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  1. #11
    Vulcan Inventor of Death 1,000+ Posts Mr Spock's Avatar
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    Quote Originally Posted by aab1 View Post
    But all the more expensive machines are the exact same speed in color or black like my Canon MF8530Cdn which is 21 ppm in either case, why can more expensive ones go as fast in color?
    This depends on several factors.
    The first is the amount of working memory on the device (128megs versus 1 gig of ram)
    The second is the amount of processing needing to be done (pc does all the work or the printer of converting print job to laser code)
    The third is the processing power/type of processor doing this work.
    The fourth is the size of data needing to be processed
    The fifth would be the amount of image quality control that the printer does to ensure the stability of the print quality
    The sixth (and last for this post) is the type of paper (the thicker the slower).

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  2. #12
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    Nah - it has to do with the process of building the image. The machines that are significantly slower in color mode all have a single drum and laser but 4 developers - each color must be built up onto an image transfer belt or drum or some such intermediate area. Some of the ITB's are longer than a single LT or A4 page (i.e. for 8.5x14 paper) but the machine must waste that extra space to register the images on top of each other - in B/W mode they can transfer the image off as soon as its put on since there is only one layer.

    Other machines have a LT/A4 sized Image Transfer Belt or DLT/A3 belt and do 2 pages at a time so those 3 extra colors don't slow it down as much. There's also extra time on some machines to do process control to ensure color balance, and on some machines the mechanism to switch developers is not terribly fast.

    Single drum machines are slower, but cheaper and tend to produce more even color. If there is a weak area in the image caused by drum, charge, or optics it is on all 4 colors and shows up as a variation in density which is a lot less noticable than a variation in color as would happen with a dirty spot in a 4 drum machine.

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  3. #13
    Field Supervisor 1,000+ Posts Eric1968's Avatar
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    Quote Originally Posted by aab1 View Post
    I understand why some color laser printers are 4 times slower in color (the page is reprinted 4 times, once for each color), but what about those that are 12 ppm in black but 8 in color, how is the 33% reduction in speed explained?

    Thanks
    There are a lot of machines that print color at the same speed of black (4 drums, 4 development units, 1 transfer belt). The ones that "reprint" the image 4 times only have 1 drum. Recent models print color/black at the same speed.


  4. #14
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    Quote Originally Posted by Eric1968 View Post
    There are a lot of machines that print color at the same speed of black (4 drums, 4 development units, 1 transfer belt). The ones that "reprint" the image 4 times only have 1 drum. Recent models print color/black at the same speed.
    Yes, the one I got is 21 ppm in either black or color, I was just curious about those that are slower in color but not 4 times slower (I understand those that are 4 times slower is because they "reprint" the page 4 times).


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