Re: Resolution and Banding

[Kennedy McEwen <rkm@kennedym.demon.co.uk>]

In article <7B2FF2DC-77AB-11D6-842E-0003931C4CFA@mac.com>, Peter 
Tattersall <ptatters@mac.com> writes
>
>On Tuesday, June 4, 2002, at 12:03  AM, SKID Photography wrote:
>
>> Peter ,
>> I don't think you'd get a moiré pattern with an Epson printer (and 
>>driver), no
>> matter what the file resolution is, as the ink dot pattern is 
>>stochastic and not
>> in a grid, whereas the pixels are in a grid....The ink pattern is 
>>very  similar
>> to the grain pattern on film, which is to say random.
>
>Easy enough to check. Sometime in the next couple of days I'll build an 
>image contrived to generate moiré patterns and I'll report on the 
>results via a C80. The inking may be stochastic, but there is still an 
>underlying grid - otherwise you could never get a nozzle check with 
>straight lines. That said, I think it will take a _very_ contrived 
>image to force a moiré pattern with the current drivers.
>
Its easy to create synthetic pattern that will alias and produce moire 
patterns - it was analysis of such alias patterns that determined that 
resampling was occurring and what the resolution of that resampling was.

Try printing a series of black and white lines one pixel wide and one 
pixel apart at around 725ppi - you get a pattern of 5 lines per inch on 
the paper, because the difference between the 725ppi and the resampling 
resolution is 5ppi.

But getting something like that actually occurring over a significant 
area of a real photograph is unlikely, to say the least.
-- 
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's pissed.
Python Philosophers
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