While not a commercial photog, with the work I did for manual prep, we would flatten the image, kick up brightness by about 30%, contrast up by 15%, and save as jpg, with no compression. Since you did not say what resolution your camera has, I would suspect that you do not need to change the resolution. The magazine editors will do that, if necessary.

Note. dpi is lot the same as pixel count. Dot per inch refers to printers, while ppi refers to the pixels on your display, or in your graphic.

Pixels Per Inch (PPI)

Suppose you have a 100 x 100 pixel image, it could be printed at many different sizes. If you set the image to print at 10 PPI, then you’d have a 10″ x 10″ image. If you set the image to print at 100 PPI, you’d have a 1″ x 1″ image. Note that adjusting this value doesn’t effect the number of pixels in the image at all, it just changes how big the print will be.

Take our 100 x 100 pixel image again. Suppose it’s set at 100 PPI (producing the same 1″ x 1″ printed image). With re-sampling off, when you adjust the PPI the dimensions adjust as well, this is how things worked in the example above. With re-sampling on, the dimensions won’t change. So, if you changed the PPI to 10 with re-sampling on, you would still keep a 1″ x 1″ image and the computer would throw out pixels to make the image stay that size. So in this case, you’d end up with a 10 x 10 pixel image in the end. If you went the other way, and changed the PPI to 300, then the computer would generate pixels to make a 300 x 300 pixel image that’s still 1″ x 1″ when printed.

Usually, the only reason you want to use re-sampling is for reducing the size of your image. For example, my scanner produces 3888 x 2592 images. These images are too big to use online (both for display and because of file size). By using re-sampling, I can adjust the size of the images to something more appropriate for online use.


DPI

Now let’s talk about DPI. DPI only refers to the printer. Every pixel output is made up of different colored inks (usually 4-6 colors, although many printers use more now). Because of the small number of colors, the printer needs to be able to mix these inks to make up all the colors of the image. So each pixel of the image is created by a series of tiny dots (you could think of them as sub-pixels). Generally, the higher the DPI, the better the tonality of the image, colors should look better and blends between colors should be smoother. You’ll also use more ink and the print job will be slower. You might want to try setting your printer to a lower DPI to save ink and speed up the job, see if you notice any difference in quality. The lowest setting where you don’t see any loss in quality should be the best one to use.

So a 1200 dpi printer uses 1200 dots of ink in every inch to make up the colors. If you were printing a 300 PPI image, then every pixel would be made up of 16 smaller ink dots (1200 DPI x 1200 DPI / 300 PPI x 300 PPI). A lower DPI would have fewer ink dots making up each pixel, which would make the color look worse. A higher DPI would have more ink dots for each pixel and should give more accurate color (especially under close examination).