Mar 25, 2017, 12:31
(Mar 17, 2015, 11:11)JohnBax Wrote:(Mar 17, 2015, 08:44)EnglishBob Wrote: The F Stop just effects the amount of light coming in, and the DoF of course. A Smaller sensor does capture less of that light than a full frame would, howeverit still benefits from the extra light a larger hole lets in.
I wouldn't day it's wasting money to buy fast lenses, as they are still superior to the slower lens you would use instead. And you don't multiply by the same number as you would for focal length.
Tony Northrup has a very detailed video on F Stop and sensor size on YouTube.
Thanks for the prompt replies I do appreciate them. It was Tony Northrup that set me off with this. His theory is that as the focal length changes with the smaller sensors then the F number must change with the calculation that the F no is equal to the focal length divided by the aperture diameter but in my mind the physical length of the lens and the size of the aperture do not change then the F no must be as stated on the lens, hence my question to get other opinions on this point. The other question this raises for me is that if a lens is made for a small sensor i.e. the Sony DT range why is the focal length not as stated as there is no cropping of the image on the sensor?
Hi I am thinking about buying a Sigma wide angle lens for my nikon D 3200 .The two lens that interest me are the 10-20 f3.5 ex dc HSM and the 17-50 f2.8 ex dc os,taking in to account the crop factor which in the opinion of other members would be the best purchase ? Many thanks MBS