Part Five - Determining Optimum Output Resolution
by Chuck Gardner
 At output resolutions above 180 ppi a 1792 x 1200 file must
to be up-sampled (i.e., additional interpolated pixels must be added
to increase the file dimensions). At 250 ppi the resampling ratio is
about 150%, meaning that one interpolated pixel must be inserted
between every two adjacent original pixels.
 When a file is up-sampled PhotoShop adds the required new
pixels by analyzing and interpolating the original data using its
resampling algorithm. Up-sampling is less desirable than down-sampling
because the new pixels which are added to increase the image size do
not have detail from the original scene and thus reduce the sharpness
and accuracy of image.
Thus there is a bit of a dilemma when attempting to make an 8 x 10 printout. All other factors being equal outputting a file at 250 ppi resolution should produce a better looking result than a 160 ppi resolution. But in the case of a 2.15 megapixel (1792 x 1200) original so much resampling is necessary to produce the file dimensions necessary for 250 ppi output that the 160 ppi printout, which consists of only original camera pixels, may produce a better looking result. The answer to the question of which is better can only be found by printing both ways and comparing the two prints side-by-side. Goto Next Page > Goto < Previous Page Goto Class Outline Goto super.nova.org my home page. |