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Re: FE 70-200/2.8 GM: Sharpest and best low-light zoom weve tested

virtualrain wrote:

We need more test results I guess. Something is not adding up.

Perhaps, but let's also look at what we do know, and perhaps remove a little internet hyperbole (shocking to consider, but it does happen).

On an optical bench the FE 70-200 f/2.8 is decent (nearly as good as the Canon 70-200 f/2.8 IS II, which is not as good as the new Nikon). Disappointing, perhaps but does not make it an awful lens. It is, for example, better than the Canon Mk I on the optical bench, which a lot of people still shoot with quite happily.

On some of the lens-camera combination tests it's truly spectacularly good, perhaps as good as the Nikon. Why perhaps? Some minor points.

1. A really good camera-sensor may pull these scores up. So you have to make sure you're comparing the Canon 5Ds or Nikon D810 when you pull up someone's test results on DxO or an Imatest lab. And even then the A7rII is higher res than the Nikon, a bit lower than the Canon.

2. Some of the lab scores are testing jpgs and in a few cases they're oversharpened. (I'm not going to open the argument about whether jpg testing is valid, but oversharpened jpg testing is definitely not.) When the resolution presented is greater than diffraction limits, even if the author claims it's an unsharpened jpg, the test is invalid, but boy oh boy, do we present that result over and over if it says what we want it to say.

3. Sony cameras probably manipulate the raw images to some degree. We know it is so for distortion and vignetting in some lenses. It may or may not be true for sharpening, I don't know for certain. But this would make the target testing results invalid.

A technical point too. As a general rule sharpness and variance at infinity and closer distances are the same. But there are some reasons this lens may be different. First among these is it has two very strong aspheric elements. One of these is in the image stabilizing unit (unusual), the other is in the rear focusing group (quite unusual) and the two are right next to each other (very unusual). More to the point, putting two aspheres next to each other requires very tight tolerances in general, yet these two groups are both moving groups.

What does this mean? I'm not sure yet. We would expect it to mean higher variation in theory, but we don't know in what way or if Sony has developed some technology to overcome it. But it could also mean this lens is going to perform differently at infinity or close up, both in sharpness and in variance. It could mean the lens is going to vary depending on the stabilizer's position and the distance the focusing group is from the asphere. And to make it more interesting, we don't know the exact how that rear group performs because it's electrically encoded, so it may not be as simple as 'at this zoom and this focusing distance' it does this. It may be very active at certain focal lengths and not at others. It may move a lot close up or near infinity, but not at all elsewhere.

What is the bottom line (well, except for fanboys, and Sony Fanboys are rapidly passing Nikonians as the most illogical group on the internet)? For almost anyone who needs a 70-200 f/2.8 lens this is the best choice. It may not be as 'bestest' as we want it to be. It's pricey. But after all the wailing and gnashing of teeth, it's the best choice.

Mar 08, 2017 at 12:37 PM

  Previous versions of RCicala's message #13952107 « FE 70-200/2.8 GM: Sharpest and best low-light zoom weve tested »