Re: FM Review: Sigma 45mm f/2.8 DG DN Contemporary
Fred Miranda wrote:
The Sigma 45's AF will never do as well in tracking mode compared to other lenses because SA glow tricks the pd algorithm. When I initially wrote the review, I thought it was a shortcoming but now understand this is a compromise to achieve a special rendering look.
So, it's not a lens I would recommend for tracking kids playing sports nor for moving portraits. It was not designed for excel at many applications but I personally love it for group portraits and still life.
I love the rendering of the lens also, which is why I find its AF so frustrating. I do wonder about the SA explanation. The 45mm picks up the target quickly and accurately enough, but it loses it. If you pump the AF-On button, it will keep on picking up the target quickly and accurately, but keeps losing it when it tries to track. So it able to make a quick accurate focus in AF-C but it can't track accurately. Given that it can do focus quickly in af-c, the problem seems more algorithmic. The algorithm may be more challenged because of the lens's SA, but it is capable of focusing so to that extent it is dealing with the SA successfully.
I have the Canon EF 50 1.2L which is infamous for its aberrations, which are tolerated because many people like its rendering. It has loads of spherical aberrations, veiling flare, and also focus shift. But even operating on a Sony body through an adapter, it does eye-AF and tracking extremely well. I only have to not bring the focus point too close to the edges. I also have the Canon EF 85II 1.2L, of which the same is true (though I have used it less in tracking situations, so I am less sure in its case).
