dmstraker

Thanks for the check, Rick, but I'm still getting it. I tried with a completely new, empty document and saw the same effect. To see exactly what colour is where, I drag from the colour picker on the right-hand Colour tab.

Gradient map Black on left, white on right Click on line Colour added is not that from directly beneath point This is pronounced when adding points in left half. It seems that rather adding points from 0 to 255, it is adding points 128 to 255.

Makes sense, @smadell. Interestingly, I applied the Dx=(max(SR,SG,SB)-min(SR,SG,SB))/max(SR,SG,SB) algorithm to DR, DG and DB, which resulted in fades in the last two columns but not the second. However, just using (max(SR,SG,SB)-min(SR,SG,SB)), a straight range calculation, gives the same results as yours (fade to black in right three columns). Looks like an alternative. Easier as macro? Also, my original method gives the same result.

Note for the curious: The conversation continues in smadell's post.

Here's a question. What should happen when saturation mapping this: You've got saturated primary/secondary colours, fading to black, white and grey. Then likewise for black, grey and white. In a pre-mask layer, presumably the primary/secondary colours in the first column are white. But what should the other columns show? And what of black/grey/white? Just musing. Edit: If you apply HSL and turn up saturation, only the primary/secondary colours in the fourth column change. Does that mean a saturation mask should only show the changed area? This would suggest: Copy layer, HSL, S up, Blend Mode: Difference. Invert.

Nice! My photography is still at the stage where 'fixing' is an ongoing necessity. One reason why I like AP so much. My wife is, slightly annoyingly, a natural photographer who just seems to get great shots in camera without really trying. Makes you want to cut off your ear . I spent ten years as a programmer, so the code was ok. I'd get stuck if dropped into the deep end now, though. Like all professions, you turn away for a moment and when you look back everything's changed.

On reflection, as colours move closer together, the result is more towards grey, which is desaturation. So max-min is an inverse measure of greyness (the smaller it is, the greyer the combined colour; the larger it is, the less grey and more saturated is the combined colour). Saturation is then calculated as this ungreyness as a proportion of the most saturated colour. So if RGB are spread out, the result is less grey (=more saturated) and max-min is a larger number. This is then normalized as proportion of the largest value to give a value 0..1. If it was divided by the minimum, the result would be >1, possibly very much greater.

My brain hurts. Too much cerebration? Mmm. LAB. Kind of emulates the opponent-process that the eye uses to send RGB info from cones back into the brain. And then we get into perceptual stuff, which is delightfully confusing. The collision of technology, psychology and colour is a fascinating world I'm still wandering around.

Most excellent. Thank you, smadell. I shall study closely. I've been around this park on and off to the point where I've forgotten whether there is a definitive algorithm. With a single channel, presumably saturation is simply the value of each pixel in the channel, such are 'Red has a value of 157 out of a possible 255, so is 157/255 = 62.5% saturated'. The question is how saturation is calculated for three channels. Is it a simple average or is some weighting given to dominant colours or the spread of saturation across channels? Edit: Having said this, this page (with due zero exception) suggests Saturation = ((max(R,G,B) - min(R,G,B))/max(R,G,B). Hmm. Rings a bell.

Here's an effect I'm finding: Zoom into a pixel layer so you can see the pixels. Add sharpening layer above Unsharp and HP both have same effect. I tried it with several other adjustments and it didn't happen. Group the sharpening layer (Ctrl-G) so sharpening is only layer in group. 'squares' appear, as below (only after the grouping Merge Visible makes them disappear, so presumably it's a rendering thing, but it makes non-destructive editing impossible.

Ok, John. Let us know how you get on.

No photo attached, @John Rostron. Which process are you seeking to emulate (@fotoloco, my original or a combined version?). If you are using the @fotoloco version, the third step from the bottom should be HSL, not HSV, then the two HSLs above should be HSV. Groups are very handy for several reasons, including: Keeping things tidy and understandable Adding extra blend mode at group level Spot the Overlay blend in my ' fotoloco-straker method on rostron church image.afphoto', in 'Colours' subgroup or 'Fotoloco method' group that makes it react with Tones subgroup below to show original image. Constraining actions such as Erase blend mode. Think of them like a non-destructive 'merge visible'. They often act this way.

Just keeping up with Photoshop. Hold down Alt key when dragging nodes to see clipping on image (as already exists in Levels). Show vertical and horizontal lines from selected node (or maybe just while moving) help align with axes. Show percentage X and Y values for selected node (and allow input this way). And... Have an 'auto levels' button to stretch (and unstretch) the histogram to remove dead space at ends. Allow presets to be loaded here. [Edit additions] When using picker and when moving mouse around image, show point on curve with moving node to reflect lightness of underlying pixels at mouse. Thanking ye kindly sirrah/modom!

@John Rostron Here's your church interior with the @Fotoloco method (done on 1.7), and then with my HSV method (done on 1.6) to get mask, ending with curves applied to original image using fotoloco-dmstraker mask. I'm a bit puzzled as to how it actually works - something to do with the algorithm of Vivid light with an inverted desaturated blend layer... Vivid Light is: For each of RGB: If Blend >= 0.5: Result = 1 – (1 – Base) / (2 * (Blend – 0.5)) [Colour Burn] Else (Blend < 0.5): Result = Base / (1 – 2 * Blend) [Colour Dodge] Regards Dave fotoloco method on rostron church image.afphoto fotoloco-straker method on rostron church image.afphoto

Version 1.7 beta hasn't got HSV! I've asked for it to be restored.