It’s important to understand that there is a relationship between image size and dpi. For instance, if the size of your image is 40 x 55 inches at 72 dpi (as many digital cameras are) it will still be large enough when converted to 300 dpi by your designer for printing. The problem occurs when an image size (an old photo) is already small and is scanned at a low resolution. So if you scan a 5 x 7 inch photo at 72 dpi and it is converted to 300 dpi it will be a teensy weensy 1.2 x 1.68 inches. Yes, you could keep it at the same size at 72 dpi, but it will be blurry when printed.
So if you are one of those people that needs to scan your images at high resolution do the following: Open your scanner software and play around until you see dpi settings for scanning your images. Often there are settings for 72, 150, 300, 600 and even 1200 dpi. My advice is to go at least 600 or higher, especially for small images. Why? … This relates to what was said above, just in reverse. If you have a 2 x 4 inch image and scan it at 300 dpi, that’s where it must stay – two by four inches. But if you scan it at 600 dpi – the image when converted by your designer to 300 dpi will be doubled in size (2 x 4” becomes 4 x 8”!). This way you are covering your butt, making sure you get a decent size and quality.
Finally, when you send the images by email some email programs reduce the size of the image so you are back where you started. It’s best to put them in a zip file and send them through Dropbox or email one or two at a time in a zip file. Email programs can only send files of 100 mb’s or less so if you have a lot of images this may not be practical.
Well, I hope this helps clarify things and even keeps time consuming hassles at bay. If you have any other questions or comments regarding this topic please let me know.