K Rockwell argues against third party lenses because even if they are fully compatible with the camera bodies when the lens is designed and released to market, the camera manufacturer can update the firmware are at any time or introduce new bodies -- with the result the comparability is lost.

I thought just a theoretical paranoia until recently. Not so, I had a Sigma that worthed perfectly on older Nilon bodies but started having problems with new bodies and with older ones when the firmware was up graded. I can't blame Sigma or Nikon for this -- its just part of the game.

I enjoy using a hodge-poge of lenses. I've found that to really cover a lot of mili-meters with good, or great quality lenses you have to look at your shooting style, what your subject are, and where you do your shooting. Also, what type of camera do you want to use. Since I shoot both a full frame, and cropped, which lens and which body the location, and subject really dictates the selection. When adding a lens to my collection, there is lots of research, and paining over the cost vs return. My latest acquisition is a Rokinon 8mm Fish eye. It was really a inexpensive lens, all manual, but the output is something else. I received the lens on Thursday, shot a few test shots in the backyard, and worked with them in LR. I took the lens with me to meet-up with some tourists in the French Quarter. We walked, talked and shot our way through the Quarter. I pulled out the fish eye on Bourbon St. slapped it on the 6D, and shot a few under Bourbon/Conti Street sign, and along the old bar fronts on Bourbon. They loved the portraits under the sign, and wanted me to take some more fish eye of the Marganey. So we walked on the Frenchman St. Well to sum up the entire day, I paid for the fish eye, and then some. I did learn something about all this. When processing in LR using this Rokinon, in the Lens selection, pick Sigma 8mm fish eye. This selection will pull the picture from a floating ball, to a nice full frame effect.

Oh, to HoHoHo, California heat is nothing, come to New Orleans, in August. Your bones will melt in the humidity.

I enjoy using a hodge-poge of lenses. I've found that to really cover a lot of mili-meters with good, or great quality lenses you have to look at your shooting style, what your subject are, and where you do your shooting. Also, what type of camera do you want to use. Since I shoot both a full frame, and cropped, which lens and which body the location, and subject really dictates the selection. When adding a lens to my collection, there is lots of research, and paining over the cost vs return. My latest acquisition is a Rokinon 8mm Fish eye. It was really a inexpensive lens, all manual, but the output is something else. I received the lens on Thursday, shot a few test shots in the backyard, and worked with them in LR. I took the lens with me to meet-up with some tourists in the French Quarter. We walked, talked and shot our way through the Quarter. I pulled out the fish eye on Bourbon St. slapped it on the 6D, and shot a few under Bourbon/Conti Street sign, and along the old bar fronts on Bourbon. They loved the portraits under the sign, and wanted me to take some more fish eye of the Marganey. So we walked on the Frenchman St. Well to sum up the entire day, I paid for the fish eye, and then some. I did learn something about all this. When processing in LR using this Rokinon, in the Lens selection, pick Sigma 8mm fish eye. This selection will pull the picture from a floating ball, to a nice full frame effect.

Oh, to HoHoHo, California heat is nothing, come to New Orleans, in August. Your bones will melt in the humidity.

Thanks for the suggestion to check Bryan Carnathan's review! Now I definitely want the Sigma 50mm ART lens! His bottom line sounds like a pretty ringing endorsement:
"While I will dock a few points from this lens for occasional AF inconsistency, the Sigma 50mm f/1.4 DG HSM Art Lens is now the overwhelming favorite in the 50mm field. This lens delivers excellent image quality, has a beautiful design and for what you get, a very attractive price. The Sigma 50mm f/1.4 DG HSM Art Lens is the easy 50mm choice for those with a moderate budget."