Artefacts/Outlines in Scatter Brush

[Rosalie2435454443zj]

I have a problem with scatter brushes in particular. When I use them in my cloud document, it seems to work perfectly fine; i can also export to .png no problem.

However, when I export to an .ai on my computer or as .pdf the brush get these weird artefacts like there is an outline drawn around each singular dot (see image). It's supposed to be all black.

I was able to fix it once by re-colouring the lines and contours, but it just keeps re-appearing once I do anything else. I need to share this document with others so it's important that it works when exporting...

Can anyone help me find the problem? Thanks in advance 🙂

[Monika Gause]

Can you please share a file that contains the brush? Or better: a line drawn with the brush, so that we see what kinds of appearances are involved?

Change the file extension to PDF so you can upload it here.

[Rosalie2435454443zj]

I've attached a pdf with the brushes.

After changing my gpu settings, this seems to happen only after export - before export and in pngs, it looks like this (as it should):

And it only happens with my own brushes, in the attached file I have used a calligraphy (I think) brush preset for comparison.

[Monika Gause]

Your brush has a raster object as the base object, and that object is CMYK, so it has anti-aliasing along the edges. I'm only seeing the artifacts in certain zoom levels.

This could perhaps be better, when you set the element to multiply, but then the image you paint might or might not look as intended. Or you could try a bitmap (1 bit) image as the base element.

What you are doing there will create a huge, complex file which might lead to issues with the final drawing and the output of the file.

[Rosalie2435454443zj]

Same here, I only see it in certain zoom levels.
When I set the elements to multiply, it comes out in the pdf like this:

I also tries using a bitmap (8bit) image which creates the same results as before in a pdf... 
If there is nothing else you can think of - do you have any suggestions on which brush/brush settings to use instead? In order to keep up performance and output but also allow some tweaking on brush appearance..

[Monika Gause]

Bitmap should be 1 bit.

Needs a higher resolution probably. But still: you'll get a huge file.

[Rosalie2435454443zj]

Edit: And apparently it only shows up after downloading and opening the pdf file...

[Ton Frederiks]

Smooth images in preferences from Acrobat slows the whole file down.

But you could improve your brushes, the ones I had a look at had the same image twice.

Removing one and rasterizing the other as bitmap at 300 or 600 ppi with transparency and alt dragging the result over the brush in the brushes panel (to replace it) gives a much better and faster result.

It is probably better to create the bitmaps in Photoshop to avoid rasterizing the soft edges as checkerboards.

[Ton Frederiks]

And the bitmap brush creates smaller filesizes than its vector equivalent.

[Rosalie2435454443zj · Accepted solution]

Edit: I found a solution. Not sure if this was obvious, but previously I had used a pixel-based image from Photoshop, imported and rasterized it, then turned it into a scatter or art brush. I fixed it by turning the shape into a vector shape first (by tracing the image), adjusting the traced image, then turning it into a brush. Now there's no lines or overlaps when exporting.