Gray Test Images & Screen Patterns

Which gray test image should you use?

A 5% grey test image is the best first check for OLED vertical banding and near-black blotches. A 10% gray image shows whether the same defect survives into brighter dark scenes, while 50% gray is best for dirty screen effect, broad patches and sports-related uniformity problems. Use 1% only in a very dark room; on many screens it is intentionally difficult to distinguish from black.

Testing a TV from a USB stick

Copy the PNGs to a FAT32 or exFAT formatted USB stick, plug it into the TV and open them with the built-in photo viewer. Set the picture mode to Filmmaker, Cinema or Standard first — Vivid and dynamic contrast will hide and invent problems in equal measure — and turn off any automatic brightness limiter you can find.

One caveat worth knowing: many TV photo viewers scale images and add sharpening. That is fine for the solid colours and gray levels, which is what pixel and uniformity testing needs. It is not fine for the checkerboard, which only means anything at an exact 1:1 pixel mapping. If the checkerboard looks like gray mush rather than crisp alternating pixels, the viewer is scaling and you cannot judge sharpness from it.

Which patterns for which problem

White finds dead and dark pixels. Black in a dim room finds stuck and bright pixels, plus backlight bleed and clouding. Red, green and blue isolate one subpixel each, so a partially failed pixel shows on one file only. 50% gray is the single most revealing image for the dirty screen effect, and 1–10% gray is where OLED near-black banding and blotches live.

The starfield is the odd one out: it is single white pixels scattered on black, and its purpose is calibration of your own eyes. Once you have seen how nearly invisible a genuine single lit pixel is, you will stop mistaking dust for defects — the same idea as the dead pixel simulator, in a form you can carry to a shop.

Projectors and consoles

For a projector, the useful files are white (for uniformity and lens falloff), 50% gray (for the same, with less glare) and black (for contrast and light spill outside the frame). Pixel defects on a projector panel are rare but do exist, and they show on white the same way they do on a monitor.

On a console, load the images through the media player and check that the output resolution and colour range match the display's — a limited-range signal shown as full range will crush black and make the 1% and 5% gray files look identical to black, which is a signal problem rather than a panel one.