Andreas Scherer Posted January 30 Posted January 30 I've been given a set of colour values in HEX that I use in Affinity Publisher V1.10.8. When I enter the HEX values in the colour panel, the visual colours are “correct”. When I compare the RGB and CMYK values in Affinity and two online colour converters (convertacolor.com and farben-umrechnen.de), all RGB values correspond. However, I have not yet found a colour converter that reproduces Affinity's values for CMYK. Now I reentered my HEX values in Affinity V2.5.7 and the CMYK values are all different again, even compared to V1. In the Online Help I have not found a decent description how Affinity's CMYK values are to be interpreted or compared to other softwares The attached PDF was created with Libreoffice Calc, which displays the same values as, e.g., convertacolor.com. Note that I use sRGB as colour profile, so the CMYK values are not actually used in my project. I'm just curious. CMYK-V1-V2.pdf Quote
Ldina Posted January 30 Posted January 30 @Andreas Scherer Note that I use sRGB as colour profile, so the CMYK values are not actually used in my project. I'm just curious. In color managed Apps, like Affinity, you can define individual colors in any color mode (RGB, LAB, CMYK, etc), using the color sliders. Let's say you define a color in RGB using the sliders, or using an RGB Hex code. Your color will be determined by the RGB or Hex numbers AND the RGB profile of your document. The precise colors are not fully defined unless combined with a profile. The same numbers will display differently with different profiles, e.g., sRGB, Adobe RGB, ROMM RGB, P3, etc. The same is true with CMYK. There are many "standard" CMYK profiles...US Web Coated SWOP, Gracol, ISO Coated, Fogra 39, etc. When the CMYK numbers are combined with a CMYK profile, you get a specific, well defined color. Without the profile, you have a poorly defined color. The definition of an RGB color in CMYK terms involves a "conversion" from one color space to another, for example, sRGB (RGB) to US Web Coated SWOP (CMYK). Different profiles will result in different CMYK numbers after conversion. The goal behind using ICC profiles is to retain color accuracy, in so far as possible. Different devices have different color gamuts, so perfect translation of all colors from RGB to CMYK, or from CMYK to RGB, is impossible. A printing press in the USA using US Web Coated SWOP will require different CMYK numbers than a Press in Europe using Fogra 39 to reproduce the exact same color of blue. Different numbers, but the same color. This is also true of monitors. I don't know anything about convertacolor or farben-emrechnen (which I can't even pronounce!), or what color profiles they use for conversion from RGB to CMYK. Affinity will normally use the profiles you set up in Color Settings...mine are Display P3 for RGB, and US Web Coated SWOP for CMYK, but most people probably use sRGB for their default RGB color space. Assuming everyone uses the same RGB and CMYK profiles, the converted numbers should be the same (however, different color 'engines' may result in some small differences, (little CMS, Apple, Adobe, etc). So, that most likely explains why the numbers don't agree. Hope that made sense. Oufti 1 Quote 2024 MacBook Pro M4 Max, 48GB, 1TB SSD, Sequoia OS, Affinity Photo/Designer/Publisher v1 & v2, Adobe CS6 Extended, LightRoom v6, Blender, InkScape, Dell 30" Monitor, Canon PRO-100 Printer, i1 Spectrophotometer, i1Publish, Wacom Intuos 4 PTK-640 graphics tablet
thomaso Posted January 31 Posted January 31 Apart from the influence of the colour profile on the appearance/colour values, a given colour in CMYK can have several variants for its definition: The additional black colour channel in CMYK allows colours to be defined in two ways: either with more CMY and less K, or with more K but less CMY. Below three different colour definitions for the same look of the brownish swatch. The two ways are called GCR (Grey Component Replacement) versus UCR (Under Colour Removal). It can be relevant for the printing process because the two methods need a different amount of ink = cause different TIC (Total Ink Coverage): more ink -> more moisture -> longer drying time. And it also affects the colour/ink setting when printing: More CMY ink offers more options to influence the printed colour than more K ink, for example to counteract a colour cast. Accordingly, more CMY ink may require more precision to avoid a colour cast than more K ink. In Affinity we cannot choose between the two methods when converting RGB to CMYK. In your example PDF it seems that Affinity prefers UCR (more CMY, less K) while the Online Converters define your swatches as GCR (more K and less CMY = less total ink). Ldina and Andreas Scherer 1 1 Quote macOS 10.14.6 | MacBookPro Retina 15" | Eizo 27" | Affinity V1
lepr Posted January 31 Posted January 31 11 hours ago, Andreas Scherer said: I have not yet found a colour converter that reproduces Affinity's values for CMYK Affinity uses colour management when converting RGB to CMYK, and so the values produced by the conversion depend on source and destination colour profiles. Online converters have no concept of colour management and instead employ simplistic formulae and are of no practical use. These formulae are described at many sites, such as https://www.rapidtables.com/convert/color/rgb-to-cmyk.html 11 hours ago, Andreas Scherer said: I reentered my HEX values in Affinity V2.5.7 and the CMYK values are all different again, even compared to V1. The difference will be because your sRGB v2 and sRGB v1 documents will be using different CMYK profiles when converting RGB to CMYK. Andreas Scherer 1 Quote
Andreas Scherer Posted January 31 Author Posted January 31 8 hours ago, thomaso said: In Affinity we cannot choose between the two methods when converting RGB to CMYK. In your example PDF it seems that Affinity prefers UCR (more CMY, less K) while the Online Converters define your swatches as GCR (more K and less CMY = less total ink). This is plausible. Thanks. Quote
Andreas Scherer Posted January 31 Author Posted January 31 3 hours ago, lepr said: The difference will be because your sRGB v2 and sRGB v1 documents will be using different CMYK profiles when converting RGB to CMYK. I'll check the settings on my computers and in the two program versions. Thanks. Quote
Ldina Posted January 31 Posted January 31 UCR and different levels of GRC can be built into CMYK profiles, (and often are), so the CMYK profile you choose for export will alter the amount of ink on all 4 plates. I have many custom profiles I created with ProfileMaker5 with different levels of GCR (light, medium, dark, and Max black) for different types of images. When I wanted more black ink and less chance of any color cast on press, (e.g. silverware, pewter, more monochromatic images, etc), I'd use a heavy GCR. When I had extremely colorful images and wanted more vibrant colors, especially if I was not concerned about possible color casts, I'd often use a light GCR, which used less black and more CMY inks. Less black ink also makes it a bit easier to tweak colors on press at a press check. Most of the time, I stayed with a standard CMYK profile, like US Web Coated SWOP v2, or Gracol Coated, but there were times when a custom profile was very beneficial, depending on the nature of what I was printing. At least with Adobe, I'd edit images in PS and save them with the desired level of GCR/UCR (black generation), on an image by image basis when exporting them. Then, I'd place my images (sometimes using different GCR recipes) into InDesign and make sure I didn't convert the numbers of my placed CMYK images on final export to PDF using the printer's Device CMYK. This allowed me to use whatever amount of black ink I wanted on an image by image basis within the same InDesign file. I've never sent a Publisher job to press, so it is probably different, and perhaps more limited. Attached is a Zip file with the same image exported from AD v2.5.7, one using a Light GCR profile, and the other using a Heavy GCR profile. They look almost identical, but the ink on each plate is different. The blacks are a bit deeper in the heavy GCR rendition. Anyway, this will illustrate how the CMYK numbers can be very different, but the appearance will be the same. Light-Heavy-GCR.zip Quote 2024 MacBook Pro M4 Max, 48GB, 1TB SSD, Sequoia OS, Affinity Photo/Designer/Publisher v1 & v2, Adobe CS6 Extended, LightRoom v6, Blender, InkScape, Dell 30" Monitor, Canon PRO-100 Printer, i1 Spectrophotometer, i1Publish, Wacom Intuos 4 PTK-640 graphics tablet
lepr Posted January 31 Posted January 31 5 hours ago, Andreas Scherer said: I'll check the settings on my computers and in the two program versions. Thanks. Your Affinity 2 results are sRGB to SWOP v2 Your Affinity 1 results are sRGB to FOGRA39 Andreas Scherer 1 Quote
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