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  • Ultimate 2022 Channel Selection

    I had hoped that the new Channel Select feature in Ultimate 2022 would at last mean I didn't have to switch to Affinity photo as an external editor each time I wanted to be able to do any color channel manipulation, but now having spent some time.with the new feature I am actually at somewhat of a loss to find a real world application for it.

    For instance I have not found a way using it to copy one color channel into another.. Copying the green channel into the red channel was part of an old but very effective Photoshop "red eye removal" technique, and one I still use in Affinity Photo.

    ACDSee's Adam very briefly touched on it in his video https://www.youtube.com/watch?v=UdTKl36kBIs, using it in conjunction with a Clarity Adjustment, but didn't explain why one would want to apply clarity to only the red channel, and the video didn't really show the effect of the change. More over, when I try to duplicate his steps, as soon as I select the clarity adjustment from the tools in the layer panel, the active selection overlay disappears. A check of the Select menu shows Deselect is now also greyed out, which sort of confirms the "red channel selection" is no longer actually active, and that suggests the clarity adjustment would then apply to all channels in the selected layer..

    Perhaps someone can show me a workable real world example of the benefits of this tool.

  • #2
    I don't know what "copy a channel into another" does, but you certainly can combine the selections based on Channels. You can select one channel, save it as a mask, select another channel and combine with mask either adding, substracting or intersecting the two selections. Everything can be save to the Selection Basket and re-used with any effect. For example, I drew 3 squares on a black background, Red, Green and Blue. I select the Red Channel, save as mask, select the Green channel, add mask to selection and I end up with the Red and Green boxes selected. I'd really like if Adam could do a Workshop on Channels so I can better understand what it does.

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    • #3
      Just a thought, re: a way using it to copy one color channel into another. What happens if you create two layers, one for each channel, and apply one of the Blend modes to "blend them together"?

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      • #4
        Here a test. I created a Blue Channel Selection, applied the RBG Adjustment Layer. Note that the selection disappears as noted, BUT a mask was applied to the Adjustment Layer. Do the same without the channel selection, and the Adjustment Layer will be white, i.e. without a mask. Hence the effect is applied to the Blue Channel only. Note that when I turn down all 3 RGB sliders, all but a small outline on the blue square disappears and not the red or green, which confirms that only the blue channel is affected. The small line remaining is the antialiasing transition. I couldn't get a "pure colored" squares without any antialiasing. The top squares are Red, Green and Blue, the bottom squares are 75%, 50%, 25% grey respectively.
        Attached Files
        Last edited by Regor250; 10-07-2021, 01:12 PM.

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        • #5
          Originally posted by Regor250 View Post
          ...Note that the selection disappears as noted, BUT a mask was applied to the Adjustment Layer.
          Yes, thank you, I had completely overlooked that if a selection is active when adding an adjustment layer, the selection will be added to the mask.
          I think that resolves the issue I mentioned about the video.

          I created 3 colored squares on a transparent background as per the screen shot below. These are colors which contain a mix of the three primary colors Red, Green and Blue. As you can see, I marked each square with the RGB values. The test image was saved as a 48bit TIFF with embedded sRGB-IEC61966-2.1 color profile.

          Click image for larger version

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          If I open that image in Ultimate 2022 Edit, and from the left Filter column select Exposure, set the "Apply to channel" to Red and reduce the exposure slider setting to -67 (-2.01eV), then as expected I see that the drop in exposure effects the left square most, because it has the greatest Red content, and the other two squares progressively less because of their lower Red content.

          Click image for larger version

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          If I open the test image again in Edit, and this time use the Select>Channel Selection, set it to RGB Red, click on Set as selection, then apply an Exposure Adjustment layer. As noted above, that applies a mask to the layer using the Channel Selection. If I now change the Exposure to -2eV, what I would expect to see is the same as in the previous test. Well unfortunately no, that's not what I get.

          It does affect the left most square most, and the right square least, but the result significantly different to that obtained using the filter.

          Click image for larger version

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          Which leaves me now wondering why the results are different.

          But also, getting back to my original question. As I see it, what ever adjustment is made using the Channel Select method is going to affect individual colors in a color photo to a varying degree, depending on their RGB color makeup, and I'm looking for examples of real world applications for this tool.

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          • #6
            I'll try the same tomorrow, the only explanation I can think of is that the 2 exposure corrections aren't the same. How did you arrive to -2EV in the first use case from -67 slider value?

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            • #7
              Originally posted by Regor250 View Post
              I'll try the same tomorrow, the only explanation I can think of is that the 2 exposure corrections aren't the same. How did you arrive to -2EV in the first use case from -67 slider value?
              The color change seems to move in a completely different direction in the two methods. .

              The eV value appears above the slider when you move it off of the 0 setting

              Click image for larger version  Name:	Exposure.jpg Views:	0 Size:	83.3 KB ID:	57582
              Last edited by Greyfox; 10-07-2021, 10:57 PM.

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              • #8
                Here one thing I see, and I don't know if this is by design or a Bug. Without using Adjustment Layers, I tried both methods (the top row squares have the same RGB values as your example)

                1. selecting Red Color Channel in the Exposure filter drop down, or
                2. selecting the Red Channel in Select > Channel Selection and applying the Exposure filter to RGB(normal) on the selection. (See attached example)

                In the first use case, only the R value is affected, whereas in the second all 3 R,G,B values are affected, but only where the Red Channel selection found a Red component value above 0, consequently it did not affect the Pure Green of Pure Blue squares (2nd row), which weren't selected by the Select Red Channel method. In other words, the Select Channel method identified the pixels with a Red value, but the change of exposure applied (is this unique to the exposure filter?) affected all 3 RGB values, not just the R value of that pixel, whereas the Apply to Color Channel within a filter, only affected the value of the R, G or B component for the selected color channel. Is that a Bug or a Design difference? I'd like to run that by Adam to see what he thinks.

                Addendum: Behaves the same with RGB Adjustment Layer
                Attached Files
                Last edited by Regor250; 10-08-2021, 06:33 PM.

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                • #9
                  Originally posted by Regor250 View Post
                  ... I'd like to run that by Adam to see what he thinks.
                  I have emailed Adam and asked him to have a look at this thread and hopefully provide some guidance.


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                  • #10
                    I hope he does. I interpret Select > Select Channel as meaning "Select pixels that are associated with a specific Channel" as opposed to the pull-down channel menu, which mean apply to the specific channel of the pixels that are selected. Not saying that it is wrong, but the nuance between the two "channel selection methods" is important to understand and the result clearly different.

                    e.g. For the Red Channel, the first one = select all pixels with an R value > 0, whereas the second one = modify only the value of R for the selected pixels.
                    Last edited by Regor250; 10-11-2021, 07:54 AM.

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