Sharing Galore


Sharing Galore

or, Why This Community is Awesome

Community member and RawTherapee hacker Morgan Hardwood brings us a great tutorial + assets from one of his strolls near the Söderåsen National Park (Sweden!). Ofnuts is apparently trying to get me to burn the forum down by sharing his raw file of a questionable subject. After bugging David Tschumperlé he managed to find a neat solution to generating a median (pixel) blend of a large number of images without making your computer throw itself out a window.

So much neat content being shared for everyone to play with and learn from! Come see what everyone is doing!

Old Oak - A Tutorial

Sometimes you’re just hanging out minding your own business and talking photography with friends and other Free Software nuts when someone comes running by and drops a great tutorial in your lap. Just as Morgan Hardwood did on the forums a few days ago!

![Old Oak by Morgan Hardoowd](upload://84XLkVeF3nzkoRudGnde4x7ikFN.jpeg)
Old Oak by Morgan Hardwood cbsa

He introduces the image and post:

There is an old oak by the southern entrance to the Söderåsen National Park. Rumor has it that this is the oak under which Gandalf sat as he smoked his pipe and penned the famous saga about J.R.R. Tolkien. I don’t know about that, but the valley rabbits sure love it.

The image itself is a treat. I personally love images where the lighting does interesting things and there are some gorgeous things going on in this image. The diffused light flooding in under the canopy on the right with the edge highlights from the light filtering down make this a pleasure to look at.

Of course, Morgan doesn’t stop there. You should absolutely go read his entire post. He not only walks through his entire thought process and workflow starting at his rationale for lens selection (50mm f/2.8) all the way through his corrections and post-processing choices. To top it all off, he has graciously shared his assets for anyone to follow along! He provides the raw file, the flat-field, a shot of his color target + DCP, and finally his RawTherapee .PP3 file with all of his settings! Whew!

If you’re interested I urge you to go check out (and participate!) in his topic on the forums: Old Oak - A Tutorial.

I Will Burn This Place to the Ground

Speaking of sharing material, Ofnuts has decided that he apparently wants me to burn the forums to the ground, put the ashes in a spaceship, fly the spaceship into the sun, and to detonate the entire solar system into a singularity. Why do I say this?

Kill it with fire!

Because he started a topic appropriately entitled: “NSFPAOA (Not Suitable for Pat and Other Arachnophobes)”, in which he shares his raw .CR2 file for everyone to try their hand at processing that cute little spider above. There have already been quite a few awesome interpretations from folks in the community like:

A version by CarVac
By MLC/Morgin
By Jonas Wagner
By Jonas Wagner
By iarga
By PkmX
By Kees Guequierre

Of course, I had a chance to try processing it as well. Here’s what I ended up with:


Ahhhh, just writing this post is a giant bag of NOPE*. If you’d like to join in on the fun(?) and share your processing as well - go check out the topic!

Now let’s move on to something more cute and fuzzy, like an ALOT…

* I kid, I’m not really an arachnophobe (within reason), but I can totally see why someone would be.

Median Blending ALOT of Images with G’MIC

![Hyperbole and a Half ALOT](upload://e5HlMunUy1hB3X7PHE1LstfsSF4.png)
The ALOT. Borrowed from Allie Brosh and here because I really wanted an excuse to include it.

I count myself lucky to have so many smart friends that I can lean on to figure out or help me do things (more on that in the next post). One of those friends is G’MIC creator and community member David Tschumperlé.

A few years back he helped me with some artwork I was generating with imagemagick at the time. I was averaging images together to see what an amalgamation would look like. For instance, here is what all of the Sports Illustrated swimsuit edition (NSFW) covers (through 2000) look like, all at once:

![Sport Illustrated Swimsuit Covers Through 2000|605x800](upload://jraV7njUaHyKahItB3Os7d59dN3.jpeg)

A natural progression of this idea was to consider doing a median blend vs. mean. The problem is that a mean average is very easy and fast to calculate as you advance through the image stack, but the median is not. This is relevant because I began to look at these for videos (in particular music videos), where the image stack was 5,000+ images for a video easily (that is ALOT of frames!).

It’s relatively easy to generate a running average for a series of numbers, but generating the median value requires that the entire stack of numbers be loaded and sorted. This makes it prohibitive to do on a huge number of images, particularly at HD resolutions.

So it’s awesome that, yet again, David has found a solution to the problem! He explains it in greater detail on his topic:

A guide about computing the temporal average/median of video frames with G’MIC

He basically chops up the image frame into regions, then computes the pixel-median value for those regions. Here’s an example of his result:

P!nk Try Mean/Median
Mean/Median samples from P!nk - Try music video.

Now I can start utilizing median blends more often in my experiments, and I’m quite sure folks will find other interesting uses for this type of blending!

This is a companion discussion topic for the original entry at

I’m really grateful for @David_Tschumperle as well. It’s quite amazing to me that I can make a suggestion for a custom CLUT filter and about 5 hours later it exists. :astonished:

Speaking of which… Anyone interested to write an article about how this filter works and can be used to process photographs ? That could be really cool to have a page here on describing this filter, with a use case or something like this :slight_smile:

I’d be happy to get started writing something. The CustomCLUT filter, right?


Yes. I think this filter is not so easy to understand at a first glance.
For people who don’t know what a CLUT-based mapping is, of course, but even for those who know, there are some controls that may look a bit cryptic.

On the spider above, I used the “customize CLUT” filter. With it I replaced the purple/blueish color (light purple and dark purple) with the the forground “brown” color (railing). I locked this forground “brown” color. I locked as much colors on the spider as there were actions possible. I used also Spatial regularization to keep the texture of the railing as much as it was before, but can’t remember the setting. I used 8 keypoints.

Thereafter I used this as new layer with a high opacity, but not 100%, therefore it is still a little bit purple at the top.


I started to right something last night, but would rather have not do it all myself. Perhaps we can collaborate on the article.

I’m not sure how we would do it, but here is what I started with.

Customize CLUT – A bit like 3D curves.

Curves are one of the most versatile and often used tools for manipulating photos. The basic principle is that you can take an input value and map it to a new output value. Typically the user will set a few values to change and the software will interpolate a smooth, predicable change between the user set changes and all of the other values. Curves, however, are limited to one dimension. That is, you are only changing the intensity of one channel (eg red or green or blue).

Digital photographs are represented in three dimensions, each dimension is a colour channel and it forms a 3D cube of all of the possible colours in the image.

A Colour Look Up Table (CLUT) is list of all of the colours in a colour cube and new values that each colour should be changed to. Explain more here.

The Customize CLUT filter allows a full Colour Look Up Table to be made by specifying input and output, just like curves, but in three dimensions. It’s not complicated. It’s as easy as specifying an input colour you want to change and the colour you want it changed to. All of the other colour changes are interpolated from known points to produce smooth colour changes across the whole colour cube, just like the rest of the values are when using curves.

Lets look at an example. To keep it simple we will use a black and white image. If you set the input colour white to replaced in the output with black, and black to replaced in the output with white, all of the values in between are interpolated and you get a negative of what you started with.
We could replace white with cream and black with navy and get a split tone effect.

To make things easier the filter allows you to ‘lock uniform sampling’ which has a number of options to make certain colours stay the same in the output unless you override them.

Yes we can certainly do that. Do you have access to the Lounge category? We can make it a community wiki topic.

Yes, I can see the lounge category, but I don’t know anything about community wikis.