The Sigma 70-200mm F/2.8 EX OS for Canon mount has so far proven to be fairly impressive. We performed a very quick and dirty sharpness test on Day 2 and today we’re doing some pixel peeping. What we found in our non-scientific test may amaze you.
Method of Test
I pasted a sign on my wall and focused on different parts of it for each focal length. The camera was set to aperture priority and at ISO 800. Additionally, the white balance was set to Tungsten. The camera was set down on a tripod. To focus, I selected the Live View function in order to check that the focusing spot was consistent.
Since the camera was on a tripod, the OS function was turned off. Because of this, I shot in the delay shooting mode.
Please note that at 100mm and 135mm Lightroom 3 told me that the lens was at 97mm and 128mm respectively.
Also, despite how dark these images were, exposure compensation was not touched and the images were not post processed except for cropping them down to around the critical areas towards the center.
70mm (Focus on the word lightly in step 3)
100mm (Focus on Corner and Repeat)
135mm (Focus on Sure)
200mm (Focus on Drywall)
The first thing that jumps out to me is 135mm F/2.8 to F/4. I thought that maybe I had made a mistake—but I realized that that makes no sense because I checked the focus in the Live View screen before shooting. This posting was delayed from the other Sigma postings in this series for this reasons.
The test was repeated and I was able to accurately repeat the results.
Otherwise, the images look very standard: that being that the lens reaches peak sharpness around F/5.6 and tapers off a little after that.
More testing will be done in real life use to see if these problems continue to happen. Stay tuned!
Editor’s note: you will see in the next posting in this series that in real life practice and on the 7D that the lens is indeed quite soft at 135mm.
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