A couple of things which i cant figured out why. can somebody explains them to me
1) How do i determine the min aperture of a lens when they always only show the max? eg : canon EF 28-90mm f/4-5.6 has a min aperture of f/22-32. Why is it not shown? is it not important?
2) And why is it that the min & max aperture changes when i shoot at different focal length?
3) I notice that the price of a lens gets higher as the aperture gets bigger. In the case of a wide angle lens, lets say a 24mm lens with f/2.8 is so much cheaper than one with f/1.4. why is this so?
I understand that as the aperture gets bigger, the DOF gets shorter. isnt this the killer for landscape photographer who needs max DOF when they uses wide angle lenses. Then why is it that they wants to get a lens with a bigger aperture which costs so much more?
4) What is the best way to test for the quality of a lens?
How do i check whether is there any dust particles in the lens?
5) Lastly, what does it mean by angle of view of lens, in term of diagonal, vertical and horizontal? and how do i read those degree?