CS6 roundoff error

kpt · Post by **kpt** » Mon Dec 24, 2012 6:02 am

I wonder if I have stumbled upon a bug in CS6? I have two layers, the same size. The top layer should cover the layer underneath but I can see the bottom layer, even though they both have their edges on the same pixel.

This YouTube video shows what I mean: http://www.youtube.com/watch?v=7SG6i2B19OY

(I have a cold, so pardon my croaky voice.)

I checked afterwards and both layers were 208 px from the top. I can't see this problem in CS5.

Has anyone else experienced this? It has implications to clipping masks, i.e., you should not be able to see the mask behind when both layers are the same size.

kpt · Post by **kpt** » Tue Dec 25, 2012 5:13 pm

I realized it would be easier to download this file: http://pixbookdesign.com/upload/tmp/linjedemo.psd

Can anyone else see a faint line above her head, when zoomed in at 100%?

(Both layers are of the same height and aligned vertically.)

Mike Hale · Post by **Mike Hale** » Wed Dec 26, 2012 1:09 am

I don't have CS6 to test but are you sure that what you are seeing in really in the document?

I know that with other versions of Photoshop you can see this kind of layer composting artifact you describe in your video depending on zoom level and video card settings. But if you flatten the doc, stamp visible, or dupe merged the artifact does not appear in the final document.

So first I would make a dupe of your test document and flatten the dupe to see if the rounding error is really in the flattened image. If it is not then check your video setting especially if you are using openGL.

kpt · Post by **kpt** » Wed Dec 26, 2012 5:18 pm

That's a good and valid question Mike! Here is the flattened JPEG file for everyone to see:

http://pixbookdesign.com/upload/tmp/linjedemo.jpg

undavide · Post by **undavide** » Wed Jan 02, 2013 8:27 pm

I guess the problem lies on the Smart Object. If you place Sofia as a flattened layer, sized 699x524px, it covers perfectly the black layer.
So there's something weird happening in the upsampling of the SO :-/

Davide

Mike Hale · Post by **Mike Hale** » Wed Jan 02, 2013 10:40 pm

With CS5, if you open the SO layer for editing and convert the background layer of the SO to a normal layer then flatten the document and save/close the line goes away. I don't have CS6 to test but does that work in that version?. In other words could there be something wrong with that smart object in particular and not smart objects in general in CS6.

kpt · Post by **kpt** » Thu Jan 03, 2013 7:09 am

undavide: correct, that's what I have found as well.
Mike: I'm not sure I follow: "convert the background layer of the SO to a normal layer"? The SO is a plain JPEG file.

Some of the things I tried (all in CS6):

rasterize the SO => no change
flatten the image => no change