resolution

[stuart wanuck]

in cropping an image from full sensor would 9x6 image size with resolution of 240 make
a decent 12x18 print?

[Roger Clark]

in cropping an image from full sensor would 9x6 image size with resolution of 240 make
a decent 12x18 print?

Stuart,
when upsized to 12x18 the image resolution would be 120 ppi, which would appear pretty soft. Generally speaking, 240 ppi is considered the beginning of a high quality sharp print, with 300 ppi better. If the printer has the capability, 450 to 600 ppi would appear even sharper if the original image has the detail. A 12x18 at 600 ppi would be 77.8 megapixels whereas at 300 ppi would require only 19.4 megapixels. Such large prints at high ppi generally require a digital mosaic or large format film.

Roger

[Mike Milicia]

Epson printers require 360 PPI for a print without the "Finest Detail" box checked
which you would normally not check for an image (intended mainly for vector graphics).
If you hand the printer driver less than 360 PPI, the driver will automatically upsize your image
on the fly to get up to 360 PPI for the print size that you requested.
If you hand the printer driver more than 360 PPI, the driver will automatically downsize your image
on the fly to get down to 360 PPI for the print size that you requested.
Your best bet for maximizing quality is to resize the image yourself in Photoshop so that it
has 360 PPI at the desired size so that the printer driver will just pass it through and not
muck with it.

In your case, you would be looking at upsizing a 1440x2160 pixel image to 4320x6480 pixels
which would be tripling the size in each dimension. You can often get away with doubling the
number of pixels in each dimension but upsizing more than that can get problematic.
But the only way to know for sure is give it a try an see if it meets your quality standards.

You might find this useful :

http://people.csail.mit.edu/ericchan...tml#native_res