Question regarding preparations for printing

[polloloco81]

So far, I've mainly done digital photography for web output, but I'm going to print out some of my photos as a birthday present for a friend. I was just wondering what's the best set up for an image to get the highest quality printouts possible.

I know my G5 takes photos at 180dpi. Does 180dpi still give a good image output? I'd like my images to be as big as possible while still retaining a nice visual quality. Should I leave my images in RGB or turn it to CMYK? I hear from some that RGB is better, and some told me that CMYK is better. Should I leave my photos in JPG format or convert it TIFFs or does it even matter? Any help is greatly appreciated.

[civis]

Reading this might (or might not) be informative:

http://luminous-landscape.com/tutorials/understanding-series/und_resolution.shtml

Remember, a digital camera (regardless of what the file properties might indicate) does not actually take a photo in pixels (or dots) per inch or per mm or per anything. Until you constrain those pixels to a definite print width and height, it is dimensionless. You can't know the density of a quantity of items until you know what to put in the denominator (in this case, inches). Until you know how many pixels AND how many inches, you can't know how many pixels per inch - pixels/inch. In the case of a G5, 2592/(inches of print width), and 1944/(inches of print height).

You have ~5,000,000 pixels, but how large of a print will they be spread over? The larger the print, the less pixels per inch. The smaller the print, the more pixels per inch. If we print a 4x6, that's ~430ppi - assuming that the printer can even print that high of a resolution (remember, photo labs use a continuous color process for printing photos, at least for the smaller pics, though perhaps not the poster-sized prints, which are likely to be done on a inkjet), so don't think things like "my home inkjet can do 720dpi, so 300dpi dye-sublimation printing must be crummier!", because it's a very different thing.

If we print a 5x7, that's ~370ppi. If we print an 8x10, that's ~240ppi. If we print an 11x14, that's ~170ppi, and so on. How large can a 5mp file and still have it look really good? That's subjective, to a degree, and it depends a great deal on what you think of the print. Remember that for really big prints (20x30, for example), you probably aren't going to be looking at them from a foot away (unless it's a satellite or spy-plane photo, and you're trying to count crates in an ammo dump).

[cprevost]

Most people agree that the average eye can't descern a quality difference above 300 dpi. Below that some people can tell. It really depends on the image. Close up portraits can do well at a lower resolution. Pics of things farther away with lots of details don't do as well with lower res. You really have to try it. Keep your images in rgb mode. Save as Tiff.

[civis]

If your files are already in JPG format, I don't see what you'd gain by converting them to TIFFs. You can't create quality and detail that wasn't there in the first place by converting them to a lossless format; no silk purse from a sow's ear, so to speak.

Of course, you do want to save them in lossless format if you intend to do editing and saving in more than one session, but if you're just going to print what you already have, all you'd gain by converting them to TIFF before printing is larger file size.

[oldslr]

i don't think it matters so much on the preparation as it does on the type of printer. If you are using an older 3 color as opposed to a newer 6 color type, the outcome will still be less than hoped for.