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The pictures on this site are shown at screen resolution, highly reduced from their original form. This is to present them in an attractive way using common web browser tools and allowing them to load quickly with internet protocols. This is unsatisfying at best, for people who share my desire for sharp details at high resolution. Eventually, when bandwidth is less expensive and display technology can match the discrimination of human vision, photographs on the web will be a rich and satisfying experience. In the meantime, our visual appetites are merely whetted by the proxy pictures we place here.

There is another problem with images on the web: color reproduction. The colors you see are determined by the display hardware you are using, not the colors that I scanned. Most of my images are very uncritical of color, but all pictures are sensitive to the tonal scale used (the digital assigment of the shades of gray between black and white). The pictures on this web site are encoded using the sRGB proposed web standard which utilizes an approximate gamma 2.2 transfer function.

If your monitor is calibrated to this already, great. Otherwise you can use the tools below to make a crude calibration using the brightness and contrast controls on your monitor.

An excellent description of these two mystery knobs is given by Poynton, from which I reproduce this distillation:

This icon indicates the Black Level control, sometimes called Brightness. This control should be adjusted so that black picture content displays as true black on your monitor. Misadjustment of this control is the most common problem of poor quality picture reproduction on computer monitors, video monitors and television sets.

This icon indicates the Picture control, sometimes called Contrast. It affects the intensity that is reproduced for a full white input signal. Once Black Level is set correctly, Picture should be set for comfortable viewing brightness.

So, here's the brute-simple calibration routine:

 

Set the Contrast/Picture control to a comfortable white level, probably full-on.

 

 

Adjust the Brightness/Black Level so that you can just distinguish the first (coarsest) shadow step in the pattern below (don't worry about the finer scales).

 

Look down the scales to find the one where you can still make out the steps. You will probably find the steps easier to discriminate at some specific position along the scale. If the steps all blend about equally, congratulations, your display is visually equidiscriminant and you are unlikely to notice contouring artifacts. This is not the goal however, read on.

"Equidiscriminant" is not the correct tonal scale for the images. The more important indicator is what position along the scale represents "middle" gray. The following tool will help get this right:

If your display matches the sRGB tonal encoding used in my photos, the gray patch on the right will match the average gray produced by the tight checkerboard pattern (blur your eyes or step way back to blend the pattern to a uniform gray). If you are viewing on a Macintosh, the pattern may look closer to the left hand gray patch.

 

 

The only effective control you have available to match them is the Brightness/Black Level knob again. Adjust it so that the center matches the right side. This may cause the shadow steps from the previous pattern to blend together. You must now make a tradeoff, balancing between getting the midtones correct and obtaining good shadows (the highlights will take care of themselves).

I encourage everyone serious about viewing and working with images to obtain monitor calibration software. It's the first step toward looking at what the author intended us to see!

 

 

Copyright 1999-Apr-27

Thor Olson