1) elements of photography -> this is basically a free IOS application .this contains sections on focal length, shutter speed, aperture, ISO settings. elements of photography is the most comprehensive application on the marketplace on photography. EOP includes chapters, tools, quiz, and tips- designed in a way to help amateur and budding photographers.
2)photography 101 -> this is also a free application .this application is a great introduction to photography basics. there are over 12+ excellent video tutorials within the application.
3)understanding photography basics-> in this application basic videos are free. but, if you want to master this course then there is a $5.99 in-app purchase that complete the series.
4)master your DSLR camera-> this is a paid application which takes $9.99 from your pocket. but, as name suggests this app is for DSLR camera , after using this application you can stop auto setting your DSLR camera.
these are 4 free application by which you can improve your photography application.