Canon EF 24-85 mm f/3.5-4.5 USM review - Image resolution

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Canon EF 24-85 mm f/3.5-4.5 USM

22 September 2007

Arkadiusz Olech

4. Image resolution

The model that we were provided for testing could be described simply as: “the longer the worse”. The behavior at the 24mm focal length is very good. From the open aperture the MTF50 values increase above the 30lpmm level and stay at that point almost up to f/16. At the 50mm focal length range, the situation is weak for f/4.0 to f/4.5 but at f/5.6 the picture resolution is acceptable. Unfortunately, the situation deteriorates at the 85mm focal length, where the f/4.5 and f/5.6 diaphragms result in blurred pictures. Even stopping down to f/8 does not bring results anywhere near close to the diffraction limit, and at these parameters the lens performs weaker than at the 24 and 50mm focal length.

Canon EF 24-85 mm f/3.5-4.5 USM - Image resolution

This situation is clearly shown in both RAW format and the slightly improved JPG format. The testing table clipping has been photographed at 24, 48 and 85mm focal lengths and at wide aperture. The results can be observed in the pictures below. The pictures’ deterioration at increasing focal lengths is clearly visible.

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A similar situation can be observed at the corner of the frame, where the best situation is for the widest angle and the worst is at 85mm focal length. At the 24 to 50mm focal length the maximum picture resolution in the corner of the frame is close to 30lpmm, which is a typical result for an inexpensive lens, but still nothing to be proud of.