Jose Angel 
, Feb 09, 2012; 02:07 p.m.
Out of curiosity, and after reading several times about the higher optical quality of the Ai/AiS version (which, supposedly identical, at least in design, to the AFD), I have had the opportunity of performing a fast dirt test, wide open and f8. I`m in a hurry, so no time to make it better.
I was convinced my AFD was at least more contrasty; the only difference I have found is that the Ai at f8 transmit a bit more light than the AFD. I must say that the Ai is way more used, both lenses bought new time ago. The AFD is in very good shape.
I took several pics to compare focus, all pics taken with Live View. The AFD version is really difficult to focus manually, as it shows the classic AF "shift" or "jump". The Ai, a pleasure in comparison.
Wide open, I cannot see any difference. At f8 the Ai looks very slightly sharper, but I suspect it could be the mentioned focus problem, or maybe a decentering issue. Anyway, I think that difference is negligible.
Jose Angel , Feb 09, 2012; 02:10 p.m.
First, wide open: Left column, two shots with the AFD - Right column, two shots with the Ai version.
Jose Angel , Feb 09, 2012; 02:12 p.m.
Now, f8. Same as above: Left column, two shots with the AFD - Right column, two shots with the Ai version.
Jose Angel , Feb 09, 2012; 02:14 p.m.
Typo; I wrote AiS instead of Ai. The tested lens is an Ai.
Forgot to mention the camera is a D700.
John Farrar 
, Feb 09, 2012; 02:20 p.m.
Thanks Jose, useful. I assume this was a test at relatively close distance. The impression I get is that my 24/2.8 AIS is better close than at infinity. Agree it's a joy to focus. Good to know that 'upgrading' to the AF won't lead to any gain in IQ.
Jose Angel , Feb 09, 2012; 02:27 p.m.
Ooops, focus distance was exactly 2.5 meters (7-8 feet). Important. The USAF test chart in the center of the frame.
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With the AF/AFD the only benefit is the AF, which makes it worth the expense, IMHO. The MF ring is hard to use in my AFD.
I have thought about it... I too wonder if they are optimized for different focus distances. Correct testing takes a lot of time!
Rodeo Joe 
, Feb 09, 2012; 05:06 p.m.
The real test of any wideangle is how it handles the edges and corners though Jose. I'd be interested to see your comparisons taken a bit - make that a lot - further out from the centre. I don't think anyone's unhappy with those lenses' performance in the centre of the field.
John Hinkey , Feb 09, 2012; 07:19 p.m.
Having owned the 24/2.8 AIS for some time and tried to find a used AF-D version to replace it I can say that the only difference I've found is that the AIS lenses hold their optical characteristics extremely well while the AF-D versions seem to get out of alignment quite easily due to time and use and abuse.
So a new AF-D should be just as good as a good condition AIS unless sample variation comes into play.
Chris Brandt , Feb 09, 2012; 11:05 p.m.
I just bought a used 24 AF-D and it may be one of the sharpest lenses I own. This one was built in the late 1990's. That says something...
Wouter Willemse , Feb 10, 2012; 04:00 a.m.
I use an Ai 24 f/2.8 on DX - I like the lens a lot, and use it frequently. In the centre, for me, it's plenty sharp from wide open on. But the extreme corners do not look not terribly sharp till ~f/5.6. So I've always wondered how it would be on full frame in the corners.
Otherwise, looks indeed there is little difference between the AF-D and Ai version. I'll stick to my MF version then :-)
