Whether used as a final touch-up tool or early in the workflow to set up the structure of an image, Local Contrast Enhancement is a processing technique which improves realism and tri-dimensionality in pictures: it's like being in front of the subject rather than a mere bidimensional reproduction of it.
Beautiful! The best $30 I've spent since I got a computer. Thanks.
Rick Dahms, Seattle, WA, USA>
Improvement of local contrast.
Humans don't see things like cameras do: the software running in our brain and constantly processing the visual information passed on by the eyes is enormously more sophisticated than any camera chipset. When we look at things out in the world, we're continuously calibrating and extracting detail depending on the subject we are looking at and also on its surroundings. We were gifted with a built-in local contrast enhancement routine which always runs, and that's why the comparison of the pictures shown below, before and after the application of our tool, are remarkable examples of successful image processing.
ALCE with radius 200 at 100% opacity +12 saturation on the ALCE layer - Original resolution. 7210 by 5410 pix - No masking layer.
Thank you for the creation of ALCE!
Zisiang See, Reina Images,Kuala Lumpur, Malaysia>
More detail and structure in the shadows without any detail loss in the highlights.
The algorithm analyzes the image through a user-defined value (called "radius"). Such radius defines a neighborhood of interest, and within that area a contrast-enhancing manoeuvre is carried out without any clipping. This way, highlight details are safe and enriched, while the structure of shadows is boosted and yet preserves the original information.
ALCE with radius 20 at 100% opacity +avanced layers options as described in advanced tutorial - Original resolution 7210 by 5410 pix
I Love ALCE!!!!!!!! Just wanted to let you know that I am using ALCE
on all the images I use at work. I don’t know how I managed without this.
Bev West, Creative Director, Lawrence, KS, USA
Global and Local contrast
A global adjustment of contrast sets the balance of the entire picture: the standard method is that of establishing a highlight point, a shadow point, and then re-allocate contrast in the midtones, possibly even tuning quarter-tones and three-quartertones. Whatever tool we use for this, the fact is that a lot of contrast still lies, hidden and unexploited, in the image. We need to process every area of the picture separately to make the most out of it, so that all of the image's features may be greatly intensified.
ALCE, radius 200 at 100% opacity + ALCE, radius 20 at 30% opacity + ALCE, radius 1 at 100% opacity. Original res. 3228x 3060pix. - © Francesco Piras
Just the best investment I ever made in CS4. Bravo. Gracie
Jean Pierre Bammatter, Geneve, Switzerland
Excellent local sharpening, 3D look
A standard way to apply a form of contrast enhancement which mimics a "true" local contrast routine is known as HiRaLoAm sharpening, after Dan Margulis' definition. It is, in practice, Photoshop's Unsharp Masking filter with High Radius and Low Amount. If properly controlled, it yields remarkable results. Nevertheless, Local Contrast Enhancement is a different algorithm, conceptually and practically. Still, to an unexperienced eye, the processed image looks sharper as if some kind of filter to boost three-dimensionality were applied.
ALCE with radius 200 at 100% opacity - Original resolution 5794 by 4093pix
ALCE has got such an important part of my workflow. You did a truly fine piece of software!
Rupert Larl, Innsbruck, Austria
No artifacts in soft nuances
Any image processing routine aimed at boosting contrast and detail tends to emphasize transitions between light and dark areas: artifacts and noise in smooth areas almost invariably are an unwanted by-product of such filters. The choice of an appropriate radius helps to minimize this issue, and simple masking will minimize unwnted halos. Check the advanced tips&tricks section below in order to master some useful techniques that may come in handy when you need to tweak the processed result.
ALCE with radius 20 at 100% opacity - Original resolution 3228 by 3060 pix
I have tried using ALCE in Black and White images, particularly on some quite old photographs. The results were fantastic considering it was all done with a single slider. ALCE repaired the old photos to some extent but the great thing was the contrast value with the whites becoming much "whiter" and the black becoming real black without any loss of detail.
Ern Matters, Melbourne, Australia
See the image before and after in full resolution.
This synchronized Zoomify split frame will allow you to navigate across the high-resolution image, and you will be able to compare the processed and unprocessed version. We believe the best way to show what the routine can do is let people see with their own eyes, and especially see the original high-resolution files.
Click inside the window or use the slider to enlarge the image up to actual pixels. Navigate by using the mouse or the arrows. Left: before. Right: after LCE.
NG Manfrotto Booth, Photokina 2008 - ALCE with radius 20 at 100% - Original resolution 3060 by 3228 pix.
The National Geographic Bags Corner in the Manfrotto Group booth at Photokina 2008. The client was very satisfied with this picture. This seems to be a very simple shot, but it isn't: the available light was quite bad, with very dark and very light areas. From ground level, the perspective was not so interesting due to the uninspiring floor whic takes up a large part of the picture. The height of the subject was another problem. My tripod was the Manfrotto 269HDBU lookout stand from 12 feet high.
Camera: Hasselblad H2 with 528 digital back, Lens: Zoom HC 50-110 at 50mm, Exp.1,6 sec.f/11, ISO 50. Planning to apply ALCE I saved the image preserving lights and shadows detail. Of course, the basic file was too smooth. The final result, after the application of ALCE, was very good.
© Roberto Bigano 2008
Your action is really nice. I travel and speak to professional groups in the USA and would like to mention your product.
William Branson III, Durham, NC, USA>
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Help & Troubleshooting page
The FAQ page on login, purchase, install and use of ALCE2 here>
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See more images compared
You'll be able to pixel-peep more real-world examples from Roberto Bigano's archive in a comparative high-resolution Zoomify or "before and after" by clicking on the thumbnails below.
A shot that's in the same time relaxing and dramatic. The file seen at actual pixels was very pleasant but print results was not so good. The application of ALCE delivered a more dramatic impact to the image and a print result by far better than original.
Camera: Hasselblad H1 with 384 digital back, Lens: Zoom HC 80, Exp.1/250 sec.f/5.6, ISO 50.
Planning to apply ALCE I saved the file in linear mode.
© Roberto Bigano 2005
see before/after comparison >
This painting has been lightened with two Elinchrom Flashes using the crossed-polarization technique. Then the file was saved in Flexcolor, Hasselblad's proprietary software with the option "Reproduction Mode" which delivers a stunning tonal range of tones and colors.
Camera: Hasselblad H2 with CF528-39 digital back, Lens: HC 120 Macro,f/11, ISO 50. Lighting: Elinchrom Flashes with cross-polarization.
© Roberto Bigano 2008
Seattle skyline from ferry to Bainbridge
ALCE with radius 200 at 100% with the Mario Olivotto technique as described in our Advanced Tutorial
Here I was testing Leica M lenses on the new Olympus Pen EP2. The results were excellent with the Summicron 50, but surprisingly bad with the the 35ASPH Summicron. This one was shot with the 35. Due to the bad performance of the lens and the heavy vibrations of the ferry the image is not sharp and the microcontrast not good. The application of ALCE at 200 strongly enhanced the local contrast and improved the overall rendition of the colors.
Camera: Olympus Pen EP2 - Lens: Leica 35ASPH Summicron M, Exp.1600 sec. f2.8, ISO 125.
Stitch of three shots.
© Roberto Bigano 2009
3865_64 from "Plastic Girls Series" - Luisa Spagnoli Shop Windows, Vicenza
ALCE with radius 200 at 100% opacity +12 saturation before application of the ALCE layer - Original resolution. 3000 x 4000 pix.
Since I started with photography I was fascinated by dummies. So in the last 30 years I never stopped shooting them. Recently I discovered the Canon G9 that, for this very peculiar kind of shooting is a very good tool.
Camera: Canon G9. ISO 80. Zoom Lens at 12,7 1/6 sec f 5.6. LensMate Hood.
I shot this picture without a tripod but I placed an adhesive pad on the hood and delayed the shot by 2 sec, therefore the camera was totally still.
The new cs4 script is great, the website for it is also fantastic. It is wonder that you and Davide share so much information.
Brud Jones, Digital Labrador, Kansas City, MO, USA>
Roberto Bigano | Tips and tricks
I tried ALCE in very different working conditions and on different subjects. The scope of the following notes is that of transferring this know-how to you.
Default value and slider
First of all consider the ALCE layer like a slider to modulate the local contrast boost. in general expecially at lower radius values you have to reduce the opacity. We chose radius 100 and opacity 100% as standard values, but consider it a very general indication. Consider also that the effect of the radius value depends on the size of the image. I personally very often use high radius, also 200 (my files are very big) because I've found it yields very good results without any further modification.
When starting to use ALCE, try to apply it with different radius values on smaller and larger files, so you will experience the difference that, for instance, is huge between 20 and 200.
Then, try different blending options, mainly switching from the default normal to lighten or darken. Please see the advanced tutorial for further information on blending options.
Below you can see an example with original, ALCE in luminosity, lighten and darken mode.
High radius vs low radius and High Pass technique
In general a higher radius delivers a result almost "ready to use", and a lower radius requires further modifications like layer-masks, multiple blending options etc.
Otherwise lower radius settings are to be preferred if you are looking for a High Pass kind of result for your pictures.
When you apply ALCE it makes a copy of your file, flattening the layers, and the processed ALCE layer is then copied onto a new layer in the original file on top of the existing layers. This allows you to make any kind of modifications.
When developing your raw files, you should foresee using ALCE. Dont apply high clarity values, keep USM a bit lower than your standard and allow a slightly flat contrast. We use these settings to obtain a better looking image and to avoid a lack of contrast and sharpness, but ALCE can replace such settings much better.
In the example below the second image seems to be better but the first one, with ALCE will generate a much more better result.
ALCE for print
Often our files are very nice when seen on a good monitor. They look sharp and with a very good modulation and colors. But when we print them we often notice a very big difference.
ALCE can greatly improve the quality of your printing files as far as sharpness, tridimensionality and color tonal separation are concerned.
Perceptive color saturation
Although ALCE doesn't produce color shifts you may sometimes think that ALCE layers have lost saturation. Why? By default the blending option of ALCE is set to luminosity and doesn't shift colors. Yet our brain expects that increased saturation is needed to match increased contrast. Therefore our perception is that the image has lost saturation. in this case it's enough to apply a tonality/saturation adjustment layer with a Saturation boost between 10 and 20, according to the subject, before ALCE is applied.
The image below is a very good example of "perceptual saturation". On the left the original file, in the center standard ALCE applied and on the right an increase of saturation (15 pts) plus ALCE. Measuring the colour values you will see that in the second image, colors are the same but the feeling is that the image has lost saturation. The third one is better: we expect that a bump of color corresponds to a bump of contrast.
Davide Barranca, a brief presentation
My name is Davide Barranca, I’m a 34 years old color-correction freelance and I live in Bologna, Italy. I currently spend two thirds of my working time with photographers involved in the (strange indeed) contemporary art business, while the remaining third is ﬁlled with maybe more conventional image enhancement routine and prepress for an italian ﬁne-art publishing house. Another third is devoted to research and developing (scripting, PixelBender language, plugins). I plan to add a third soon, for future projects I will happen to be involved into, and and ﬁnal extra third for learning again math and dig deeper in the AS3+Flex mix that seems to be the future basis of CS5 developing for those, like me, who are not hardcore coders. All the rest belongs to my lovely wife Elena and our bright daughter Anita.
Acknowledgements by Davide Barranca
I would like to thank deeply Marco Olivotto, Francesco Piras and Pietro Bianchi, whose suggestions helped me a lot understand what ALCE actually is, and Roberto Bigano who not only provided the pictures, but friendship and constant support and encouragement as well. Also, I would like to thank Jay Ryness, whose original research was the starting point of the ALCE project.