A handy online guide for photographers who do contemplative photography, landscapes and what not, is the famous, DOFMaster charts and calculator.
To truly understand your camera and lens combination, you need to learn the relationships of lens focal length and film or sensor area that is recording the light. This site has a quick reference chart for most digital DSLR cameras and just about ANY film format you can think of. There are apps for both iOS and Android as well.
This site can also be a great learning tool to understand the physics behind the ratio of focal lengths and film/sensor size. It might give the digital-only shooter an appreciation for what medium format and large format photographers have known for over 100 years: size does matter! Both in presentation and resolution.