Episode 134: Dynamic Range T(h)errory

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The German word “Terrorie” was coined by a kid in a Physics lesson of my late colleague Helmut Mohr in Hamburg. It is what it sounds like – and today’s video is full of it. No GIMP, no images, only the blackboard and me talking. Please consider this as a WARNING. 😉

We had a lively discussion in the forum about the theory behind making images, circling around the term “dynamic range”. There is a big difference between light and dark parts of our world, often more that a camera can catch. And nearly always more than fits onto paper or a computer screen.

The process of squeezing this big range into the small output range is called Post Processing. Either you do it via RAW anf GIMP – or the smart chip in your camera does it while saving your iage as JPEG. What I forgot to say – if you do it, you can redo it. The RAW file still exists. If the chip does it, the RAW file is discarded and you are stuck with the version of the image made by the chip.

I got a lot of information about this subject from a wonderful paper by Karl Lang at Adobe(R). Worth to download and read, even if you decide to skip the video this week.

The TOC

02:04 Orders of Magnitude
04:00 How much light is in a scene? (Dynamic range ramp up)
06:00 There is no black and white
06:30 Dynamic range of a scene
06:50 Dynamic range of LCD and prints
08:50 Dynamic range of the camera
09:50 Exposure = slide the dynamic range
11:05 Post processing by the camera
12:15 RAW -> GIMP -> print
13:00 Slides and egatives in analog photography
15:05 A source at Adobe(R)
15:15 8 Bits – a problem (sometimes)
17:10 Why is it possible to make images? Because our eyes are no camera and our brain no computer.

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“Meet the GIMP”  by Rolf Steinort is licensed under a Creative Commons Attribution-No Derivative Works 3.0 Germany License.
Permissions beyond the scope of this license may be available at http://meetthegimp.org.

Episode 028: Are 8 Bit enough?

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This is a new thing on Meet the GIMP!, an interview. I talk to Joel Cornuz from the Linux Photography Blog about the differences in 8 and 16 Bit postprocessing.

Where is Swizerland?But before that you’ll learn a bit about the Confoederatio Helvetica (Latin) Schweizerische Eidgenossenschaft (German) Confédération suisse (French) Confederazione Svizzera (Italian) Confederaziun svizra (Romansh) Swiss Confederation (English) and


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Geneva, Genève, Genf, Ginevra or Genevra. You’ll learn a surprising fact about how the Swiss cope with living an a country with four different mother tongues and nothing about Chocolate, Cheese and Swiss Army Knifes. Neither about CERN, the Red Cross and all the other institutions in Geneva. As we talk all the time in a video podcast I’ll show you a slide show of Joel’s images from his town and country.

I went into the interview knowing that I am not missing much with 8 Bit only in GIMP. But now I miss the 16 Bit option and hope that GEGL will solve this problem soon. 8 Bit is not a problem with images which contain a lot of colours and which get not much post processing. But if you tweak the curves of a nearly monochromatic image too much you are in trouble because you loose colours by interpolation and rounding errors. And so you end with 100 instead of 256 different shades – and that’s not enough for a smooth image.

As you perhaps recall I have taken ways around this problem by using two differently converted files from one RAW image. This would often not be necessary with 16 Bit.

Joel shows another way around this problem – post processing in cinepaint. That’s a hypertuned image processing engine in an old and a bit rusty GIMP 1.9x chassis. I’ll look into that and do a video about it in the future.

The TOC

00:23 Welcome
00:38 Interview with Joel Cornuz from the Linux Photography Blog
23:43 Linux Photography Website
25:25 The End
TOC made by paynekj

Contact me!

Did you like this interview? Shall I make more of them or do you feel this was a waste of time? Please tell me your opinion. You can leave your comments on this blog or write me a mail.

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Creative Commons Attribution-Share Alike 2.0 Germany License.