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!
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.
Here's a pitch test print starting at 59.96 under a 6x4 piece of 60 LPI lenticular lens (lenticules are parallel to the 4 inch side) placed against a straight edge.
Position your head right above the lens (at the viewing distance the lenticular lens is to be viewed from - very important) and slightly tilt your head left and right (possibly, closing one eye). The non acceptable LPIs give an impression of "running" bands. The best LPI is the one that gives you the widest flip from solid black to solid white (it should flip over the full width of the lens). Depending on the width of the lenticular lens, there may be several LPIs that are acceptable (the wider the lens, the fewer acceptable LPIs). If that's the case, the best LPI among the acceptable ones is the one that gives you the quickest flip from solid black to solid white. On the picture above and video below, the lens width is small and it's not that clear which LPI is the best. It would be much better/easier to have a larger lens at the same LPI and from the same manufacturer (one that covers the whole pitch test print). Please, keep that in mind!
In the little movie above, you can clearly see that, when the camera is shifted, lines 60.02 to 60.06 flip from solid black to solid white over the whole lens (that's what you want to see). You're gonna have to trust me on this but you don't get that effect on line 60.01.
In the case shown in the picture and movie, acceptable LPIs range from 60.02 to 60.07. If I were to do some interlacing for that printer/paper/lens combo, I'd choose 60.04 as my "true" LPI. Again, it's better/easier to do the pitch test with a wider lenticular lens but sometimes, you have to make the best of what you have.
Check the Creating and Using a Pitch Test by microlens for another interpretation of the pitch test.