steve_stoneblossom wrote:
Some zooms have a reduced 'effective' focal length at the long end of their zoom range when focused at shorter distances. My 28-300, for example, produces an image roughly equivalent to a 150mm lens when focused closer than 5 feet.
Would anyone know if this lens is subject to this phenomenon?
Ah, focus breathing. I haven't heard anything about it. I generally don't worry about it - it just means i have to get a bit closer to my subject compared to a similar focal length that does not exhibit breathing to get the same composition. I have not been negatively affected by it so far. Nearly all internal focus lenses primes and zooms alike - exhibit a focal length change at minimum focus distance.
The only lenses I own that do not do this are my 24, 45 and 85 mm PC-E lenses - they do get longer as they are focused closer, and the maximum aperture gets smaller as you get to 1:2 magnification. My 85mm F2.8 PC-E lens becomes an 85mm F4.2 lens at 1:2, it's maximum magnification.