HDR and CLAHE Pre-Release Available

I am back from basically taking a vacation for the last few weeks.   I have been doing development in that time, and have a pre-release beta ready of the next version that includes the HDR and CLAHE functionality.

If you’re interested, let me know and I will send you the URL.  This pre-release is not a general release and I am not wanting to talk about it too much so that I can save the major points for the actual release in a couple weeks.

I will be setting up a private discussion are up for those download the beta.  Any comments would be appreciated, especially since the HDR and CLAHE both ended up being very expansive and useful, to the point of expanding on what was supposed to be one generic function for each CLAHE and HDR implementation, and moving them into 8 different specialized-yet-generic function sets, with another 40 one-shot presets. 

To download the beta, you need the following:

  1. A license for the 4.0+ release of Sagelight.
  2. A username on the discussion board.
  3. Send me a note through the discussion board (http://forums.sagelighteditor.com) if you’re interested, and I will send you the URL and also give you access to the private discussion area.


Pre-Release Notes (and some examples)


1. This release only has the HDR and CLAHE functions in it.  The Lanczos resizing as well as a few other things, such as various bug fixes and the plugin improvements are in another development thread, and I am working to merge all of this in the next couple weeks.

2. The intention and usefulness of the HDR and CLAHE routines, and some examples:

At first, I intended to just implement the CLAHE and then move into the HDR.  But, it was pretty obvious that they shared so much of the same functional base, that I might as well do them both at the same time.    I am glad I did, as I don’t think the CLAHE implementation would have come out so nice had I waited with the HDR.  This is because the HDR (aka Range Compression) function set really required a lot of surrounding functions and new algorithms to deal with it properly, especially when wanting to use HDR with single-frame images. 

It is important to know that, while the HDR and CLAHE functionality, as shown below, supports many great effects in the sense of traditional, artificial & artistic HDR, the main reason for putting them into Sagelight was for the purpose of photographic enhancement.  Of course, that can mean many different things to different people; the main thing is that the purpose is to support generating work from the original image and not specifically to create artificial images in nature.  As it turns out, these routines can do this really nicely on a lot of images, so, I supported it with many different options and functions. 

A lot of the new algorithms I developed to support the HDR and CLAHE revolved around color reproduction and halo reduction.  I ended up developing a nice “color recovery” algorithm to recapture colors in the shadows in a lifelike manner (as opposed to the pale or over-saturated result you get depending on whether you’re converting back from XYZ or LAB mode, etc.), as well as a number of halo-free tonemapping curves. 

I also developed a generic function set that allows you to augment the HDR (without having to create it and then move back into the Quick Edit Mode) with all of these tools together. 

The main thing here is about halos.  Sagelight hates halos.  But, it is hard to avoid them.  I would say that a very large percentage of the work and length of time in developing the HDR & CLAHE routines were directly related to either avoiding halos or managing them (in the case of CLAHE, as halos are just a part of life with the generic algorithm). 

The main emphasis for the implementation of the HDR and CLAHE here is along the lines of getting great results, and blending and using partial results via the Undo Brush is a big part of it.  

The examples below, for the most part, are blended versions (i.e. as a setting available in the HDR or CLAHE function itself), so that the RAW, harsh result is not used by itself, but mixed with the original image. 

The HDR and CLAHE routines are broken down into a few different function sets.  Here are some examples with descriptions of their basic orientation in the HDR and CLAHE functionality:

(these are all generated with the current pre-release.. Today, in fact.  ‘Before’ versions are shown where relevant). 


Flower.  Generated with the ‘HDR Details’ function.

This image demonstrates the idea of generating details while keeping photorealism.  The end result here was a very defined and colorful image.

This image was generated with the “Black and White” HDR function.  The effect of this function is to take a color picture, or pre-existing black and white picture, and create what I can only described as an Ansel-Adams type of black and white pictures: contrasty and well-defined.  In this case, the original color picture was fairly plain.  the HDR/Compression Range function was used to generate great detail, and the other HDR/tone-mapping functions in the HDR function set were used to create the dramatic mood.  A subtle vignette was also added for effect afterwards.


Here is another example.  In this case, a lighter compression range was used.   This was originally a fairly bright color picture, as well. 


Another image where the ‘HDR Details’ function was used.  It’s hard to see the complete different here.  The HDR function added a lot of definition in the clouds as well as the sand and the boat itself.  Also not that the Range Compression (i.e. HDR) function brought down the light on the cabin area.   

Here are the links to the originals, since it is hard to see what is going on in the small thumbnails (these are roughly 3000×4000)




HDR Fill example. 

Another function called “HDR Fill Light & Details” was used for this function.  The HDR function can generate fill areas throughout the entire image without any halos (or very light ones in extreme cases).  While the fill light and Light Blender functions in Sagelight, as presented, are very useful, the HDR Fill can get into more areas without either generating halos of light areas or keeping the edges shadowy.  With the color-recovery algorithm implemented in the HDR routines, the color comes up very naturally instead of washed out. 


Here is another example.  This turns out to be a very challenging example because it is very susceptible to halos.  In this case, the HDR Fill function was able to bring out the light with no halos.   Note: you may see a small halo in the middle-right.  This was already there, and another reminder for me what happens when I grab images from Flickr that already have been worked on and have halos. 

Here is the full-sized result: http://www.sagelighteditor.com/db/hdrbeta/circlebridge-new.jpg


Here is another example where I used the “HDR Fill Light & Details” function and purposely added more range compression to bring out the details.  As all other examples, the original source (for me, anyway) was a medium-level-compressed 8-bit per-channel JPEG image.


Here is a full-on, artificial/artistic HDR result.  This was also done with the HDR Details function with aggressive settings.  This can also be done in the ‘Artistic HDR’ function as well. 


Abandoned Escalator.  The HDR Details function was also used on the original image to give it an artificial/over-the-top HDR look.

Here is a link to the larger version: http://www.sagelighteditor.com/db/hdrbeta/hdr-escalator-new.jpg


Here are a couple CLAHE examples.  The CLAHE is also a very powerful function, and these examples show a very small example of its overall capabilities:


Here is the same bridge image from above.  With the CLAHE it came out brighter and without any halos (except the ones that were already present in the original).  This has much less to do with the CLAHE (as the actual result has significant haloing) and more to do with the Tonemapping mask curves implemented in the HDR and CLAHE functions.


Here is a before and after example.  This shows how nicely the CLAHE can work within an image when it is blended back into the image (in this case with just a slider movement).  The result image has much more definition.  It ended up with a lot more color too, which is something you can control (I decided to leave the color in to add a small artistic element to it). 

As with some other examples, the effect is hard to see.  Here is the full-sized result that really shows off the enhanced definition: http://www.sagelighteditor.com/db/hdrbeta/clahe-truck-new.jpg



That’s about it for now. The above represents a fair idea of what the HDR and CLAHE functions can do, but are also hardly comprehensive. There are also 35+ “one-shot” HDR and CLAHE functions where you can do many different effects (photographic and otherwise) with some control, but without having to get into many controls.

You can also use the main HDR and CLAHE control panel where you can change any setting and do much more.

One thought on “HDR and CLAHE Pre-Release Available

  1. Hi Rob,

    Whilst I am flat out trying to absorb the existing magic options of Sagelight, you keep the magic coming, hey no complaints 🙂

    This latest teaser showing what can be done in the examples is very exciting, hurry them out of Beta so us mortals become totally absorbed with the variety of possibilties.

    My utterances above probably sound way over the top but your Sagelight is truly a magic editor that enables me to experiment in unlimited ways, which has given me sheer pleasure with the final results of some of my many travel photographs.

    I am not skilled or experienced enough to be part of your Beta Tester Group but can’t wait for when you upgrade.

    Thanks once more for extreme quality editing software.


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