Legacy manual-focus prime lenses can be purchased at very low prices compared to their modern equivalents and are therefore very tempting for photographers and videographers working on a budget. However, the optical quality of these lenses is often called into question on Photography forums, with many claiming that even a modest modern kit lens is superior to a legacy prime. With this in mind, I have put together this very unscientific comparison of 3 budget legacy 28mm prime lenses against two modern Sony Kit lenses.
The lenses are:
Pentax-M 28mm f3.5
Canon FD 28mm f2.8 (New FD)
Sigma Mini Wide II 28mm f2.8
Sony 28-70mm f3.5-5.6 SEL2870
Sony 16-50 f3.5-5.6 SELP1650
I have tested them on both a Full-frame Sony A7S and APS-C Sony A5100.
In all cases the images were taken at f8.0 and at 1/250s exposure time. All images are crops of Jpegs taken directly from the camera with no post-processing.
Jpegs are used so that the in-camera lens correction on the modern kit lenses is included against the uncorrected legacy prime lenses. Obviously RAW images could be processed to remove chromatic aberration and distortion in the legacy lenses, so the legacy lenses are at a disadvantage in this test.
In all images, in-camera sharpening has been turned as low as it will go (-3).
Full Frame Centre Crops
At the centre of the frame there isn’t much to choose between the lenses on the 12MP Sony A7s, though there are significant differences in terms of brightness and contrast.
Full Frame Edge Crops (Left Side)
The Pentax-M outperforms the others here with less CA and better sharpness. The Canon FD is only slightly softer, but also has a hint of chromatic aberration. The Sigma clearly demonstrates more Chromatic Aberration than the others. The Sony Kit lens is just terrible on the left side despite having the benefit of in-camera correction. Oddly, the Sony is much better on the right side (almost a match for the Pentax), with quite a few owners complaining of this issue on the forums.
Full Frame Corner Crops
The Sony SEL28-70 Kit Lens remains the bottom of the bunch for corner performance with very poor detail. The Sigma again shows lots of CA and the Canon FD is just behind the Pentax.
APS-C Centre Crops from the 24MP Sony a5100
These last crops are provided to give an idea of resolution on a sensor with a higher pixel density (24MP APS-C Sensor).
There isn’t a lot to choose between them at the centre of the frame, leading me to believe that all of these lenses can continue to provide good results even with modern high resolution sensors.
The budget SELP1650 lens has surprised me while performing these tests and actually provides much better results than the SEL2870. I suspect that Sony deliberately crippled the Image Stabilization of the SELP1650 on the A7s because if provides superior results to the SEL2870 in APS-C crop mode on that camera.
It is possible that I have a bad copy of the SEL2870, however I did test this against a Canon 18-55 Kit Lens, and the Sony SEL2870 definitely outperformed the Canon, so I just don’t buy any argument that modern kit lenses consistently out-perform legacy primes.
Finally, the Canon FD 28mm was the better of two copies of that lens that I purchased (the other was softer) and despite the Sigma’s poor Chromatic Aberration, there is a pleasing quality to the images from that lens, particularly at larger apertures. The original mark 1 version of the Sigma Mini-wide (without the “II”), is vastly inferior and should be avoided.