Episode 195: Whose RGB?

rgb
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Colo(u)r ist the topic this time. You are in for a ride from the electromagnetic spectrum to the biology of color vision and the infamous Mantis Shrimp. (Link to the fabulous Oatmeal!)

Grassmann’s Law gives a clue how to create a color sensation in the brain by mixing up some wavelengths out of the spectrum. The CIE finally defines what is visible for a “Standard Observer” and Microsoft & HP (sRGB) and Adobe (Adobe RGB) build their color spaces on that foundation.

Elle Stone, Bruce Lindbloom and Cambridge in Colour help along the way, passing a Black Body emitting radiation according to Planck’s Law at 6500K just to give us a White Point.

Then I organize a shootout between sRGB and Adobe RGB – and I’ll stick to sRGB for the forseeable future.

Finally I cover the question of Intent while converting between different color spaces – Perceptual or Relative Colorimetric?

Links

Elle’s fine writeup about All the Colors.

The Color Space Viewer (at the bottom of the page)

Pascal’s tutorials about color management on Linux – really hands on:

https://encrypted.pcode.nl/blog/2012/01/29/color-management-on-linux/
https://encrypted.pcode.nl/blog/2013/11/24/display-color-profiling-on-linux/
https://encrypted.pcode.nl/blog/2013/04/14/display-profiles-generated-from-edid/

The TOC

00:00:00 Intro
00:00:15 Submit to GIMP Magazine
00:00:50 Light as part of the electromagnetic spectrum
00:01:43 Biology of color vision
00:06:14 World Champion of Color Vision: The Mantis Shrimp!
00:06:40 Grassmann’s Law – mixing colors from spectral primes
00:07:22 CIE 1931 Color Space – the standard observer
00:09:00 Elle Stone’s blog – a lot about color!
00:09:50 sRGB
00:11:40 D65 – the White Point for sRGB
00:11:56 Black Body Radiation and White Points
00:13:44 Bruce Lindbloom has a Color Space viewer
00:14:30 Adobe RGB (1998)
00:15:50 Why not ProPhoto RGB?
00:16:20 Preparing some test shots in the lab
00:16:59 Comparing sRGB and Adobe RGB camera setting
00:18:42 Conclusion – stick to sRGB
00:19:34 Converting between color spaces
00:20:06 Intent: relative colorimetric or perceptual?
00:21:14 Consequences
00:23:10 Winding down
00:24:09 EOF

Meet the GIMP Video Podcast by Rolf Steinort is licensed under a Creative Commons Attribution 3.0 Unported License.
Permissions beyond the scope of this license may be available at http://meetthegimp.org.

Episode 194: A look into digiKam (1/2)

194Download the Video! (28:46, 96 MB)

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This week nachbarnebenan shows how to use the KDE (and Windows) photo organizer digiKam. There is more to it, a second part will follow. I don’t know much about digiKam because I use Gnome Shell as my desktop environment and digiKam is made for KDE. It would run on my system, but I would have to install a lot of other stuff too. Linux users have a lot of desktop environments to choose from.

nachbarnebenan talks also about his 100 day photo challenge and has some valuable tips if you are up to a similar thing. He is also responsible for a lot of the content of the Meet the GIMP Wiki.

The TOC

00:00:40 Linux and the “Desktop Wars” (Gnome, KDE et al)
00:05:10 Setting up digiKam
00:07:18 Starting digiKam
00:08:22 Declutter your screen
00:09:10 Selecting a dark theme
00:10:10 adding image collection paths
00:11:20 templates for image meta data
00:12:00 Kipi plugins
00:14:00 Insert: the 100 day challenge and a confession
00:20:10 Tagging images
00:22:40 The timeline
00:23:22 Fuzzy search – doesn’t work properly now
00:23:50 Face recognition and tagging people – also not now
00:24:10 Geographic search of geotagged images
00:25:15 Nesting albums
00:26:00 Selecting images with buttons – useful for tablets
00:27:20 Rating images and attach colour labels
00:27:30 Filtering images
00:28:20 Good Bye!

Meet the GIMP Video Podcast by Rolf Steinort is licensed under a Creative Commons Attribution 3.0 Unported License.
Permissions beyond the scope of this license may be available at http://meetthegimp.org.

Episode 193: A Mondrian UI

193Download the Video! (11:50, 41.3 MB)

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After a too long summer break I give you a preview of one feature in the next version of GIMP – the unified transformation tool. It combines the tools for moving, rotating, scaling, shearing and for changing the perspective in one tool with a nice and sleek user interface.

The UI design has been done mostly by Peter Sikking.  He has also had his hands in the nice free selection tool design.

This unified transformation tool shall be used with visual feedback on the canvas. The old tool will stay around for work where numbers are important.  So this is not a replacement but an addition.

You can read a bit more in the developers mailing list and on the GUI wiki page.

The TOC

00:00:00 General rumblings
00:01:20 GIMPMagazine 4
00:02:26 GIMP 2.9
00:02:26 The Transform Tools of 2.8
00:04:00 Loss of sharpness – unavoidable with transformation
00:04:35 The new Unified Transform Tool UI
00:07:50 Better results due to only one calculation
00:09:00 Peter Sikking, UI architect
00:10:20 The UI design determines your work flow
00:10:41 No replacement for the traditional tools
00:11:33 Final words
00:11:50 End of video

Image credits for the Autobahn sign: Wikimedia, User Mediatus.
Creative Commons License
Meet the GIMP Video Podcast by Rolf Steinort is licensed under a Creative Commons Attribution 3.0 Unported License.
Permissions beyond the scope of this license may be available at http://meetthegimp.org.

Episode 192: Look Down! – A Challenge

192Download the Video! (45:45, 86.9 MB)

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There was no show for quite some time – and there will be a gap until the end of summer. I move back to Bremen – and that takes a lot of time and creativity away. But in Bremen I will have nearly 2 hours more time each day, because I can walk to school and don’t need to ride the famous Berlin S-Bahn Ring Line.

In the meantime I have a challenge for you! Present the place where you live to us – but look down on the sidewalk for that! The best results will be published in the GIMP Magazine #5 and of course here on the blog. The exact rules are below.

This Challenge is a perfect rip off from a challenge by Andrés (Twitter) (Website), an illustrator from Buenos Aires, in the now closed forum of Tips from the Top Floor. Make a mosaik of images of the sidewalks in your city and try to transport the atmosphere.
Rolf's Example
This is my take on the Silvio-Meier-Strasse around the corner from my flat in Berlin.

The Rules

  1. Make a mosaic of at least 3×3 images.
  2. All images have to be shot straight down
  3. All images are in the same scale, use the same distance to the ground and the same focal length.
  4. All images have to be linked to each other in their theme by being from one city, one journey …..
  5. Publish your image online and post a link to it before September 1st in the comments to this blog post.
  6. License your image as CC-BY or better and allow this site and the GIMP Magazine to publish your image under CC-BY (here) or CC-BY-SA (GIMP Magazine).
  7. Rules 1 to 4 may be broken, 5, 6 and 7 have to be followed exactly.

You may download the template for my version from above or build your own one. You are free to make other forms than a square – circles or a spiral anyone?

There will be hopefully a discussion in our forum.

The TOC

The video uses chapter marks, you can jump between TOC entrys!

00:00:00 Pause until end of August
00:02:05 A contest for you – introduction
00:03:42 The contest rules
00:04:50 My example
00:06:04 Selecting the images
00:08:00 Scaling down and exporting in Shotwell
00:08:40 Calculating the image size
00:09:30 Create the file
00:10:20 Save as XCF.gz – compressed to save space
00:11:05 Creating a “Contact Sheet” for reference with Imagemagick
00:13:00 Make a movable layer mask with “multiply mode”
00:16:00 Building a stack of layer groups and fill it with images
00:23:00 Filling images into the layer stack
00:26:45 Isolate the layer groups with “lighten only mode”
00:27:55 What do these layer modes do? Blackboard explanation
00:33:08 The last image – a Memory to Edith and Tina Wolff
00:34:30 Fine tuning the mosaic – exchange images
00:36:08 Adjusting contrast between the images with the curves tool
00:39:20 THE CHALLENGE
00:41:05 Variations: Soften the borders between fields
00:43:08 Final words about the Challenge
00:44:15 Exporting and scaling down for publication
00:45:45 End of video

Creative Commons License
Meet the GIMP Video Podcast by Rolf Steinort is licensed under a Creative Commons Attribution 3.0 Unported License.
Permissions beyond the scope of this license may be available at http://meetthegimp.org.

218.22.2X.X in Hefei, China – Please don’t scrape the site!

Meet the GIMP and the GimpMagazine have been offline for hours today, because someone needed to download all the content in parallel. I have no idea if this is flattering or an attack. I have blocked the IP and will re-open it after I got a mail from you

This was simply too much load for the machine.

rtm_692051918086

Edit: Now the machine should be able to keep up, I limited the memory consumption of Apache. It will be slow, but will stay up.

The next video is in the works, I can start editing tomorrow after the grades meetings are over. Lots of stuff happening here, more in the show.

Links 191-192

Not so many links this time, I forgot to take notes…..

There was a meeting of GIMP guys at the LGM 2013 and Michael Schumacher took some notes. I like especially the part about getting good knowledge about GIMP out.

Pat David published some time ago a method to average images with ImageMagik. I stole one of his new results to illustrate this posting. A bit creepy, but you should have a look at his Playboy centerfold collection!

Really dry, with a blue suit and tie – but gooood! IBM has a nice introduction to Scribus, “the” Free and Open Source Desktop Publishing Program.

Not sure which Creative Commons License to choose? Petapixel has a graphic guide.

Rosie Hardy is a professional photographer and uses GIMP. Libre Graphics World shows some of her dreamy self portraits. She sells tutorial DVDs, BTW…….

This exhibition in Berlin sounds interesting, It’s not Nikon, but I’ll have a look.

And a new camera design, stolen from the bugs. (Thanks, Bob!)

 

 

 

Episode 191: PNG or JPG – The Big Fight

This is a PNG in JPG lookDownload the Video! (26:07 49.7MB)

In the last Episode I looked under the hood of JP(E)G and PNG. This time it gets a bit more practical – which is better for what?

I tackle two examples from the GIMP Magazine web site and test, if they would be better saved as JPG or PNG. The Plugin “Save for Web” is really usefull for this task.(The image for this blog entry is a PNG by the way, showing JPG compression artifacts. As a JPG it would be five times the size. )

I “developed” a method for comparing two layers – just set the top layer mode to “difference”, make a new layer from visible and check that with the threshold tool for pixels, that are not completely black. After locating the problematic zones in an image with this tool, one can decide what settings are “good enough”.

Conclusion: It depends. It depends on the file, your use case, your level of “good enough” and your compassion for people on a mobile device in EDGE-Hell.

The show starts with a little extension of the last show, Pascal mentioned some options for saving a JPG file that I had overlooked.

The TOC

00:00:00 Start of video
00:01:00 Progressive mode in JPEG
00:04:09 Progressive mode is not fully supported by browsers
00:04:23 Optimized mode
00:05:56 Baseline?
00:06:17 The quality setting
00:07:09 GIMPMagazine and MTG header image – PNG or JPG?
00:09:23 Checking for quality loss in JPG
00:10:03 Comparing two layers with difference mode
00:10:48 Using the histogram for analysis of the amount of difference
00:11:25 Locating the differences
00:13:50 Trying 85, 75 and 90 as quality settings
00:16:13 When in doubt, compare different settings
00:16:36 Save your work as XCF.GZ
00:17:12 Second example – a drawing
00:19:56 Conclusion
00:23:19 Stay at 4:4:4 for subsampling with photos
00:25:16 Final words of wisdom
00:26:07 End of video

Creative Commons License
Meet the GIMP Video Podcast by Rolf Steinort is licensed under a Creative Commons Attribution 3.0 Unported License.
Permissions beyond the scope of this license may be available at http://meetthegimp.org.

Links 190-191

The links for the gap between #190 and #191. I accept suggestions under info@meetthegimp.org. Even blatant plugging of your own stuff, if I like it. 😉

The competition isn’t sleeping. And the sound will get better soon! Short and on the point – exactly where I suck. 😉

A link to a German site (from Bremen! 🙂 ) with more quick tutorials. Get more Drama into shots with sky in them in 3 minutes.

Monitors for Photography – A Primer from On Taking Pictures.

An academic paper about Noise, Dynamic Range and Bit Depth in Digital SLRs. Looks interesting and is here also as a bookmark for me.

Darktable, the RAW converter and management program, has released a new version, 1.2. Cool stuff about camera specific noise and much much more! And they seem to get masks …..

Do you have a scanner, paper documents to process and run Linux? Then Konrad Voelkel has something for you:After having bought a new flatbed scanner, I re-investigated how to scan and OCR pdfs, how to produce DJVU files that are incredibly small and how to get metadata right. It turns out what I really ever wanted was to create PDF/A compliant documents (I just didn’t know what PDF/A was before). But let me explain the details after presenting you the quick solution. At the end, I have a shell script that scans directly to PDF/A.”

The Rule Of Thirds on Steroids – Alfred Eisenstaed’s compositional system in an analysis of some of his images and a Degas painting. I am not sure if this is over-analysed or not, but it’s an interesting read.

My income is in the top 1%! Where are you on the Global Rich List?

Not a lake. Look at the “beach” on the left side.

What are we taking photos of? A survey of questionable statistical value but from an interesting site for teachers. Perhaps Germans include more under “random stuff” than other people…..

GIMP is now a Professional Photo Editing Software, available in a bundle with Blender and much more for only GBP 2.89 or US $4.37. Whow. Or better not, it’s free on other sites.

Episode 190: JPEG and PNG, what’s in it?

190Download the Video! (36:10 68.8MB)

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The last episode was for absolute beginners, this one is for Geeks. I try to explain (and understand on the way) how images are stored in PNG and JPEG files. PNG (pronounced “PING”) does this lossless, the image can be retrieved in the same quality as the original. PNG works wonders with graphics with a lot of lines and clear colour areas, comics and logos for example, but it creates monster files out of photos and similar images. JPEG looses details, aquires artefacts and generally mangles the image. But it has so beautifully small files and the losses are in most cases invisible – except in the area where PNG is good. So both have their niche to live in.

How is this done? I try to explain this without the math, using analogies, plaing with GIMP to reenact some stages and reducing the complexity a lot. If you want to know the exact facts, read up in Wikipedia, which was also my source of information, or look for other sources. I hope that I never crossed the border between simplification and telling wrong stuff – but I am really not sure. The math is really over my head, last time I had to tackle such a level a Pentax ME Super was still a new camera model. I am happy about any comments that improve my understanding – and all other comments too.

The TOC

00:00:00 Intro
00:02:22 Basics about digital images – pixel, RGB
00:05:25 Storing the colour values in the computer
00:06:24 Palettes for reducing the image size
00:06:50 Run length encoding as simple compression method
00:07:20 PNG, JPG and a WARNING
00:08:44 The PNG format
00:10:12 HexDump and structure of a PNG image
00:13:32 Compression in PNG
00:15:15 PNG is suitable for …
00:16:26 JPG analysed – file structure
00:18:13 First stage: Change the colour model to YCbCr
00:18:54 Decomposing an image to YCbCr in GIMP
00:20:32 Reduce the colours
00:22:20 Testing the concept with GIMP
00:26:17 Splicing into blocks and DCT
00:28:41 quantization
00:29:53 Summary
00:31:20 Testing the compression
00:35:19 Final words
00:36:10 End of video

Creative Commons License
Meet the GIMP Video Podcast by Rolf Steinort is licensed under a Creative Commons Attribution 3.0 Unported License.
Permissions beyond the scope of this license may be available at http://meetthegimp.org.