File:Zone plate boys.png: Difference between revisions

This is an image for testing LCD, plasma, OLED, and DLP displays on digital connections. It is less good (though still useful) with CRTs and VGA cables.

The image should be displayed as-is. The PNG is marked as being in the sRGB color space; your viewer should not mess with this. The image is correctly displayed when the grey noise patches match the grey reference colors right above them.

In addition to color (backlight+swizzle) and greyscale (no backlight or swizzle), try the test image in swizzle-only and backlight-only modes. You may need to mess with a /sys filesystem entry.

Use the best camera you have. To avoid vibration, use a tripod and either remote shutter or time-delay shutter. Take "camera raw" photos if you can, not just JPEG.

Start with a whole-screen photograph. Be sure to include all edges of the image, particularly the frequency scale at the bottom edge.

You'll need to take a few zoomed in images as well. Most cameras advertize subpixels rather than full pixels. You need to get multiple full camera pixels for each laptop subpixel. Nyquest's theories would suggest that you need 2x in each direction FOR AN INFINITE DISPLAY, but you'll need 4x or 5x to do a decent job. That's more like 10x when you're counting subpixels. So each subpixel of the screen should be covered by a 10x10 patch of subpixels in your camera.

This can be trouble. That is a LOT of images. To cut that down a tad, concentrate on:

• anything that looks defective
• each individual noise patch
• measurement markings

The noise patches get analysed with an FFT. The measurement markings are needed to scale the image correctly and to locate various artifacts on the zone plate.

It is probably a very good idea to take additional pictures of the test image on a regular laptop screen. This would be to determine which defects are caused by your camera.