Test procedures FDM 3D printers
GeneralThe videos from "How Open Is This Gadget" show the operating functions of a projector and give you a first impression of the quality the device delivers. However, I deliberately do not give any ratings for the tested gadgets in the videos! I want to leave that up to you, because only you know what you expect from a projector. Furthermore, slogans such as "The best machine at price X" are usually obsolete just a few days after a video has been published, since there are many manufacturers in the middle to lower price range, all rivaling for the best price.
So have a close look at the high-resolution photos taken of the testpatterns to get an own opinion. When making the videos,
For all tests there is: if you can't see any real differences between two devices, then consider them equal and focus on other things, such as the openness of hard- and software! Don't start interpreting the smallest differences in the photos of test results, because that's simply not relevant in practice. Keep your feet on the ground and don't listen to all those self-proclaimed experts (myself included).
The test pattern was generated with a Python script. Both, the script and the test pattern in various resolutions are available as download (290kB).
Ideally, the projection surface should be illuminated evenly in all colors. I use a white, red, green and blue test projection.
Test patternThe test pattern shows several weak points:
The grid lines should be parallel.
The lines should not be broken anywhere.
The lines should be as sharp as possible across the entire image.
If possible, no colored fringes should be visible on the grid lines. This is particularly noticeable with black grid lines on a white background. Such "chromatic aberrations" can usually be seen on lines on the outer edges. Fuzzy edges with color fringes are the most noticeable error of the projector lenses. The cheaper the device, the more obwious the colored edges, or to put it another way: the sharper the edges, the better the optics.
The higher the physical resolution and the better the optics, the easier it is to identify lines that are close together as individual lines. This can be seen with the five "stars" in the test pattern.
For the projection of the test pattern, the projector is aligned as perpendicularly as possible to the center of the screen and with the projection alignment of the firmware is set to 0.
Since my camera inevitably has to be set up next to the projection line, the projection is not a perfect rectangle.
Since my SLR camera, with which I take the photos of the test pattern, is of course not perfect either, I take 5 detail from the test pattern. The sections show the four corners and the center of the pattern.
Photographing the colored projection with a camera and then displaying it on a screen literally calls for falsifications. Nevertheless, I inserted rectangles with the colors red, green, blue, cyan, magenta and yellow in the test pattern. Each color is shown in 14 shades. the more nuances you can spot, the better.