devilprinters.co.uk
Active member
Hi Everyone, DPI and the way each manufacturer represents their products is very annoying, misleading and confusing for everyone.
When Xerox (and many other manufacturers) refer to their bit-depth they are referring to the different shades each individual C, M, Y or K toner dot can be on the page. 4-bit therefore means that each individual CMYK toner and can be 1 of 16 shades meaning a dot-group size of 4x4 per toner. 8-bit would be 1 of 256 shades meaning a dot-group size of 16x16 per toner. And so on...
So technically if every 4-bit dot-group has 4 vertical and 4 horizontal dots then 600x600x4-bit is 2400x2400dpi (some manufacturers convert to 9600x600dpi). An earlier poster and quite a few other online places state that 600x600x8-bit is equivalent to 2400x2400dpi but based on 8-bit having a dot-group size of 16x16 I make it 9600x9600dpi. If my calculations are wrong then feel free to correct.
There is a physical reason why machines need to clump toners of the same colour together into the same dot-group rather than allowing true 2400x2400x1 or 9600x9600x1 to be achieved (other than slower print speeds and higher file sizes). Each manufacturer achieves the stated bit depth using a mixture of techniques. Xerox tends to lower the DPI of the printer (say from 1200x2400x1 to 600x600x4) to provide enough space around each dot for "clumping" to take place. (This also helps processing times and print speed.) Then to create the bit depth they simply vary the intensity of light being shone onto the photosensitive drum to create higher and lower static charges meaning more or less toner particles clump together around that single static dot space. This is why the dot-group comprises of all the same colour toner.
However, 600x600x4 is NOT the same as 2400x2400x1 since the former is limited to individual shades of colour per 16x16 dot-group whereas the latter would have complete freedom.
Also, it is commonly documented that higher DPI's using finer toner uses less toner. If higher bit depths means the clumping together of multiple toner particles in a dot-group then this could mean that more toner is used to print a given document. From our experience using Xerox machines, we've found that selecting a lower DPI and higher bit depth guzzles more toner than a higher DPI with a lower bit depth. Your experiences may differ so I'd be interested to hear your findings.
Just a final thought, if a manufacturer were to combine CMYK together when talking about bit depth then 256 shade combinations using 4 toners requires considerably less dots in a dot-group. The mathematics are beyond me but here's a site that allows you to work out the number of unique combinations: https://www.mathsisfun.com/combinato...alculator.html
It turns out that for a CMYK printer just 7 dots will provide 330 (including white) unique combinations! Using this method a 600x600x8-bit printer would then only be 600x600x7 = 2,520,000 dpi = 1587x1587 dpi (or some combination of). I don't know if any manufacturer uses this when quoting bit depths. Personally I doubt it.
Anyone have any thoughts on this?
Cheers
Nick
When Xerox (and many other manufacturers) refer to their bit-depth they are referring to the different shades each individual C, M, Y or K toner dot can be on the page. 4-bit therefore means that each individual CMYK toner and can be 1 of 16 shades meaning a dot-group size of 4x4 per toner. 8-bit would be 1 of 256 shades meaning a dot-group size of 16x16 per toner. And so on...
So technically if every 4-bit dot-group has 4 vertical and 4 horizontal dots then 600x600x4-bit is 2400x2400dpi (some manufacturers convert to 9600x600dpi). An earlier poster and quite a few other online places state that 600x600x8-bit is equivalent to 2400x2400dpi but based on 8-bit having a dot-group size of 16x16 I make it 9600x9600dpi. If my calculations are wrong then feel free to correct.
There is a physical reason why machines need to clump toners of the same colour together into the same dot-group rather than allowing true 2400x2400x1 or 9600x9600x1 to be achieved (other than slower print speeds and higher file sizes). Each manufacturer achieves the stated bit depth using a mixture of techniques. Xerox tends to lower the DPI of the printer (say from 1200x2400x1 to 600x600x4) to provide enough space around each dot for "clumping" to take place. (This also helps processing times and print speed.) Then to create the bit depth they simply vary the intensity of light being shone onto the photosensitive drum to create higher and lower static charges meaning more or less toner particles clump together around that single static dot space. This is why the dot-group comprises of all the same colour toner.
However, 600x600x4 is NOT the same as 2400x2400x1 since the former is limited to individual shades of colour per 16x16 dot-group whereas the latter would have complete freedom.
Also, it is commonly documented that higher DPI's using finer toner uses less toner. If higher bit depths means the clumping together of multiple toner particles in a dot-group then this could mean that more toner is used to print a given document. From our experience using Xerox machines, we've found that selecting a lower DPI and higher bit depth guzzles more toner than a higher DPI with a lower bit depth. Your experiences may differ so I'd be interested to hear your findings.
Just a final thought, if a manufacturer were to combine CMYK together when talking about bit depth then 256 shade combinations using 4 toners requires considerably less dots in a dot-group. The mathematics are beyond me but here's a site that allows you to work out the number of unique combinations: https://www.mathsisfun.com/combinato...alculator.html
It turns out that for a CMYK printer just 7 dots will provide 330 (including white) unique combinations! Using this method a 600x600x8-bit printer would then only be 600x600x7 = 2,520,000 dpi = 1587x1587 dpi (or some combination of). I don't know if any manufacturer uses this when quoting bit depths. Personally I doubt it.
Anyone have any thoughts on this?
Cheers
Nick
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