Negative Scanning Service 

Should I still have their old prints scanned, or should I use a negative scanning service instead?

If you still have the negatives, use them. A professional negative scanning service almost always produces better results than scanning the prints made from those same negatives.

Here's why. When a print is made from a negative, the enlarger loses some of the tonal detail during exposure. The paper captures a reduced version of what the negative holds. Shadows get clipped, subtle color gradations flatten, and fine texture softens.

Negatives, when stored in sleeves in cool conditions, also tend to age better than color prints from the same era. If your color prints from the 1970s or 1980s have gone yellow or magenta, the negatives are often still in usable condition.

Anyone hoping to scan photos to digital files with the best possible quality should look for negatives first and prints second. Missing negatives, damaged strips, or heavily modified prints are exceptions where scanning the print becomes the better option. Otherwise, negatives usually win.