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Photoshop CC white squares on screen - graphics?

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Old 04-18-2016, 09:17 PM
Spittle Spittle is offline
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Photoshop CC white squares on screen - graphics?

If I'm working on a 5k file with 50 layers or so, along with masks. I sometimes get this problem - random white squares obscuring any chance of working in that particular area. Workaround is to zoom in until the square moves somewhere else.

I tried different variations in how the file is setup in preferences - 'tall flat' etc.

Several colleagues have the same issue - Windows 7

Hitting the keyboard doesn't fix the problem.

Edit - white squares are visible when you print screen
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Old 04-19-2016, 01:20 AM
John Wheeler's Avatar
John Wheeler John Wheeler is offline
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Re: Photoshop CC white squares on screen - graphic

Hi Spittle

Turn off Graphics acceleration in Preferences to make sure it is not a graphics card issue.

Does the problem go away viewing at 100% magnification and/or if you stamp all visible Layers to another Layer. If this is the case, you likely have an interaction with what you have in the layers and layers mask with the resizing rendering when viewing at sub 100% magnification.

Adobe takes shortcuts for speed such as instead of applying the match associated with Layer Masks to the image pixels and the resizing/rendering for display, it resizes the image pixels and mask pixels first and separately and then combines the mask and image at the reduced resolution. Great for speed of display yet can create artificial artifacts in the display.

Here is a PSD file example. Open it up at 100% and then zoom out to 50%. You will likely see an anomalous image I created an anomaly that impacts every pixel on the image just knowing how they are created. If you flatten or stamp the Layers of my PSD, the issue disappears. Your issue may be similar yet without having access to your Layered file, it could be a lot of different things causing the issue.

Hope this helps you get to the root cause of your issue.
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Old 04-19-2016, 06:16 AM
Spittle Spittle is offline
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Re: Photoshop CC white squares on screen - graphic

Wow that's interesting - I'll try your suggestions next time I get the problem.

Out of interest - how did you create this example?
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Old 04-19-2016, 11:44 AM
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John Wheeler John Wheeler is offline
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Re: Photoshop CC white squares on screen - graphic

Hi Spittle
A bit of background on the creation of this example as there are many more that could be easily created.

First I tried to understand the source of the problem.
In the Layer stack, what happens on printing, merging, or flattening is that each final pixel is determined from the entire set up pixles and adjustments in all Layers below including interactions with transparency, masks, and blending modes --- and after that is done, resizing is applied

For speed in display, apparently what is done (from a lot of experiments) is that each Layer pixel, Layer transparency, and each Layer mask is resized first and then combined vertically.

So why is this a problem? If you have two adjacent pixels that are black and white, they can be averaged out went rendered to be smaller to gray at the transition point. Off hand this would be a slight blur yet when you do this with masks or even between Layers with certain blend modes, you can get artifacts.

Now I engineered the PSD file to create a worst case. The Layer above the base image is just a pure checkerboard of black and white pixels. When viewed at greater than 50% magnification, it will look gray until you get to high enough magnification until you see the checkerboard.

What happens when you reduce the magnification to a low enough Layer, for display calcualtions in PS, that Layer checkerboard is average so that the values of all pixels of the checkerboard are considered all gray (as opposed to alternating black and white).

I used a hard mix blend which when the pixel is either pure white or pure black, what should be visible is just that upper Layer. However, when viewed at 50%, the pixels are considered all gray (incorrectly). When you have a gray Layer with the blend set to Hard Mix, it basically means show the Layer below (which it does).

There are many cases when with Layers, Transparency, Masks, and associated blends that using a reduced size/averaged representation is used as a shortcut in display can cause all sorts of anomalies.

If your problem does not go away with turning off the graphics card, I suspect that you just stumbled on one of the many ways display anomalies can be created in PS. Without seeing your full Layer stack, it would be hard to pin point the issue yet I suspect it very likely would be the same root cause as I have mentioned.

So the process ---- understand root cause of the display anomalies and then exploit that information to create a worst case dramatic example. It is an academic exercise to reset peoples thinking that PS is not necessarily WYSIWYG.
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