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Kostas:
>Karl can you
alaboarate on these points?
.. hardware rips even more so, except
that printers themselves have RIPs onboard that often can do the job
surprisingly well.
The prinetr it's self will apply the
algorythms and fuzzy logic required to upsize the image and produce the best
image it can without pixellation.
Do all printers use this?
Hi Kostas. Yes as far as I know these days all printers
and the software that comes with them have this ability. In the past some
or many printers needed all the specific information fed to them in their
language as to what was to be done in making a print.. if the image fed to it
was 300 x 300 pixels and the printer printed at 300 pixels per inch
resolution than all you could get out of the printer was a 300 pixel or a 1
inch image. Any upsizing done in the printer settings (say if you said
make it 10 inches in size) resulted in a 10 inch image, but each inch contained
blocks of 30 pixels - and visible pixelation. So a diagonal line
from the bottom left corner to the top right would have looked like
stairs.
RIPs (raster image processors) are made for many purposes, For
example architectural RIPs are designed for precise scaling, so the upsized
image will show no linear distortion and measuring off a plan will be as
accurate as calculating from the original numeric specifications.
Some RIPs for graphic design are designed to produce the most accurate
colour renderings using the specific print known inks of a known printer (4
color type like used in magazine or carton printing) . Our photographic
printers use this too, especially since each printer has it's own special inks
these days rather than in the previous example where inks came in tins like
house paint. So our photo printer RIPS are tuned to take a RGB or
CMYK colour and render it accurately with an ink set that might be (using a 6
colour canon as an example) C lC M lM Y K, Other printer RIPS are
designed for greyscale printing and without the need to desaturate an image in
your software, the full colour image can be fed to the printer through the
software RIP that knows how to best render the colours into a natural looking
greyscale*.
*I should say 'natural looking' is a bit of sales pitch since
eyes interpret colour adtones differently - this is a complicated area for
another time, but think of it like this, black and white films had different
colour sensitivities.. so which was the most natural, FP4 or T-Max? - red, blue
and green were rendered differently by each of these films ..
But one of the most useful things in modern printers is the
interpolation of the image in upsizing.. so sending a 300 pixel image to a
printer and saying 'make this 10 inches long' rather than showing blocky pixels
as happened before, the print driver applies whatever upsizing algorithms it has
in the program to the job and seeing that line from bottom left to top right in
the example above, it preserves that detail and gives you an image with a line
rather than stairs. We take this all for granted now but not long
ago this would have been considered pretty much magical. In fact we take
it so juch for granted we often don't look when we compare printers to see
whether one brand does a better job than another brand at this sort of upsizing,
we just assume they're all good as one another - but different brands use
different RIPS .. I've never compared or tested them though.
It's a bit like the fight for automation in cameras - consumer
cameras had auto settings, the camera that took the best pictures automatically
was the one consumers wanted, it got so good that almost all pictures from all
cameras looked good - so not many people stopped to compare what or how the
automation varied, or tried to find when or why one camera took better images
than another under conditions that might push the cameras automation.. they just
went 'oh that one didn't work' when the automation failed.
Often this ability (the RIP at work)
is mistaken for a dpi setting below the normal quality barrier (300 ppi) - it's
not usign a lower ppi at all but rather an interpolation programmed into the
printer.
here i have lost
you.... Sorry ;) You know photo printers have high DPI settings,
say 4800 dpi.. so up to 4800 dots of whatever ink are needed are squirted out to
make the fine gradation of colours and tones. That's the sales guys taking
the technical specifications and using them to impress customers. Sure
it's lots of dots, but so what? OK more is better but only up to a point
where we can differentiate it's not that relevant to us really. you'd be
hard pressed to see the difference in the colour range produced by a 1200 dot
printer over a 4800 dot printer. Unfortunately throwing those numbers
around can confuse people .. really we only need to know a couple of
things and that's the number of pixels per inch we can differentiate (usually
300 at normal viewing distance) and the size of the image we need to
make a good print.
It's true for a wall sized image a lower number of pixels can
be used per inch as you'll stand back further to look at it - BUT think of any
large picture you've seen lately, is it pixelated when you get up close?
These days I'd doubt it.. If we were printing with only a basic RIP or without a
RIP of any kind like older printers did, printing at 50 ppi you'd easily see
blocks as the pixels grew larger - you'd see those 50 little squares across an
inch.
even at 200 pixels per inch at normal viewing distance pixels
can be noticed, that's why we went for 300 .. it's really hard to see 300 little
blocks across an inch but someone with good eyes could spot a 180-200 ppi
print was made up of little blocky square pixels - but this doesn't happen any
more because again the printer RIP actually
does some interpolating and resizing when we scale the image to lower settings
that 300.
Nowdays when a printer is fed a 300 pixel (one inch) image and
told to make it 6 inches across, rather than seeing a 50 pixel per
inch image with noticeable blocks the printer smooths it out and - yes sure it
may look a little fuzzy - but there's no pixels visible. This is what I
meant in the comment above - it can lead people to think that it's OK to
print at 50 ppi and that 50 ppi is what they're getting.
the image was sent at 50 ppi, but the printer is really just
upsizing that image to a fuzzier, larger image at an effecive 300 ppi (it
knows what 'the good' setting is)
Sure it'll look OK at distance but again the RIP automation
has taken over and done the hard work with no thinking involved from us and we
can misunderstand what we're seeing. End result itll look fine (or not)
but it's not really a 50 ppi image.. that's just what the RIP had to work with
before it did it's magic. A better way to think of it would be 'my printer
can make a pretty good 8x10 image print from a 400x500 pixel image' rather than
thinking of it as printing a 50ppi image.
Since we're photographers and we're trying to make the best
images we can then aiming for 300 ppi at normal viewing distance is what we try
to do as even the fussiest eyes will see that as smooth.
These days with so much automation in everything it can be
tricky knowing what's going on - sometimes it almost doesn't seem worth trying
to understand when the results can seem so good, but it's like automation in
cars - everything is great when it works.
Στις 4:46 μ.μ. Τρίτη, 7 Μαρτίου 2017, ο/η
JW Faul <nyce2jan@xxxxxxxxx> έγραψε: Roughly 4x5”
I have a client with a
jpg that is 1770 x 2041 at 75 ppi.
How large a print can she make from that and expect to
get decent quality?
Art Faul The Artist Formerly Known as
Prints
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Stills That Move: http://www.artfaul.com
Camera Works - The Washington
Post
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