Ok, lite nya recensioner då...
Sigma 35 1.4
http://www.photozone...2-sigma3514dgfxNikon 70-200 f/4
http://www.photozone...onafs702004vrfxDenna är bra, läs!
http://photographyli...70-200mm-f4g-vrIntressant jämförelse om närgräns och skärpedjup, mellan 70-200 f/4 och 70-200 f/2,8VR, saxat från recensionen ovan.
5) Lens Breathing and Depth of FieldAs you may already know, the Nikon 70-200mm f/2.8G VR II was a disappointment for some photographers, because it suffers from a “lens breathing” optical design, where the focal length of the lens varies depending on subject distance. At close distances, the 70-200mm loses quite a bit of the range, which can be a problem for those of us that like to fill the frame with small objects. The Nikon 70-200mm f/4G VR does not have this problem – I measured its focal length and it was exactly 70-200mm, no matter how close or far I focused (compared directly to other lenses with similar focal lengths). Its optical formula is similar to that of the Tamron 70-200mm f/2.8 Macro, which also measured about the same.
Now why is this important? If you lose some focal length at close distances, it also means that you will have to zoom in closer with the f/2.8 version to get a similar field of view. And as you may already know, longer focal length translates to better subject isolation and smoother bokeh (if the camera to subject distance remains constant). When comparing bokeh on the two lenses, if I focused with the 70-200mm f/4G VR at 116mm at a distance of about 5 feet between the lens and the subject, the Nikon 70-200mm f/2.8G VR II required me to zoom in to 200mm to get a similar field of view! That’s a pretty significant difference in focal length…
If we use a
depth of field calculator, we can plug what a 116mm lens at f/2.8 is like compared to a 200mm lens at f/4, both at 5 feet subject distance. The calculator says that the 70-200mm f/2.8 will yield a depth of field of 0.09 feet, while the 70-200mm f/4 will have 0.04 feet, because of massive difference in focal lengths. Hence, at close distances, the 70-200mm f/4G is actually a better lens to use for subject isolation. I know what you will say: “but the field of view is different”. Yes, true, but think about photographing a small subject at close distances. With the 70-200mm f/2.8 VR II, you cannot zoom in any further to get the subject to appear bigger – the only thing you can do is add a teleconverter. Whereas with the 70-200mm f/4G VR, you can make the subject appear bigger (and even bigger with a teleconverter) and you have more options for better subject isolation.
Now 5 feet is obviously too close, so let’s do slightly more realistic numbers. When doing my lab tests, I measured that the Nikon 70-200mm f/2.8G VR II at 200mm is equivalent to the Nikon 70-200mm f/4G VR at 170mm, both at a distance of 13 feet. If I plug those numbers to the same calculator this time, I end up with 0.29 feet of depth of field for both lenses. What this all means, is that the Nikon 70-200mm f/4G yields shallower depth of field than the Nikon 70-200mm f/2.8G from the closest focusing distance to about 13 feet, again because of difference in focal lengths. Past 13 feet, the Nikon 70-200mm f/2.8G starts to take over, because the lens breathing effect starts to wear out and the lens recovers most of its focal length. Again, this shows that the 70-200mm f/4G would be much better suited for close-up work than the 70-200mm f/2.8.
Redigerat av Mikael_R, 20 February 2013 - 15:22.
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