Here's my advice for digitizing and preparing photos for uploading to the internet. This is my personal opinion based on experience:
It is best to scan photos into a computer at 400dpi resolution and save in a lossless format (as .tiff format is better than .jpeg). Pretty much any desktop printer with scanning capablility could do this, or a stand alone scanner- no more than $100 investment if you were shopping, but you probably know someone who has one you can use. Clean the glass frequently with a proper screen cleaner. Old photos shed dust like crazy!
Last resort is to take a photo of the photo with a cell phone and save that to a computer as a .jpeg file (which you could convert to a .tiff file to help prevent degradation). This can be a surprisingly workable compromise, but you should probably note that this is what you did because it is likely to introduce a greater amount of distortion to the proportions of the subject and the colors than using a scanner. There are scanning apps for phones that try to correct skew (it's impossible to hold a phone perfectly centered and perpendicular to a photo or page of a book). Try to have the photo as flat as possible on a table or counter. A pocketfull of steel nuts or washers from the hardware store are very helpful in this endeavor because you can find some heavy enough to effectively weigh down the very edges without becoming intrusive. These can be cropped out at a later date.
Of course, the best quality photos quickly lose value if you fail to attach notes and descriptions of who, what, when, where, why, how, and who has custody of the photo and gave permission for use at the date it was reproduced. Store each photo with the same file name as its description (they will have different file types so this works) and store them together in the same file folder. The folders can have as many photos as you like, just make sure each photo has a description with matching name. This method is a bit less technical than explaining how to work all this information into the photo's metadata.
Once you have the photos and notes digitized, then you are ready to upload them to Wikitree...
