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loss of colours and effects when flattening images

Forum|Forum|4 years ago
May 1, 2021
5 replies
11465 views

Hi, im having trouble flattening or merging layers as im loosing colours/effects on my artwork when trying to flatten an image before saving as jpeg. this has just started happening in the last two days. would love some help.

Correct answer davescm

thasnk for your input but im still not undesrtanding your point and i have re-read your first response again carefully. as for your they do match at 100%? the flattened image and the 100% view match in the sense that they both show the image without the colour but im not sure how this helps me figure out why this is happening or how to solve it.

Hi

The point is that at 100% zoom the preview you are seeing on screen is accurate and therefore will match the flattened image. If you zoom out, let's say to 50%, every pixel on screen represents more than one image pixel. In the case of 50% zoom, 1 screen pixel represents 4 image pixels. Now here is the issue, for previewing, that average of 4 pixels down to 1 pixel is done on each layer before blending the layers together. However, when flattening, each pixel is blended from individual layers after which the 4 pixels are averaged to one screen pixel. That is why the two previews can look different. At 100% zoom there is one screen pixel for one image pixel so both preview and flattened image look the same.

There is also a further complication in that at zoom levels less than 66.7% 8 bits/channel are used even when the image is 16 bit.

All this is done for speed - can you imagine the delays in blending a zoomed out view of a 300,000 x 300,000 pixel image multi-layered image if every pixel had to be calculated individually for previewing?

So to "solve" it, always check your preview blending at 100%. As D.Fosse said earlier, it is the only fully accurate preview.

Dave

K

kkrip

Participant

I know this is an old post but I just experienced something similar that is really troublesome. I flattened and saved an image as a jpg. As soon as I flattened it, the overall color changed (fairly drastically). As some have mentioned, I did not see this at 100% but I can not judge overall appearance at 100 % because the file is so large. What I did was to take the flattened jpg and pull in back into the original layered file to compare and the difference is very apparent. So my question is how to avoid this but also why would two files of the same image (one flattened and one in layers) viewed at the same magnification, appear different?

D Fosse

Community Expert

I did not see this at 100%

By @kkrip

That's the giveaway.

Whenever something seems to change when merging layers, it's because you are not viewing at 100%. The merged result is correct. The preview is misleading and incorrect.

100% has nothing to do with size. It means one image pixel is represented by exactly one physical screen pixel.

For performance reasons, all blending and adjustment previews are calculated on the on-screen sample of the image. When you are zoomed out, that means a resampled and softened version of the image. Pixel levels are averaged out. You get a lot of intermediate values that aren't there in the full original data.

When you merge, commit an adjustment etc, the numbers are re-calculated on the full original data, pixel for pixel.

Viewing at 100% is the only way to avoid this, and get an accurate preview of the final result.

There is a feature request to calculate all blending and adjustment previews on the full pixel data. The problem is that this slows Photoshop down considerably, and would lead to a load of other customer complaints. So what we want is an option, transient and non-sticky, that allows this while also stating clearly what the implications are.

K

KBlab

Participating Frequently

Having the same exact problem. When working with many layers and adding effect to them (ex: screen, leghten, darken etc etc) when flattening it takes away the effect completely. Is there a way to flatten without loosing the effects applied to each layer? The same happens when you merge different layers with apllied effects on them.

davescm

Community Expert

@KBlab Check your preview at 100% zoom. That shows the real blend, I.e. every pixel blended individually, and should be identical to the flattened version

Dave

K

KBlab

Participating Frequently

Absolutely not but thank you for the try. Yes, I've seen many people saying that, but artist like us that work with many layers and placing effects on them, that change when we flatten them is absolutely huge! The flattened layer gets back to normal and erases any effect that was applied to it, that is the reason. I need a solution to the problem and the problem is not a view % at all unfortunately. As soon as you flatten or merge any layer, it goes back to "normal" instead keeping the values for screen or lighten or else

barbara_a7746676

Community Expert

Colors can change if you are converting from one color space to another. For instance if you are converting from CMYK to RGB.

NB, colourmanagement

Community Expert

@barbara_a7746676 "Colors can change if you are converting from one color space to another. For instance if you are converting from CMYK to RGB."

Just FYI Barbara, that would be correct, but it's far from good practice to ever convert CMYK to RGB.

In any case, I don't think the OP is doing a profile to profile conversion, simply observing the result of flattening the file

I hope this helps
neil barstow, colourmanagement net - adobe forum volunteer - co-author: 'getting colour right'
google me "neil barstow colourmanagement" for lots of free articles on colour management

D Fosse

Community Expert

It's most likely a misleading preview because you're not viewing at 100%. In other words, the flattened version is the correct version. The preview was wrong.

100% is a significant number. It has nothing to do with size. It means that one image pixel is represented by exactly one screen pixel.

Is this a very noisy image, like a starry night sky? Or a "binary" image like line art or halftone dots? If you're zoomed out below 100%, what you see on screen is resampled and therefore softened. All those crisp pixel-level transitions are replaced with blurred intermediate values.

The problem is that adjustment and blending previews are also calculated based on this downsampled and softened version. So the starting numbers per pixel are wrong. This is done for performance reasons. Photoshop has always worked like this, but it doesn't matter with a "normal" photograph. This is only an issue when you have sharp pixel-level transitions.

When you commit the adjustment, it's calculated on the full image data again, so you get the correct result.

Bottom line - for a reliable preview, always, always check at 100%.

G

glogicalAuthor

Participating Frequently

thansk for thiis info, although i dont fully undersatnd what you mean, ive tried looking at not 100% but when i try to flatten the image its looses some parts of the image, [i.e some of the colours. this isnt a photogragh its a digital collage piece of artwork ive created using photoshop.

D Fosse

Community Expert

Please show screenshots of 100% crops of the affected areas.

barbara_a7746676

Community Expert

This can happen if flattening some layers and not all layers.

Are you flattening all layers?

G

glogicalAuthor

Participating Frequently

yes im flattening all layers.

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