Color Remap - in regular use?

[MikeG]

Some time ago there was some discussion on the Color Remap transform.
Mostly here: http://dl-c.com/forum/comments.php?Disc ... e=1#Item_0

I must confess I'm still struggling to get my head fully around this.

Is anyone using Color Remap on a regular basis? If so, to what ends?

Or is it really for special situatiions that no other transform will handle at all, or handle as efficiently?

Thanks in advance,

Mike.

[den]

Because Remap adjustments tend to better blend into the transformed image than if the same adjustments are made with the ColorCorrect with its single Radius adjustment and/or the single Color Balance mid-tone adjustment [pre-PWP5]... my preference is to use the Remap transform for what I used the ColorCorrect transform in pre-PWP5 versions, such as:
(1) adjust 50% R, G, B, C, Y, and M saturations to preferences [sRGB High-Impact Color]
(2) apply ElieD's suggested Velvia presets
(3) adjust an image's mid-tone 50% color cast and at times including the 25% and 75% tone color casts to create mid-afternoon or mid-morning ambience lighting
(4) neutralize an image's mixed lighting source color casts if present
(5) decrease skin color saturations
(6) increase the blue saturations of sky or the green saturations of grass
...etc.

These adjustments are sometimes made with image area masks, a Vibrance mask, or the Extract-ed HSV,S channel Converted to 8-bit BW as a mask for further Amount control.

An understanding of the HSV color space model and the ColorCorrect transform will help the Remap transform to become more intuitive.

[JML]

Mike:

I have used Color Remap several times with considerable success. Color Correction does the same thing but is less adjustable and often requires a mask to avoid spreading the effect too far across the image. Color Correction has a radius but remap is much more precise in how we can control the colors changed in our image.

To approach this experimentally, notice that if you sample a point on an image and set Chroma Radius and Brightness Radius to zero and move the sample point to a different place on the color cube (even far away) nothing changes in the Preview. As we increase Chroma Radius more hues (different from the sampled point) are included in the change. As we increase Brightness Radius more pixels whose brightness differs from the sampled point are admitted into the change.

Tightness defines a closeness of fit hue and brightness and presumably saturation must match to the sampled point be changed. As we relax Tightness, more colors (hue, saturation, and brightness) are admitted into the change.

All of these changes probably have a feather built in to avoid abrupt transitions.

The only problem with Color Remap and other methods is that changing hue a substantial degree is prone to posterization in the image. I have found this with other methods including using LAB in polar coordinates (in other products).

Jim

[JML]

Mike:

As a practical example, the colors in the Mountain Ash berries in the image below were not rendered correctly by the camera (partially due to gamut clipping). In the process of restoring a better hue to the berries, the red fringe around some of the leaves was mostly lost. In the image below, look at the leaves between the berries and at the top of the plant.

Rather than mess with a mask, I used Color Remap to restore the fringing red almost exactly w/o changing the hue of the berries.

[JML]

Mike:

Another less obvious use for Color Remap is to reduce specular reflections on leaves. I have long used Color Correction for that purpose. If memory serves me correctly, Bob Coutant mentioned in a post long ago that he also uses C-C for that purpose (if not my memory needs more than a color correction).

The technique for C-C is to sample a specular area on leaf that still has a bit of color and then use the probe to sample an area on a leaf with the desired color and draw the arrow. Sometimes, it was necessary to remove the default white anchor on the color cube and juggle around both ends of the arrow, so controlling the change was more difficult with C-C.

Color Remap offers much more precise control over the change and does a fine job of reducing the specular areas on the image above (not shown).

A polarizer is the best approach, but I had not yet purchased one for the lens in use in the above image. I now have one, and if I can only remember to put it in my pack on my hikes I will be in good shape.

Jim

[MikeG]

Many thanks, Jim and Den,

I do use CC quite a bit. Now I'll try again with Color Remap knowing that mastering it is well worth while. Your tips will make that much easier for me.

Mike.

[couman]

Mike, Jim, Den -- you guys are killing me -- now I'm going to have to upgrade my computer so I can upgrade my PWP and do these things

[MikeG]

Bob - It'll be worth it!

Jim/Den,

Getting the hang of it. After a bit of re-familiarisation and experimentation with a leaf with blown pataches, I loaded a photo with a badly blown sky. Pride insists that I make it clear that I did NOT take this photo! Actually it's a composite of two photos taken by another.
I was delighted to find that I could transform the photo from badly blow gray to cloudy blue very quickly and, as you both said, with a good level of control. I know the sky could do with more work to get a better result, but the ease of getting to this point was most encouraging.

I'm a convert!

Mike.

Comp 01 gray sky.jpg (48.69 KiB) Viewed 8717 times

Comp 01 cloudy blue sky.jpg (48.13 KiB) Viewed 8701 times

[JML]

Mike:

Interesting that you post this example as I did the same thing on a winter scene with a scuddy gray sky interlaced with darker clouds. With Color Remap I moved the light gray toward blue with minimal impact on the blue cast on the snow.

But I ran into a problem last night where I made the change I wanted with Color Correction, a few anchors, and an adjusted radius but Color Remap with three color pairs had made little progress — it was looking like C-Remap would require a dozen or so color pairs. Relaxing the constraints (radii and Tightness) tended to splay the change all over the image — so Color Correction is still in the toolbox for me.

Its nice to see actual examples of PWP in action, and I will make my annual suggestion — allowing posting of a bit larger image say 600 pixels on the long side and say 80 KB to lessen the jpeg compression effect would probably be an incentive for people to post more examples and better illustrate the problems/solutions. Of course its always easy to spend other people's money.

Jim

[MikeG]

Jim,

That's a little disappointing. I'd rather assumed that I'd be able to replace CC with CR! Now I shall have to be a little wary.
I shot, near where I live which is an inner suburb of Sydney, the top of a tree nicely illuminated by the sun on it's way to setting, against a blue sky. I thought that I'd see how the shot might benefit from Color Remap using Den's HSV,V 50-90 HSV,S 50-60 color swatches. I had to move Chroma Radius and Brightness Ratio all to 1.0 to produce a significant effect, and I thought the result very pleasing.

I'll post them below and provide a link to larger files on Flickr which may help illustrate the short comings of the size restrictions of this board that you referred to. For those who don't already know, the magnifying glass labelled 'All sizes" in the middle of the row of icons immediately above the flickr image provides access to different image sizes. Max seems to be 1024x768 but I don't know the file size limit at this size. Someone else might know this.
Here's the Flickr links:
Before: http://farm4.static.flickr.com/3492/378 ... e8c199.jpg
After: http://farm4.static.flickr.com/3509/378 ... a471ee.jpg

I'd welcome comments on use use of Color Remap for this purpose. How to use it better, or ways to produce a superior result.

Mike.