A few points of clarification:

There are two types of photographic film emulsion that are widely 
(commercially) available today. Traditional monochrome films use silver 
bromide as the light-sensitive component. Chromogenic emulsion films 
use color dyes in addition to silver bromide to produce the image on 
the film - the silver being removed during processing and leaving only 
the dyes. This process is used for typical color films as well as come 
monochrome films such as Ilford XP 2 and Kodak BW400CN.

The fixed silver in the traditional process is very long-lived, and 
assuming that the substrate and binders are durable and well cared for, 
the images, as already noted, can last many decades.

The chromogenic images are less secure; color prints and transparencies 
fade.

Film R&D has resulted in various improvements to the emulsion layers of 
these films as well as the substrates over the intervening years, and 
current color films may last longer than earlier emulsions.

There are several qualitative differences between silver halide 
emulsion recording and the recoding method used to create digital 
images, including this important media distinction.

But a silver halide image is not the same construct as a series of 
pixels on a video display screen. Photons trigger a reaction that 
changes (some of the) silver ions present in the molecules to elemental 
silver, and through further chemical processing, this molecular silver 
becomes the image you see. The final silver arrangement is not uniform 
in size or shape or evenly distributed across the surface of the film 
or paper.

There is much more uniformity to chromogenic dye images, which is why 
some of these films are capable of greater enlargement than a similar 
speed silver emulsion. The three dye layers overlap each other, which 
is analogous to the concept of 'dithering' in digital imaging.

Digital images are by definition uniform, as a grid of pixels displayed 
on screen or as bits described by a JPEG or TIFF file format, whereas 
ink-jet output approximates the dye-layer model. Many digital cameras 
record at a resolution well below the resolution of traditional 
photographic film, but even 2400 dpi is low comparatively.

As already noted, digital graphic files have other limitations, 
especially in regard to storage media, which obviously has undergone 
many big changes since the first ~28" diameter disk drives or 1/2 inch 
high density magnetic tapes.

Of course, 'real programmers' use COBOL and punch cards (not).

-L.D.




On Feb 24, 2005, at 12:02 AM, MUSEUM-L automatic digest system wrote:

> Date:    Wed, 23 Feb 2005 16:10:12 -0500
> From:    [log in to unmask]
> Subject: Re: No Negative
>
> The state of the art has advanced in digital printing:  Epson now 
> makes an
> ink set that will last for around 150 years if printed on the proper 
> paper.
> I think the resolutions on the prints is now up to something like 
> 5660x2880
> dots per square inch or thereabouts. (invisible to the naked eye unless
> you're about sixteen) These are eight color printers that use lighter
> shades of cyan magenta and black (so its gray) which makes for a very 
> good
> print, as the older - four color - printers could only make pastels by
> dropping the resolution and mixing white (the paper color) .
>
> The news is even better for black and white photographers:  ink sets 
> are
> available that will actually use four to eight different shades of 
> gray to
> make B&W photos with no grain at all.  (Google Jon Cone, if you're
> interested.)  You need to buy special drivers, but the prints will last
> longer than Cibachromes.
>
> It is the digital camera that is the problem:  film, negative and 
> prints
> (which are also made up of little dots, just like the pixels on a 
> computer
> screen or the drops from an inkjet printer) have a huge resolution 
> compared
> to the average photo enthusiasts camera.  The pros use much more 
> expensive
> - higher rez stuff.
>
> As to the idea that digital photography is somehow inauthentic, (a
> 'simulation', I think the term was) the same was said about photography
> when it was invented.  Also, it was considered inauthentic for a 
> person to
> use those new-fangled, store boughten, pre-mixed paints when *they* 
> first
> came out. REAL artists were supposed to mix their own paints - like
> Leonardo.  Painting on canvas - instead of a decent wall - was 
> considered a
> cheat.  So the only REAL art is painted in caves with charcoal and mud.
> All the rest is just new-fangled tomfoolery.
>
> Media drift and storage are the other problems:  the formats are 
> changing
> so rapidly (can you say eight track?  Betamax?) that the technology 
> becomes
> literally unfixable - which is why really important stuff is still on
> microfilm:  you can cobble together *something* to look at microfilm.  
> The
> typical CD is good (read: 'dependable for archival purposes') for 
> about six
> years;  archival CDs will last somewhat longer.  But you can depend on 
> a
> properly prepared and printed digital print lasting longer than most 
> other
> photographic processes printing on paper.
>
> John Moriarty

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