Hello I just finished reading your post concerning the sigma 50mm lens with the man from lensrentals stating that the issues of this lens concerning front or back focus is routene for this lens? Although I applaud the build and fit and finish of the sigma lens being robust. I personally would try to avoid a lens with this problem. I have just purchased the Canon 50mm 1.4 lens with supposedly 60 dollars off, and also the sigma 30mm 1.4 lens with a 200 dollars off instant rebate which should come this week sometime. And yes I too am worried about front or rear focousing issues it might have.