[Scribus] Dot intensity in laser printing

[jon]

Am 02.05.2007 um 13:37 schrieb william f. maddock:

> On May 2, 2007, at 1:10 AM, ols6000 at sbcglobal.net wrote:
>
>> At 07:15 PM 5/1/2007, you wrote:
>>> That is physically impossible. In a laser printer a dot is either on
>>> or off, you cannot vary the intensity.
>>
>> It is conceivable to me that dots of different sizes could be
>> printed. My recollection is that that is what HP does, but I don't
>> have the manual handy. Since a printed dot is not the same as a
>> particle of toner, there could be lots of ways of changing the number
>> of toner particles in a dot, hence its intensity.
>>
>> There is no reason in principle why the same trick could not be done
>> with color, though, again, I don't know if anyone does it.
>
> Refocusing the laser beam does not vary the intensity of the dot,  
> only its size. The dot is either there or it is not there. There is  
> no in between intensity. A laser printer works by magnetizing the  
> image drum, then rolling that drum through a vat of toner, causing  
> the toner to stick to the magnetized portions of the drum. The  
> paper is then brought over the drum, moving the toner off of the  
> drum to the paper, which then goes through a baking process to melt  
> the toner into the paper.

> Color lasers do this one color at a time. there is no mixing of  
> colors within a dot.

Though this is a fine description of the process I think this isThis  
is not completely it.
My - our - laserprinter/copier uses transparent colors and
70 to 90% dots are always overlapping slightlty (4c). Overlapping  
will always occur within 90 to 100% tones.
Opaque toner (4c) or tints cannot, in my opinion, be used to print  
dark browns/greens/blues -
also I don't think it is possible to print these colors without  
transparent colors and without overlapping.
Most non spot colors in any printing device are transparent or semi  
transparent and mix.

Therefore I think it is possible (using transparent colors), though  
it may be not very practical for comsumer printers,
to generate different intensities out of one color by "simply"  
overprinting them at the same spot - may be hard to hit
(with an "accuracy" of 720ppi the point size is 0,003 mm) but "hmmm"  
some kind of possible.
There has been an campaign a few years ago where some manufacturer  
Epson/HP/Canon?? advertised transparent variety.
Don't know what happens to that, did they gave up?
What I don't think is, that you cannot really depend on this for proofs.

Another option is still the direct variation of the chemical  
composition of the ejected drops.
Don't know if any manufacturer does use this.

And of course there still is half autotypical and conventional  
gravure print wich produces real halftones.
But this does not belong here.
jon