On Sat, 19 Dec 1998 10:25:25 -0800, Jan Steinman <jans@xxxxxxxxxxx> jammed all
night, and by sunrise was overheard remarking:
> But there is still a great difference between photographs and ink-jet
> prints. I boils down to:
>
> 1) the "DPI" myth: ...Effective resolution is no better than the area in
> which all four inks can
> be displayed, or 720 DPI.
> 2) To make fully saturated or extremely light colors, the printer
> must "dither" or utilize adjascent 1/720th cells, further reducing the
> effective resolution to 360 DPI or less.
Actually, that's changing. Some of the latest printers use translucent
inks and drop-modulation technology, for much better control over the
actual color of each dot than they've had before. HP's "PhotoRET II"
claims to do with, with up to 16 drops of ink per pixel (clearly this is
both mixing and modulation, since they only print in 3+1 colors). See
http://www.photoret.hp.com. I have not seen actual print samples from
the latest printers, but they started using this kind of technology in
the 700 series a year or so ago, and did get the absolutely best ink
jet 600x600 results I have seen.
Of course, there have been non-inkjet technologies in the consumer price
range for awhile, such as wax and low-cost dye sub printing, which has
the potential for much better quality prints, by increasing the actual
color resolution of each pixel.
> 4) the "dots vs grain" myth: no consumer-grade inkjet printer delivers
> "continuous tone" prints, which is what a photograph is.
That's only true if you limit it to inkjet, which of course excludes
dye-sub an other technologies. Low-cost "photo printers" which do
dye-sub printing at relatively low resolution, usually for 3x5-5x7 only,
have been around for awhile. I have not been especially impressed with
the results yet, but then again, most of the demos I've seen in stores
grab the images directly from digital cameras. I'm not which is the
weakest link.
Poloroid has a similarly priced unit for snapshots, which basically just
exposes their normal everyday instant film under computer control. It
produces photographic quality prints, certainly, at least if a 3"x3"
square fits your definition of "photograph".
The Alps Electric line of printers, for example, offers a normal
"micro-dry" ink (basically like dry wax printing, but they use a polymer
rather than wax, so the result is a bit more stable and doesn't stick in
photocopiers) in 6+1 colors, but has an option for dye-sub. In the form
that's been around for awhile (1200x600 dpi), the micro dry inks are at
least as good as inkjet, though like inkjets, if they're not in percise
alignment, you'll see print-banding (as opposed to color/dither banding)
.
Just the other day, I saw the MD5000, their new one which does 2400dpi,
and I'll have to admit, it's stunning. Of course, this was in a computer
store and I didn't have hours to examine the output, but they had some
samples there that were amazing. The 2400dpi black & white print they
had might have passed for a photograph, probably taken with a medium
format camera, if I didn't know any better. The color photo they had at
2400dpi (6+1 color ink) was nearly as amazing, though the odd surface
patterns (in the gloss) pegged it as a computer generated image. And you
can always suspect that the demo photos shown on display are hand picked
for what the printer does. Still, if the dye sub is even better than
that, it'll rival anything I have seen from the more typical $3000+ dye
sub printers. This one is currently under $600 -- not really the same
league as a $200 Epson, but affordable for a serious home user. I would
do more research (and very well may).
>(Dye-sublimation
> prints and Iris ink jet prints with certain formulations can deliver
> contone prints.)
Again, some dye-sub technologies are well into the consumer price range
today. No continuous tone ink jet has been done yet, but overprinting is
pushing it in that direction.
> It is argued that the grain of a photograph or negavite is
> "equivalent" to a certain DPI, but this is only even vaguely true for
> continuous tone devices, because the dot-matrix printer has a combination
> of dot grid and dither grid to consider. The dither grid is rarely
> specified, and (as pointed out above) is generally MUCH coarser, by a
> factor of four or more, than the marketeer's advertised DPI.
Of course, the very notion of dithering implies a grid, and chance are,
they're using some of the more sophisticated algorithms these days, not
a simply regular 4x4 grid, since the dithering itself is an obvious
artifact if done too simply.
On the other hand, especially for 35mm (this is the Olympus list, after
all), the target isn't ever going to be delivering a printer technology
that matchs photo paper resolution (you certainly can make the
comparison; papers are, ultimately, made of dots of silver oxide, or
dyes where the silver oxide once was, etc), simply because it doesn't
have to be. The print resolution only has to be high enough, pixel and
color-wise, that it's a match for the largest meaningful 35mm negative
scan. Maybe that's something like 3000 pixels on the long edge, maybe a
bit more or less depending on the film, but there is a value you could
pick today, with some reasearch, beyond which you're just fooling
yourself.
> In addition,
> film grain is stochastic, or random, and so is much less distracting than
> dot grids or most dither grids.
Most printer drivers support a diffusion dither, at least recent ones,
which is pretty artifact free when done right. It's a matter of having
enough pixels to work with (and of course, it only works better if you
get multiple colors per pixel). It's reasonable to expect dithering to
evolve with everything else.
> Sure, at arm's length, a print from a $200 ink-jet printer looks great --
> albeit on paper that costs as much or more than photographic paper, but
> take a loupe to it, or set it in a sunny window for a while, and you'll see
> why photographs aren't going to disappear any time soon!
Yeah, I have to agree here.
--
Dave Haynie | V.P. Technology, Met@box Infonet, AG | http://www.metabox.de
Be Dev #2024 | NB851 Powered! | Amiga 2000, 3000, 4000, PIOS One
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