I Still Don’t Believe It

 Hi Everybody,
1. In the distant  past, I have made the audacious claim that ink jet printers can not get 300 dpi where dpi seems to mean lines per inch.  Lines per inch has also been called dots per inch, printer pixels per inch, screening, and half  tone cells per inch.  The Graphics Industry Handbook recommends calling it FM spots per inch.  Let us use FM spots per inch.
2.  The FM spot is composed of tiny microdots sprinkled around in a pseudo-random fashion within an FM spot.  They are called droplets, micro-dots, drops, dots, etc.  I like micro-dots.
3.  The ink jet crowd has always double talked how many micro-dots  per inch that they can get.  They now have “optimized” dots.  I could not find anything on the internet which explains “optimized” other than that it gets you stunning images.
4.  I will therefore assume that in reality they are getting 2400 microdots per inch for an expensive ink jet printer.
5.  Now for a rough and ready calculation.
6.  There are basically four colors – CMYK.  Assume an eight bit per channel tonal range.  Thus you need space for 256 microdots  per color to go from zero to full color.  For four colors, you then need space for 1024 microdots.  A square FM spot is then 32 by 32 microdots wide.
7.  From which --  FM spots per inch =  2440/32 = 76 FM spots per inch.

CONCLUSION:  Ink jets do indeed make “stunning images”.  Even my $65 HP makes great images.  75 FM spots per inch happens to be a very high resolution for FM spots.  High quality magazine printing is mostly 150 AM spots per inch.

Phil

PS:  Can anyone back up the claims by the ink jet crowd that they can get 300 FM spots per inch.