Info Panel - Sampler size and Color space

[Ldina]

I have some questions about the color samplers in the Info Panel of Affinity Photo. I use CMYK samplers a lot when doing critical color work, especially on skin tones. 

1. What size is the sampler? (1 pixel, 3x3, 5x5, etc?) I am assuming it is a single pixel sample, but I am not sure. A single pixel can be misleading, so I'd like to use a larger average sample size.

2. Can you change the sample size? If so, how? Will the Info panel sample size be same as what you select using the EyeDropper Tool if you select something other than "point sample"? In other words, if I select a 5x5 sample size with the Eyedropper Tool, with the sampler in the Info panel also be a 5x5 average sample?

3. When selecting various color modes for the samplers (i.e., RGB, LAB, CMYK, HSV), what color space is used to report that data. For example, if I am working on an sRGB document, but wish to set a sampler to CMYK, which CMYK profile is used to report the numbers. A conversion is required from one color space to another to report accurate numbers. Does AP use the default color spaces and rendering intents to do this conversion, or is it some sort of generic table?

Thanks.

[Pšenda]

https://affinity.help/photo2/English.lproj/pages/Panels/infoPanel.html

https://affinity.help/photo2/English.lproj/pages/Tools/tools_clrpicker.html

[Lisbon]

Hi @Ldina

19 hours ago, Ldina said:

What size is the sampler? ... I am assuming it is a single pixel sample, but I am not sure.

Your right its a 1x1 sample.

19 hours ago, Ldina said:

A single pixel can be misleading

Precisely.

19 hours ago, Ldina said:

...so I'd like to use a larger average sample size.

I use a workaround for this.
I have a macro that averages every pixel by a 3x3 or 5x5. So if you use the info panel on one of these layers you are not sampling 1x1 but 3x3 or 5x5.
These layers are obviously a little blurry, so after making your adjustments, delete these layers.
You can download the macro at the end.
I use A.Photo v1 so i dont know if this macro works on v2. Fingers crossed.

19 hours ago, Ldina said:

Can you change the sample size?

A few months ago i have made a request, but you know how these things work. Lots of work, different priorities... etc.

Sample 3x3 - 5x5.afmacros

[R C-R]

From what I can tell from testing, the Info panel sampler size is always 1x1 px & there is no way to change that -- it does not use the sample size set for the Color Picker Tool.

I do not know what color space is used for samples.

[Ldina]

Psenda, thanks for the links. Unfortunately, the Affinity Help menus are pretty basic, lack examples and details, and don't shed any light on this issue. The Help menus could be much better if they were expanded to anticipate user needs more completely.

Lisbon, thank you for your feedback and the Macro. The Macro does work in Affinity Photo v2.0.3. I tried it out and it is very helpful. Thank you very much. I appreciate it. A point sample is sometimes useful, but most of the time, it is simply misleading since it isolates a single pixel. The 3x3 and 5x5 averages are much more helpful for most of what I do. Serif needs to provide options for different average sample sizes right in the Info Panel. It would also be helpful to specify what profiles are being used for the numbers being displayed. 

R C-R, I did some dried testing and have concluded that the numbers reported in the info Panel are based on the current document profile, and whatever other profiles are specified in the default Color Settings for other color spaces. So, if I am working on an sRGB document and selected a CMYK Sampler in the Info Panel, the CMYK numbers will be converted from sRGB to the CMYK profile I have set as my default CMYK in Preferences. In my case, the conversion from sRGB to CMYK will use Coated GRACol 2006 (ISO 12647-2:2004), Relative Colorimetric and Black Point Compensation, since those are my defaults CMYK.

Those converted numbers come closest to the displayed CMYK numbers. I tried a bunch of different CMYK profiles to see which came closest. However, if I use the Mac Colorsync Utility to convert from sRGB to the above CMYK profile, the CMYK numbers differ somewhat from what is displayed in the Info Panel. Perhaps that is because Colorsync uses the Apple default color engine and Affinity Photo is using the Serif color engine. Still, the default profile I selected in Preferences is definitely the closest. 

Thank you all for the helpful responses. 

 

[Pšenda]

1 hour ago, R C-R said:

I do not know what color space is used for samples.

[R C-R]

@Pšenda, as I understand it, color space (what in Affinity is referred to as Color Format) like sRGB or web coated & color model like CMYK or RGB are not the same thing, & the former is what the OP is asking about.

[Ldina]

1 hour ago, R C-R said:

as I understand it, color space (what in Affinity is referred to as Color Format) like sRGB or web coated & color model like CMYK or RGB are not the same thing, & the former is what the OP is asking about.

R C-R...Exactly right. I'm talking about the specific color profiles used for converting color numbers so they look the same visually, insofar as possible. Color gamuts vary and often overlap, so some colors that work in one color space will be impossible to reproduce in another (i.e., some colors will be out of gamut). RGB, HSL. CMYK and other color models require the numbers AND a profile to interpret them. RGB or CMYK numbers without a profile are meaningless. LAB is unique in that it is device independent and is a model of human perception, a sort of universal interpreter. There are many different RGB color spaces (profiles, such as sRGB, Adobe RGB. ROMM RGB) and there are many different CMYK color spaces or profiles (FOGRA, US Web Coated SWOP, Euroscale, etc). If you convert from sRGB to CMYK, for example, the final CMYK numbers will be very different depending on which profile and rendering intent you use. 

RGB -> CMYK is a change of color mode. Adobe RGB -> sRGB is a conversion to a new profile within in the same color mode (both are RGB color spaces. sRGB -> US Web Coated SWOP is a change of color mode and color space (or profile).

[NotMyFault]

3 hours ago, Ldina said:

R C-R, I did some dried testing and have concluded that the numbers reported in the info Panel are based on the current document profile, and whatever other profiles are specified in the default Color Settings for other color spaces.

You observation sound like as excellent reverse engineering of how Affinity works. 
You can’t expect any more extensive or precise answer before Serif staff return from Xmas Closure.

Using that assumption, it explains how out of gamut colors are treated: exactly the same as if you convert a document to the new color mode and color profile.

3 hours ago, Ldina said:

However, if I use the Mac Colorsync Utility to convert from sRGB to the above CMYK profile, the CMYK numbers differ somewhat from what is displayed in the Info Panel.

This has been reported before, and your comment about different color libraries (I think littleCMS is used by Serif) explain the differences.