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Even though displaying of images is not the primary purpose of M92 it still does a nice job showing gray-scale images. If there wouldn’t be a little distortion of the shade smoothness it could be just perfect.

Viewing images a lot, I have noticed that the darkening steps of the 16 gray tones are not smoothly distributed between black and white. With other words, if you display all 16 shades of gray on a palette there is a smooth increase of darkness for the first 11 levels (from white to black), then there is a sudden disproportionately increased darkening between 11th and 12th. Again follows smooth darkening between 12,13,14th levels, and a second unwanted sudden increased darkening between 14 and 15 levels. The transition from 15 to 16 is smooth again.

You can see what I mean if you take a look at the attached image gray_scales_on_M92.jpg. This is the photo taken of M92 displaying the image gray_scales.gif. Basically there are two disproportionately large jumps of darkening, while there are some adjacent light shades hardly distinguishable. Unfortunately this results in a strange photo viewing experience. If the photo is light it will produce a very nice picture where the shades from 1 to 11 are used. Then if there is a slightly darker area there will be a sudden jump of darkness sometimes creating a caricature-like distortion.

This can be seen on the sample_on_M92.jpg photo where the full_color_sample.jpg is displayed on M92. The left corner and edge of the mouth is exaggeratedly darkened. The same effect is visible at the corner of the eye on the left and the edge of the face and hair. It creates an impression of badly developed black&white photo, or a distorted image. If you convert the original full_color_sample.jpg into 4bit gray-scale (16_level_gray_sample.gif), and display it on a PC screen these distortions will not be visible. It is not too bad on this photo, but it is quite disturbing on darker photos. This is definitely a bug in M92. Most probably a software bug that uses an uneven gray-scale level distribution.

Did anybody else notice this phenomenon yet?

If it really turns out to be a software bug, I would really appreciate if the developer community or Onyx could fix it because this would make the difference between fairly usable vs. perfect photo quality image display. I am sure there are many users like myself who use the M92 for viewing photos, graphs, and drawings, so it is not an unimportant feature. In my case in fact, the ability to display 16 gray levels and a large screen were important factors while deciding to buy this E reader.

Cheers,
Joe