I have a 50D with EF-S 18-200mm 1:3.5-5.6 IS lens. I have couple of issues related to exposure, shutter speed , aperture and ISO.
(1). Is there any rule of thumb/best practice of setting the shutter speed related to the focal length when you are not using a tripod ? Should the shutter speed be 1/focal length ?
(2). If so when you are taking pictures in outside the best (probably easiest ) setting would be using Tv (unless you have an intention of controlling the DOF of the subject). So you can change the shutter speed based on the focal length you have. Correct or wrong ??
(3). Is there any rule of thumb/best practice of keeping the minimum ISO level of your camera in all possible times ? For ex in a sunny day outside should you keep your ISO at 100 or 200.
Actual Problem :
When i m taking pictures outside i usually set the shutter speed to 1/200 (if i am not using a tripod) and try to keep the ISO at 100/200 (in day time and increase it to 800 at evening or night). So the only option left is to control the exposure is the aperture. Even thought i have set it to the maximum (this will vary based on the focal length but most of time its 5.6) , the image produced is underexposed.
(4). What should i do in order to get correctly exposed photos with out shakes ?
(5). What are the best combinations of aperture and shutter speeds to be used generally ?
(6). Should i consider of using a lens with much higher aperture ?
(7). What is the lowest shutter speed to be used generally when not using a tripod ?
(8). How productive, suitable of considering the exposure meeter of the camera ? Because most of time i have heard professional are telling that they never believe the inbuilt exposure meeter. (I think some practical situations also avoid considering the inbuilt exposure meeter , such as using an external flash). So how can they know the correct exposure ? How do they know the best aperture, ISO and shutter speeds to give ???