You did it! You have truly created a masterpiece. But when you printed it out, it looked all pixilated and blocky. Dang, you must have a bad setting somewhere. You go back, double chek all your settings, hit render again and wait. It still looks the same when you print it. You start glaring silent threats at your printer. Well before you decide to make good on those threats, you might want to try one more thing (your printer will thanque you for it).
You may have overlooked the whole DPI issue. While it’s true that Blender has some nice preset render sizes, if you don’t understand how that relates to printing, you will be forever glaring at your printer.
First let’s look at what DPI actually is.
DPI is a printing term that describes the number of dots/pixels that are defined in the boundary of a square inch that are used to create an image. The more correct term is pixels per inch, however dots per inch is often used instead. (The image can be a font or graphic). In general, the more dots, the better and sharper the image. DPI is printer resolution. DPI is not image resolution although frequently used that way.
Ok, now that we know what DPI is, let’s look at how it applies to Blender. Blender renders images out at 72dpi, which looks okay on your screen, but not printed out. In order for it to look good for print, you have to render your image bigger and then resize it smaller in your favorite graphic program. Essentially what you will be doing is swapping physical dimensions for resolution. Take a look at the following chart (fig. 1). It shows some common render sizes in pixels and the corresponding physical sizes at 72dpi (which Blender uses) and a good print resolution of 300dpi. You can see that the physical sizes become smaller as you increase the resolution.
This may seem overly complicated, but really it is not. There is a very simple formula you can use to get the proper settings. Basically you multiply the desired resolution by the desired physical size to get the pixel settings/size you need for Blender (fig. 2).
Once you have rendered your image using those settings, you need to go into your favorite image program and resize your image. Most image programs worque similarly, so figuring it out in your program shouldn’t be difficult. I will be using Photoshop to explain this part, because that is what I have.
Step 1: Open your image
Step 2: Go to Image>Image Size, a dialog box like fig. 3 should open.
Step 3: At the bottom of the box, unchek “Resample Image”
Step 4: Next locate the “Resolution Box”, enter your new resolution. The Width and
Height boxes should automatically update to reflect the new size at that resolution.
Step 5: Hit the “OK” button and save, you are all done and now your image will print like you expected it to.
Okay, so now you have a better understanding of dpi and how to get the proper dpi for printing, but what dpi resolution is best for what you need. As a general rule, you should choose a resolution between 150-300 dpi. This resolution is good for most print projects. If you are having something professionally printed, it is always a good idea to chek with your printer and find out what resolution their equipment runs at.