My question was prompted by this DPReview review of the Nikon DX 18~200mm, wherein on page 3 the author reveals some significant sharpness and distortion issues, leading to final assessments of
Pronounced distortion across much of the range
and
Extremely soft at 135mm
These seem like major problems to my beginner eyes... yet one can find many, many satisfied owners around the internet, see B&H's store page to give one example.
These two realities - that of the carefully tested review and the cumulative experience of the masses - seem quite difficult to reconcile in this particular case.
If we assume the reviewer is competent and the lens tested is representative of the model's performance at large...
- are the reviewer's standards out of touch with all but the most serious photographers?
- or is this subtle, widespread (perhaps even subliminal) buyer's remorse performance bias based on the relatively high cost (for DX) of this lens?
- something else entirely?
Answer
The reviewer may have used a sample of one. Lenses will vary.
The reviewer is measuring scientifically in the lab, pixel peeping using test charts and compiling MTF curves. Owners of the lens are taking vacations shots and pictures of the family dog.
the reveiwer has experience with a number of other lenses, including pro lenses. Owners of the 18-200mm? It may be the only lens they own.
the reviewer is measuring 1% distortion that most users will not see in real life images. Most wouldn't know what pincushion distortion is, or notice it unless you pointed it out. I have the lens and distortion is only noticeable to me in shots of brick walls or skyscrapers, and photoshop corrects it anyway!
the reviewer is using test charts meant to expose any weaknesses in the lens. An owner of the lens is just taking pictures in real life situations and probably can't tell which images were taken with the 18-200mm and which were with the 50mm prime. I can't, not in terms of sharpness or distortion.
the reviewer is judging the quality of the lens vs cost to arrive at a overall value relative to other lenses. He will no doubt think it's pricey and may judge that you could obtain a better value (either sharper or less expensive). But an owner of the lens has already paid (or overpaid) and paid the credit card bill and they're not concerned about how it compares on a test chart against another lens. They're taking pictures, and able to zoom to 200mm or out to 18mm and catch shots they wouldn't get if they had to switch lenses, or left the other lenses at home.
I would also wager than 90% of amateur photographers don't know about or care about vignetting or chromatic aberration either. Even the trendy bokeh is probably not in most people's vocabulary :)
I bought the lens expecting it to be reasonably sharp, but mainly versatile and convenient, for a walk about lens. It's amazing that a super zooms exist IMO, much less that they are reasonably sharp. If I had experience using professional lenses, I might feel this lens was a bit soft or slow. But hey, it's basically a kit lens. Most of the people buying these are not pros and not interested in test charts.
What he says about distortion is probably true of all samples. Not sure about the softness at 135mm, I've not noticed it, and other reviewers like Thom Hogan didn't mention it. To be honest, I use the lens mainly between 18-50mm, and occasionally zoom out to 200mm to get some detail. I would rarely use 135mm.
I have done basic testing of my 18-200 at 50mm f/8 and compared to my prime 50mm at f/8. I didn't use a proper test pattern, but some newspaper. To my eye they were almost the same. The prime had a bit more contrast, and slightly sharper. If it had been a normal picture of a landscape I don't know if I could tell them apart to be honest.
As much as I love the my 85mm prime and a few others, if I could only own one lens I guess I'd stick with the 18-200mm for versatility. For that versatility it's worth the price IMO. So I'd give it a good review, but if I worked for dpreview and had all the gear to measure it against a database of other lenses, I might be more lukewarm in my assessment.
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