SMC Pentax M 28mm f/3.5 on Sony A7
Another old wide angle that is about the same size as the OM, is it as good?
This is a baby sized prime, with fine build quality. It has a front aperture ring with 1/2 stop steps from wide open to f/22 (1 stop step between f/16 and f/22). The focus ring is smooth, and the front element is nearly flat. The lens is small, but with adapter on the A7 it is nearly twice as long. The two combined are about the same size as the E mount 30mm macro.
The SMC Pentax M, M for miniature, is their compact series of lenses introduced in the late 70s. This lens is a 6 element 6 group design. With its modest 0.3 m minimum focus distance, the magnification should be similar to the kit zoom. The filter threads are standard 49mm and the lens is fairly light at 180 g.
Spec wise this lens is nearly identical to the Olympus OM 28mm f/3.5 lens, more like the later MC model than the G model I tested recently (http://erphotoreview.com/wordpress/?p=4087).
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 resolution and sharpness are excellent in the center at all settings, but the corners are a bit weak until f/8.
Distortion is better than average at 0.75% barrel.
Lateral CA is noticeable in the corners/midfield, but is not severe.
Flare resistance: Haven’t checked.
Measured Focal length is 30mm at 1:35 magnification
Pros and Cons
- Compact and sharp stepped down
- Corners could be better at large apertures
This is just a quick review to get the basic performance up. Too many lenses to test them all thoroughly, although I think this one moves onto the next round.
Consider donating, it is about $50 a lens to rent.