Mat, First let me say that both of these women are very attractive models----If they are friends or family, you should take full advantage of thier willingness to model for you.


Now--for your question: I don't have any experience with either the camera or lens your working with----but, I have had similar frustrations from my equipment. So, my suggestions are this, go back to default autofocus settings on your camera.


#1--First: rule out the human factor. If you don't have a top-o-the-line tripod use something else that is rock steady----I used a kitchen countertop and placed my camera upon it with books to achieve the proper lens elevation. I shot out my back doorat a subject in the yard.


#2--Second: using the timer on your camera or a shutter release take at least 10 shots of a properly exposed subject---Use the autofocus on your camera.


#3--Third: Turn auto focus off and manually focus using the X10 magnification on the camera display screen---again shoot 10 shots with the timer or shutter release at the same subject and exposure.


Compare the results: if both are satisfactorily sharp--then it's you---get a good tripod or practice handheld


If the camera/lens (#2)autofocus is satisfactory-----get a good tripod/practice hand holding


If you can manually focus, but can't auto focus, try setting your camera to single point focus---if this still doesn't work to your satisfaction, try the microadjust---if this still yields unsat results, send the lens to canon for calibration.


Note---I solved about 90% of my "soft/out of focus" problems with a high quality tripod.


Hope this helps, Let us know how it goes for you.


Bob