Article Index

Lab Tests

Please note that MTF50 results for APS-C and Full-Frame cameras are not cross-comparable despite the same normalized [0:1] range used to report results for both types of cameras.


Resolution: Pentax APS-C

Pentax smc DA 70mm f/2.4 showed an excellent performance on an APS-C camera. Resolition is pretty solid throughout the aperture range, but the lens excells in the f/4-f/8 range, where both center as well as border image quality is simply superb. Regardless of the aperture setting, performance is quite even across t he entire frame. The lens is capable of delivering very good 19in prints in f/4-f/8 range and decent 24in prints in the f/4-f/11 range. Conclusion? Absolutely no weaknesses throughout - these are some of the highest resolution numbers seen in a medium telephoto..



Chromatic Aberration: Pentax APS-C

The lens showed very manageable amount of chromatic aberration on an APS-C camera. Center CA is minimal throughout the aperture range and never exceeds ~0.4px even at the widest aperture setting. Border CA is slightly higher, particularly at f/2.4 and f/2.8, but even there CA does not exceed ~0.7px, which while might be noticeable in some shots, should not be an overwhelming problem for most users.



The lens showed minmal amount of barrel distortion. At ~0.3%, distortion should not be visitible in general type photography.



Vignetting is pretty well controlled, thanks to the APS-C camera's smaller sensor and the moderately fast aperture of the lens. At f/2.4, the lens shows light falloff at ~0.7EV, slowly dropping to even smaller levels with stopped down aperture. Nothing to be concerned about.


Chart Crops: Pentax APS-C

Here are 100% crops, taken with an APS-C type Pentax K2000, comparing image borders at f/2.4 and f/8.