I just got my senior pictures back and want to print them professionally. They were shot with a Canon EOS Rebel T5 and specs are 2400 x 3600, 240 dpi. My photographer uploaded them to her website and I saved them as JPGs, then did some mild teeth whitening in Photoshop and saved them as TIFs. I know nothing about photography, but would I be able to get a nice quality 16x20 print with these specifications? Keep in mind it will hang on the wall and people likely won't go up close to view them, however I still want them to look relatively nice at a close distance.
Also, if I order straight from my photographer will the quality be better because she has the original files?
The aspect ratio of your 3600x2400 is 3:2 (meaning, longest dimension is 1.5x more than shortest dimension). 3600/2400 = 1.5.
The aspect ratio of 16x20 paper is 4:5 (longest is 1.25x more than the shortest). 20/16 = 1.25.
Not the same shape. 16x20 is a bit "more square" than your image, which is a longer rectangle.
Slight cropping of the long dimension is necessary to fit image shape to the shape of 16x20 paper. The photo printer will do this cropping, it is not a choice if it is to fit the shape of the paper. The printer (the automatic printing device) cannot judge, for example, it could cut off a bit of the head.
But HOW it is cropped is a choice, from which end, or some from both ends? If you would prefer to first see and approve the cropped result, it is advised that you could crop it yourself first to 2400x3000. 3000/2400 = 1.25. Or your photographer could choose a pleasing crop.
Or instead, you could print 16x24 inches, and include all of the image.
Other 3:2 shapes of paper are 4x6, 8x12, 12x18, 16x24, 20x30, etc.