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ch22

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  1. I'm not sure how DR evaluated in the equation? This is not a real equation, but a kind of pseudo-code. DR is the previous DR in the right hand side and the new one in the left side. For instance, the product blend mode would be obtained with DR=DR*SR (to be understood as DR_new=DR_previous*SR). Only the right hand side is to be entered into the AP box roundup(0.5-0.3*SR-0.59*SB-0.11*SB) Should that be 0.59*SG? Of course. I suffered from many mistakes in the process, I corrected a lot of them directly in the AP box and I did not always reported these corrections in my text processor... and unfortunately I used this text version to prepare my post. Sorry! Actually, I did not dare to directly deal with color pictures. I began the work with grey pictures, where the code is far simpler. Not that simple to get it right the first time, but I succeeded fast enough to be reasonably confident to tackle the color case. Now, I want to emphasize that my misadventures are not at all a condemnation of this Apply Image menu. Simply, in case of complex equations, better to have a true text editor at hand with a compatible copy and paste function!
  2. First, thanks to dmstraker and Cecil for their encouragements. As for the English conversion... sorry, but that's another story ! Now, returning to the dmstraker's experiments with the Apply Image menu, I tried too. And incredibly —but VERY painfully— I succeeded in emulating the Contrast Negate blend mode. The issue is that equations to be entered are fairly long (see below) so that entering them by hand without errors is nearly impossible. You must prepare these equations on a separate text editor and then copy and paste them into the right box in Affinity Photo. Using word processors (such as Word or Text Edit) is a poor idea as the pasted formulas are not understood when they are too long — I suspect they are ruined by undesirable hidden formatting characters. Better to use a true text editor ; unfortunately, I use a very old one (AlphaX), and the copy and paste from it to AP does not run ! Eventually, I mixed parts of copy and paste with parts of manual typing, and finally I reached the holy Graal, I mean the identity between the blend mode and its emulation... The pseudo-code for the equations to be entered is as follows : DR=(1-DR) * SEL + DR * (1 – SEL) ; DG=(1-DG) * SEL + DG * (1 – SEL) ; DB=(1-DB) * SEL + DB * (1 – SEL) where SEL is the logical expression ((SL<0.5) AND (DL<0.5)) OR ((SL>0.5) AND (DL>0.5)) , where SL and DL stand for the luminosities (lumas) in the source and target layers, that is SL=0.3*SR+0.59*SB+0.11*SB and DL=0.3*DR+0.59*DB+0.11*DB. Then, as pointed by dmstraker, replace the conditional expressions such as (SL<0.5) or (SL>0.5) by numerical evaluations roundup(0.5-SL) or roundup(SL-0.5), then replace AND operator with a mere product , and OR with a mere addition (this is valid in this special case). We thus get DR= (1-DR) * ( roundup(0.5-0.3*SR-0.59*SB-0.11*SB)*roundup(0.5-0.3*DR-0.59*DB-0.11*DB) +roundup(0.3*SR+0.59*SB+0.11*SB -0.5)*roundup(0.3*DR+0.59*DB+0.11*DB -0.5)) + DR * (1 – ( roundup(0.5-0.3*SR-0.59*SB-0.11*SB)*roundup(0.5-0.3*DR-0.59*DB-0.11*DB) +roundup(0.3*SR+0.59*SB+0.11*SB -0.5)*roundup(0.3*DR+0.59*DB+0.11*DB -0.5))) and similarly for green and blue components. These are the real formulas to be entered into AP If you get to this point and AP is not grumbling about your formulas, congratulations! You should have reproduced the result of the Contrast Negate blend mode!
  3. Indeed, the macro results only in the invert adjustment through the selection about luma comparisons (this can be seen in the video). Its purpose was simply to give the same display as the investigated blend mode, without modifying the RGB components of the layer; additionally, the selection can be recovered for any other fanciful operation you could imagine on this layer. My current version is 1.7.3 Let me some time to consider your formulas —so far, I never walked through this menu in my exploration of Affinity Photo (my personal project consists in in-depth explanations of the software for French photographers through a set of video tutorials, french speaking, of course! The job is not ended. See http://www.oitregor.com/numeric/affinity_photo/contenu.html )
  4. Sorry, Dave, I cannot open your file with my current version (1.7.3) —I got the warning “The file includes features from a later version of Affinity“. As for the right operating process, I join a short video demo_contrast_negate.mp4
  5. By November 2017, dmstraker was asking for information about Contrast Negate (https://forum.affinity.serif.com/index.php?/topic/49811-your-big-friendly-guide-to-layer-blend-modes/&tab=comments#comment-250891) . As I found nothing about this point in more recent posts, I give my opinion. I think that the luminosities of the two layers are analyzed, but in the sense of lumas, i.e. L'=0.3R'+0.59G'+0.11B' where all quantities are normalized quantities varying in the (0,1) interval. First a selection is built of areas where lumas are both below 0.5 ou both above 0.5. Then, the upper layer is replaced with its negative within the selection. I enclose a macro, simu_Contrast_Negate.afmacro which (hopefully) does this job —to be imported in the Macro panel. Select the upper layer and run it. An Invert adjustment should be created above the upper layer (allowing to recover the selection from the adjustment mask) simu_Contrast_Negate.afmacro
  6. Another method for obtaining the saturation mask or the equivalent saturation selection, which requires no HSV capacity : (1) open an HSL adjustment, put saturation to -100 and put the blending mode to "difference" (2) open a level or curve adjustment so as to get a x2 gain (for instance, with levels, put the white glider at 50%). This amplifying step will allow to get a full saturation mask, i.e. with white or black corresponding to fully saturated colors or gray tones. At this stage, the (max, med, min) triplet for color components is replaced with (max-min, xxx, max-min) where xxx is lower than max-min (3) in order to retain only the difference (max-min), open the channel panel and successively (i) right-click the red line for " load in the pixel selection", (ii) and (iii) right-click the green and the blue lines for "add to the pixel selection" —this is equivalent to choosing the highest of the three RGB components. We then have the wanted saturation selection.
  7. Additionally, switching to English in Preferences dialog makes the Overlay item reappear in the drop-down list with seemingly the expected behavior.
  8. I confirm. The second occurrence of the "Superposition" (Screen) mode is not a mere mistake in the drop-down list names, it really calls for the Screen mode.
  9. In my opinion, the new filter is much less satisfactory than the previous version. The only progress I agree is that the halos along the discontinuity lines have apparently vanished. In this message, I report a behavior that seems to me anomalous. When I apply the Shadows & Highlights live filter to a homogeneous patch R = G = B = 5 with a 100% strength , the luminosity does not stabilize at all when the range goes from 0 to 100%, contrary to what happened with version 1.6. The figure below summarizes what happens. Incidentally, the figure also shows that the 100% range is limited to the medium gray, i.e. lighter tones are not affected. Why not to allow the filter effect to cover the whole range from black to white?
  10. I confirm we are speaking of the new S&H filter. Below is a picture showing the effect on a gray chart, with the original and the modified chart together with the histogram of the modified chart (this histogram comes from Photoshop). The ray widening is characteristic of the action of S&H filters.
  11. Actually, since a RAW file does not contain any ICC profile, the luminosity and the colors of a RAW file just opened does not matter very much. It's only at the output of the raw software that a ICC profile is added to the file and that RVB components are given a true color meaning. However, the camera JPEG file or the display by the system commodities or Adobe software (and many others, of course) are in reasonable agreement and thus offer a convenient reference with which Affinity Photo should comply — and unfortunately it does not always. Under MacOS and with Serif RAW engine, I observed nothing special with NEF, CR2 or ORF files, but I actually got this odd darkening with RAF files. However, it disappeared when I switched to the Apple RAW engine. Below are compared screen copies for RAF and CR2 between AP 1.6, AP 1.7 and Photoshop (in this case, with no correction) and a screen copy with the Apple RAW engine :
  12. The Shadows/Highlights Filter has been rewritten and I find its new version far less satisfactory than the previous version (incidentally, I hardly understand how such a filter may run without the Radius glider) I enclose below an example of comparison. Increasing the correction intensity in 1.7 would lead to a picture even more grayish
  13. I'm just one year late, roughly, but I discovered this discussion only recently by chance and I'm grateful for the appreciation. Actually, I wrote these tutorials with true beginners in mind and I tried not to lose them when advancing in the intricacies of AP. Now, by the beginning of 2019, many of the tutorials which were missing by the time of the jmmermet post are now in line. Only for french speaking people, I'm sorry, nobody is perfect ! Let me repeat the adress http://www.oitregor.com/numeric/affinity_photo/contenu.html
  14. Under MacOS, I compared various prints of a gray chart on a matte paper, on the one hand from Photoshop with perceptual intent (without black point compensation), and on the other hand from AP, either perceptual or relative, with or without black point compensation. All of them are practically identical.
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