You might be downsizing your images in Mail.
When sending photos directly from the Mail app it is possible to automatically downsize them. Once this is chosen, it tends to stick for subsequent emails. Usually a good thing. So, if Mail has decided you want to send Small image files then it will keep doing so until you tell it otherwise.
Before sending an email with images, be sure to check the right side of the Cc: field for an Image size estimate. If the picture is small enough, it may not show this option, but almost all photos and/or screenshots taken on newer iPads or iPhones will be large enough to trigger the option.
If you tap on the Cc: field it will expand. Along with the other addressing options you'll get a choice of several physical sized to send your photo as; along with an estimate of how much storage the photo(s) will take.
Mail doesn't tell you the actual pixel x pixel dimensions of the small, medium, large, and actual size choices; probably be cause it varies a bit depending on the device and original picture size. Here is a list of sizes. It's a bit out of date and does not cover the older or newest iPads, but it should give you an idea of what it all means.
Screen Shot on Retina iPad (3rd generation and later)
- Small = 320 x 240
- Medium = 640 x 480
- Large = 1366 x 1024
- Actual = 2048 x 1536
Camera on iPad (3rd gen) thru iPad Air
- Small = 320 x 240
- Medium = 640 x 478
- Large = 1296 x 968
- Actual = 2592 x 1936
- Small Sq* = 320 x 320
- Medium Sq* = 640 x 640
- Large Sq* = 1280 x 1280
- Actual Sq* = 1936 x 1936
* Sq = the Square aspect mode that came out with iOS 7
As you can see, Small is really very small, and will be either very small or blurry when displayed on most modern computers and tablets. Medium may also look blurry. Large generally looks decent, and is good enough for showing someone something on a screen. If you expect them to work with it or print, or want them to have the best copy, Original is the way to go; but can slow down email deliver due to it's size.
