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

Started Jan 25, 2022 | Discussions thread
OP (unknown member) Senior Member • Posts: 1,684
Re: I like Ephotozine …

kenw wrote:

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.

Makes sense. I think that's why Photography Life didn't show quite as good corner performance on the 70-200 as did Ephotozine.

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.

That's my point: the basic gist is that we know what aperture the lens performs its best.

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.

Makes perfect sense.

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.

Agree with this.

Another thing, with compositions, even a portrait photographer might have his subject off to the left — or off to the right — and thus in this case it is important that the edges (or at least the mid-frame areas) perform well also.

The same thing is true with birds. If I take a dead-center shot with a bird, then I don't care about the edges. However, if there's a particularly interesting scene, I may want the bird composed in the upper left corner, lower right corner, etc. Again, in these cases, how lens performs out toward the edges becomes important.

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.

Yes.

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.

Good to know.

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.

Yes again. Aside from the example I gave of the 58/G, there is almost an obtuse denseness not comprehending the purpose for which a lens is made. A lot of reviewers don't rate macro lenses correctly, for example, and couldn't take a good macro shot to save their life. I basically look at their graphs, and ignore their opinions.

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.

Exactly. Again, that's why I like Photography Life, because the guy post the graphs to look at, but he also is able to take photographs a connoisseur would aspire to take, or at least can appreciate, which conveys a level of understanding that lab geeks will never have.

When somebody who really knows what they're doing tests a lens, handles the lens, and takes photographs with the lens which conveys he not only knows what to do with it, conceptually, but can actually make it sing in the field — that's the guy whose opinion I'm going to care about.

By contrast, the guy who spins around in his office chair, snaps a photo of his dog, takes a photo of his shoe on the floor, and then copies and pastes "general information" in order to complete his review — is a guy whose articles/tests I won't click on again.

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".

Well I want to see the MTF graphs, but I understand it's not the only way to evaluate.

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

Sure.

If you look at my post in response to anotherMike, an actual owner of the subject lens, his review basically echoed my original summary, which itself was harvested from the Ephotozine review.

In other words, despite the titanic digressions which morphed out of the OP, the posted review link was pretty much spot-on ... which defaults back to this particular heading as to why "I like Ephotozine" 😄

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Please forgive: I use voice text, so there may be typos. Hopefully it still makes sense
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