Hi there Toyds!
Generally speaking, you'll want to use the least amount of compression for best printing results. Of course, the specific degree of compression will be determined by the ultimate size of the print you wish to produce. That is, the larger the print, the less compression you'll want to shoot with. To help determine this, keep in mind your photo file will need to be in the range of 300dpi at 4x6 or 5x7 or 8x10 or 11x14, etc. This translates to approximately 1200x1800 or 1500x2100 or 2400x3000 or 3300x4200, etc. See where this is going?
Now having said all that, you can still print with lower file sizes and resolution, but you'll notice a decrease in image detail and quality.
If you already have images that were shot at high compression, you can use software to interpolate to a higher degree of resolution up to a point but you won't increase the quality of the detail. What's lost is lost.
Hope this helps you.
