High Pass LCE

[Phile]

I have been using a workflow suggested by 'den' on 22 April 2009 for a High Pass local contrast enhancement and it works great. I would like suggestions on
adapting this method to use with black and white ( grayscale) images.
thanks
Philk

[den]

I believe your are referring to the posting here: http://www.dl-c.com/cgi-bin/discus/show ... #POST29761.

If Img0 is a 16 or 8 -bit B/W image, the workflow would be the same as for a color image except that there would not be a need to do the Part 1: HighPass LCE -- Step 2 conversion... ...just use the resulting Step1 image as the Step4 Overlay image.

[Phile]

Thanks den; that is what I decided to do and just needed some verification. I also tried processing bw images through an HDR application which worked quite well. I have both sns-HDR and Oloneo. The sns-HDR is great and does a great job on aligning hand held shots, but it takes about 30 minutes to process a set of 3 bracketed shots.( color images)
thanks again for your help
Phil

[Marpel]

I have just tried the process referenced in this thread and must say I am, so far, quite impressed by the result.

A couple questions, however:

In Part 1, step 1, an amount of 50 - 150 for the radius is indicated. It appears the dialogue limits the radius to 128. As I have 6000 x 4000 pixel images, I was looking to try a higher radius. I presume this is merely a misprint rather than a change in maximum radius between versions 3 and 5??

In Parts 1 and 2, a suggested range (20 - 65 and 38 - 65) is identified for the white portion of the mask and appears the idea is to "massage to taste for a particular image". However, I am unsure what I should be looking for when determining the best number(s). Is this strictly related to the amount of haloing, or is there something else to look for when moving the slider?

Thanks,

Marv

[den]

In Part 1, step 1, an amount of 50 - 150 for the radius is indicated. It appears the dialogue limits the radius to 128. As I have 6000 x 4000 pixel images, I was looking to try a higher radius. I presume this is merely a misprint rather than a change in maximum radius between versions 3 and 5??

The maximum radius for the Blur transform and its High Pass mode is currently 128 [PWP5]... if you are looking for a larger radius, there is nothing to prevent one from making a further High Pass blur of a prevously High Pass-ed image version... ...my experience has been that a LCE radius larger than 100, regardless of over-all image dimensions including mega-sized panoramas, that the light/dark gradients become so diffuse that their effect becomes barely discernable... ...perhaps selecting a radius based upon the approximate (pixel diameter/2) of an major visual element in the image would be a good starting point...

In Parts 1 and 2, a suggested range (20 - 65 and 38 - 65) is identified for the white portion of the mask and appears the idea is to "massage to taste for a particular image". However, I am unsure what I should be looking for when determining the best number(s). Is this strictly related to the amount of haloing, or is there something else to look for when moving the slider?

You are correct to look for [...the usual suspects... ;-) ] objectionable light/dark halos/auras... and perhaps also the loss of detail in significant visual elements in an image... but also one needs to take a look at the image in total... does it have the visual impact that you wish to convey to a casual viewer? ...sometimes, the barely discernable artistic softening of halos/auras [glow] provide a more 'romantic' ambiance to a scene than perhaps crisp edges and stark contrasts...

Another thing to possibly keep in mind is that LCE/Edge Sharpening as described here is 'Creative' sharpening optimized on a monitor that will potentially be processed again for intended 'Output' media... ...print, projection, web resolutions, etc...

[Marpel]

Thanks for the clarification Den. I will try out some of your suggestions.

Marv

[den]

Since the posting in 2009, I have developed an advanced High Pass LCE/Edge Sharpening technique using masks to separately set the shadow/highlight tone ranges and mid-tones Amounts while at the same time, limiting the light half of LCE/Edge Sharpening to 2/3's (or another preference) of the dark half of LCE/Edge Sharpening.

This technique with slight variations also has application for adjusting light/dark halves of Sharpen, Heavy Sharpen, USM, Bilateral Sharpen, and Advanced Sharpen transforms; and Soft Light or Hard Light filtering an image with itself while controlling the Amount of changes separately in the shadows/highlights and mid-tones...

The technique has been shared with a few in off message board communications but if there is a general interest, I can post it... it is fairly simple to do but an understanding of what the suggested masks' black/white amounts and the curves are doing is not necessarily obvious...

A primer for this technique which describes the first part is my posting here: http://www.dl-c.com/board/viewtopic.php ... 2474#p2459 and here: http://www.dl-c.com/board/viewtopic.php ... 2474#p2461 ...So an understanding how this suggested mask can separate shadows/highlights and mid-tones and can be used to control a transform's effect in the mid-tones separate from the shadows/highlights will go a long way to understanding the complete technique alluded to above...

...Let me know if there is further interest...