alundeb wrote: gdanmitchell wrote:
DXO has the veneer of objectivity and, as a result, gets a lot of attention. But the context is so complex and often of questionable relevance to real photography that the results often do not mean what the \"values\" assigned to lenses seem to suggest.
A simple test is to make some photographs with the lenses in question (likely the 16-35 f/2.8 L II, 17-40 f/4 L, and 16-35mm f/4 L IS) and look at photographic results. In terms of the real world effect of choosing among these lenses, this will be a lot clearer and straightforward than trying to sleuth out what the DXO numbers do and do not mean.
Dan
If it only was that easy. First, we need access to the lenses in question. Then we need to do everything right in the test. This requires some skills and thoughtfullness. Many members here on FM are up to that tasks, but there are also many examples of home made tests that are directly misleading.
Regarding DxO numbers, I do not recommend trying to interpret the metrics and scores, as they are obscure and represent some odd weighting choices. My point in the response above was only that you cannot use the oddity in the scores to dismiss the individual measurements without even bothering to read the explanation. Looking at the field maps or profiles gives fast access to a general idea of how many lenses perform at the magnification / subject distance used in the test.
You don\'t need to own all these lenses or run all these tests. There are enough people who know how to use the lenses to make fine photographs that you/I/we have access to plenty of very useful information on the performance of the new lens relative to the other options.
Sometimes the interest in objective test results blinds us to several things. First, we can tell an awful lot about the performance (and often some to the most useful and practical aspects of performance) by using the lenses to make a range of photographs, whether we do it ourselves or we view photographs made by others. Second, it is easy to slip into the mode of trying to quantify performance in entirely numerical fashion, which has the effects of focusing our attention on those things that can be described numerically in a relatively simple (or simple-appearing, as in DXO) way and perhaps giving them more attention than they warrant relative to actual photography.
A bottom line in this case is that when it comes to optical performance, as evidenced by both testing and extensive use by quite a few people, we can \"know\" some important thing about the new 16-35 that matter:
- it produces excellent image quality that clearly exceeds that of the prior 16-35 and 17-40 lenses in general way.
- the new lens improves specific performance aspects such as larger aperture and corner performance.
- it adds the feature of image stabilization.
As is always the case, each photographer, taking into account his/her own needs, expectations, and finances, may come to a different conclusion about the actual value of these things: Is f/2.8 more important that some improvements in overall IQ or than the addition of IS? How does one feel about losing the 35mm-40mm range? How important are the improved corner performance and large aperture performance?
DXO is a tricky thing as a measuring tool. Yes, it is an \"objective\" test. Yes, if you did deeply enough you can figure out what those numbers actually mean. But once you do get an idea of what the test is telling you, how much importance should you place on the \"score?\" In my view, not that much.
On thing that is interesting is that if you talk to a lot of photographers who have used the new lens — and not just folks in the \"battle zone\" that is sometimes the world of photography forums — you get some very consistent reports about their experiences. With one occasional exception (reports that not all four corners are always equally sharp) the response is almost universally positive.
Take care,
Dan
Sep 11, 2014 at 10:56 AM
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