On Thu, 30 Aug 2012 23:32:18 +0200, Wolfgang Weisselberg
wrote:

Alan Browne wrote:
On 2012.08.26 16:19 , R. Mark Clayton wrote:

The dot pitch of my printer is 1440 and the "standard" resolution is 360
dpi. At any normal viewing distance this is imperceptible.

Not when it dithers over blocks of 64 or more.

What do you mean? If I print at 360 on the Epson 3800 (head is 1440)
the dithering for a print dot should be no more than 4x4 (16 dithered
dots). [not counting dot 'edge' to dot 'edge' dithering]. Why would it
dither to 64 blocks?

So how many colour steps and gray steps do you get at 16 dithered
dots?

I understand where you are coming from but the evidence is that the
Epson 3800 printer (at least) is not confined to the regular
deposition of drops in simple rectangular cells. See
http://gerryeskinstudio.com/ABW_sept.../image002-.jpg
Not only is it hard (?) to see any visible evidence a rectangular cell
containing dot patterns, but it is evident that there need be no
simple pattern of dot depositions.

Dots overlap each other in many places and the amount of overlap
varies from one position to the next. Drops are transluscent with the
result that overprinting causes colour-mixing and the formation of
colours other than those of the raw ink. And then there is the ability
of the printer to deposit drops of different sizes, although there is
little evidence of this in the particular example.

I don't know what the dithering algorithm is that is used by Epson but
I suggest it renders moot any analysis based on simple dot patterns
deposited in rectangular blocks or cells.

This started with comments by Mark Clayton about the printing of grey
scales (etc) by Mark Clayton. I suggest reading
http://gerryeskinstudio.com/ABW_sept08_paper/index.html
--

Regards,

Eric Stevens