Originally posted by ElJamoquio It takes a rare lens comparison for the edges to be worse on FF than on APS-C at equivalent focal lengths. This is just another myth that won't die.
On another thread in this sub-forum, this opinion was posted:
they wouldn't do it right... it would be just another ovf failure, and canikon already has the market for obsolete ff ovf cameras sewed up.
how many of you people that want ff have pixel-peeped your pentax lenses on a 36mp sensor? guess what, vignetting and field curvature are much bigger issues than you would have guessed.
yesterday i tested five 28mm primes... three of 'em were 28/3.5 lenses, and they were all so dark in the corners that i would rate 'em not usable wide open... we are talking corners down -3.6 to -4.0 stops, in imatest... it was like shooting through a porthole window.
the two 28/2.0 vivitars that i looked at were bright enough, but field curvature made 'em unusable at anything wider than f/8.
be careful what you wish for.
Ain't the Internet wonderful?
Wide angles on FF are just fine. Wide angles on FF are garbage.
Facts?
It is well known that there are issues with certain ultra wide lenses on the A7r in particular- especially those designed for short registration bodies such as Leica M.
It is also known that the performance of legacy wide angles in general on the A7r is widely variable, especially up to 28mm. Some legacy lenses are pretty good, some are not. Some are excellent.
Experience? I bought an A7r 3 months ago, primarily for use with a trio of classic Leica M lenses- early 70s 35/1.4, 50/2.0, 90/2.8. Prior to actually buying the camera, I bought an adapter and tested the lenses on a body. They were all superb. And no, I'm not a Leica fanboi. I've shot Pentax for 40 years. The Leicas are an inheritance that I've used for over 25 years. Gearhead? The A7r is a bit of an upgrade from my K20, I think.
As my main application is for landscape photography with a normal print size of 2x3 feet, for my purposes lens excellence first of all requires great sharpness at mid apertures. Secondly, I expect high flare resistance. Wide open performance is irrelevant. My reason for choosing FF was that I wanted somewhat better detail at 2x3 feet as well as the option of going larger still while maintaining what I judge to be acceptable sharpness. (I'm a retired professional just doing my own thing.)
28mm lenses? I've tested the Super Takumar first version, SMC Takumar 3.5, Pentax K 3.5, Pentax FA AL 2.8, Olympus 2.8 and 3.5- all at mid apertures. The best of the lot is the FA. Very sharp to the corners, excellent flare resistance. It's in a kit with my Leica lenses. Second best, Olympus 28/3.5. Very nearly as sharp as the Pentax, but coatings not as good. Highlights tend to blow out a bit. It's in a backup kit of other very good lenses designated for more risky situations. The rest? Olympus 28/2.8 also pretty sharp including corners, but not quite as good as the 3.5. Also some PF. Pentax K/SMC Takumar 3.5- quite decent, useable in a pinch, but noticeably softer in extreme corners than the better lenses. Super Takumar Version 1- too soft overall, corners poor- but I may play with it as a "character" lens for black and white.
UWA? I don't have much to choose from. A Tamron 24/2.5 and an SMC 24/3.5 for primes. The SMC just doesn't cut it, while the Tamron is marginal. Both are not that sharp overall, and poor to mediocre in corners. I do have a Sigma 15-30 that is surprisingly not bad, and will be evaluating it further. I rarely use wider than 28mm so it has not been a priority.
Personally, I have no idea whether a FF sensor assembly optimized for the registration distance of K mount would produce better results than the A7r with legacy Pentax wide angle lenses. I wouldn't completely rule out the possibility.
FYI, if I didn't already have the Leica lenses I would probably have held off until Photokina to see whether Pentax coughs up a FF. I may still get one if it happens. In the absence of FF, I would probably have gone for a K3 and a Sigma 18-35, as I consider 24 MP APS-C with no AA filter to be a perfectly reasonable approach to large prints.
I find the A7r an excellent platform for the sort of thing I'm doing- MF on a tripod- but I think the K3 is a much more suitable piece of gear for most enthusiasts.
Hope some of you find this useful.