You can check the technical quality of a digital picture using several factors. to do so, use "photoshop" or a similar programm like "gimp".
to check the sharpness of a digital picture, you should zoom in to 100% (1 pixel is one pixel at your screen). if you enlarge this picture to 100%, it looks like this:
the background does not have to be in perfect focus. important is the person. in this picture focus is not 100% but ok.
on a normal picture, only small parts are all black or all white. to check this, dont use just the screen, but the "histogram" (again with "photoshop" or a similar programm). the histogram of this picture looks like this:
there is only the sponsor and the harness "all black" (visible at the left side of the histogram) and nothing "all white" (right).
if a digital picture is absolutely in focus, it must have at least 200 dpi to print (a scan from a slide needs at least 300 dpi). this permits the following printable sizes:
3300 x 2300 px: A3 (poster)
2300 x 1600 px: A4
1200 x 800 px: 10x15 cm
if the picture is not in focus, it must be much bigger.
swiss glider and a lot of other magazines are printed using the so-called "late binding" - process. that means that your original data does not get optimized until just before printing.
therefore, please give the original camera-data to the graphic-designer. for single pictures, you can send it by e-mail or use the ftp-upload for a larger quantities.
it is easiest if you send a limited selection of jpgs by e-mail to the editor and the graphic-designer. they will ask you to upload the original data for their selection.