Sony 16-50 versus Pentax 28mm M f2.8

Is it worth carrying heritage primes rather than use the Sony kit zoom?

Shot as raw files using a tripod and 10 second delay. Developed in LR4, and then PS. 

Click for a larger image.

Overall view

Sony 16-50 at f5.6

Original overall view JPG 10.9MB

Pentax 28mm f2.8 M at f5.6

Original overall view JPG 12 MB

My interpretation. The elderly prime is a good deal sharper and more contrasty in the centre, while the zoom might have a very slight advantage at the edges. The kit zoom is usable, but, if there is the time available, the ancient prime is the better bet! I should have taken out the CA from the Pentax shot, the Sony image was processed using LR's auto profile for the lens. CA is a fixable problem with older glass.

Note that I have provided the processed (from raw) JPG file sizes for the uncropped images. I have found this to be a useful guide to lens performance, but the data needs to be interpreted with care. For example the light has a significant affect upon the result while a very grainy image also produces a high score. Further, I have seen an example of a lens producing an outstanding centre image result and a large file size, but with unusable edges, so you do need to look at the image as well. That said these two shots were taken in similar light, and, from a range of different images, I have noticed that good heritage lenses produce larger files than the standard zoom.

To put this into perspective, I have obtained poorer edge sharpness results at some focal lengths from the expensive but complex Canon 24-70 L f2.8 lens and a 5D camera. 

As I gain experience in using my collection of old manual focus lenses I continue to be impressed by their performance on this crop frame camera, however they are prone to chromatic aberration (CA). This is easily dealt with in Lightroom, but it adds a step to the process. You need to check all those hard edges against a clear sky!

If you are listening Mr Sigma, I want a 16-70 f4 zoom with IS in Sony E mount,  and I will pay good money for such a beast.

NEX 6