I had hoped to evaluate the Sigma FE 28mm f/1.4 DG HSM Art, which I previously tested on the Nikon D850 in DAP. The Sigma 28/1.4 is a very high performance optical design, but it seems that build quality is highly variable, and not just with the 28/1.4*.
But after two brand-new samples of the Sigma FE 28/1.4A with both unable to make a fully sharp image on the left side even at f/5.6, it’s clear that Sigma MTF is a marketing claim bereft of validity. Computed fantasy MTF is just marketing bullshit as compared to MTF testing a real lens with real light, as Zeiss does (only company in the industry to do so, AFAIK).
I am not going to try a third sample at this junction.
* I had similar quality issues with the Sigma FE 85mm f/1.4 DG DN Art, the Sigma FE 35mm f/1.2 DG DN Art, and the Sigma FE 14-24mm f/2.8 DG DN Art—all of which are terrific lenses *if* you can magically obtain a sample without optical build-quality problems. I’ve talked to other skilled photographers who went through ten (10!) samples of the 35/1.2 and just gave up, and others who have had to try multiple samples to get a satisfactory one.
However, I have evaluated focus shift on the Sigma FE 28mm f/1.4 DG HSM Art and it is an eye opener.
Includes two different examples.
James K writes:
I got lucky. The second 28/1.4 I got is excellent.
Lens skew is a big problem even with Zeiss. A while ago I tried to get a symmetric copy of a Zeiss 35mm f/2 and after three tries I gave up. I wrote to Zeiss and they told me that this is the new reality in lens manufacture. Hard to believe. I no longer buy Zeiss lenses. :(
DIGLLOYD: all lens manufacturers have issues and some have improved over time, but it’s basically a cost issue: quality control is expensive. The best quality control is Zeiss Otus (hence the high price) and Hasselblad XCD, but even they have variation.