Re: National Geographic vs. Canon print paper

On 2007-09-21 13:14:28 -0700, "HEMI-Powered" <none@xxxxxxx> said
[trimmed, snipped, edited & expurgated}

I understand the basics of scanning pretty well. When scanning half-tone vs. continous tone photos, I actually overscan from at least 2x to 3x or even more than I need for the finished size. I have found emphirically that the process of resampling down helps to eliminate the "noise", actually geometricaly regular patterns, before I need to get into noise reduction.

I scan Kodachromes at 300 res{...}

Sorry, guess it is one of my dense days. I still don't understand why you scan at only 300 DPI (if that is what you mean), unless the negs/slides are the large cut-*** kind. For 35mm, most people find that somewhere in the 2500-5000 DPI range better able to extract all the image information available, then resampling down to whatever they think is "right" for their purpose(s).

That big number is misleading...when I scan either film or reflective originals, I'm using what Canon calls 4800 x 9600 optical resolution...it sounds impressive, but it's still producing a 300 px/in TIFF image...not exactly marketing hype, but it doesn't contribute much to understanding.

will be a nice compact file for an email attachment,
especially when it gets compressed as a JPEG. but if you later
decide to blow it up to an 8 x 10 on your printer, you'll have
to rescan.

I'm further confused by your last statement. Are you saying
that you change the PPI/DPI to 72 for web and 144 for the
printer or is your dimension "300 px/in" different than what
I would call PPI (Pixels Per Inch).

I hope I explained targeting the different res for different
end use adequately. I write "px/in" for "pixels per inch" to
avoid the ambiguity of dpi vs ppi vs lpi, which is how this
whole thing started =')

Again, please excuse my denseness, as I must've missed your intent. To me, being the simple engineer that I am <grin>, when scanning, DPI is the correct term while when printing from an existing image in pixels, then PPI is the right nomenclature.

You can use whatever name you want: how about blueberries per inch? Everyone knows how big a blueberry is. right? If you refer to dots per inch, where are the dots? My printer sprays "droplets" of ink that are much smaller than the ink dots a litho press lays down on a *** of paper, even with the finest screen ruling it can reproduce. Dots per inch, in my experience, just leads to confusion. When Canon says my desktop scanner goes up to 4800 dpi, they really mean "samples per inch" which relates to how many CCDs it has and how precise the mechanism that moves the sensor is. My last scanner was a Jade II whose main virtue was very even performance over its entire live area. I don't even remember what the optical resolution was; that spec simply didn't matter to me.

As to LPI, I understand conceptually what this is about wrt the printing biz but have never found any particular use for it when either scanning photos or slides or in digital photography, so I stick with the traditional DPI for scanning input and PPI for printing output. But, as I suspected, everytime this subject comes up, there is quite a long debate, with it's attendent ambiguity as you observe.

I think you'll find that there's general agreement that a pixel is the smallest unit of information about the image. Once you really have a handle on pixels per inch--whether you prefer to abbreviate it ppi or px/in--you can move on to understanding compression, where your software is looking for pixels of the same color so it can reduce the amount of data in a digital file. Then you can answer the question "what file type is best?"
--
Cease then to grieve for your private afflictions, and address yourselves instead to the safety of the republic

.