p.21 #1 · Zeiss "Batis" AF lens line to be released for FF E-mount
philip_pj wrote:
DxO's work in this area is best regarded as pop science, and caused endless confusion and argumentation. Imatest is a guide at best. Anyone wanting to know about lens performance should put pressure on the myriad of makers who publish counterfeit measures - useful only as a guide to their designers - to put the results of their bench tests in the public arena, for all apertures too.
I think that's a little harsh on DXO
I don't think their problem is the science, it's the communication.
(which makes them like real scientists in that respect)
They are not that tranparent about what their data means.
A lot of it can be figured out by reading their explanations and drilling down into the data, but that still leaves some questions unanswered.
But just so long as you know that you aren't getting any measures of infinity performance (true of most non bench tests) there's good data there to be had, so long as you don't pay too much attention to the headlines.
p.21 #2 · Zeiss "Batis" AF lens line to be released for FF E-mount
We often have these 'travel kit' threads.
Soon you will have the possibility of two a7/a7r bodies and a set of system AF lenses in 25-35-55-85 (two being Batis), weighing all up say 950 grams for the cameras, and 335-120-280-475 = 1210 grams for lenses, at f2-f2.8-f1.8-f1.8.
So a little over two kgs, with nothing else out there even close to matching IQ at anywhere near it for size/weight. Or use an RX1 as the second body/35 and save more weight. No fuss, no adapters, no sensor Gillette.
Sony and Zeiss are slowly corralling their 'sophisticated prime' FE users in the nicest way possible.
p.21 #3 · Zeiss "Batis" AF lens line to be released for FF E-mount
David, you know people are restless, impatient and distracted these days - look around at the traffic lights! They just want to take the number and run with it, so they do = misinformation and confusion. I worked a looong time in statistics, so I know you are right and I know I am right too. ;-)
p.21 #4 · Zeiss "Batis" AF lens line to be released for FF E-mount
philip_pj wrote:
David, you know people are restless, impatient and distracted these days - look around at the traffic lights! They just want to take the number and run with it, so they do = misinformation and confusion. I worked a looong time in statistics, so I know you are right and I know I am right too. ;-)
Yes, of course you are right Philip, but I think it applies to just about all lens reviewers who give some kind of composite number. Klaus at photo zone is driven to distraction by people wingeing about how some 12mm f2 lens gets only three stars (his stars are meant to be measures of average absolute performance, so any extreme lens is never going to get many stars compared to a short tele) -- so people go on about how this 12mm lens is an Epic Fail for the price etc.
Lenscore is another example: I think their underlying tests might be fine, but just about all you get is a useless aggregate number whose method of aggregation is obscure...
Interesting question about what to do. My inclination is to not offer any take home headline number (Lens Tip manage that) but I imagine it's commercially unviable.
May 01, 2015 at 06:21 PM
Steve Spencer Offline • • • • • • • Upload & Sell: On
p.21 #5 · Zeiss "Batis" AF lens line to be released for FF E-mount
One thing to keep in mind when evaluating the distortion of the Batis lenses is that Zeiss has typically measured lens distortion at infinity, and distortion can be quite different at different focus distances. For example the well known mustache distortion of the Zeiss 21 f/2.8 is primarily at infinity focus--at closer focus distances it is a much simpler (but a bit stronger barrel distortion). A good place where you can see this is in Zeiss' own measurement of the C/Y mount 60 f/2.8C. At infinity focus the lens has about .7% pin cushion distortion. At 1:10 is has virtually zero distortion and at 1:2 it has about .7% barrel distortion. You can see the measurements here: http://www.zeiss.ca/content/dam/Photography/new/pdf/en/downloadcenter/contax_yashica/makro-planar2-8_60mm_c_e.pdf
This gives us some reason to hope that for more portrait distances the distortion will be a bit less as I believe for most lenses as the focus distance decreases the lens show less pincushion or more barrel distortion. So, it might well be that for typical portrait distances the Batis 85 might show more like 2.5% or 2% distortion, which for me wouldn't need correction much of the time.
p.21 #6 · Zeiss "Batis" AF lens line to be released for FF E-mount
Matt Grum wrote:
The problem with measuring MTF with distortion correction applied is that you're no longer measuring the MTF of the lens, you're measuring the MTF of the lens / filter stack / sensor / image processing chain system. Values measured using say the A7R would not be applicable to someone planning to use the lens on an A7.
And what if you plan to sell lenses on multiple mounts? Which camera do you chose to do the measurement?
MTFs should be for the lens only, measured on an optical bench, without the use of cameras. The only reason things like Imatest etc. exist and are used by lens review sites, is that optical benches are prohibitively expensive (unless you're a lens manufacturer or hip lens rental site) so measuring the system MTF as a proxy for the lens MTF is all you can manage. Attempting to do so in the presence of distortion correction is dubious, as demonstrated by the fact that said hip lens rental site (I'm just jealous because they're not in the UK) measured worse resolution figures in the centre after correction, when mathematics would predict better results there.
I'm not sure I entirely agree.
I certainly agree it's good to have bench MTF results.
But unless it's bragging rights for the best lens, what we also need to know is final image quality: and that's where I like DXOs method of measuring the lens on different bodies (I know some of it is mathematical interpolation, but still..)
And of course if you are adopting that method, you could give both before and after results. Which would be pretty interesting, and allow comparison of well corrected for distortion lenses (whose resolution loss is baked in the glassware) and software corrected lenses post correction.
p.21 #7 · Zeiss "Batis" AF lens line to be released for FF E-mount
arduluth wrote:
DMF was a must for me when using the Sony E 35mm f/1.8 on my NEX. I'd AF on a face, but AF doing what AF does didn't know what, exactly, I wanted to focus on. Eyebrow or nose instead of the eye, etc. The new eye detect AF probably improves on that, but it was a big frustration on the NEX until I started using DMF.
that would be a lot more useful for me if the DMF actually used the face detect box to zoom in instead of zooming in on the center. i just turn AF and auto zoom off and manual focus.
p.21 #9 · Zeiss "Batis" AF lens line to be released for FF E-mount
philip_pj wrote:
ecarlino, if you think Batis 85 corners will melt in front of your very eyes, don't buy one. Me, I trust the outfit that has been around since the beginning, to make judicious trade offs. This is exactly the art and science of lens design.
I'm not sure what you're talking about, not only do I have both Batis on pre order, but I've been suggesting I'm ok with distortion needing to be corrected if other abberations are improved.
My only points have been that measurements should disclose whether done with or without corrections and that I value whole system measurements in addition to lens only.
p.21 #10 · Zeiss "Batis" AF lens line to be released for FF E-mount
ecarlino wrote:
I've been suggesting I'm ok with distortion needing to be corrected if other abberations are improved.
Right. Or if it allows the lens to be pretty small and/or inexpensive. There's a balance point with these trade-offs. But I'm not sure these lenses hit it well. Pretty high distortion, pretty high vignetting, somewhat large, and pretty expensive, in exchange for good-but-not-mindblowing MTF. *shrug*
p.21 #11 · Zeiss "Batis" AF lens line to be released for FF E-mount
DavidBM wrote:
I think that's a little harsh on DXO
I don't think their problem is the science, it's the communication.
(which makes them like real scientists in that respect)
They are not that tranparent about what their data means.
A lot of it can be figured out by reading their explanations and drilling down into the data, but that still leaves some questions unanswered.
But just so long as you know that you aren't getting any measures of infinity performance (true of most non bench tests) there's good data there to be had, so long as you don't pay too much attention to the headlines.
Gotta laugh at DXO for saying the Sony 28/2 as sharper than the Zeiss ZA 35/1.4 and 35/2.8. They don't test at infinity and the ignore there own edge of frame performance evaluations. In the test they say the edges and corners are just a little softer than the center on the A7r! Every user landscape that include at/near infinity is poor at the edges.
p.21 #12 · Zeiss "Batis" AF lens line to be released for FF E-mount
Yeah, dxo is not worth a whole lot. And the score summaries are a joke. Nearly meaningless. I don't mind the write ups, but even their charts do not give enough information on focus distances to be worth anything. Until DXO publish their methodologies for public scrutiny, I give them little credence. I would rather pay attention to photozone and Imaging Resource. At least I know their process.
p.21 #13 · Zeiss "Batis" AF lens line to be released for FF E-mount
We certainly know photozone's methodology.
But imaging resource? What are these blur units? We are told that they are the equivalent of a unit of a photoshop gaussian blur increment. But we aren't told what the starting point is. I *think* the starting point is the peak resolution of the lens; but maybe it's the nyquist point of the sensor. In any case it's not at all clear to me. And you just don't get to the see the absolute lp/ih figures like you do with protozone (which can be easily misunderstood of course, but it's very nice to know)
p.21 #14 · Zeiss "Batis" AF lens line to be released for FF E-mount
Many shortcomings, all will surely agree. Review images that are overly individualized by the reviewer, or look like someone pointed the camera out a window.
The downplaying of manual focus lenses as somehow obsolete and a big ask for new age photographers. Inadequate explanations of methodologies. Not making the case for why a test measure is important to photographers. Zeiss not including all apertures in lens data charts, like the MTF data LC publishes - this provides so much more flavor to what is going on. Calculated MTF.
Roger Cicala, CZ and Leica are our best bets. The industry as a whole does a poor job of communicating with its enthusiast base, of informing them on even the basest of levels about their product. It's kind of: well, here it is, buy it.
So you are in the position of buying a lens that has been characterized mostly by a set of metrics. No color, no flavor, no opinion. Except photography is not a scientific field, rather it is artistic, and needs judgment and opinion, as you hear from good art critics. Segueing back to Batis, 'the distortion is 15x an Otus'.
Tongue in cheek partly of course, I am still grateful for peoples' efforts.
'protozone', lol. Reminds me of William Burrough's Interzone.
May 02, 2015 at 03:56 AM
Steve Spencer Offline • • • • • • • Upload & Sell: On
p.21 #15 · Zeiss "Batis" AF lens line to be released for FF E-mount
Lee Saxon wrote:
Right. Or if it allows the lens to be pretty small and/or inexpensive. There's a balance point with these trade-offs. But I'm not sure these lenses hit it well. Pretty high distortion, pretty high vignetting, somewhat large, and pretty expensive, in exchange for good-but-not-mindblowing MTF. *shrug*
I would call the MTF very good to excellent. Not perfect by any means and the 85 is better than the 25, but there is plenty of sharpness for my tastes in the 85 and the 25 should have good enough sharpness for all but the most demanding uses for me. I do think they are too fat as I said earlier, and of course I would want them to be cheaper, but I find these lenses to strike the balance point pretty well.
Some of the most important questions are still unanswered, however. For the 85 and my usage the quality of the bokeh will be the largest factor in whether I would want the lens, and for the 25 I would care quite a bit about the rendering of fine detail, which the 40 lp/mm line tells you something about, but it has never fully captured that aspect of a lens for me in viewing other MTF charts. We also don't know much about CA either. MTF can suggest a bit about lateral CA (CA in the focal plane), but they never tell the whole picture and can't really tell us anything about CA out of the focal plane (often called longitudinal CA). For the 85 I will also care a lot about CA out of the focal plane, but I will care about CA in the focal plane for both. The MTF charts suggest that, as might be expected, the 25 probably has more CA in the focal plane than the 85.
Once I know about bokeh and CA, I can make a much better evaluation of these lenses. If the 85 has nice bokeh, then I will almost certainly get it for my wife who shoots AF lenses and if it has good CA control that is a bonus as well. I have good hopes for this lens as I often like the bokeh of Zeiss Sonnar lenses, but the heavy use of asphericals does concern me a bit. If I don't like the bokeh, then I won't get it. If the 25 has good rendering of fine details and low CA in the focal plane, then I will probably get it for my wife, but I am less optimistic that it will shine enough for me to get it. I will have to prefer the rendering of fine details to the Sony/Zeiss 16-35 f/4 which is pretty good at 25mm and isn't that much bigger, and it will have to be quite noticeably better than the Sony 28 f/2, which is just as fast, much smaller and way cheaper. I can easily see going with the 16-35 and 28 and skipping this lens, but YMMV.
p.21 #16 · Zeiss "Batis" AF lens line to be released for FF E-mount
sebboh wrote:
that would be a lot more useful for me if the DMF actually used the face detect box to zoom in instead of zooming in on the center. i just turn AF and auto zoom off and manual focus.
That's what DMF does on my NEX. When the MF magnify is triggered, it zooms in on the face detect box or the AF point you're using.
p.21 #17 · Zeiss "Batis" AF lens line to be released for FF E-mount
re: testing metrics, I occasionally see a Wild photogrammetry camera or two on the bay, now those babies have well documented lens performance (and great paperwork)! A little annoying to find film for these days though.
But really, those things were SOTA back in the day when rectifying optical distortion was serious work. RS/Aerial work for geomatics is far more precise today, the demands on optics are greater and FWIW everything (everything) is now corrected digitally.
I gave up on online gear reviews 2 or 3 years ago when I began finding I was getting much different results on units I was purchasing based on reviews. For awhile (and maybe still) I believed that sample variation was greater than most of the performance differences I was reading about online. Now if I'm on the hunt for something I will run some searches and look at some images, ultimately I will need to try an example myself, often I end up flipping it. People need to appreciate that the root purpose of most equipment-review portals is to generate traffic, real useful information is almost an accident.
I am intrigued by this 85 Batis, anytime we can ditch adapters I think it is a step forward. For my applications (which I admit are now 90% 4K/UHD video) the single biggest problem I run into is matching lenses between a 2 camera setup. I love legacy glass but when used side-by-side with a new generation lens its often very obvious, I suspect the Batis 85 will play nice with the rest of the stable which seems to be getting newer and newer, time will tell.
p.21 #18 · Zeiss "Batis" AF lens line to be released for FF E-mount
Because IR uses image examples with textures and subtle patterns, I find it much informative than dxo. Sharpness is about the 5th thing I look for in a lens. I find out more about contrast, bokeh, micro-contrast and color rendering from IR's examples. None of these things, aside from contrast, is "measurable." Bokeh, to me, is always subjective. I know what I like (my standard for perfect bokeh is the Minolta/Sony STF), and that is good enough for me.
DavidBM wrote:
We certainly know photozone's methodology.
But imaging resource? What are these blur units? We are told that they are the equivalent of a unit of a photoshop gaussian blur increment. But we aren't told what the starting point is. I *think* the starting point is the peak resolution of the lens; but maybe it's the nyquist point of the sensor. In any case it's not at all clear to me. And you just don't get to the see the absolute lp/ih figures like you do with protozone (which can be easily misunderstood of course, but it's very nice to know)
p.21 #19 · Zeiss "Batis" AF lens line to be released for FF E-mount
arduluth wrote:
That's what DMF does on my NEX. When the MF magnify is triggered, it zooms in on the face detect box or the AF point you're using.
ah, you are right. i hadn't used DMF in so long i'd forgotten it does, you have to wait for focus lock though so the face has left the box by the time i can zoom on most of my subjects. plus it locks you out of being able to accomplish normal manual focus while you compose. useless for me.
it'd be nice if they had the magnification jump to detected faces when you hit the magnify button with a real manual focus lens though.
p.21 #20 · Zeiss "Batis" AF lens line to be released for FF E-mount
sebboh wrote:
ah, you are right. i hadn't used DMF in so long i'd forgotten it does, you have to wait for focus lock though so the face has left the box by the time i can zoom on most of my subjects. plus it locks you out of being able to accomplish normal manual focus while you compose. useless for me.
it'd be nice if they had the magnification jump to detected faces when you hit the magnify button with a real manual focus lens though.
