Sorry Andy--I am showing my age by using that term---when I say cable, I mean those 4 or 5 pin wonders they produce now.
I did not comment on Whalers Sigma lens, because I really like Whaler and greatly respect his abilites. And I do not like Sigma lenses. Sigma has been periodically problematic in the past, like...bad. After this store being in exsistance more than 50 years, I am in the process of shutting down my retail store and concentrating on my Studio, so I have not kept up with recent developments.
I am a firm believer in the camera manufacturer lenses. Almost all after-market lenses are made in China sometimes to specs that a manuf. designates, sometimes to their own, then they are marketed under multiple names. Patents are of little concern to the Asian manufacturers as a whole, but are here in the US. Sigma at one time chose to ignore that fact and manufactured a Minolta mount lens that was not licensed. The court system did not aloow them to be repaired under warranty and I am not sure as allowed Sigma to touch them. Sigma made it the consumers problem to deal with....additionally they continued to market that very lens, just stamped the bottom "unlicensed"---- When the wide angle to extreme telephotos came out, Sigma was at the forefront. While this is a good idea on paper, despite what reviews said they had issue with sharpness at both extremes an was one of the poorest constructed lenses I ever saw.
In the Photo institute I attended at the turn of the last century (Moses was in the class ahead of me and he had short hair) I took a quarter of lens design and basic abberation correction. I only learned that you should never try to figure out a lens!!! I did hear many horror stories in that class about after market stuff and have contiued to hear similar stories most weeks to this date. While there are many "would be" experts, I decided long ago, there are really about 100 people accross the US that can really tell what is good or not in costruction and design, and me not being one of them, I decided to sell very limited after- market lenses after the advent of auto-focus. I have only used manufacturer lenses in my Studio and 95% of my sales were also.
We ran the last Camera Repair place in Iowa, and closed it in 2004. While I only employed repair people and never touched a repair myself, the repair people seemed to agree. I have seen many after market lenses, most where not impressive in their construction. Having said that, there have been A-M lenses that I thought were really neat.
I hope with my comments I have not ruffled any feathers, that is not my intention, this is just my opinion.