Friday, August 18, 2023

Looking More Deeply ~ Five

Whenever I'm around and la traversée (winter or summer) is running I try my best to get down to see the event.

One of the difficult things about living where I do is that it's not easy for me to find creative people to work with.  Looking through my portraiture/people work I realize most of it was generated over a decade ago.  

The city I live in feels like it's too expensive for our economically under-advantaged creatives.  Additionally, those who might be creative have a rather curious way of presenting themselves.  They remain in hiding, as it were.  Few risks are ever taken.  It's just the nature of the culture, I guess, because I don't see this in Spain, or England or Italy.

Not having the kind of creative access I used to when I lived in the US has led me to go in search of other subjects.  The car is one thing that I've taken a much stronger interest in.  It turns out, old cars are something of a passion for the locals.  They quickly became an easier target for me and it seems as if there's often something interesting and colorful going on.

I enjoy planning my photographic automobile adventures.  I enjoy thinking about the approach I'll use.  I enjoy reviewing the works of some of my favorite photographers.  I enjoy searching for new (to me) paths to photographically wander down.  It give me something to look forward to.

In late July 2023 la traversee de Paris estivale was run with 700+ old vehicles participating in the event.  After thinking long and hard, I decided that this time I wanted to explore flipping the idea of automobile on its head.

Most of the time it's the cars that are in motion. It's why we own them, right?  They get us from one place to another.  I've done a bit of work attempting to express that.  

I'm not sure how it came to me, but what if it were the cars that were at rest and what if the environment around them was what was in motion?  That was one of the ideas I wanted to explore.

Have a squint at this.  It shares what I was after.

la traversee de Paris estivale ~ 2023


Looking a little more deeply at this work of mine, I find I'm enjoying several things about it that for me "work" on several different levels.

The Alfa Romeo Spyder Veloce is needle sharp.  The red paint is pure and rich.  The wheels are as still as can be.  Automobile as sculpture.  And what a beautiful sculpture it is (to me, at least).

There is a passing bus that gives some part of the scene a sense of motion.  I can see through the windows of the bus to catch glimpses of street lamps and other architecture.  The effect is fun and unexpected.

There is a hint of a reflection of the Alfa in the passing bus, too.  The reflection looks to me as if the the spirit of the little Alfa is in motion, dreaming of a time soon to come. 

The ancient Egyptian obélisque is as still as the car.  It stands there, timeless, watching the passing histories being made.  The Alfa and obélisque feel like anchors in a world filled with motion.

Then there are the color relationships.  The blues along the side of the blurred bus are very similar to the blue on the following bus.  There's just a hint of blue in the sky, too, where the clouds are ever so slightly parted.

More subtly, the green tinted windows of the first bus seem to announce the arrival the greens on the second.  The green of the insurance tag in the window of the Alfa are similar to the greens of la traversee plaque seen just behind the windshield wipers.

Which leads, of course, quite obviously to the red.  There's the red of the car. There's the hint of red in the reflection of the Alfa on the bus.  There's the red hat of the driver.  And there's the red in the following double-decker bus behind everything.  Red seems to announce the Italian nature of the Alfa.

The photograph was done in one "take."  One exposure.  This is what I was looking for. I feel there is a certain success after spending so much time plotting and planning.  I find it all to be absolutely delightful. 

Monday, August 07, 2023

RawTherapee Color Management ~ validating a potential solution

Opening Comment: In talking with a friend, I realize I should mention how narrowly defined this color management problem and solution are.  I've limited myself to trying to get the colors to match between cameras with different sensors at the initial stage of image processing.  I have done _nothing_ to address the issues of display to display, nor display to print color variations.  Those two topics are equally thorny and well beyond the scope of this series of blog entries.

After uncovering a hole in the color management camera list, I worked on generating the needed .dsp color "offset" files.  Now I need to take a look at the results to see it's been worth the effort.

As an overview, I took DPReview RAW files for cameras I was interested in creating .dsp files for, ran the RAW files through a two application process, then transferred the results into a Linux system where the RawTherapee image processing application lives.  Have a read through the two blog entries linked in the prior paragraph for a more complete description.


In this blog entry I compare images of the XRite Color Checker Chart with different Color Management selections.  Without further ado, here are the results. 

[As always, click on the following image and have a look at the image at 100 percent resolution to see whatever there is to see.]


RawTherapee Color Management Comparison


Comments -

Starting with the "No Color Management" option we can see that the Sony A6300, A7, NEX-5T, and A7S images of the XRite ColorChecker Chart are a little "dull" looking and the colors don't look like what we'd expect them to.  They are "off" and not correct.

The RawTherapee "Camera Standard" selection helps the image colors appear brighter and clearer.  I know, these are non-technical terms, but I think they get the point across.  There are slight camera to camera color variations even though I did the very best I could to get the white and darkest gray patches to match between the images.  This is what I observed to begin with.  This is the arrow to the rabbit hole I fell down for these three blog entries.  It was this subtle camera to camera color rendition variation that made me wonder what was wrong.

Coming to the Custom DSP Color Management solution I see that the images align very closely.  These images use the files I generated based on DPReviews XRite ColorChecker RAW files.  The A6300 yellow patch looks just ever so slightly "dull" compared with the other Custom DSP images.  The difference is very very subtle.

The A6300 has a dual luminant .dsp file built into RawTherapee.  It includes Look Table and Curves options.  The base image with Look Table enabled yellow patch appears "duller" than in the Custom DSP Color Management A6300 image.

Enabling Curves brightened the yellow patch to a more vibrant state.  It's still very very slightly different than the Custom DSP Color Management images from the other cameras.

Yes, color management is a rather tricky business.  Just the slightest differences in setting image Curves outside the Color Management system changes colors surprisingly quickly.  Further, using the Curves function inside the Color Management system changes things yet again.

All this taken into consideration, I feel the Custom DSP Color Management "offset" files give a pleasingly consistent, common color rendition between various sensor outputs.  The Adobe and XRite software appear to work.  Further, I feel it's more consistent between different sensor outputs than, say, "Camera Standard", so, therefore, worth the effort.

For the cameras that are supported with dual luminant .dsp files, I think I can accept the slight color differences between them and the Custom DSP images on my unsupported by this higher color management specification cameras.

Truth be told, my color management requirements aren't that stringent.  However, if they were, and if it were for some reason critical that I get absolute color accuracy, I could do a couple things.  The first would be to buy an XRite ColorChecker chart and create my own dual luminant daylight/tungsten temperature files.  The second would be to include an XRight ColorChecker chart in my photographs.

As I'm happy with the current updated solution, I think I'm presently "good to go."

Resources -

Adobe Color Management System

RawTherapee Color Management System

How to get LCP and DCP files into RawTherapee

Creating dual luminant .dsp files

Saturday, August 05, 2023

RawTherapee Color Management ~ looking for solutions to a problem

Opening Comment: In talking with a friend, I realize I should mention how narrowly defined this color management problem and solution are.  I've limited myself to trying to get the colors to match between cameras with different sensors at the initial stage of image processing.  I have done _nothing_ to address the issues of display to display, nor display to print color variations.  Those two topics are equally thorny and well beyond the scope of this series of blog entries.

I use RawTherapee to convert SONY RAW and to do most of the image processing "heavy lifting".  

The software became my preferred image processing application after years of hoping the good people at the Gimp could expand the color space and add RAW support on file open.  A few years ago they successfully expanded the color space (up to 32bit floating-point), but continue to recommend using RawTherapee to open and convert RAW files.

Among many many wonderful features, RawTherapee comes with a very powerful Color Management system.  It uses single and dual luminant .dcp files, has a "Curves" option and an additional "Lookup Table" that can, when available, further refine image colors.  There is a default color scheme for cameras that aren't directly supported.

To recap, .dcp files are used to take whatever information the sensor stores for colors and luminosity and modifies them to a reference set of colors and luminances.  It's like using a well controlled set of "offsets" to go from the sensor colors in a RAW file to something that matches reality.  In this way, the colors across different sensors, camera models, and camera manufacturers can be corrected and matched.

My color management problems are several fold.

I do not use Adobe products.  They cost too much for not much additional benefit.  LightRoom and PhotoShop both use .dcp color management configuration files, which could be of benefit.  Adobe has to keep up with all the latest/greatest imaging devices so they tend to provide color management support as soon as cameras are available.  

On the downside, Adobe provides _single_ luminant .dcp support, only.  As we'll recall, single luminant .dcp files provide sensor corrections for daylight color temperatures only.  So the further a scene's color temperature wanders from 5500 to 5700 kelvin, the greater the chance that the .dcp file "offset" information is not as accurate as it could be.

Dual luminant capable RawTherapee can use files that specify color "offsets" at daylight and tungsten Kelvin temperature values.  These specify more accurate color "offsets" across a broader range of white balance temperatures.  Having two points on a slope is more accurate than having just one.

But, and this is my second problem, it turns out that RawTherapee does not come with as complete a set of .dcp files as Adobe products.  In my case, the Sony A7, NEX-7, NEX-5T, and A5000 cameras are not supported with their own .dcp files.  These cameras default to something called "Camera Standard."  "Camera Standard" is a generalized color "offset" corrector that attempts to make things "better" without knowing what a specific sensor requires.  Close, perhaps, but not "spot on" accurate.

There are at least two ways to resolve the .dcp RawTherapee problem  One would be to borrow the Adobe files.  I can't find an online resource for them, so that's completely out. The other solution would be to make them myself.  Fortunately someone posted a nice set of instructions on how to do this.

I followed the outline of the process.  The details are a bit different as the software listed have been updated.  Further, I tried doing all this using Wine on Linux, but failed.  So... here is specifically what I did.

Starting with an old Windows 7 box:

1) .dcp file generation requires two applications, Adobe DNG Converter and ColorChecker Camera Calibration.

  • Search for and download Adobe DNG Converter from Adobe's website
  • Install Adobe DNG Converter
  • Search for and download ColorChecker Camera Calibration software from XRite's website
  • Install ColorChecker Camera Calibration software

2) Downloading RAW files with XRite color chart embedded.

Repeat for the cameras you want to ultimately create .dcp files for.

3) .dcp file creation

  • Open Adobe DNG Converter
  • Select the directory the RAW file(s) is(are) downloaded to
  • Create DNG file(s)
  • Open ColorChecker Camera Calibration
  • Drag and drop one of the DNG files just created
  • Run "Create Profile" being sure to select an output directory you know how to get to

Repeat this for as many times as there are .dng files.

4) Write the .dcp file(s) somewhere/somehow that can be read by Linux.  Because I'm an Old Fart I used a thumb-drive.  You can just as easily send it to yourself as an email attachment or upload it somewhere on a cloud-drive.

Moving to Linux and RawTherapee -

  • Copy the .dcp file(s) to a location in the Linux file system that you can easily access (ie: easily remember where it is so you can grab the correct file when the time comes).
  • Open RawTherapee
  • Open desired image file
  • Click on "Color" tab (commonly found between "Detail" and "Advanced" tabs)
  • Scroll down to "Color Management"
  • Select "Custom"
  • Click on "Select your own DCP..." box what has a directory symbol on the right edge
  • Navigate the directory structure of your system and select the .dcp file for the camera that made the image

To confirm that the colors are indeed changing, you can click back and forth between "Custom" and "Camera Standard."  The differences may be subtle. 

What this implies is that for cameras that don't have out of the box .dcp support in RawTherapee, you'll need to specify the correct color management file each time you load images from the unsupported camera.

There are, of course, ways of making this easier to set up.  If you don't already know how to use the various image settings management tools, let me know and I'll try and point you in the right direction.

Which leaves us with one last question.  Does all this Monkey Motion yield better color correlated images?  That will be the topic of the next post.


la traversee de Paris estivale ~ 2023


Resources -

Adobe Color Management System

RawTherapee Color Management System

How to get LCP and DCP files into RawTherapee


Thursday, August 03, 2023

RawTherapee Color Management ~ a problem

Colors between identical scenes taken with different cameras vary from sensor to sensor.

I first noticed this when comparing the RAW file output of a Sony A7S to a Sony A7R.  The A7S was visibly "cooler" looking on my Linux-based RawTherapee system.  I had _assumed_ that colors were being correctly managed by the software and that what I was seeing was differences between the sensors.

This color difference therefore puzzled me as I thought a Sony sensor was a Sony sensor and the colors and luminance would match across their product line.  The software wouldn't need to do much, and if it did, there certainly would've been a decent correction applied.

Years ago when working with Canon 5D MkII RAW files that I made in the studio I could see they were visibly redder when selecting "Flash" color temperatures using Canon software than when I set the color temperature to 5500Kelvin (which is the temperature where many flash units operate).  Canon had made a color choice and I assumed (there's that word again) that all that had been baked into the system and was somehow "correct" by the manufacturer's standards.

For years I've read where one sensor gave a beautiful rendition that others couldn't match.  There's been a long and hairy discussion over the years about Sony's "color science" compared with Canon's.  Some fanboys adore Canon, while others point out certain strengths in Sony "color science."

I felt Sony cameras dealt with this out of the box "color science" much much better than Canon.  Honestly, I don't think all that much of Canon's often vaunted "color science."  I thought Sony and Nikon do a better job out of the box.  Well, it's actually not that easy and the babbling brawling masses who've taken it upon themselves to comment at length on the topic are, well, under-informed.

Recently I noticed subtle color and luminance variations between my various Sony cameras, such as between the early NEX-5T, NEX-7, A7 and the more recent A6000 and A6300.  It was never anything that stopped me from doing what I do, but it is something I noticed and wondered about.

Digging around a bit I had the opportunity to learn a lot.  For instance, there is no standard for colors and luminance.  It's up to the hardware and software designers to decide how to handle these things.  Image processing software does its best to make things look "good."

One of the ways Photoshop and Lightroom have done this is to take a known set of colors (think XRite, Panatone, etc) and to tune an image to match the colors in a chart.  The result is written to a file that is then referred to in the software's Color Management System.  The file type is specified as .dcp

In my case, I use OSS applications and rely heavily on RawTherapee for my RAW file processing.  It uses the .dcp filetype to tune the colors of an image.  So, in concept, RawTherapee could come with .dcp files from Adobe (assuming there are no sharing restrictions) and all the colors should be the same between the various sensors and camera models.

Interestingly, RawTherapee implements a broader set of color management specifications than does Adobe.  RawTherapee comes with three additional features that can be specified in a .dcp.  One is something called dual luminant.  Another is a lookup table the fine tunes colors.  A third is the specification of a luminance curve.  

The look-up table and curves capabilities should be self-explanatory.  The difficult sounding dual luminant spec, it turns out, is pretty easy to understand.  All it is the inclusion of two color management specs, one for daylight and the other for tungsten color temperatures.  It turns out that different sensors react differently to variations in color temperature.  The dual luminant specification allows color management software to more accurately place colors by interpolating color information using two color temperatures.

With these additional capabilities, RawTherapee could, if properly configured with all the right .dcp files, be more color accurate than the industry standard Lightroom and Photoshop applications.

So, what's the problem?  The Sony sensors I have vary from model to model in what I assumed (ack! that word again!!) was a fully color managed software.  To confirm this I went looking for the .dcp file list to see which cameras my version of RawTherapee supported.

On my system, .dcp files are in the following directory - 


Scanning the list I saw that several of my Sony cameras were not in the directory.  Specifically, there is no file for the NEX-7, nor the NEX-5T, nor the A5000, or, surprisingly, the Sony A7 (generation one) cameras.  This, then, pointed to the subtle color variance I was seeing.  It also explained how the old Canon 5D MkII and Canon 7D images looks differently from my Sony files.

The question quickly became, how do I solve the problem?  Can I find .dcp files pre-made that I could copy directly into RawTherapee?  If not easily acquired, how do I create them?  

Here are the topics for the next RawTherapee Color Management blog entry.  

Stay tuned.

les jardins Marqueyssac ~ Perigord Noir 2023


Resources -

Adobe Color Management System

RawTherapee Color Management System

How to get LCP and DCP files into RawTherapee

Tuesday, August 01, 2023

Activites for 2023

As I have sometimes done in the past, here is a list of potentially fun car and motorcycle related things to do in 2023 should you find yourself around Paris...

Completed Events -

30 Juillet - la traversee de Paris estivale - Paris (Flickr album)

la traversee de Paris estivale ~ 2023


June 2 thru 8 - Rallye des Princesses, Paris (Flickr album)

Rallye des Princesses ~ Paris 2023


CANCELLED - June 17 thru 18 - Cafe Racer Montlhery

Did Not Attend - May 13 thru 14 - God Save The Car, Montlhery

April 16 thru 22 - Tour Auto - Zagato specialty year, though there weren't all that many Zagato in the flesh.

Red ~ Tour Auto 2023 ~ Paris


March 21 - La gréve des éboueurs (garbage haulers strike)

 La grève des éboueurs ~ Paris 17 March 2023

 As of 22 March the strike
appears to be continuing

March 15 - Manifestation "...450.000 personnes ont défilé dans les rues de la capitale..." (protest march) through Montparnasse 

15 March manifestation ~ Paris

It was incredible to see hundreds of
thousands of people take to the streets
in protest


February 24 - March 3 - Salon International de l'Agriculture (Flickr album)

Salon International de l'Agriculture ~ 2023

Beautiful animals, one and all


February 1 thru 5 - Retromobile (Flickr album)

 Retromobile ~ 2023

Unexpected Renaissance Painting???


January 15 - la traversee de Paris (Flickr album)

la traversee de Paris ~ 2023


With new photographic tools to play with, perhaps I'll get a decent shot or two and improve my output?  Regardless, I'll be looking to have as good a time as possible.

See you there!

Vintage Revival Montlhery ~ 2022