Canon FDn 24mm f/2.8 on Sony A7
These classic wide lenses performed poorly on APS-C cameras, do they fare worse on full frame?
The FDn lenses are good quality lenses built by Canon in the 80s, but were starting to show cost cutting. They forgo the breech mount per se since they no longer have a twisting ring to lock them down, and instead the entire lens turns like a classic bayonet mount.
The lens is fairly light at 240 g, and has standard 52mm filter threads. It has a minimum focus distance of 0.3 m, which is long for the class, providing only 0.11x magnification. The optical formula is 10 elements in 9 groups and has floating elements for better close up performance. The aperture has 6 slightly curved blades.
Note: 4k video is 2160 LW/PH
Note: HD video is 1080 LW/PH
For video, you want your MTF20 values to be at or above those numbers. The green region and up is where a good photographic lens will lie, but decent is anything better than f/22 performance, so mid yellow and up. If you can’t see the colored borders, for MTF20 Red: ~1500 LW/PH, Yellow: 2700, Blue: 3500. MTF50 values are 900, 1620, and 2160 LW/PH.
Comments on the Results
The center is excellent throughout the range. Partway points are good at f/4, excellent by f/5.6 through f/11. The corners aren’t good until f/5.6, but the lens also has a fair amount of field curvature so watch focus point.
Distortion is wavy mustache distortion which is primarily about 1.2% barrel.
Lateral CA is noticeable.
Flare resistance: Haven’t checked.
Measured Focal length is 26mm at 1:35 magnification.
Pros and Cons
- Center Performance
- Decent Value
- Corner performance until f/5.6
The 24mm or 20mm? They are both about the same. Get the focal length you need, the 20mm is much larger lens, so the 24mm is the better balanced choice. The 24mm, at least this sample, seems to have a slightly higher emphasis on central sharpness, with slightly worse edges, but overall I would call the characteristics similar.
The great thing with full frame is you actually get your wide/ultra wide lens out of the 24mm focal length instead of a very large standard wide lens. It is fine to use these on APS-C, but you don’t get a very good size/aperture ratio.
This is a good value lens, I will test this specific lens on a NEX 3 when I have a chance, but overall performance looks notably better than other 24mm SLR lenses I tested on the 3. This could be for a couple reasons, but one of which is that the larger pixels on the A7 are a bit easier on the lens. The lens is limited by the A7 so you shouldn’t see much improvement with an A7r except in the center.
As a reference, this lens is about the same in the corners as the kit 28-70mm lens, which isn’t bad at all, but not great. Compared to the Sony 16mm f/2.8 used on NEX 3 or in crop mode, this lens is much better.
So to answer my question in the blurb at the top, this lens is much better fit on FF then on APS-C. Even though the corners don’t look ideal, the larger sensor helps the overall resolution a lot. For APS-C the Sigma 19 or 30mm f/2.8 are two good choices.
Consider donating, it is about $50 a lens to rent.