Black and White Raster Graphics with 1200 DPI and some related Questions

[rs58]

I am generating PJL jobs using PCL. Specifically I am working with
raster graphics as described in the 'PCL 5 Printer Language Technical
Reference Manual'. The 'central part' here is the 'Transfer Raster Data Command'
([ESC]*b#W[raster data]) to send the graphics bytes to the printer for
the individual black dots. Generally things are working fine and I am
able to control each individual printed dot on the paper this way.

But I have noticed some oddities/shortcomings which I cannot explain to me.

1. When using my 'Laser Jet Pro CM1415fnw color MFP' (with
resolutions up to 600 DPI) I do not only see black dots but
occasionally also color dots. Is this expected behavior?
I really wanted to have a true black and white printout
because later I am using some monochromatic light when
viewing the printouts and colors might cause some troubles
then. So my first question is: is there a way for me to
control each individual dot on the paper and also guarantee
that no color dots are printed?

2. Because I did not find a solution for (1.) I recently bought a
'HP LaserJet Pro M404dw'. With this (black and white) printer
there is some chance that no color is printed;-)

Also the printer is advertised to support 1200 DPI. So I
adapted my PJL job to produce print files for 1200 DPI. But
on the paper I do not see the 1200 dots per inch. Everything
is working fine up to 600 DPI, though! When looking at the
'PJL VARIABLES' (with @PJL INFO VARIABLES) I get:

RESOLUTION=1200 [3 ENUMERATED]
300
600
1200

So the printer should be able to produce 1200 DPI output.
However, on the paper I do only see 'scaled objects', .i.e.
the 'global size' corresponds to 1200 DPI but they only seem
to be made from 600 dots per inch. For instance I do not see
a difference in dot size if I just send ONE single bit in my
[raster data] or if I send TWO adjacent bits. I know, Dots
are overlapping to some extend but I do not see any difference
here. So my second question is: is this expected behavior
or should I be able to really produce 1200 individual dots
per inch on the paper? Actually I'd have expected this since
the printer is advertised to support 1200 DPI. And yes, in
the mentioned PLC5 manual for the 'Raster Graphics Resolution
Command' they indeed only mention resolutions up to 600 DPI.
Might this be the reason things do not work with 1200 DPI?
Or is it just that the manual has not been updated to reflect
latest products?

3. Some other questions are these:

@PJL INFO VARIABLES also tells me this:

BITSPERPIXEL=8 [3 ENUMERATED]
1
8
2

What do these values mean? Might I even set some 'gray values'
for the dots? Or is it just that the BITSPERPIXEL says something
about how the bits in the [raster data] are organized and
assigned to the dots on the paper?

Also, in the printer specification I can see terms
like 'HP FastRes1200' or 'HP ProRes1200'. Would these techniques
be somehow useful for me and/or how would I activate these?

Perhaps PCL5 is not suited for my situation and I'd have to
get familiar with PCLXL for instance?

Or maybe I'm just not setting all the needed PJL VARIABLES in
my PJL job? Which PJL VARIABLES might I have to set besides
RESOLUTION for example?

Sorry for this long post (it is my first one in this forum) and I am
tempted to promise that future posts get smaller (even 0 bytes long)
if/when all my questions are answered;-)

[Repairatrooper]

Not all printers that claim 1200 DPI output are actually producing 1200 DPI. Quite often an extrapolation is taking place to simulate 1200 dpi output. I am not sure if that is true for the M404 but something to check into. Typically when clients are looking for this type of resolution they are going to an inkjet printer not laser.

[rs58]

Well, perhaps the M404dw is one of these 'cheap printers'? Is there a way to find out?

Yes, inkjets might be better to get high resolution but I'm not printing too much so I

fear I get problems with dry inks...

Concerning my other questions might there be a chance to get some documentation

(from HP or elsewhere)? I fear, opening a service call to HP's hotline might not be too

successful and directly contacting some developer will probably also not be an option?