Basic Print Submission Info: Resolution and Color

[tugrik]

When making prints for other artists the two most common questions I get are:

• What resolution should the image be set to?
  
• How can I make sure it prints with the right colors?

This LJ entry is a brief attempt at answering these. If you already know what you're doing with resolution and color profiles you'll probably scoff at the simplicity of these little how-tos, but I figure they're worth posting anyway.

I'll use this post to talk about the first question: resolution. When you're dealing with a printing service like mine I need to make sure that the image you provide will look good at the size you request. The output quality is determined by the DPI (dots per inch) of the file when it's printed at the requested size. The DPI is determined by dividing the number of pixels (high or wide) in the image by the number of inches (high or wide, similarly) the image is. The resulting number will let you know how it's going to look. Here's a quick guideline:

• Higher than 300dpi: Often more than you need. While more data is better, it makes for larger files that are harder to send around. Also, super-fine details much higher than 300dpi may not be reproduced properly on paper; they're too fine for the printer. The exception to this are technical drawings with low color but fine, high-contrast detail. Examples of this are CAD drawings or thin-line pen illustrations, where detail is more important than color. Those can be done at 600dpi pretty nicely.
  
• 300dpi: This is just about perfect for fine-art printing. It uses the printer to its full color-resolution potential. 300dpi (and higher) images are suitable for up-close inspection without seeing pixels.
  
• 150dpi: This is good for fine-art printing that's going to be viewed from standing distance, such as on a display board or mounted on the wall. Up-close inspection looks a little softer but is still good.
  
• 72dpi: This is fine for large-area posters or images designed to be viewed from a few feet away. Resolution is soft, but manageable. Close inspection will be less than optimal, though; it'll look less like art, more like a computer print.
  
• 50dpi and lower: Only really suitable for mega-sized images viewed at a distance, such as outdoor advertising or large wall-graphics. Up close viewing will show large individual pixels.

Using these DPI targets it's easy to estimate how big an existing image of yours will print. While you can calculate it manually, it's easier to let the computer do it. I use Adobe Photoshop, but most all image editors have a similar functionality. In photoshop, the 'calculator' for all this is in the Image Size dialog.

The key here is to turn off the "resample image" checkbox. This way you're not actually changing any of the actual pixels -- instead, you're using the dialog to check or set the DPI. Set your Width and Height to inches and the resolution to pixels/inch.



This now functions as a calculator. Type in a DPI and you'll be shown the size (in inches) the image will print. Conversely, type in either the width or height you want the print to be, and it will display what the resulting DPI is. Keep in mind that you don't need to have exact DPI numbers. If your chosen image size has a resulting DPI of, say, 285 -- that's pretty close to 300 and will work just fine.

Now, if you're creating a new image (destined for prints) from scratch and want to know how big of a digital canvas to use, you can do the same thing with the "File/New" dialog. Change the Width and Height to "inches" and the Resolution to "pixels/inch". Now simply type in how big you want the image to be when its printed. Then pick the resolution you want it printed at (most often 300 for fine-art, as per above). The program will then create a canvas of the right pixel dimensions to achieve this.

Don't be surprised if your 20x30 @300dpi image ends up being crazy-huge. :)

Comments

[neogeen.livejournal.com]

Thank you for taking the time to write all of this up! I am keeping it handy to send towards people that ask about this stuff, it comes up all the time.

(+memories)

[darkwolven.livejournal.com]

Oo, you might want to mention that if the image will need to be enlarged from the size they are sending, 600+ DPI or higher is preferred, depending on the size of enlargement. I've been sent images before when I was doing wide format stuff that was 300DPI, and when the customer was told that the image would be fuzzy when going from 8"x10" to 36" x 48", they got annoyed. Always good to add in a "cushion" for yourself if you do enlargements.

One time I had to do I large light box on translucent material that was something crazy like 96" wide from a magazine scan. Now THAT was fun. ;)

[scyllacat.livejournal.com]

Thanks for the run-down. As I rarely have to do stuff like this, I never remember what would be reasonable (like someone who does it every day).

[loranskunky.livejournal.com]

Working on 4 color shops, it's always at least 300dpi or better. At least for print, when you're doing flexo, it varies because of the materials. There's also a huge amount of screen patterns and angles to deal with too.

Also don't forget that you can also remove DPI, but you can not add DPI.

[darkwolven.livejournal.com]

Well, technically you can add DPI, it's just that it doesn't usually work so well from a practical standpoint... :P