AP: Does image quality change when converting an Image layer to a Pixel layer?

[Rich]

I am editing high-rez 16-bit AdobeRGB photo images. I see that in order to copy/paste a selection from such an image I must first convert the Image layer to a Pixel layer. When doing this is there any change of image quality, such as in the smoothness of gradients or in the overall tonal quality? Thanks.

[David in Яuislip]

I don't see any issues but you can prove it for yourself
Duplicate the image layer, rasterise it and set the blend mode to Difference
The canvas should be black meaning the layers are identical

ps with Windows a marquee selection can be copied from an Image layer by using Edit/Copy flattened. I believe this didn't used to work on a Mac but don't know if that is still the case

[Old Bruce]

1 hour ago, Rich said:

I am editing high-rez 16-bit AdobeRGB photo images. I see that in order to copy/paste a selection from such an image I must first convert the Image layer to a Pixel layer. When doing this is there any change of image quality, such as in the smoothness of gradients or in the overall tonal quality? Thanks.

Should be able to use the Marquee for a slection and then use Edit > Copy Merged, no rasterizing  needed.

[David in Яuislip]

11 minutes ago, Old Bruce said:

Edit > Copy Merged

Aha, is that what it's called in MacLand?

[Old Bruce]

In this one instance it is.

Then there is the Flatten in the Document Menu. That is called Flatten on Mac, I presume it is the same in Windows because that command does exactly what the tin says.

[David in Яuislip]

7 minutes ago, Old Bruce said:

In this one instance it is.

A bit odd then??

Yes, the Document/Flatten appears to be the same

[Rich]

Thanks David and Bruce. Coming from Photoshop, the Image layers vs. Pixel layers for various editing functions in AP is new to me.

I used the example of copy/paste earlier, but my main concern is how does this conversion affect final image quality in subtle areas like smooth gradients, micro-contrast, tonal rendition or anywhere else. 

I was hoping this was a topic already well known in the Affinity community that could be answered to save me a few hours of testing and pixel peeping. Thanks.

[Old Bruce]

2 hours ago, Rich said:

I am editing high-rez 16-bit

 

6 minutes ago, Rich said:

my main concern is how does this conversion affect final image quality in subtle areas like smooth gradients, micro-contrast, tonal rendition or anywhere else. 

With 16 bit you shouldn't have to worry. I don't.

[R C-R]

2 hours ago, Rich said:

I used the example of copy/paste earlier, but my main concern is how does this conversion affect final image quality in subtle areas like smooth gradients, micro-contrast, tonal rendition or anywhere else. 

From the Image layers help topic:

Quote

An image layer has a container which retains the placed image's original color space, resolution and physical dimensions (when placed at native resolution).

So when rasterizing an Image layer, it is converted to the document color space, which might have a visible effect if the document color space is different from that of the image layer.

As has been mentioned, the best way to check this for acceptability is to test it using a copy.

[Dan C]

16 hours ago, David in Яuislip said:

17 hours ago, Old Bruce said:

Edit > Copy Merged

Aha, is that what it's called in MacLand?

I can confirm this difference is logged with our developers, I've 'bumped' this issue with your report here

[Rich]

4 hours ago, Dan C said:

I can confirm this difference is logged with our developers, I've 'bumped' this issue with your report here

Glad my post helped to solve an AP problem, but unfortunately not my own.

I was hoping for more information than to just go find the answer myself via my own testing. Doesn't anyone else care about non-destructive image editing? Most professionals do.

 

19 hours ago, R C-R said:

As has been mentioned, the best way to check this for acceptability is to test it....

Thanks.

[Old Bruce]

10 minutes ago, Rich said:

I was hoping for more information than to just go find the answer myself via my own testing. Doesn't anyone else care about non-destructive image editing? Most professionals do.

There were two responses to your question about rasterizing. There may not have an explicit "Just use Edit > Copy Merge/Flatten" but that is what they boiled down to. The rest of the responses are about the Copy Merge/Flatten difference between Mac and Windows.

To recap,

23 hours ago, Rich said:

I am editing high-rez 16-bit AdobeRGB photo images. I see that in order to copy/paste a selection from such an image I must first convert the Image layer to a Pixel layer. When doing this is there any change of image quality, such as in the smoothness of gradients or in the overall tonal quality? Thanks.

You do not have to Convert the image layer to a Pixel layer before copying. You can just Copy Merged/Flattened. 16 Bits is plenty of depth to hold onto all the detail.

[Fixx]

On 11/2/2021 at 8:10 PM, Rich said:

I must first convert the Image layer to a Pixel layer. When doing this is there any change of image quality,

If you have image layer instead of pixel layer in your document you have placed images to your document, as layers. If you have selected document resolution wisely it will work OK. In rasterizing image layer the resolution converted to that of document resolution (as I have understood), which may mean that detail are lost if document resolution is lower. If lower resolution layer is then manipulated it is possible to get a lower quality image compared to that if manipulations had been done to original image layer.

Anyway, if document resolution is right there should be no problems.

[lacerto]

1 hour ago, Fixx said:

Anyway, if document resolution is right there should be no problems.

It is still good to understand that if there is upscaling [EDIt: or downscaling] involved, it can have undesired side effects. I would personally never upscale rasterize uncritically, without being able to choose the resampling algorithm:

rasterization.pdf

 

 

Edited November 6, 2021 by Lagarto
Updated attachments to show the effect of both upscaling and downscaling