Viva La Resolution!

I don't intend this to be a be-all end-all post about resolution, but something to give you what you need to understand what it is, determine what resolution you should be working in, and what resolution your final output should be.  Resolution questions seem to be common on message boards.   So I thought it might be a good subject to attack.

What is Resolution?

To put it simply resolution is how many pixels wide by how many pixels high an image is.  This is typically measured by inch, as in PPI (pixels per inch), or as it correlates to the print world as DPI (dots per inch).  Since a lot of digital work is done with print in mind, people typically refer to resolutions in DPI no matter what the final output is, and so will I.

Why do we need to even refer to resolutions "per inch" in the first place?  Well, if we were only looking at the image on a screen, we wouldn't.  Since we like to print stuff, though, we need to know how many pixels correlate to how much space on a page.  So an image can be 1000 x 1000 pixels, and then we can choose to give it any DPI, which will effect its size when printed.  Which leads us to the all important topic of:

Screen Resolution Vs. Print Resolution

Here's something definite:  Screen resolution (the resolution of your computer monitor) is 72dpi.  Even if there's a higher resolution assigned to the image, it will still display on screen at 72dpi.  That's not saying it shrinks:   a 1000 x 1000 pixel image will display on screen at 1000 x 1000  whether it was assigned 72dpi or 1200dpi.  It's a good habit, though, always to save things intended for screen at 72dpi.

Less definite is print resolution.  Why? Because the optimal DPI for print can depend on what you're printing.  Its also dependent upon the capabilities and limitations of the print house.  Since we're talking about comic books here, let's look at some good rules of thumb for comic books, and various printed publications (keep in mind these rules may not apply to, say, billboards).

The basic rule for print is 300dpi minimum.  This is generally considered the point where there is no pixelation visible to the naked eye.  What I'm talking about here is 300dpi at print size.  That is, if you wanted to print a 5" x 5" page, at 300dpi, that would be 1500 x 1500 pixels.  Get it?  Got it? Good!

There are a lot of folks out there who, I'm sure, are ready to flame me for suggesting 300dpi as a minimum.  But I can say, in good faith, as a graphic designer working a lot in print, 300dpi is usually all you need for your final files.  An exception would be straight black and white linework, which tends to show off some jagged edge pixeliation at 300dpi.  There I would suggest shooting for 600dpi if at all possible. 

In any case, if you can work/save/print at higher resolutions than these, I say go for it.  Operating at a higher resolution leaves options open for other applications.  Forethought can save you a lot of trouble.  I know a lot of webcomics artists who've saved all their work at a good size for screen display, but are mortified when they find out they can't use those same files to print!  Its a good idea to work at a high resolution, and save new files with different names at the smaller sizes as needed.  Which leads me to the next point: