Photoshop cut & paste leaves a seam

[heynewt]

When I cut and paste to a new layer in Photoshop, I figured - since I'm pasting in place - that the paste would theoretically be seamless.  Yet I have a faint seam (see image).  Is there a way to avoid this?

[D Fosse]

It's an on-screen artifact. When you merge it should be seamless again (try it).

However, you should be careful to not do any transforms or resizing in this state, because then it will be permanent. Copy/paste is safer than cut/paste.

[c.pfaffenbichler]

»t's an on-screen artifact.»

I disagree.

A pixel at 100% opacity is not the same as the same pixel twice at 50% Opacity, so if anti-aliasing or a Feather are involved in the Selection there is actual damage. 

But your advice to copy/paste is spot on. 

And additionally I would recommend using a Smart Object for any transformations. 

Edit: The screenshot shows what happens with a feathered Selection and Layer > New > Layer Via Cut for example. 

[D Fosse]

You're right. I didn't check before replying, which I should have. It must be something connected to transparency blend gamma.

I assumed this was the same as the familiar faint lines you get with e.g. Auto-Blend, but it's not. There you have no choice but to trust that the lines disappear when merging - and they do (and they aren't there at 100%).

Everywhere else, I always err on the cautious side and assume it's real, so I copy, never cut, then paste.

[DamienKeffyn]

Hi, further to this guide, is there something I am doing wrong when trying to copy and paste a tile which is seamless to a separate file? I select all (cntrl A) and then paste into the new window.
I have flattened layers, and it still shows this. I print fabric so these lines can not be present when printing.

[c.pfaffenbichler]

Why copy/paste at all and not just create the Pattern in the original image (Edit > Define Pattern)? 

Can you provide the file for testing?