When you have a digital option for your Kickstarter or web store, there’s a few things that are important to consider when packaging your comic for your end customer.
**DISCLAIMER** — these are my own thoughts/opinions of the topic, but they are influenced by years of being a consumer of digital comics, a graphic designer and software engineer, and creator of my own comics.
First and foremost, the PDF you get from your pre-press person (or make yourself, depending on how you’re doing things) is not the same PDF you should be giving your customers.
The print ready PDF is at least 300 DPI (and often much higher), meaning the images are *very* high resolution so the printer can capture the maximum detail but those same large files offer a large burden to your digital-reading customers and no real benefits.
In fact distributing a huge file to your backers can hurt your comic in the long run. I’ve personally been given 300 or 400mb files from a one issue (24–28pg) comic I have backed, which is insane! This means:
- More storage space on their hard drive for your customer, which is absolutely not needed
- The computer performance needed to read PDFs this large (in a a dedicated comic reader or just Adobe) is high and files that big cripple older computers/devices and make the reading experience terrible, including zooming and scrolling.
- Many folks, including myself, read comics on a tablet and many comic readers that import CBZ/PDF (Panels, in my case) have hard file size limits and break with huge files like this
A primer on resolution
When you export your comic as a PDF it’s essentially just a small wrapper around all your pages, each of which is a single high-resolution image. So understanding how image resolution works, and compression, is important.
In printing DPI stands for “dots per inch” and stands for the number of printed dots in an inch. But since almost all comic art is being done digitally now (even traditionally drawn media is being scanned in and becoming a digital image), DPI is a misnomer. Artists and creators throw it around a lot but when they are working digitally what they are actually referring to is PPI (pixels per inch) but those are generally used interchangeably now so you might see both used . Resolution that is generally considered “high enough resolution” for print is a minimum of 300 dpi. Up until relatively recently producing content for digital consumption was standardized @ 72 dpi but recently more monitors and smartphones have higher dpi values and can properly display higher resolution images better.
Worth nothing though, computers are very good at scaling images up — for example you probably look at lots of images online on a retina display (ipad, macbook, etc) that are 72dpi images but upscaled/interpolated and they display to you visibly just fine. There’s lots of research/info on what the human eye can generally see in screen displays but generally from further than 10–12" the human eye cannot discern anything more than 300dpi. All of the above is background info that helps you understand how devices display your beautiful comic book images, but the takeaway here is that the max you should ever, ever have to distribute to get the highest possible resolution out of any display on the market would be 300 DPI. If you wanna learn more about image resolution check out this article which goes into more detail: https://www.creativebloq.com/graphic-design/what-is-dpi-image-resolution-71515673.
Not just about resolution
Resolution impacts things visibly obviously, but there’s more at play than just that. The other factors to consider are performance, delivery, and storage. Distributing 300 DPI files would be great if it had no tradeoffs, but unfortunately it sure does. A 24pg 300 DPI comic PDF is roughly 90–110mb. This can work for many folks but can sometimes see performance slowdowns for scrolling/zooming on older (less powerful) computers or old phones, and using up 100mb of hard drive storage for a single issue comic is pretty crazy and makes for longer downloads or transfer to tablet devices (which often have limited storage space in the first place)
In my experience, the sweet spot is 150dpi. This gives you ~25mb files and still looks great on all devices and performs fast, with minimal download time for your customers and storage retention requirements. It’s nice to offer each option to the customer, a lowres (150dpi) and high res (300dpi)
Other notes about exporting for digital
If you’re preparing a file for offset printing, the color palette will be (should have been at least!) done in CMYK. But when you export to a file intended for reading on screens you should convert to RGB. If you leave the color palette as CMYK it’ll still be readable but it will become the job of the device to convert the color palette to RGB at the time of reading and that logic is not always the same on all devices so your readers might be seeing slightly different things. So you’re better off converting it yourself and distributing in a digital file with an RGB file.
The file you have designed for print should include bleeds on all edges (except possibly inside if you’re doing offset printing, depending on your printer). When you export for your digital files for reading, you should make sure to export with no bleed so the pages are sizes correctly and have the right aspect ratio.
Depending on in what format you’re setting up your print file you might have live text in the lettering, title pages, etc. It’s important that this text is rasterized when exporting otherwise in some weird PDF viewers it might not be displayed correctly, the user might accidentally select the text, etc.
CBZ/CBR is a format that many comic readers can natively support. They are essentially just packaged archives with a folder full of images(pages). These archives are ZIP files (in the case of CBZ) or RAR files (in the case of CBR). To make them you just export the pages as PNG/JPEG, name them in some sane way (usually 00 , 01, etc), compress them into an archive, and change the file extension. Comic readers that support these formats use the first page as the cover.
DO I NEED TO OFFER CBZ/CBR??
Back in the day, PDF was a *HEAVY* format for document sharing and included a ton of extra/unneeded crap which bloated the filesize. When CBR/CBZ first were created it was a lean way to bundle a set of ordered images and add some compression. Nowadays the PDF wrapper is much leaner and does a better job without all the extra bloat, and cmic book images are not ideal candidates for compression and you don’t get much. So long story short you don’t get any real advantage offering CBZ/R files in my opinion, unless you are using VERY high resolution files (where the compression can be more beneficial). But some old-school digital readers still like them, so I include them anyway.
So how do I create these digital files??
If you have somebody doing pre-press for you, just ask for a digital file @ 150DPI and one @ 300DPI.
If you are doing it yourself in indesign, export as “Adobe PDF (Print)” and in the “compression” tab, set images to use ‘bicubic downsampling’ to 150 for color and grayscale images, and set compression to JPEG with ‘Maximum’ image quality.
Also make sure you have all the ‘bleed’ options unchecked and set to 0 in the ‘Marks and Bleeds’ section
You might have seen elsewhere not to use JPEGs for compression, but JPEG at a high quality level and high enough resolution (in this case 150dpi) still maintains great image quality and offers some benefits of file size. It’s true that the artists, and sharing inks to colorists for colors, etc shouldn’t be using JPEG, but for this final export for digital consumption JPEG is ok as long as it’s set to maximum.
I ALREADY HAVE A HUGE FILE FROM MY PRE-PRESS PERSON AND NO WAY TO EDIT IT!!
Not a problem. Adobe offers a free online tool that can help you: https://acrobat.adobe.com/link/acrobat/compress-pdf
Here’s an example where I exported a copy of my #0 issue of THE IGNIS QUADRANT @ 400 DPI and uploaded to adobe’s compression tool. You can see the original PDF is 121 mb.
Using their “Medium compression” it gives me a file with a size of only 20mb. They don’t explicitly say what kind of compression or downsampling they are doing but upon inspecting the file it’s a combination of downsampling (to 300dpi) and some JPEG compression. You can see even if I zoom in really close.
Zooming in REALLY far (this figure is about 1" wide in the printed version FYI) you can see the differences.
ORIGINAL, zoomed in @ 400 DPI:
COMPRESSED, zoomed in @ 300dpi w/ JPEG compression
Obviously you can see the differences — the edge lines aren’t as crisp, color transitions, etc. But here’s the entire panel zoomed back so you can see it (as a customer would be reading it):
This is the compressed version BTW — which looks GREAT on my ipad and high-resolution macbook retina display, easy for a customer to store/download and absolutely readable still.
My personal recommendations (and what I appreciate seeing as a reader/customer of digital comics as well is):
- A compressed, 150DPI version of an issue, labelled as “low resolution” somehow (usually ~20–30mb)
- A higher resolution, 300DPI version of an issue, labelled as “high resolution” somehow (usually ~100–120mb)
- A CBZ version of the high resolution copy (usually ~100mb)
- The ability to download each of these files independently so I don’t have to download a huge zip of all of them, then delete the ones I don’t want but can just choose to download the “loweres” version for reading on my tablet, for example