Re: Dmax
| July 03, 2005 05:30PM |
Steve,
Be careful with the Dmax numbers you're referencing. The stuff the scanner manufacturers tout are classic "marketing numbers" (this from someone who's a career marketeer
" />). Most simply use a theoretical max based on the number of bits in their Analog to Digital converters or a slightly rolled off approximation therof.
A very few (I believe Minolta does this, for example) do "measure" their Dmax and provide "measured" numbers, but since there's no agreed upon measurement standard they can reference, these are still pretty meaningless numbers, at least for any comparative purposes.
It's unlikely you're going to see a real Dmax of 4.0 out of ANY CCD based scanner. No matter how many bits in the ADC, the CCD itself just doesn't have the ability to get that kind of Dmax out. The standard wisdom is that even mega-buck PMT (Photo Multiplier Tube) based drum scanners - the gold standard for Dmax - only approach 4.0.
About the best you can say is that if a manufacturer claims 3.6 for one of its models, and 4.0 for another, you'll PROBABLY be able to get better shadow detail out of the 4.0 unit. Probably. Go between manufacturers, though, and about the only reliable way to judge Dmax is to scan and compare. Even then, differences in scanning software, and operator knowledge and technique can mask the real hardware capabilities.
In our next installment, why dpi (which really should be ppi) numbers are almost as irrelevant.
Just kidding... (about there being another installment, that is - spec'ed dpi does not equate to resolution capabilities, but enough is enough. This is a NG forum after all. Ahem.)
Scott
Be careful with the Dmax numbers you're referencing. The stuff the scanner manufacturers tout are classic "marketing numbers" (this from someone who's a career marketeer
" />). Most simply use a theoretical max based on the number of bits in their Analog to Digital converters or a slightly rolled off approximation therof.A very few (I believe Minolta does this, for example) do "measure" their Dmax and provide "measured" numbers, but since there's no agreed upon measurement standard they can reference, these are still pretty meaningless numbers, at least for any comparative purposes.
It's unlikely you're going to see a real Dmax of 4.0 out of ANY CCD based scanner. No matter how many bits in the ADC, the CCD itself just doesn't have the ability to get that kind of Dmax out. The standard wisdom is that even mega-buck PMT (Photo Multiplier Tube) based drum scanners - the gold standard for Dmax - only approach 4.0.
About the best you can say is that if a manufacturer claims 3.6 for one of its models, and 4.0 for another, you'll PROBABLY be able to get better shadow detail out of the 4.0 unit. Probably. Go between manufacturers, though, and about the only reliable way to judge Dmax is to scan and compare. Even then, differences in scanning software, and operator knowledge and technique can mask the real hardware capabilities.
In our next installment, why dpi (which really should be ppi) numbers are almost as irrelevant.
Just kidding... (about there being another installment, that is - spec'ed dpi does not equate to resolution capabilities, but enough is enough. This is a NG forum after all. Ahem.)
Scott
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