Ephotozine Review: Z 100-400/4.5-5.6 S VR

Started Jan 25, 2022 | Discussions thread
kenw
kenw Veteran Member • Posts: 7,082
Re: I like Ephotozine …
2

RazorSharpWO wrote:

kenw wrote:

I’m not sure I’d call anything from that site a “real review” as their MTF results are frankly notorious for their inconsistency.

Interesting. I've heard other people say they don't have good protocols.

I hope you are not concluding that from ephotozine’s test of the 70-200 since they tested the 70-200 on a Z5 and the 100-400 on a Z7II. See point above - never compare ephotozine results between lenses even on their own site much less to any other site. Ephotozine couldn’t test their way out of a wet paper bag.

That's a good point to bring up, that the measurements are not exactly comparable, for the reason you state. One can only surmise that the 70-200 scores would go up, tested on a better sensor, but I believe the "shape" of the graph would remain the same.

In other words, if the sharpness is at its uttermost wide-open (like the 70-200 is), then this would be true regardless of what camera one is using. Maybe the figures would go up higher on the Z7 II, but the shape of the graph should remain the same, n'est-ce pas?

Yes, that's the general idea. However, the "shape" can actually shift a bit as you go to a higher resolution sensor. As a simple thought experiment you might test a lens on 12MP sensor and because the sensor simply can't resolve the very finest detail the MTF results would show the center, edges and corners perform nearly the same. Take the same lens and test in on a 60MP sensor which can resolve much finer detail and now you will likely discover that the center naturally measures much higher than on the 12MP sensor but that corners don't improve nearly so much.  So on the 60MP sensor now you can see the center actually is a fair bit sharper than the corners while on the 12MP sensor they appeared much closer in performance.

But yes, you'd in general still expect to find the same "best aperture" with different resolution sensors.  On the higher resolution sensor the differences would be magnified a bit.

Another important wrinkle, especially when comparing between reviewers, is how were the "center", "edge" and "corner" focused.  That can dramatically alter the "shape" of the curve, especially at wider apertures.  One approach is to focus only on the center and then measure everywhere from that single exposure.  The other approach is to refocus on each location and then measure from each of those separate exposures.  In the first case you are testing for a flat field and any field curvature can penalize the off axis MTF numbers.  In the second case you are compensating for field curvature and will end up with higher off axis MTF numbers that represent performance if you focused on a subject in that part of the field.

For the field curvature case there really isn't a "right" answer as to which way to test because it all depends on use.

An astrophotographer buying a 50/1.2 would really care about the first "flat field" test because of course their subjects are as perfectly flat a field as you can imagine and they want to shoot wide open for the shortest exposures.  If a review reports through the roof MTF off axis, but they got that by refocusing the edges, the astrophotographer is going to be disappointed when they end up with blurry stars on the edges of the field despite the review's measurement of excellent edge MTF.

In contrast a portrait photographer buying a 50/1.2 doesn't care about a flat field at all, if the subject is off axis that is where they will focus and the rest of the frame is going to be out of focus anyway.  If a reviewer doesn't refocus off axis for the MTF test and then reports the lens is "soft" off axis that's not going to match the portrait photographer's experience with the lens at all who will report it is "razor sharp right to the edges" from their daily use.

Of course the most reliable sites document which they do and they typically in the text report separately whether there was significant field curvature.  That's sort of the best of both worlds.

It does, though not based on anything on Ephotozine. It is a site one can safely ignore as far as MTF results go.

The reason why I say I like Ephotozine is that, regardless of the variance in standards which you point out, their conclusions are pretty solid. For example, Lens Tip, in their review of the 58/1.4 G, just tore that lens apart. Downgraded it, trashed it. The Lens Tip author even said, "There must be something I'm missing," acknowledging he couldn't comprehend why Nikon would make such a lens.

Ephotozine, on the other hand, acknowledged the lens' shortcomings — but correctly saw its strengths — saying that, this is "a niche lens," that although it can be out-performed by other 50-ish lenses, it's rendering is sublime, and those for whom this is important, place the 58/G in a class by itself. That means the guy is a photographer, not just a lab geek running numbers.

Yes, absolutely!  My goodness, LensTip is the perfect illustration of how overall review approaches may be just "different" as opposed to "better" and "worse".  LensTip is fairly consistent on their technical approach and, while nothing is ever perfect, does put a significant amount of effort into making sure their own reviews are at least comparable to each other.  As you point out though they draw some utterly baffling editorial conclusions!  I've lost count of the number of times they've maligned some lens without even for a second contemplating what the lens was designed for.  This Ferrari has horrible gas mileage, and I can't fit a 4x8 sheet of plywood in the back of this Smart Car.

Honestly I feel Ephotozine would do themselves a service if they just stopped posting MTF results at all and similarly LensTip would do themselves a service if they just stopped writing some of their bizarre conclusions!  We are, however, lucky of course to have them both such that we can synthesize as much as we can out of the various reviews.

EDIT: To be clear, I’m bashing on Ephotozine and not the OP! Just fair warning to people not familiar with ephotozines lame attempts at MTF measurements. And despite that, thanks to the OP for posting the link. Much of the review and sample images are still super useful. Just remember to always ignore MTF results from that site. They are worse than useless, often the are grossly misleading.

No worries, and thanks for clarifying. We are all entitled to our opinion — and we can both be right. The variance in protocol is worth mentioning, but I think their conclusions are spot on, more often than not, based on owning many of the lenses they've tested.

Yes, that's what I was trying to convey in my edit.  Ignore their MTF stuff but pay attention to the rest of the review.  And that's a really important message because I often feel the whole MTF comparisons thing gets completely overblown when people compare lenses.  I sort of wonder if places like Ephotozine feel "forced" into doing the whole MTF thing because various readers demand it but perhaps don't understand how insidious it can actually be - even when done "right".

And also, thank you for providing a short summary of the review rather than just a bare link.

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Ken W
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