Thanks for the information. I did not understand the low aberration coating , but your explanation makes perfect sense. I also was not aware the Sigma lens was not a constant aperature.
The adage "You get what you pay for." is ringing true here...but I was hoping that the lenes would perform well enough. But I would be very unhappy if I experience soft prints because of the lens.
I just have to recognize that I have an expensive hobby.
Thanks!