Lower opacity creates strange line

[adriaanjms]

I'm working with a simple polygon to fill in some negative space and when I lower the opacity this strange line keeps appearing. Both the grey circle and my polygon are set at the same opacity (52%) and set at the color (pure black: 000000). My polygon does not have a stroke, only a fill. Please help me figure out how to get rid of strange line.

Attached is a picture of the issue: 

[Brad @ Roaring Mouse]

Hard to tell exactly from your screen grab, but when you overlap two objects with transparency, where they overlap may end up darker. If you unite your shapes, this should go away, but it looks like there's something else at play here. Show us your artwork in Outline.

[adriaanjms]

Thank you Brad, I will try uniting them. 

[Willi Adelberger]

1. You do not tell us what PDF settings to create a PDF.
2. You do not tell us, if you activate antialiasing or not in your Acrobat Preferences.

I suppose you are flattening transparency. This will create stitching lines. 

If you place PDFs in InDesign you should use PDF/X-4, never PDF/X-1 or X-3. You can use AI and PDP files also.

[adriaanjms]

Thank you for your advice. This is my first time asking for advice so I will know to include those in the future.

[Laubender]

Hi adriaanjms,

are you sure that you are posting in the right forum?

It looks like your screenshot is not from InDesign, but from Adobe Illustrator.

Regards,
Uwe Laubender
( Adobe Community Professional )

[adriaanjms]

Oh geez, I'm always using InDesign and I messed up this time. 

[Peter Spier]

There are some screen draw issues in InDesign related to GPU acceleration on Mac that look like this. Might be affecting Illustrator as well.