poor print quality after resizing

[jenslee]

i am trying to print high resolution digital camera pictures on a HP 1005 laser printer.

however if i enlarge the images, even by a small amount the, print quality becomes poor, but the image quality remains the same on the screen.

also if i reduce the size to 5x3.5inches and print 4 images on one page, the print quality is also poor.

but if i print three to a page, the quality is good.

why does this happen, and can i solve the problem??

all the files are jpeg and at 180 dots per inch (changing the dots per inch setting does not help). i have tried on 2 different printers with the same results.

 

[DansDadUK]

Almost certainly something to do with the relative resolutions of the source (JPEG), and the target (screen or printer).

Most screens are less than 120 dots per inch (typically 96 dpi), whilst most modern laser printers are 600 or 1200 dots per inch.

So if you have a source which describes an area of pixels at 180 dpi, these pixels have to be reduced (for screen) or magnified (for printer), unless you want rather small printed output.

Simple magnification can produce 'blockiness' ('jaggies'), and (if the resolution of the target is not a multiple of that of the source), then simple repetition of pixels is not sufficient, so drivers resort to techniques such as dithering, to try to reproduce the original shades/colours.

Having said all that, I'm not sure how you can circumvent the problem, other than by perhaps arranging that the source resolution is an exact sub-multiple of the target resolution?