07-28-2013, 11:51 PM
Hi,
Please can anyone explain how residual spherical aberrations adversely affect the performance of the Canon 24-70 f/4L IS? I understand that the focus point shifts backwards when the lens is stopped down but I am not sure how this affects focusing in close up photography which is this lens' main party trick (i.e. the 0.7x macro mode).
Does this mean that if the camera is in Program mode and meters, say, for f/5.6 at 70mm, the camera has focused on an object near minimum distance and the image appears in focus in the viewfinder the focusing point would shift backwards causing loss of focus when the shutter is released?
I hired a 24-70 f/4L IS recently for use with my 650D and found the close up focusing performance to be unreliable for flowers and other small objects. The tiny working distance precluded the use of flash, unless you like arc shaped shadows. I am not sure whether this was caused by wind and / or not selecting AI Focus. I used either auto or manual focus during the 3 day hire. When the lens did focus correctly the results were markedly better than my old 24-105 f/4L with less distortion and chromatic aberration. I want to like this lens but the idea of buying a lens with an apparent design fault (even if common to lenses without a floating focusing mechanism) is a potential deal breaker.
I am thinking of getting a 6D soon either with a 24-70 or a Canon 35mm f/2 / Sigma 35mm f/1.4 plus a macro.
Many thanks,
Martyn
Please can anyone explain how residual spherical aberrations adversely affect the performance of the Canon 24-70 f/4L IS? I understand that the focus point shifts backwards when the lens is stopped down but I am not sure how this affects focusing in close up photography which is this lens' main party trick (i.e. the 0.7x macro mode).
Does this mean that if the camera is in Program mode and meters, say, for f/5.6 at 70mm, the camera has focused on an object near minimum distance and the image appears in focus in the viewfinder the focusing point would shift backwards causing loss of focus when the shutter is released?
I hired a 24-70 f/4L IS recently for use with my 650D and found the close up focusing performance to be unreliable for flowers and other small objects. The tiny working distance precluded the use of flash, unless you like arc shaped shadows. I am not sure whether this was caused by wind and / or not selecting AI Focus. I used either auto or manual focus during the 3 day hire. When the lens did focus correctly the results were markedly better than my old 24-105 f/4L with less distortion and chromatic aberration. I want to like this lens but the idea of buying a lens with an apparent design fault (even if common to lenses without a floating focusing mechanism) is a potential deal breaker.
I am thinking of getting a 6D soon either with a 24-70 or a Canon 35mm f/2 / Sigma 35mm f/1.4 plus a macro.
Many thanks,
Martyn