Problem with print, looks ok on the computer, HORRIBLE in print!

Alright..another dilema here. I have the camera set to take "large" pics as my format (saleslady told me to leave it set that way ,rather than medium or small..for better quality pics). When I download (upload, whatever) the pics to the computer, they are rather large. I take one photo for instance, crop it a bit..then e-mail it to Costco for print, and whether it's a 4X6, or an 8X10, it's VERY pixilated..blury, color is terrible..etc. It looks soooo different on the computer. So..should I change the format of the pics to medium size..I am unsure as to what size I should leave (or make the pic) before sending it off for print. The gal at Costco wasn't very helpful in this area either! I need to take baby pics this week, and then obviously print them, but I don't know if I can, why are they looking so bad in print? Is there something else I am doing worng? I had much better results with my Sony Cybershot for goodness sake!
Oh..the camera I am using is the Canon Rebel XSi.

What is the resolution of the photos you are emailing to Costco? The file size?

You can only crop so far. If the original photo you send them for a 4x6 isn't at leas 1800x1200 pixels, you'll have quality issues. The smaller it is, the worse it gets in print. 4x6" on your computer screen does not directly translate to 4x6" on a piece of paper. The bigger print you want, the bigger file you have to send them. An 8x10 print is ideally 2400x3000 pixels, although you can get away with a little less if the original file has good sharpness. Mismatched color is a result of your monitor not being calibrated.

Need more information about what you're sending to Costco. Try this:

• Open an image that's in exactly the state you send to Costco (after you've finished editing and cropping).
  
• Go to Image > Image size. That will open the Image Size dialog box.
  
• Post a screen shot of that box.

HTTP response: NOT FOUND | MIME changed to 'image/png'

cdifoto wrote in post #6001439
You can only crop so far. If the original photo you send them for a 4x6 isn't at leas 1800x1200 pixels, you'll have quality issues. The smaller it is, the worse it gets in print. 4x6" on your computer screen does not directly translate to 4x6" on a piece of paper. The bigger print you want, the bigger file you have to send them. An 8x10 print is ideally 2400x3000 pixels, although you can get away with a little less if the original file has good sharpness. Mismatched color is a result of your monitor not being calibrated.

Thanks..very helpful, the lady at Costco did mention something about calibrating my computer with theirs?? Going to a site called DryCreek (which they use)..sounds complicated to me. Gee...and I thought taking pics was supposed to be fun !

Also, is your monitor calibrated in any way?

Edit: I guess your post answers the question
Calibrate your screen.

Here is a post about some options: Click.

Easiest way would be to get a calibrator. (Some options, from cheap to more expensive; Huey, Spyder2, Spyder3, EyeOneDisplay)

You don't calibrate your computer to theirs...you calibrate your monitor to a standard, which they're also calibrating their machines to (if they're good, which by most accounts, they are).

Get a Pantone Huey calibration kit (or similar) and you'll see closer colors. It's an actual hardware system that you attach to your screen so it can compare colors that are put out to colors that are known and it'll adjust accordingly.