From: Larry Roohr (lrryr@home.com)
Date: 01/03/01-06:48:50 AM Z
FWIW, I ran a completely un-scientific test on both my scanner and Piezo
output on the 1160. I scanned in a negative of an Airforce resolution test
target from my Contax G1 (>80 lpmm) at 2500 dpi on my Agfa T2500 scanner,
got ~45 lpmm, then expanded it 2x (so I could read the numbers) in photoshop
and printed it out (at 1250 dpi) on Epson matte paper with the piezo driver,
got ~9-10 lpmm. Pretty sharp against the old '8x10 at arms length perceived
sharp at 5 lpmm' rule of thumb but certainly not near whats achievable with
a large negative contact print, if ultra-sharpness is what floats your boat.
I find these prints very sharp, without doing any side by side comparisons
to say a 20 lpmm analog equivalent which I trust would be a percievable
difference.
16 bit printing was discussed lately on the piezo list and the Cone guys
believe the difference between 8 and 16 bits would be negligible.
Dan, any word on the transparency material you were running your survey on?
Larry
----- Original Message -----
From: "Jeffrey D. Mathias" <jeffrey.d.mathias@worldnet.att.net>
To: <alt-photo-process-l@skyway.usask.ca>
Sent: Tuesday, January 02, 2001 1:30 PM
Subject: Re: Piezography
> Jack Fulton wrote:
> > ...For sure, I'd like to know why such a low res. We cannot see a
difference so
> > far in tests sending higher res files but our tests are not at all
complete
> > as of yet.
>
> A test to try is to make an image of alternating white and black
> pixels. Use various resolutions (ppi) and send to the printer. If the
> result is gray, rather than white and black, either the printer is
> beyond its capable resolution or the printer (and driver) are
> interpolating (which may be the case for a high resolution output
> requiring only 270 or 360 dpi input). If the printed result is black
> dots at the frequency dictated by the image resolution, then it should
> be safe to say the printer is capable of providing an acurate rendering
> at that resolution. (At least of the accuracy of details, tonality and
> its posterization are another mater.)
>
> The important part of the test is not how good the final print looks,
> but how accurately it has reproduced the original information (digital
> data).
>
> Two important advancements I am hoping to see from the Cone products
> (quad inks and software) are the rendering of fine information
> (regardless of tonal density) with factual information and a uniform
> distribution of density steps throughout the density range. Another
> important factor I have not yet seen addressed is the production of
> enough number of density steps to render posterization unnoticeable.
>
>
> It is one of my hopes that Dan Burkholder will provide some comparisons
> of photgraphic negatives versus digital negatives (ala Cone products).
> One way this might be attempted is to scan both at a very high
> resolution and display the enlarged results at 72 ppi for viewing over
> the web. This can be like using a microscope to compare identical
> portions of each negative. The scan should be much finer than the
> intended lines-per-inch of the final print.
>
> Another aspect could be to investigate various tonal regions of
> negatives for the purpose of investigating posterization. Scannig only
> a limited range (say one or two zones) as if full range of the scanner
> may be able to provide useful data without influencing the original
> posterization with the inherent posterization of the scan.
>
> So Dan, what say you? You are one of the very few I know of to have the
> ability, experience, and access to equipment to provide such
> information. You know I would be doing it myself if I could.
>
> --
> Jeffrey D. Mathias
> http://home.att.net/~jeffrey.d.mathias/
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