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Gary
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[*] posted on 6/17/2005 at 17:10
What is raster?


What does the term "raster" mean and how does one determine what it is? Can someone fill in the blanks here? Examples?
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lam
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[*] posted on 6/17/2005 at 17:27


Raster means screen.
"Photogravure or Lithography is easy to distinguish;..... the fine screen of dots of which the design is composed can be clearly seen with the aid of a magnifier..."
The Stamp Collector's Encyclopaedia; R.J.Sutton; Sixth Edition; 1966; p.245
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Gary
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[*] posted on 6/18/2005 at 17:59


We need examples.
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oldteddy
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[*] posted on 6/18/2005 at 19:51
Yes, Sir!


This is an example from one of the best researched sets with different rasters (there was a detailed article in Rossica journal) - Moscow-800. It's the same stamp but the left one has screen consisting of squares and the right one - or horizontal romboids. It's the highest resolution my scanner allows, but I think the difference is visible somewhat.

rasters.jpg - 26kB
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jlechtanski
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[*] posted on 7/7/2005 at 14:40


Oldteddy’s example got me interested.
I looked through my examples of Scott 1132-1146 (800th Anniversary of the Founding of Moscow).
It wasn’t that easy using the cheap magnifier I had.
But the example below of Scott 1141 (Grand Kremlin Palace) was relatively easy to see.
Using a borrowed scanner I was able to produce the scan below at 1600 dpi.
The left one shows the square raster and right one shows the horizontal diamond raster.

Some quick research shows that Zagorsky lists three types of rasters; Liapin lists six.

The three that both list are:
square
vertical rhombus (diamond)
horizontal rhombus (diamond)

The additional three listed by Liapin are:

negative square
negative vertical rhombus (diamond)
negative horizontal rhombus (diamond)

The first group is illustrated as black shapes on white; the second group as white shapes on black.

Using Scott 1132-1146 as an example, all three types of raster are used on one stamp or the other.

There is an interesting note in Liapin indicating that the negative vertical and horizontal rhombus raster exists on this issue and that “the listing will be continued.”

raster1.jpg - 131kB
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Gary
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[*] posted on 7/7/2005 at 16:52


Yeow! I need to take an electron-microscope with me to shows from now on.:!!
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