Digital Photo Printing
What about color ?
How many print dots are needed for color?
Consider a 3888x2592 image printed 13x19:
- The Canon Pro9000 uses 8 ink colors to interpolate 24-bits of RGB color
resolution per image pixel.
- Visual color differentiation is only about 64 of 256; or 6-bit -- 8x8 DPP minimum.
- So, a 400 DPI print requires about 400/8 = 50 PPI to achieve the this
color resolution; higher PPI would cause color quantization increasing
the print color error.
- This also means only a 650x950 pixel image is required to print 13x19
with 50 PPI; or less than a 1 MPix image!
- However, at 50 PPI, the pixels would be easy to see at 23 inches viewing
distance. We'd need 8x that or over 15 ft viewing distance to eliminate
the pixelization effects.
Clearly, some limits are needed as well as some compromises.
- Starting with 3888 pixels, printed over 19 inches means 205 PPI.
- The Canon Pixma 9000 can print clearly at 400 DPI but this means only
2x2 DPP giving a 2-bit qcolor quantization.
- Yes, color is visible. No, pixel color is inaccurate.