Re: Mike: Restating your explanation

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"Randy Gardner" <RandyGardner@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message news:969E674F-D52D-4CDB-9B9E-4132E40E4102@xxxxxxxxxxxxxxxx

I worked through the issue of logical and physical measurements on
monitors when I remembered that pixels on monitors(dot pitch) come
in different sizes, or setting as you explained, i.e., the error. Printers
on the other hand are very high resolution (600x600, per square in.)
and even better on some models so they can get the physical measurment right.

It's not the fact that monitors have a lower resolution than printers that causes a logical inch on a monitor to be a different physical size than a real inch (whereas on printers they are the same size). It is simply that actual size of a monitor pixel is not known to Windows, so Windows has no way of knowing how many monitor pixels will measure a "real world inch". There are various reasons for this, but one of the reasons is that there are so many different sizes of monitor. For example, the size of a single pixel on a 21 inch moinitor running a 1024 x 768 display will be larger than the size of a 17 inch monitor running the same 1024 x 768 display. Add to this the fact that Windows does not generally know what physical size the attached monitor is, and even if it did it would not necesarilly be very much wiser because monitor manufacturers have traditionally lied about the size of their displays (particularly with CRT monitors), and some lie more than others! So, Windows just sets a specific number of "pixels per inch" and it uses that value when it draws stuff to the display. It calls these inches "logical inches", and there isn't really any problem with it. Printers are different because printer manufacturers know exactly how far the print head will travel across the page for every pixel, and on a 600 pixels per inch printer for example they deliberately arrange it so that the printer head travels exactly one inch across the page when it draws a line of 600 pixels.

Mike



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