Line weight changes when using Align to Pixel grid

Question

When I select Align to Pixel Grid in the Transform Panel, I see line weight changes occur. I try to change the line weight in the either the Stroke or Appearance panel and it will not change, no layers locked, any ideas how to change the line weight?

Answer 1

Chouettecacahuete wrote:
... I noticed that the line increases from 0.5pt to 1pt mainly (although not always) on straight lines, anything with a bezier curve seems to remain as 0.5pt.
Just try this, with snap to pixel grid on, create 10 pixel long straight horizontal 1pt line with the pen or line tool. You won't be able to change the stroke weight to other than whole numbers. But if you rotate the line with only 0.01 degrees by typing this for rotation in the Transform panel, then you can change the stroke weight to 1.25 for example. When creating artworks for for screen display always verify the result with View > Pixel Preview turned on.
tonyharmer wrote:
...I only referred to Photoshop to illustrate the behaviour - vector tools aside, everything you do in Photoshop has to be whole pixels
As I said, Photoshop doesn't have  snap to pixel grid feature like Illustrator. You can easily create fuzzy lines in Photoshop if you are not drawing them precisely in the middle of the pixels. To check what I'm talking about try this In Photoshop, create a new document with a very small pixel dimensions like 20 x 20 pixels and zoom to the maximum 3200% to see clearly the result. Fill the image with light gray color so you can see the pixels when View > Show Pixel grid is on. Then with black color try drawing a straight line with any tool that creates pixels like a hard brush or the line tool used in pixel mode, and try using constraints like holding Shift while dragging. You will see that unless you draw the lines exactly in the middle of the pixels it will be fuzzy and not clean. The only way to ensure not fuzzy lines in Photoshop is to turn  off the anti-aliasing. You do this by unchecking the anti-alias for tools that have this option and instead of burshes use the pencil tool (which is brush without anti-aliasing). And Illustrator works the same too if you turn off Anti-aliased Artwork in its general section of the preferences and view the result with View > Pixel Preview, you don't need to have the Align to Pixel Grid on, the aliased result will be the same like in Photoshop.