RE: Digital negative novice needs help.

DEAR LIST,
Am I right that the # of lppm also influences the possible number of values
(tones) that a medium can reproduce as well as the resolution? Yes, I know
that digital printing varies the dot size to produce various tones but, it
is a basic principle of info theory that the possible number of tones that
can be produced is proportional to the number of pixels per unit area in the
final image. This was similar in film technology; not only did fine grain
film (or larger format film for the same final print size) allow the
reproduction of finer detail but also the reproduction of more possible
tones.
Sooooooooo, am I right that BOTH lppm AND possible dot sizes at that line
frequency influence the possible number of tones that can be reproduced with
that medium regardless of whether or not one can resolve each pixel
visually?
                CHEERS!
                        BOB

 Please check my website: http://www.bobkiss.com/

-----Original Message-----
From: Sandy King [mailto:sanking@CLEMSON.EDU]
Sent: Thursday, April 20, 2006 8:48 AM
To: alt-photo-process-l@usask.ca
Subject: Re: Digital negative novice needs help.

Yves,

Most people would agree that the practical threshold of resolution is
around 5 lppm at typical viewing distance. The maximum is based on
the size of optical receptors and is around 20 lppm. This means that
it is possible in theory that in optimum viewing conditions some
people might be able to discriminate up to that limit, and tests
suggests that this is indeed possible.

The issue with medium is one of pattern as well as resolution. On a
smooth silver surface you can actually see the dithering pattern
produced by an inkjet printer, an artifact that allows one to easily
tell if the print was made with an in-camera or digital negative. The
pattern on art and drawing papers (as typically used in most
alternative processes) is broken up.

Sandy

>Sandy,
>
>I don't understand the logic of trying to get a better final resolution
then
>our eye can resolve. Is there somekind of effect that gives us the
>impression a print looks better at a higher resolution then our eyes can
>see?
>
>For example, we have say a 5x7 in camera neg resolving 40 lines and we
>manage to get the best scan possible from this same negative. I think you
>would agree with me that there is always some lost when you reproduce an
>image, negative or positive. Let's say in this case we manage to get a
>resolution of 35 lines. If the printer and medium we use to make our
digital
>negative results in a further loss as expected we may get down to only 30
>lines. If I understand you correctly from what you wrote below, we
shouldn't
>be able to tell which was used even if printed on silver-gelatine paper?
>
>That's what I would think also but then you basically say in cases where
you
>want some magnification that you try to get a final resolution of twice
what
>is considered by many to be what our eyes are capable of or about 5 lines
on
>average, I know, this is an average and it means that the number can and
>will vary by a few lines on each side depending on who is looking. In other
>words, if we target the final print resolution at 5 lines say 6 to be
>conservative this should mean on average most people wouldn't see a
>difference for any prints of higher resolution then 6 lines, keeping all
>other factors constant of course.
>
>I have a feeling you will tell me this is theory and in practice things are
>lets say more complicated then that, right?
>
>Regards
>Yves
>
>
>
>----- Original Message -----
>From: "Sandy King" <sanking@clemson.edu>
>To: <alt-photo-process-l@usask.ca>
>Sent: Wednesday, April 19, 2006 10:55 PM
>Subject: Re: Digital negative novice needs help.
>
>
>> Matt,
>>
>> Etienne has a good response to your question and I agree almost
>> completely with his observations. I will just add a couple of more.
>>
>> >
>> >Would it be reasonable to think that I could get good enough scans
>> >from my 5x7s on a good flatbed to make up to 12x17 negs, or do you
>> >really need imacon/drum scans?
>>
>>
>> In my opinion you do not need an Imacon or drum scan for 5X7
>> negatives if print size is limited to about 3X the original. An Epson
>> 4870 or 4900 scanner is capable of about 40 lppm, so at 3X
>> magnification your are still at 10 lppm, which is beyond the
>> resolution of Epson inkjet printers.
>>
>>
>> >
>> >What level of resolution and apparent sharpness can be achieved from
>> >out putting on a high end epson ink-jet? Do the negs stand up well
>> >when compared to analog enlarged negs in this respect?
>>
>> About 8-10 lppm. That is also about the limit of resolution of a
>> Pt./Pd. print on most of the popular papers used with this process.
>>
>>
>> >Any advice and description of people's process and equipment set-up
>> >would be greatly appreciated. I would be interested to how and what
>> >people are doing in this field.
>>
>>
>> I scan 5X7" negative with an Epson 4870 scanner. The scan is done at
>> 3200 dpi, and I then down size for storage to 1600 dpi, which gives
>> an effective resolution of about 35 lppm. The maximum print size I
>> make from these scans is about 2.5X, which keeps resolution at 14
> > lppm or more, well beyond the threshold of resolution of the human
>> eye at the optimum viewing distance of 10-12".
>>
>> Printing with Pt./Pd. digital negatives from the Epson 2200 give
>> results that can not be distinguished from in-camera negatives with
>> most papes. On some hard surface papers one might see a slight
>> advantage to an in-camera negative.
>>
>> In contact printing with silver gelatin papers in-camera negatives
>> are definitely superior in most cases to inkjet negatives. With
>> carbon, it depends on the final surface, but on many papers an inkjet
>> negative gives results as good as an in-camera negative.
>>
>> Sandy
Received on Thu Apr 20 07:42:39 2006