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©2003-2008 Keith Cooper

Image usage information

ACR DNG profiles from a ColorChecker card

Creating DNG profiles for RAW processing

The Ricoh GX200 used as an example

Keith recently reviewed the Ricoh GX200 and was impressed by the fact that it used DNG as the format for its RAW files. Unfortunately there is no Ricoh software to process the RAW files on Apple Macs, which we use.

Note - these techniques are applicable to -any- camera that ACR can work with.

Adobe Camera Raw (ACR) supports processing these files, but has no built in profiles, so relies on the camera info in the DNG file. This short article shows how you can use the DNG profile editor and now build camera profiles for ACR with a ColorChecker card. It covers general purpose profiling and making a specialist profile for working with 'Energy Saving' light bulbs (profiles downloadable).

Digital Camera colour management

When it comes to ICC colour management for printers and monitors there is no question about the benefits offered -- but input devices such as cameras are more problematic. I've covered some of the issues in scanner profiling in another article, but camera profiling and its effectiveness is a much more contentious issue. Most of the time I'm happy to use the supplied profiles in RAW image conversion software, if my camera is a supported one.

Even though I can process RAW files from a GX200 perfectly well with Adobe Camera Raw, there are no ACR 'built in' profiles for this camera.

Some RAW processors allow you to use ICC camera profiles - DxO Optics Pro for example, supports the building and use of ICC colour profiles for cameras. Unfortunately it doesn't support the GX200, so I couldn't try that route.

I looked at using the ColorChecker SG card for camera profiling a while ago. The ColorChecker card and software are designed to produce full ICC camera profiles (for converters that support them).

Adobe Camera Raw (ACR) does allow for some considerable degree of adjustment of its colour handling and there have for some time been scripts available that allows you to perform a 'calibration' process using photographs of such cards.

Profiles for ACR

In the design of ACR, Adobe has gone for a different profiling process, not using ICC style profiles. Until recently this was a closed system, not available for us to tinker with.
The script based adjustments mentioned above, only augment the existing 'profiles'.

If you have ACR 4.5/6 (PS CS3) or ACR 5.x (PS CS4) then you can download a test version of some new camera profiles and an application called DNG Profile Editor.

Note. If you have an older version of ACR then you can still use the ACR profiling scripts mentioned on the CC SG review page - they are not quite so easy to use and probably not as flexible, but at least you won't have to buy a newer copy of Photoshop.

There is some very good documentation and tutorials on the Adobe site, so I'm not going to go into great detail about how to use the software.

The process of making a camera profile is: (this on a Mac - Win PC is similar)

• If you've not got it, Download Camera Raw 4.6 from http://adobe.com/cameraraw (note that this won't work with versions of Photoshop before CS3)
  Mount the disk image and drag the file 'Camera Raw.plugin' to:
  /Library/Application Support/Adobe/Plug-Ins/CS3/File Formats/
• Download Beta Camera Profiles from http://labs.adobe.com/wiki/index.php/DNG_Profiles and run the installer.
• Download DNG Profile Editor from http://labs.adobe.com/wiki/index.php/DNG_Profiles and unzip.
  Drag it to your Applications folder.
• If you were trying this for a camera that doesn't produce DNG files then you should:
  • Launch Photoshop and open the RAW file of your ColorChecker target.
    In ACR, click Save Image... Choose DNG as the file format and save it.
• Launch DNG Profile Editor.
• From File>Open select your DNG File.
• Choose the DNG file you want to work with.
• You can white balance the image by right clicking on the second grey square.
• Select the chart tab in DNG Profile Editor.
• Move the coloured circles to the centre of the matching coloured corner square in your RAW file.
• Click 'Create Colour Table'.
• Choose File/Export <Camera> profile... Give it a meaningful name and save it.
• Exit DNG Profile Editor.
• Quit and re-launch Photoshop and open a RAW file. In Camera Raw, on the calibration tab, you should now see the profile you just saved as an option.

That's the basic version and it just works...

The measurement process and much more, is explained in the DNG Editor tutorial.

A refinement is that Adobe ACR profiles are built from two sets of measurements, one at 2850K and one at 6500K. You can produce similar profiles by taking two shots of your card - one illuminated with Tungsten lighting and one in daylight.

ACR profile for the GX200

I took several photos of a standard ColorChecker card, outdoors in sunlight and indoors under a halogen ceiling light (the sort with a built in reflector).

Actually, as you can see in some of the images below, I took loads of pictures...

I also took some photos of the card in my hallway, which is lit with an energy saving light bulb.

I hate these bulbs, from a lighting point of view - they mess up colours a treat. In fact when I'm doing interior photography of somewhere like a hotel, I take a box of 'ordinary' light bulbs of different sizes with me, to temporarily replace them.

I've a number of screen shots showing different aspects of the process outlined above. I've some observations on the process and some things to watch out for in the conclusions afterwards.

In this first picture, I've two (RAW) photos of the target opened up. One is at a white balance setting of 5200/2 and the other 3000/5

The small circles are the target identifier marks that you move to the corner patches.

Although not recommended, you can have the target taking up a smaller part of the image.

I also have a specialist white balance 'grey card' in the picture (see my review of using it for more info)

If you are using two images to get a better general purpose profile, then each image contributes to one table in the profile (tables contain the 'correction' information for the profile)

Here's where I've told the software that this image is for the 6500K table.

And here, the 2850K table.

Note that the software is smart enough to allow for the fact that your images were not shot at exactly 6500/2850.

The profile is generated in a few seconds, and can be exported.

For a specialist profile like the one below, you can use just one image.

Here's a target lit by an energy saving light (ESL) bulb - the camera thinks a WB of 3200/19 is OK, but right clicking on the second grey (from the left) gives a value of 2550/17.

I've created this profile (ESL) from just this one shot.

Conclusions

Do note that all the images here are what you are seeing in a web browser - colour is notoriously difficult to get right on the web - also, these are JPEG images, and although I've saved them at high quality, the compression process doesn't take highly saturated colours too well.

Remember too that a pleasing picture is not automatically the most colorimetrically accurate picture, hence the slightly more saturated colours in the ACR 'Standard' profile for the GX200.

Using the new profile for the GX200 gives slightly richer and slightly more contrasty images. I'd have been concerned if there had been much difference, since that would indicate that Ricoh had inaccurate camera data in the DNG file.

I tried to come up with a web example that would show the difference using the new 'Standard' profile, but given the problems I mentioned earlier, I decided that it would be far better to show the differences using the custom ESL profile.

The first image shows the default or 'embedded' DNG profile.

If you move your mouse over the image you can see the 'standard' profile I made from the two pictures of the target.

The second picture shows the difference between the embedded and custom ESL profile.

The picture shows some of the 120 year old floor tiles in one of the corridors of my home (I only have ESL bulbs in bits of the house I don't spend much time in ;-) - yes they could do with a proper clean... it's on the list!

The ESL profile handles this lighting well, while the 'standard' is slightly better than the 'embedded'

The whole profile making process works fine for me - I'll be taking the ColorChecker card with me next time I'm shooting (with a Canon 1Ds Mk3) in unusual lighting.

I've found that 'proper' icc camera profiles can be of use in well defined lighting setups, but the ACR profiling certainly seems to be happier handling situations where there is some variation in basic lighting.

What about using the wider ranging ColorChecker card SG for making even better profiles? The colours are not quite the same in the patches that duplicate the original ColorChecker card and at the moment, Adobe's software only supports the original.

The example below is from the ColorChecker SG - i1 camera profiling review I wrote a while ago and shows a benefit of camera profiling under fluorescent lighting.

Adobe have this to say in their DNG Profiles FAQ, about the profile editor (PE)

• Can the Chart Wizard be used with other charts such as the ColorChecker DC or ColorChecker SG?
• No. PE currently only supports the 24-patch ColorChecker Chart.
• The ColorChecker SG contains a block of patches similar to the 24-patch ColorChecker Chart, but they have different spectral reflectance values and hence should not be used with PE.

If you want to check profile accuracy then there are some useful scripts that work with different types of card, listed below in the More info section.

Although the sun is out, the card below is pointing to the sky in the North East. The colour temperature is a cool 7050K, and with a tree nearby which could easily affect some colours.

Try and light your card evenly with the light (sun) off to one side and in the case of studio/home lighting, far enough away so that the card is evenly illuminated.

Watch out too for reflections from nearby brightly coloured objects - our eyesight effortlessly adjusts for this sort of effect, so it's very difficult to see.

Using ACR DNG Profiles

If you'd like to try the basic GX200 files then...

Download Keith's GX200 ACR DNG profiles (zip file) - 'Standard' and 'ESL Bulb'

Where to put them

Restart Photoshop and when you next open an appropriate image, the new profiles will appear as choices in the ACR Camera Calibration section.

Here it is for the GX200 profiles (if you want to use ones for other cameras that are already supported, then look at building your profiles on top of existing 'base profiles' - see more Adobe info)

If you'd like to experiment, I also have the two base recipes that were used to make the profiles available for download. You could use them to fine tune profiles based on my measurement data. One file is based on two measurements and the ESL one on just one. Please do let me know if you find them of use?

Summary

Quick and relatively easy to use.

Works very well in more unusual lighting conditions.

DNG profiles offer a way of improving the RAW conversions for a camera like the GX200 (full GX200 camera review), and can be applied to any raw files openable by ACR.

Unfortunately only usable with the latest versions of Photoshop.

More Info

Colour management links on this site
http://www.rags-int-inc.com/PhotoTechStuff/ColorCalibration/
Very useful scripts for Photoshop and ColorChecker cards (other card types included).
Camera Profiles and DNG Profile Editor
Info from Adobe.
Eye One scanner profiling - review
Using the Eye One with a scan target to get better results form your film or flatbed scanner.
The Spyder2 Pro - review
The Eye one Display 2 - review
Review of the printer profile editor in Eye One Match.
Calibrating ACR - by Bruce Fraser.
http://www.brucelindbloom.com/ - has useful info on many colour related areas, including lots on the original ColorChecker.
http://www.colorremedies.com/realworldcolor/downloads.html
Useful resources - related to the 'Real World Color Management' book.
http://www.babelcolor.com/main_level/ColorChecker.htm
Lots of ColorChecker related info.

Other areas of our site that may be of interest...

You can create your own customised A3 size wall calendar from a choice of 90 of Keith's images. Pick your own images for your own custom printed calendar - 12 months starting any month of the year. There are even more images in the updated gallery

Digital Black and White. Based on an interview Keith gave to a magazine article about digital black and white photography. We have an expanded two part version covering some of his thoughts, techniques and tips for those interested in a digital approach to black and white. There is a growing collection of photography Articles and Reviews on the site aimed at helping you get the best out of your own photography.

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It won't save extra money we're afraid, but it will help in the running of the site, and we'd really appreciate it...

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