I am trying to determine the origin of the 2438.4 resolution standard.
2400 ties to 300 dpi because it is a multiple of 300
2540 is a logical metric conversion from 1000
2438.4 does not tie to a standard english unit of measure or metric. I have looked at the
various point size standards and none of those seem to line up. I do know that Hp Indigo
presses use 812.8 dpi which is a factor of 2438.4. The 2438.4 resolution has been used
a resolution on output devices back to the early film days. 2400 and 2540 seem to be the most prevalent within the industry.
I haven't been able to find any info in my library - so the following is speculation.
Remember that technically "dpi" is actually a measure of addressability rather than "resolution"
2400 dpi was probably chosen because it is the lowest resolution where the imaging mark was below the resolution threshold of the human eye. I.e. at normal viewing distances you can't see a 10.6 micron dot. (10 micron dot for a 2540 dpi device). So, to use a higher dpi would have been a waste of processing and imaging time.
2438.4 dpi may have come from the imaging mark size of some early film/paper imagesetters especially those that were scanners used to output film. I've only seen it referenced in ppds like this for the Fuji Celix 4000
*Resolution 1219dpi/1219.2dpi: "1 dict dup /HWResolution [1219.2 1219.2] put setpagedevice"
*Resolution 1828dpi/1828.8dpi: "1 dict dup /HWResolution [1828.8 1828.8] put setpagedevice"
*Resolution 2438dpi/2438.4dpi: "1 dict dup /HWResolution [2438.4 2438.4] put setpagedevice"
*Resolution 3657dpi/3657.6dpi: "1 dict dup /HWResolution [3657.6 3657.6] put setpagedevice"
*Resolution 4876dpi/4876.8dpi: "1 dict dup /HWResolution [4876.8 4876.8] put setpagedevice"
gordo