![big aperture and small aperture lens difference big aperture and small aperture lens difference](http://4.bp.blogspot.com/-Z174o-EmwZE/UZUmoSNALII/AAAAAAAABQw/F98ectrv1Bw/s1600/aperture_fstops.jpg)
Shorter focal length lenses tend to have larger apertures as their most resolving. Focal length is the main determinant from my own testing experience. What allows a lens to work better at a larger aperture? I have found two main factors: focal length and price. When working at the same magnification, the f/2.8 lens will almost invariably out-resolve the lens that works best at f/8. One lens may be best at f/2.8 and another may be best at f/8. I address this issue in my lens tests.Īnother point to think about is that all lenses don't have the same aperture as their most resolving aperture. If you open the lens up further, lens aberrations will start to negatively affect the resolution. It does mean that if you want the most resolution, you should open the lens up to its most resolving aperture. That doesn't mean that you should just open up the aperture to its largest size (smallest number). So, what does all this mean? The main point is that decreasing the effective aperture will increase the potential resolution of a system. This decrease is a result of worsening diffraction as the effective aperture rises. As the effective aperture goes up, the resolution decreases. You will see that all the lenses but one cluster quite close to a smooth curve. The graph shows the MTF10 (resolution) as a function of effective aperture. Below is a graph of all but one of the lenses that I have so far tested for this website. I have said this before, but wanted to make the same statement in graphical form. The effective aperture has a direct association with the resolution of a system. the effective aperture is easily calculated:Įffap = N *(m+1) (where N = aperture setting, m = magnification) This is where the effective aperture come into play as it accounts for the size and the distance that the aperture is from the focus plane. If the aperture is twice as far away from the focus plane, it will have to be twice as big to make the same relative angle with the focus plane. The angle determines the amount of diffraction, and diffraction is the ultimate determinant of resolution. These two factors determine the angle that the rays exiting the aperture make with the focus plane. The size of the aperture is not the only factor, as the distance that the aperture is from the focus plane also determines the resolution.
![big aperture and small aperture lens difference big aperture and small aperture lens difference](http://4.bp.blogspot.com/-lDbbM2wvrno/UjLPcC8IdsI/AAAAAAAAAGQ/XlP_-v0HfL8/s1600/01_aperture_basics_2.jpg)
The larger the aperture, the more potential resolution in the system. We have already discussed the effect of aperture on resolution.