Paul wrote:
> Hi,
>
> How many shadings is available in a black
> and white laserjet printer such as the
> HP Laserjet 1010? For example, I'm
> printing a photo that has 16 million colors.
> Using the black laserjet... how many
> shadings would it convert it to? 256?
> 1024? 50K? or 16 million shadings??
A laser printer can print exactly 2 shades. 100% black, and
0% black (ie white of the paper). No more, no less. To
achieve something looking like grey they dither. The number
of acceptible looking shades you get will depend on the
resolution of the printer, and the dithering function within
the driver. Since these are variables you have no control
over, there is no one simple answer.
If I wasn't happy with the default output from the printer
driver, I'd convert the image to a B/W image in photoshop,
and play with the dithering settings until I got something
respectable. Important to make sure the image is at the
printers ACTUAL print resolution when doing the conversion.
Be aware that some printers claim figures like 2400dpi or
more, but it is not real dots per inch, it is "perceived" -
IOW, marketing speak. Most laser printers are 600dpi actual
resolution.
>
> Now a color inkjet printer with separate
> black and tricolor cartridge such as the
> HP Deskjet 2560. How many colors would
> it produce in the paper? 16 million colors?
Most of the modern inkjets are capable of a few techniques
to extend the number of colours/tones an individual dot can
hold. A basic printer, or a colour laser can deliver
2^[number of colour inks] distinct colours at a dot. However
techniques such as variable droplet size and/or layering
extend this somewhat. Most modern printers are capable of
between 3 and 9 shades of each colour on a single dot
(counting 0% or white as a a shade), so the number of
distinct colours of a single dot increases to [no of
densities]^[no of colour inks]. Once again to increase the
number of perceived colours they employ dithering. In most
cases the standard dithering algorithms in the drivers are
capable of delivering true photo quality output. Another
thing to be wary of with inkjets is that again their print
resolutions are more marketing speak than actual resolution.
"9600dpi" doesn't mean it puts down 9600 distinct dots in an
inch, instead it means that over an inch it may have fired a
nozzle 9600 times. It's probably more like 1200 actual dots,
but it layers each dot up to 8 times, giving the 9600dpi figure.
>
> J
--
Have you ever noticed that all legal documents need to be
completed in black or blue pen, but we vote in pencil?
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