I actually had a lot of trouble with this and wish Amazon would make a significant update to the Kindle Comic Creator software. It wasn't very intuitive and I crashed the application many times before successfully creating a useable file for Kindle Direct Publishing (KDP). If you're here, you've probably already pulled out some hair so chill and read on soldier...
First - The Kindle screen size must be 800 pixels by 1280 pixels because the comics creator won't let you increase the page size greater than that. So find your aspect ration of your pages and down size in scale to something that fits into those parameters. My book ended up being 800 X 1225. Now, you'll want to select the page resolution. Set this too high and the Kindle will "Blow Up" a small image. Set it too low and you're creating a low quality graphic.
I tried a slew of resolutions from 100 ppi, 150 ppi, 220 ppi, 400 ppi, and 600 ppi. Unfortunately, I wasn't thrilled with the quality of any of those settings but 400 ppi was slightly less blurry on zoom.
Original, 300 ppi and 150 ppi examples to the left. The main problem here is that the team went and created these amazingly detailed pictures that the technology
can't view. I'm sure that whatever the latest kindle model is can handle a zoom of this level but the Kindle Comic Creator won't produce a result this sharp. :(
Per the KDP dashboard, they will accept different file types
and you don't have to use the Comic Creator to make your .Mobi but it's a shame that the provided software doesn't provide a near-perfect solution.
STEP 1: Create your page files in JPEG or .PDF format. STEP 2: Open the Kindle Comic Creator. -Select Language -Would you like to create Kindle Panel View? - If you have any dual page spreads in your comic, you MUST click no on this option. -What is the orientation of your book? If you have any dual page spreads in your comic you MUST click Unlocked on this option. -Select your canvas size in correct aspect ration that is less than 800 x 1280.
For the Metadata inputs, use what you want reflected in the downloadable file. Some of these show up in your customers kindle app.
Once in the creator, add your pages in order. This part is easy but you must note that if your file sizes get much bigger than 1mb per page, All Hell Breaks Loose!!!!
To Create Dual Page Spreads - NOTE - you must upload each side of your spread as individual pages (yes in the correct aspect ratio of a single page) - Cntrl + Click on sequential pages to highlight them. Right click on them and select "Page Settings" and then "Double Page Spread".
Then build and preview. Switch the orientation of your book to check that your pages all look good. Then you can can FILE - Export As KF8 Book for uploading to KDP.
Hope that helps. Comment or question below.