I got the Canon EF-S 15-85mm IS USM this week after a lot of deliberation as an upgrade to my 18-55mm IS kit lens for my Canon 550D, and did some trial shots using it and found the images to be on the softer side, especially on the wide end even at f/8. I even tried manual focusing using the LCD screen to check whether there was a focusing issue, and toggling IS to see whether it made any difference.
My expectation from a lens upgrade were:
- Better image quality than the kit lens in terms of colours and sharpness, especially after having read that this was one of the best EF-S lenses in league with the Canon 17-55mm f/2.8 IS USM (this review with the sharpness comparison was one of the guiding factors for the potential)
- Faster & accurate focusing - the USM focus seems to be quite fast, but I have not yet had a chance to try the Servo mode which would throw better light on this
- Longer & wider - the 15mm end is definitely a lot wider than the 18mm of the kit lens, but the lens is also very soft at this end. The 85mm is also significantly longer and covers the ideal portrait range.
At the moment, the lens seems to be no better than the kit lens in terms of image
quality sharpness. The wide end seems to be especially soft even when stopped down (reviews seemed to indicate that the mid range is the weak spot of this lens). The longer end seems decent, though not a great jump over the kit lens. So, effectively, points 2 & 3 seem to be served, but point 1 is a question mark.
I was wondering whether this is due to some defect in the lens or is this the expected output. I understand that zoom lenses in particular can have weaknesses at some focal lengths in their coverage, and also that there can be some quality issues, or just that my copy of the body and lens don't go well together. So, I would like to ascertain which case it is in order to make my decision.
Below are some 100% crops from the wide and telephoto end from the centre of the frame at f/8. I have also uploaded a series of shots at different focal lengths on flickr for details. Note that the images were shot using the Neutral picture style as high quality JPGs.
15mm 100% centre crop
85mm 100% centre crop