Could this be the ultimate black and white converter??

May 30, 2009

Converting digital images to B&W is a bit like the Swiss fondue recipe: everyone has a different version and each person is convinced to have the best. I previously blogged about the subject with a “blind comparison” between different methods – with the comparison’s result.

Now during the recent Libre Graphics Meeting, there was a short talk (I don’t remember the speaker) about “What’s new in GIMP 2.6?” and one of the hotness is the very explicitly named c2g feature, conveniently buried in the GEGL operations (sub-)menu.

And guess what? c2g is a black and white converter… maybe the ultimate one.

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G’MIC, next-gen GREYCstoration

February 7, 2009

I received an email from David Tschumperlé (interview, web) the author of GREYCstoration (blog), introducing G’MIC, GREYC’s Magic Image Converter. GREYCstoration’s capabilities (read: algorithms) have been moved to this new high potential framework: all the operations are now filters written in an easier-to-program macro language (gmic). That makes it more simple to add new custom made filters while retaining the power and infrastructure of G’MIC.

G’MIC is available here as a command-line tool or as a GIMP plug-in.

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B&W conversion: which is which?

August 6, 2008

It was great to read so many comments and opinions about the Black & White conversion comparison. Thanks to all of you who took the time to write your preferences. And now here is the formula:

A = Luminance curve from HSL
B = Jpeg2BW
C = Desaturation from RawStudio
D = Channel mixer

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Comparing B&W conversion methods

August 1, 2008

Although I have already blogged about it, converting images to Black & White is a bit like the recipe of the Swiss Fondue: everyone has his own touch to it and claims his way to be “the genuine one”. So I decided to revisit the subject (B&W converting that is, not the fondue) and try several conversion methods and see what results are offered. The methods are:

  1. Simple desaturation with RawStudio
  2. Use a channel mixer
  3. Use the Luminance curve
  4. Use the special Jpeg2BW tool by Thomas Baruchel

The picture I will use as an example is that one, taken on the side of the Lake of Lucerne.

By the way, speaking of Fondue and Lake of Lucerne is timely, since August 1st is the Swiss National Day :)

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From noise to grain

July 9, 2008

While watching the DCRaw (web, wiki) presentation from the last Linux Graphic Meeting in Poland, Dave Coffin mentioned that DCRaw offers denoising before RAW demosaicing, which is the best way to deal with noise – ie as early in the process as possible. The “Treshold” slider in UFRaw allows for an easy control of this parameter.

Since I have already blogged about noise, talked about GREYCstoration and even interviewed David (the author), I decided to have a go at comparing the output of UFRaw vs GREYCstoration on one image.

And this made me think some more about noise and how to treat it.

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Enfuse – multi-exposure blending and a proper HDR

April 25, 2008

In a comment on my previous post about HDR, Felix Hagemann recommended Enfuse as an alternative to HDR. Enfuse doesn’t require to build a “real HDR” image that you tonemap afterwards. Instead it blends together images that are exposed differently – a lot more simple and direct. Let’s see what the results can be and compare them to proper HDR and “mere” RAW processing.

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Love it or hate it, HDR is here… and it’s on Linux, too

March 5, 2008

These days, it is hard to avoid HDR when you are interested in photography. Just for the record, High Dynamic Range is a way to combine different exposures of the same image: you end up with an image that has a wider range of shadow and highlight that what you normally see on printed paper or on your monitor. You then rearrange this extra dynamic to fit into a file that you can see on your monitor or print.

The result is an image that has a lot of details in both shadows and highlights – in my opinion, most of these images look very unnatural (not to say ugly) and very rarely do I come across “good taste HDR”. Like every post-processing, it is only when you don’t notice it that it is done right. Other people, of course, will disagree and process every single one of their pictures in HDR.

To know more about HDR, have a looks at the wikipedia article as well as the HDR Flickr gallery.

Although I won’t cover HDR in all details, I decided to give it a go out of curiosity, especially since Linux does it – via Qtpfsgui, that’s right GUI means: “no command line” :)

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