great stuff from Stewart there. If it sounds complicated, don't panic - as Stewart says, understand the exposure triangle and what aperture, shutter and ISO are doing in a digital camera and it is actually quite simple. It can take some time to get your head round it though so persevere.
Also, don't be afraid to use auto and scene modes. Modern cameras are pretty good at guessing the best combination of shutter/aperture/iso for what you are doing. You can then look at the images and the settings the camera used later and hopefully learn what worked and what didn't and hence how you might want to use the A, S and M modes in the future.
Does seem a bit complicated for me, but tried some different settings with kit lens. I can set shutter and aperture individually ie I can set shutter in S MODE, Apeture in A MODE, but I cant get all three at once if you know what I mean.? Do I have to say, set shutter in S Mode then let the camera decide on aperture and ISO ?.or vice versa with aperture in A Mode then camera decide shutter and ISO, I have ISO in auto but it does not change when setting shutter ect.
Really sorry if these are stupid questions.
Not stupid questions at all. Everyone had to start with the basics!
To answer these questions directly: you are basically right. In S mode (shutter priority) you set shutter (and ISO if not in auto ISO), the camera sets aperture (and ISO if in auto ISO). In A mode (aperture priority) you set aperture etc.
If you set M mode (manual) you can set both aperture and shutter and ISO (if not in auto ISO mode). But if you are setting all three then (as Stewart said) you have to balance the exposure triangle yourself as it really is manual - the camera will not be adjusting exposure at all.
If you have auto ISO on and it is not changing then that means the camera has either run out of ISO range (ie it is already on the maximum ISO allowed) or it doesn't need to - eg. if you are in shutter priority, auto ISO at 1/300s and the camera has selected f8, ISO 100, then change to 1/600s the camera will change to f5.6 and leave the ISO alone. Ditto, change to 1/150s and the camera will use f16 and leave the ISO at 100. However if you then change to 1/1200s (and your largest aperture is f5.6 on the lens) then the camera will set the aperture to f5.6 (it as large as possible) but then increase the ISO to 200 to get the correct exposure.
With my D7100 at least there is a gotcha. If you are in auto ISO mode but still set the ISO to say 800 then that becomes the minimum ISO that the camera will use. I sometimes do that by mistake and then wonder why it appears to be "stuck" on a high ISO even though there is plenty of light.
btw. of the two methods Richard and I outlined above (shutter priority vs aperture priority) I would go with Richards. He is right that in very poor light shutter prority gives you the best control and concentrates on the most important aspect. Once you get used to that and how the shutter speed and aperture and ISO affect your image you might want to try aperture priority (or even manual with auto ISO) .
Lastly, keep asking questions, it is the only way to learn
