Hi Duncan,

I think we are basically talking about the same thing.

A lot of people confuse DPI with print quality.

You can have a 1200 DPI, 1200 DPI high quality, 600DPI and 600DPI Draft settings.

The 1200 DPI high quality will be visibly darker, the 600 DPI draft will be visibly lighter. A "standard" 1200DPI and "standard" 600 DPI setting on the same printer should use slightly less toner on the 1200DPI setting.

I can do a print to file or a print to paper, the upside with a print to file is I don't have to count the dots.

Grayscale is still the most common laser printer, color lasers are more common then before, but no where near the level of grayscale.

I could do the images as black and white only, all that is going to do is slightly increase the white pixel count, as some of the gray pixels will fall to white instead of black, it won't really change it much.

My background with this is about 12 years ago, I implemented a print quote system that actually took into account the coverage on the page to charge the student accounts the "right" amount. Ie if some stupid student decided that they liked reading white text on a black background, they would get billed about about 20x as much as printing black text on a white background. When you setup the environment you tell the system the cost per toner cartridge, the rated coverage from the MFG, the cost per sheet of paper, etc.

The software was called "printbill", the most recent update was in 2006... http://sourceforge.net/projects/pqadmin/files/printbill/4.2.1/ looks like the official website is gone, but this page has some info on it: http://linuxappfinder.com/package/printbill and the archive.org version of the official site: https://web.archive.org/web/20090202073731/http://ieee.uow.edu.au/~daniel/software/printbill

-Harry




On 09/15/2014 03:10 PM, DSinc wrote:
Harry,
I will give you what you believe. No harm, no foul! I just don't get your discourse. I only did 33 years supporting these beasties; and yes, 'Print Quality' was the primary service call. But still, I could be wrong. Will not be the first time! Yes, spurious toner isa problem. I don't speak to this. I assume the developer housing seals are OK.Please let's not have a tomAtoes/tomahtoes
disucssion.
OK. Why 2 grayscale images? Grayscale seems to be some special setting. What does 'grayscale' prove?

Why not print a 36 point (or even larger) 'A' at both 1200dpi and 600dpi? There should be a visible difference.
I'll assume you have an eye-loupe or a magnifying glass.
JMHO,
Duncan

On 09/15/2014 17:28, Harry McGregor wrote:
Hi,

So I went a step farther, I generated two grayscale images.

600x600 DPI, 1 inch
1200x1200 DPI, 1 inch

In each is a rendered letter "A", and it was saved as an LZW tiff, so no lossy compression involved.

I only looked for "White" pixes, counting anything with any shading in it as "using toner", which is a little overkill.

hmcgregor@hmcgregor-Satellite-L75D-A:~/Documents$ convert 600dpi_A.tif -format %c -depth 8 histogram:info:- | grep white
    300762: (255,255,255,255) #FFFFFF white
hmcgregor@hmcgregor-Satellite-L75D-A:~/Documents$ convert 1200dpi_A.tif -format %c -depth 8 histogram:info:- | grep white
   1205231: (255,255,255,255) #FFFFFF white

I took the white pixels in the 1200dpi and divide by 4 to get the equivalent area coverage of 600:
1205231/4 = 301307.75000000000000000000

I subtracted the white pixels of the 600 DPI image from the white pixels of the 1200 DPI image, and found:
301307.75-300762=545

So that means the 1200 DPI image has more "white" in it, but not by much.

If you want to look at the grayscale aspects you can as well, but overall, unless the printer is printing "lighter" at 600 DPI (ie using the 1200DPI size pixels, and leaving space between pixels, which printers tend to only do when in "Draft" mode), lowering the DPI does not save toner.

This does not take into account "waste" toner, and some printers, especially color lasers have more waste toner collection then others. Most grayscale printers don't have waste toner collection, and instead the waste is re-used within the toner cartridge.

-Harry



On 09/15/2014 01:44 PM, DSinc wrote:
Harry,
I am so glad you disagree'd. But, you miss the point. Itis not 'skipping dots'! It is how many dpi the printer does. The 'inch' is a fixed number. On my old BrandX printers we did 90K dots/sq in. This produced a totally black square 1in.x1in. The way the printer 'IT' is how the IG 'draws' IT. I accept your pix of two resolutions, but I do not agree. Our 1 inch/square printed 'targets' just got lighter; nothing more. There wasnohorizontal/vertical difference. Thank you for your () add, but the other axis is quite part of this whole equation. All your pix shows me is 'character spacing.' That is totally IG control. Has little to do with resolution.
HTH,
Duncan

On 09/15/2014 15:26, Harry McGregor wrote:
I don't agree that it has a direct relationship.

I really depends on how the printer deals with it.

If the printer does 600 vs 1200 DPI by "skipping" dots, then lower DPI would save toner.

ie (linear only, not showing the other axis)

600 DPI "skipped"
X X X X X X
 X X X X X X
X X X X X X
 X X X X X X
X X X X X X
 X X X X X X


Vs

600 DPI "Big"
XXXXXX
XXXXXX
XXXXXX
XXXXXX

1200 DPI may use a bit more or a bit less toner depending on the way the printer renders it, but in most cases I would not expect a significant change unless the printer was sill using 1200DPI dots, and skipping pixels.

-Harry


On 09/15/2014 11:15 AM, Thane Sherrington wrote:
At 02:58 PM 15/09/2014, DSinc wrote:
Thane,
There is a complex formula and special page image that most priter companies use to help them compute (fabricate/lie) about their printed pages/catridge. Please note that this business does NOT use 100% coverage. I just do not know many folk that print fully black pages. I have to claim age/time/forgetfulness for not recalling what the 'coverage' percentage was/is. But I do recall that there is a specification about this the all printer makers try to meet/exceed. And, alot of this has do do with various makers 'image generators.'

Hi Duncan,
Yeah, I know about the page used (I've seen a copy from Lexmark). I was just wondering if they are printing this page at 300dpi or 1200 dpi when they come up with the number of pages a toner will print.

I was sitting down with graph paper trying to figure out the dot coverage, so I appreciate your help. :)

T









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