A lot of the "rules" you read/see from camera shake to DoF, to
print DPI/PPI are based on roughly an 8x10 (or 8x12) size print
viewed at reading distance. If you go smaller than 8x10 you still
want the 300 or so PPI but any out of focus problems scale down
accordingly.
As you get bigger you can in theory get away with fewer PPI.
However it is best if you scale/resample the image to at least 250
or so PPI. The detail will not be "better" per say, but you don’t
want the viewer to notice the pixilation effects in the event that
the viewer gets inside the acceptable viewing distance.
Basically what you are doing is providing extra pixels so that that
human eye will not know there is something wrong. You will not be
adding detail, but you will keep the eye from noticing a problem
unless it is something like Text in which you know what the shape
should be.
The bottom line is that up-sampling will make the print look
better. Another issue confusing things is that the Printer Driver
has its own set of conversions it does. It may do its own
up-sampling. Thus it may be OK to send one printer 150DPI and it
will look ok where a different printer driver may look blocky.
The main goal of a good scaling approach is to keep edges from
smearing/blurring, but this can come at a LOSS in detail. Genuine
Fractals is the most widely talked about and it does a good job of
keeping edges and people like the look overall, but it definitely
looses some fine details. Some people do not like the GF effects,
particularly on people and smooth curves, but overall it seems to
be the preferred scaling package.
I think most people agree that the results you are quibbling if the
scaling amount is less than 2X. Above 4X GF is generally preferred
(although I don’t have much I have ever blown up that much. In
the 2X to 3X range I use Panorama Tools Spline36.
Most of my panoramas are printed at 12 by N inches since I have an
Epson 1270 Printer with roll paper. If I shoot with a D30 in
“Portrait Mode” then I am going to get 2160 Pixels from the camera
in height. After Warping and cropping there will be less than 2000
or so “real pixels” (what counts as “real pixels” after warping,
which is a scaling operation?) or on the order of 150PPI and 160PPI
over 12 inches. That is more or less on the line for doing pretty
good job of scaling by several methods. One could even argue that
a 12 by 36 print would probably be OK at 150PPI without scaling in
most viewing situations, but Scaling is free so why not.
Karl
Thanks
Guess I'll just have to try some out and find out which one works
best for me.
Have you made any wide format prints of your panos? If yes how did
they come out? Did you need to upsample them or was the resolution
density good enough because of multiple shots? Sorry for so many
questions but large pano prints are one of the things I really want
to achieve.
DJM
--
Karl
