In an attempt to understand why the images from my new Sony NEX-7 w/18-55mm f/3.5-5.6 kit lens are soft, I ran some basic tests earlier today. I wasn’t satisfied with the results for a variety of reasons (wrong ISO, not enough variables and general sloppiness) so this afternoon I repeated and expanded the tests. The results are shown below. All exposures were at ISO 100. Click to see the image in full-res.
- On the Sony NEX-7 body, the Nikon 35mm f/2D prime (via an adaptor) is sharper than the Sony 18-55mm, both at f/5.6. No surprise on this one.
- The Sony 18-55mm has less chromatic aberration at 35mm than the Nikon 35mm prime (both at f/5.6).
- The Nikon 35mm prime is equally sharp on the NEX-7 (24mp) and the Nikon D7000 (16mp). (The Sony’s extra megapixels don’t help, but it’s just as good as the D7000 in this regard.)
- None of my tests at 35mm explain my soft images from Saturday’s shoot. So I tested at 55mm…
- The Sony 18-55mm is noticeably soft at 55mm wide open (f/5.6), but stopped down one f-stop (f/8) it looks quite a bit better.
- Not shown here, it gets soft again at f/11 and beyond. At 55mm, the Sony 18-55mm is a “keep it at f/8” lens.
- Also not shown here is the fact that the NEX-7 underexposed this test one full f-stop. This was corrected in Lightroom 4. No other corrections (sharpness, noise reduction, CA removal) have been applied to any of these images.
To see the full test charts, click on the images below. Mouse over to see which is which. These high-res JPEGs were made 1:1 from the original RAW files using quality 80/100.
I’m curious to know if it’s just my copy of the Sony 18-55mm that’s soft or is it common to all copies. I’m also curious to see if the Sony 18-200mm zoom is much better. I’ll have copies to test this coming weekend.