filmscanners: OT: dyesub printers (long)

[Arthur Entlich <artistic@ampsc.com>]

I realize this is off topic to the general list discussion, but I
believe it will be of interest to many considering output from their
film scanners.  To all others please hit "delete" now.


IS Dye sub your "final answer"  copyright A. Entlich

Dye sub printers are once again beginning to be introduced in the
marketplace, as more and more people look for the holy grail for
photographic results.  However, they are not without some drawbacks.

As you might know, dye sub printers work like fancy thermal printers.
They have a heated "head" (sometimes a stationary "bar" which is similar
to that in a fax machine, only much more sophisticated.)  The "head"
contains elements which are spaced 150th, 300th or 400th apart, or if it
is an actual movable head, move at that rate, and these elements can be
actuated to heat to usually 256 different temperatures.  For color
printing, the heated elements pass over a mylar ribbon or panel
containing sublimation inks of one of three or four colors, CMY, or
CMKY.  The inks, when heated become gaseous, and are deposited on a
receiving sheet which has a special surface which allow the ink to
resolidify within it.

Most quality dye sub printers use a roll of mylar as wide as the maximum
width the printer is capable of printing.  This mylar roll has panels of
dye sub color inks adhered to it, the full dimension of the maximum size
the printer can print.  So, if the printer is capable, say, of 8.5 x 11"
prints, there is a panel of mylar with magenta dye, followed by one of
cyan, followed by yellow, optionally followed by one black, optionally
followed by a clear-coat..

The printer does a color separation, and prints each color onto the
receiver sheet for the full print, then it pulls the sheet back in, and
lays down the next color, up to five times (since dye sub inks are very
unstable (heck, they sublime under heat) usually a final clear coat UV
filter is added.  As you can imagine, the mechanism to do these things
are not cheap; lots of movement and very perfect registration is required.

Dyes subs look good because of 3 factors.  One, since the inks are
transparent, and they are laid directly one each other, and since there
are 256 levels for each color, they can literally produce 16.7 million
color variations, or 24 bit color.  No inkjet printer can do this
working with one or two color ink dye densities, so they create their
color variation by illusion (very successfully, I might add) by using a
mixture of very high resolution matrixes (up to 2880 dots per inch) and
variable dot sizes).  This is how dye subs "get away" with 150, 300 or
400 dpi and look great, because each dot ultimately corresponds to one
pixel, and is the color of that pixel, while inkjets use upwards of a
dozen dots to represent one pixel in the same size area the dye sub
created one (possibly overlayed) dot, using various combinations of the
few colors they have to work with.

The second reason dye subs look good is because the edge of each dot is
soft, so the dots become blurred, more like the irregular grain patterns
found in photographic prints. BTW, this also why text or CAD on dye sub
printers looks poorly.

And thirdly, dye subs can only print on one or two specialty receiver
stocks which are designed for the dye sub inks, so they look
photographic, but are quite limited in paper stocks.

Now, having said all this, what are the downfalls of dye sub?  Well
several.  The first is cost of consumables, which is quite high.  For
each print, regardless of the size of the print or the amount of color
on it, you go through a receiver sheet (they aren't too expensive) but
you also use a full series of panels.  So, place just one dot the size
of a period anywhere in the image, and the printer will use up a full
set of ink panels to do that.  Consumable costs are constant.  You do
not want to waste dye sub prints.  Unlike an inkjet where you can do
small tests, or stop printing early if you see a problem with color
balance, etc, no such luck with dye sub.

Alps tried to resolve part of this and lower consumable costs by using a
series of ribbons rather than panels, but they could never fully resolve
the problems with banding caused by the way the inks were laid down on
the transfer sheet.

The other problems with dye sub are that it is relatively slow, since up
to five separate layers have to be put down, one at a time, and the inks
are still not archival (sound familiar?). Lastly, you can never make a
print larger than the full panel size, so dimension is limited in both
directions.

Several companies have recently introduced small dye sub printers that
can be plugged into computers or digital cameras for producing snapshot
size images.  Canon is one.  The thing to find out is cost per print and
time to print.  In the cost per print, keep in mind that unless the unit
comes with some very sophisticated color management, you will be tossing
some of those prints due to problems with color, etc.

Regarding black and white... some companies do produce a separate mylar
ink rolls that only has black ink and UV protective panels on it.
Obviously, these cost a lot less, since they only use two panels per
print, rather than up to 5, and the black ink is cheaper to make also.,
so if you are only doing black and white of a set size, or you can
"gang" several images on a sheet, then a dye sub printer might be a good
answer. You should look at some examples of B&W prints before 
considering a dye sub.  The black only ink is sometimes a bit thin in 
the darkest areas.  They probabaly should produce a two ink panel 
process for B&W to build up the density needed.

So, yes, dye sub prints can be quite impressive, but keep in mind they
have their drawbacks as well.

Art

Ian Jackson wrote:

 > Michael,
 >
 > I've got to be careful here as this is a scanners BBS not a printer 
BBS but
 > I wonder why there are so few people film scanning then printing with dye
 > sublimation printers?
 >
 > Surely these would fully complement say a 4000 dpi scanner?
 >
 > My only questions are:
 >
 > (1) B&W - I see no mention of this is any Dye sub printer literature
 > (2) Where do I find an A3 Dye sub printer under 2000 UK Pounds?
 >
 > Ian