[Leica] Erwin's adventures in digiland. part 2

[Erwin Puts <imxputs@knoware.nl>]

Print fumdamentals.
The ubiquitous inkjet printer generates a color by splashing small 
droplets on a location on the paper. These droplets can be next to 
each other or they can overlap. The smallness of any individual 
droplet is not a measure of resolution or sharpness impression. It 
merely tells you how smooth the colorblends may be on the paper. As 
the typical inkjet printer has 6 colors only a limited range of 
colors and colorshades can be produced. All other colors and shades 
demand the use of a halftone or raster technique. If the printer 
would use a 2x2 matrix  5 additional shades can be produced. If we 
need the full range of shades a 16x16 matrix will b used. But such a 
raster needs space. It is quite simple. The larger the raster area 
the more shades can be faithfully  reproduced. But the larger the 
area of such a matrix the greater the loss of resolution or 
lines/inch. This is analogous to the discussion 35mm print or medium 
format print. The latter can give a much smoother image (at the same 
area of print enlargement) because it has more silver per unit area 
for tonal recording.

If we print at a 1440 dpi, we get a very smooth image, but not 
necessarily a high resolution (or even more relevant: a high micro 
contrast).
Photo-quality printers use at least a 2x2 raster-cell to reproduce 
the tonality of colors, so the 1440 should reduce to 720 or even 300 
dpi in print. And rasterisation will always show when looked at close 
enough. So with an image-resolution of 150 to 300 pixels per inch we 
reach the threshold of current highquality  inkjet printers.   To get 
better images on print a fully digital printer is needed. That is yet 
another story.
As an aside: a 1800 x 1200 pixel image has a total of 2.1 million 
pixels. There is no direct relation between a image pixel and a print 
dot. So a 1440 x 720 dpi print area ( 1 million dots) does not relate 
to the 2.1 million pixels in a 1:2 relation. The 2x2 matrix cell will 
intervene.
What about the 2700 x2700 negative scan. The 7 million pixels here 
will be forced into the same 1 million dots (plus rasterization). So 
for the inkjet print is it overkill.
Next installment: a real comparison
Erwin