. With recent versions of ArgyllCMS I've found it doesn't matter too much what the tone curve exactly is and I'll often now just use the colprof tool's -am. option in which case it just assumes linear gamma. In this mode I'd avoid doing an actual gamma correction of the camera tone curve for obvious reasons... Bumping up the white point to normalize exposure levels is still a good thing but in a rush I've skipped this in some cases. Doing a full accurate linearization of the grayscale would in theory give the best results in this mode as the profiles going to be output as perfectly linear even if the image data is not...
AR:I'd like to see good peer review on this subject! I'd like testing to be well defined. I'd like to see a number of savvy users (not the DP review crowed) to give the two processes a try then report their findings. Can this be done in your product, ideally even in demo mode? If so, are there specific steps one should follow to build both sets of profiles and then use them?
Demo mode will watermark images with red text which could throw off profiling tools... However, given a custom ICC profile for an image you could load that in the demo just fine for viewing.
DNG currently can only be of the original color matrix type and must be embedded into a DNG image file. No support for loading of standalone DCP format color profiles at this time in Iridient Developer at this time. So you need to profile the DNG and then embed the custom profile back into the DNG file. Again could load custom DNG profile data out of a DNG file for viewing with the demo, but I do not support export of DNG files for profiling.
for Iridient Developer to output an image for profiling:
1) Disable all color management by checking the checkbox on the Out pane of the settings window.
2) White balance the reference image if necessary
3) Adjust camera tone curve either to accurate linear gray scale or gamma 2.2 or sRGB or I've even done some work with LAB grayscale too (close to gamma 2.4). Some tools will be picky about the tone curve and will expect image data in roughly 2.2 or 1.8 gamma. Some like ArgyllCMS will work with just about anything you toss at them.
4) Export as TIFF ideally 16 bits/channel (critical for linear data) if the profiling tool supports it.
After profiling the created profile will generally be tied to the camera tone curve used above. Uncheck the disable color management option and choose the ICC profile in the Input Profile popup menu after copying to one of system ICC profile folders (/Library/ColorSyc/Profiles/ etc). You can modify the camera tone curve, but you'll lose accuracy just like you do if you modified an RGB tone curve to a carefully calibrated image from a scanner.
Most of my default camera profiles where I am not be hyper sensitive to getting accurate color I'll actually just go and modify the camera tone curve to normalize exposure and smoothly roll off highlights, etc even though the ICC profile was created under the assumption of perfectly linear data. As long as the curve is largely linear especially through the critical mid tones I think this is OK...
That is, I don't believe X-rite has any special information about the Adobe processing pipeline, I believe they build a DNG profile using the publicly open info on this spec and process. What this may mean is one could build a DNG profile and use it in ID and LR on the same raw file and assuming we could figure out a good default setting for everything else the converter does, we could have a closer apples to apples comparison of what a DNG versus an ICC profile bring to the party.
I am still struggling with the basics. I have now managed to get the color balance in the ball park. However.
I have exposed after the reading of a Pentax spot meter. The raw file opened in ID, displayed through my Canon profile, which is linear, looks as exspected. The middle gray patch of the CC reads around 72 RGB. This is linear. If I apply a curve of gamma 1.8, either in ID, or on the converted TIF in my editor (PhotoLine), the middle gray patch reads around 132 RGB instead of 102-103 (ProPhoto), and the image looks all foggy. If displayed in ID with the camera default profile, the middle gray reads 106-105-107, and the image looks normal, meaning not foggy.
What's going on?
This is going to be a most challenging task. I doubt the testing will end up fair enough for everyone.
Another issue is what software is going to build the ICC profiles? Argyll? Different profile building softwares are going to make different decisions about how to move colors around. Are we also testing for how well a software builds a camera profile along with DNG vs ICC? We cannot do both at the same time.
As Brian said, "You can modify the camera tone curve, but you'll lose accuracy just like you do if you modified an RGB tone curve to a carefully calibrated image from a scanner." I don't see another way of getting both ACR and ID to a normalized (matching) state without tweaking some curves in ID for ICC profiles. We already know the neutral setting points for both software - all sliders zeroed and all curves linear. They match very closely, at least for my image of the CC, and differ slightly because of differing profiles.
It might aid in the DNG vs. ICC profile debate a bit, at least if neither (or one) really sucks! That the DNG profile could be raw processor agnostic is interesting.
As it might happen, there is alternative view (http://www.c-f-systems.com/Complete/CalibratingDigitalImages.html#Pitfalls), that both are bad...
I don't actually know the algorithms and formulas for the color transforms to create these profiles, and since DNG profiles are by nature perceptual, each profiling software is going to have its own unique recipe.
This is getting confusing quickly, with increasingly greater number of issues to test, with multiple possibilities for things to screw up. We want to be able to point fingers and the right things causing these screw ups, and avoid them if possible. Can we reduce the number of variables and unknowns enough to make that happen?
In the end, much of our preferences will be subjective unless one process produces poor results. I've seen that in the past with ICC camera profiles so I'd like to know what reason DNG profile creation and use seems to be far more reliable or if that's even the case among multiple users.
In a strictly controlled setup for copy work and reproductions, with carefully selected lighting (probably handpicked light sources to match two or more lights), it is possible to make excellent ICC profiles, especially with a color target like the SG, I am told. The shot must be more or less "right" in camera by getting the lighting ratios and angles right, so that no additional curves are applied in post processing, just a neutral rendition from the raw converter, coupled with an ICC profile.
Shall we start a new thread on the Color Management forums about DNG and ICC profiling? I think Hening as already got what he needs for shooting targets.
I've seen that in the past with ICC camera profiles so I'd like to know what reason DNG profile creation and use seems to be far more reliable or if that's even the case among multiple users.
I'd like to see if there are raw converters like ID that can accept both types of profiles.
Not a bad idea.let's continue into a new thread (http://www.luminous-landscape.com/forum/index.php?topic=75480.0) then. :)
As it might happen, there is alternative view (http://www.c-f-systems.com/Complete/CalibratingDigitalImages.html#Pitfalls)
"the BAYER interpolation usually used on digital camera images does adjust the red value of a pixel differently according to the readings of nearby blue and green pixels. But this is done according to the geometric relationship of several surrounding pixels and the values each pixel is sensing. Geometry within the image is the key. A specific pair of blue and green pixels will influence the red pixel value in different ways depending upon the geometry of placement of the pixel values within the image."
Really?
"the BAYER interpolation usually used on digital camera images does adjust the red value of a pixel differently according to the readings of nearby blue and green pixels. But this is done according to the geometric relationship of several surrounding pixels and the values each pixel is sensing. Geometry within the image is the key. A specific pair of blue and green pixels will influence the red pixel value in different ways depending upon the geometry of placement of the pixel values within the image."
Really?
and camera profiles destroying that?camera profiles shall be considered only along with the code that applies them...