01-28-2015, 06:23 PM
f/4 is f/4 is f/4 all day. The f number is arbitrary as is the focal length.
Three things drive the design complexity of wide-angle lenses:
* angular coverage (sensor size does not matter - field of view does)
* f number
* telephoto ratio. If the BFL is >> the EFL the design is very difficult. Increasing this is what drives the difficulty of wider and wider angle lenses. Because the angle on the back is fixed (i.e sensor size) the only way to widen the field is to shrink the efl. The reason full-frame SLR wide angles tend to be better than smaller format ones overall is because the EFL is longer to achieve the same field, thus the telephoto ratio is closer to 1.0 and the design is easier in that respect.
Three things drive the design complexity of wide-angle lenses:
* angular coverage (sensor size does not matter - field of view does)
* f number
* telephoto ratio. If the BFL is >> the EFL the design is very difficult. Increasing this is what drives the difficulty of wider and wider angle lenses. Because the angle on the back is fixed (i.e sensor size) the only way to widen the field is to shrink the efl. The reason full-frame SLR wide angles tend to be better than smaller format ones overall is because the EFL is longer to achieve the same field, thus the telephoto ratio is closer to 1.0 and the design is easier in that respect.