SPOILER-WARNING: If you really, really want to buy this lens, DON'T read on!
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Next problem: Focus quality
1. When adjusting the micro-focus of the D300 for this lens with test-charts in 1-3m distance dialling in +12 seemed to give the best results. But it snagged me a little when I saw that the perfect micro-focus adjustment (and thus sharpness) depended a little upon from which direction the AF came: Coming from infinity yielded a little different results than coming from say 1m perhaps to the tune of 3 untis of micro-focus adjustment.
Well yes, I thought nothing of it, berated myself for being a pixel-nerd and decided that this would not be the reason for giving the lens back.
2. Getting ut of the lab into the wild everything seems fine at close proximity. But as a landscape/nature shooter I often try to capture a scene from some distance, say 10m and beyond. That was when I found out that some times 1 out of 2 shots was not critically sharp
. I checked whether the optimal micro-focus for distant subjects was perhaps different than for close subjects but no, this was not the case.
I should have known that micro-focus was not an issue when I saw that some shots nailed focus perfectly and others didn't.
I'll give you example
crops at f/1.8, 1/500sec, ISO 200, -1EV, shot within a few seconds of each other focussing at the same spot: an edge of a forrest a good 20-30m away.
I opened both images side-by-side in CaptureNX and did a screen capture. The interesting thing: I used a magnification of only
66% in CaptureNX so we're not even at 100% pixel-peeping level yet. And still you can clearly see the difference in sharpness esp. when you look at the fine twiggs. From the left image you'd say "Yes, this lens is sharp!" from the right image you'd say "This lens produces mush!".
Unfortunately I cannot prove that the lens has set a different focus distance as the resolution of the internal distance reporting is not fine enough: it treats everthing from a certain distance as 18.84m whether it's 20 or 50m away
But I have other examples with other subjects that could be easily produced under good, contrasty conditions: One shot is a match, the next one is mush.
That nails it for me: I'm giving this lens back! I have to rely on focus accuracy and don't want to check every single shot on the lcd-screen under high magnification to make sure that the image is as sharp as the lens is capable of. And capable the lens is. I will underpin this assertion with some Siemens-stars in a later post!
Now this is a sad story and it hit me like lightning from a blue sky: I never thought that a highly appraised fixed focal from Nikon could ever lead me to send it back. It's a pitty as I love the wide aperture and the focal length in such a small package and that lens would have certainly become an often used complement to my Nikkor 35/2.0.
And what nags me too: I don't have a feeling whether this is a single bad lens or a case of design deficiency. And even if you might say "everyone else is loving this lens so your's must be a bad copy" I'm not consoled: Many lab-tests just pick the best focussed shot to analyse the lens's sharpness and they often measure only lateral CA but not longitudinal CA.
So be it. Take my review as a warning that even with the most innocuously looking and well-tested lens there might lie some problems that can seriously limit the fun you have and the quality of the images you take.
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Thomas (beware: Nikon-fanboy and moderator!)
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