As you probably know, lenticular lenses have a certain number of lenticules per inch (LPI). For 3D comfortable home viewing, it is common to use 60 LPI. You get the 3D effect by printing an interlaced version of the left and right images and placing the lenticular lens on top. The left eye will only see the left image and the right eye will only see the right image thanks to the interlacing and the geometry of the lenticules. In the real world, lenticulars have intermediate images, not just the left and right images but that has no effect on the pitch test, of course.
Before you can even start to think about making 3D lenticulars using an inkjet printer, you need to calibrate the printer, paper and lenticular lens you are planning to actually use. This calibration will determine the proper LPI (lenticules or lines per inch) for your setup.
The first step is to print a line screen test using SuperFlip from the fine folks at vuethru:
- click on Utilities->Print Line Screen Test...
- input a proper "starting lines per inch"
- select "just doublet"
In the printer "Properties...", select something that looks like photo paper, set the print quality to best and use portrait orientation. Of course, you have to print on good photo paper! You are also supposed to use the same paper for the pitch test and the actual interlacing of your image sequences because the pitch test is affected not only by the printer itself but also the paper.
What's a proper starting lines per inch (LPI)? Well, personally, I choose the LPI of my lenticular lens minus a few cents. For example, if my lens is 60 LPI, I am gonna start at 59.96 and go from there depending on the results given by that first print.
It's a bit hard to explain how to actually do the pitch test once the line screen test has been printed but the following video explains the process quite well (It's actually quite simple.):
The key is to put down the lenticular lens at an angle and then rotate it slowly until you see the solid bands. In my case (60 lpi lenticular and hp officejet pro 8000 printer), the lines 60.02 to 60.06 produce the best flips so 60.04 is probably the correct lpi to use in the interlacing process. The whole process is a bit harder when you have lenticular lenses on the smaller side, like a 4x6 lens for example. Bigger lenses, like a 8x10, produce more accurate results.
Check the Creating and Using a Pitch Test by microlens for another interpretation of the pitch test.