Would like some info about dimensions and dpi for Illustrator designs for print on demand

[EltonRay1]

Newbie question here about creating files in Illustrator for print on demand:

I amusing RedBubble to create print on demand products with my designs that I create in either Illustrator or PhotoShop, and I have a few questions about the dimensions and dpi for my products.

Firstly, RedBubble recommends that I use CMYK for my designs then upload PNG files (with background transparency) in sRGB to use on my RedBubble products. This is for their DTG printing (Direct to Garment) for their apparel.

For their requirements they say the following on their blogs … "We'd recommend starting with 7632x6480 pixels (suitable for the king-size Duvet Covers). Images above 300Mb, or 13500x13500 pixels in size, cannot be accepted on the site due to the heavy load they place on our servers."

They also list the separate dimensions for all their various products, too, if I want to use those instead, but I would rather scale down with those dimensions mentioned above when uploading some of my designs if I want to use multiple products, if that would be okay to do.

Also, they say (when using vectors) … "Because vector images are not pixel or dot-based, they can be scaled up or down in size without losing quality. Once you’re happy with the size of your vector graphic, you’ll need to rasterize and save it as a PNG to upload to the Redbubble marketplace."

So my questions to you, therefore, are these:

1 – Since I had troubles exporting PNG files at the size of 7632x6480 pixels in Illustrator (I was using 300 dpi while designing, and using CMYK), was this because the dpi was too high? They said to me that the dpi is not all that important when I upload the PNG files, so do I design in 300 dpi, reduce to 150 dpi (for example) before exporting the PNG file so that I can use these dimensions above and not exceed their 300Mb or 13500x13500 pixels maximum size? Or do I design and export in 150 dpi … is this good enough for print?

2 – Do I need to change the color mode from CMYK to RGB in Illustrator after I finish designing and before exporting the PNG to make sure that it is in the sRGB profile, or does the PNG file automatically use sRGB when exporting even after using CMYK? Is there a way to check this beforehand (if it is going to use sRGB for the PNG file)?

3 – Do I really need to “rasterize” my vectors before exporting the PNG, as they had said … if so, please let me know how to do that.

Looking forward to hearing from you guys, and thanks so much!

[Monika Gause]

They are probably telling you to design in CMYK in order to keep you from using colors that are not printable. It's OK to stay in CMYK, but PNG as a file format does not support it.

What will happen when you export to PNG, is that Illustrator will convert the colors to your RGB working color profile (and in some cases to sRGB). But it won't embed that profile into your file. So afterwards you'll need to open the exported file in Photoshop or the like to embed the profile. But maybe redbubble has taken measures for that case anyway and has some instructions for how to convert your file?

As for the pixel dimensions: In case you have set up for file size in pixels: export at 72 ppi to keep the size.

The ppi you enter when setting up the file is the raster effects resolutions. leave it at 300 ppi for smooth effects (drop shadows, glow etc). But this setting doesn't have an influence when doing the export.

[EltonRay1]

Thanks for responding.

So, just to be sure (correct me if I am wrong in any of the steps, and I also have a few more questions):
In Illustrator:

1 - I create the artboard in the dimensions of 7632x6480 pixels

2 - I choose CMYK

3 - I choose 300 dpi

4 - After finishing the design, do I "rasterize" it like they mentioned to me? If so, how do I do that?

5 - When exporting as a PNG file with a transparent background, I choose 72 dpi then check "use artboard" (that will give me a file of 7632x6480 pixels?)
Then in Photoshop:

1 - Open it up in Photoshop to embed the profile (question: how do I do that?)
2 - Then I export again as PNG and use it in RedBubble?

Again, thanks so much 🙂

[Monika Gause · Accepted solution]

4- when you export it the PNG it will be rasterized automatically. PNG is a raster format.

5- exactly. When setting up your artboards before you start designing: make sure the corners are on round pixel values, nothing that has a comma.

In Photoshop open the file.

Then Edit > Attach profile and select the profile you have set up as working RGB color profile in Illustrator (it's in Edit > Color settings). Ideally you are using the same profiles in Illustrator and Photoshop.

Then save the file and make sure the profile gets embedded.

[EltonRay1]

Thanks so much for your help in this. I understand what to do going forward!

Have an awesome day!

[Monika Gause · Accepted solution]

You're welcome!

There's one thing, just in case.

If the redbubble folks tell you that 72 ppi does not fly with their system (it should, but you never know), then you can use Image > Image size in Photoshop to change the ppi. Uncheck the resampling and just enter 300 ppi. The pixel dimensions do not change when you do that. It just changes some metadata