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Archive 2013 · A7/A7r testing procedure with RF lenses

  
 
Emacs
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p.1 #1 · p.1 #1 · A7/A7r testing procedure with RF lenses


I doubt guys that tested lenses on A7/A7r did it properly. I am sure in that proposition in fact.

Factors:
#1: inifinity position is likely the most troublesome, causing maximal angle of incedence at least for lenses with floating back glass, like Summilux 50 ASPH:
Infinity:


MFD


#2: there are adapters that pass lens over the infinity and thus make issues even more severe, not to mention lowering resolution compares to their true infinity position.
#3: lenses work differently as well. With my Novoflex adapter both Lux 35 and Lux 50 (ASPH FLE and ASPH respectively) are spot on infinity for NEX-5n. While both Super Elmar 18 and APO-Summicron 90 ASPH goes slightly over it.
#4: Sony has quite a poor QC with their NEXes. With my first NEX-5n (broken) and SE 18 I had color shift at bottom and right edges. With a second they are gone. This factor can hardly be passed though, so it should be excluded from consideration.

Proposition:
Do not use infinity focusing position exclusively. Do infinity + several shots below it. Then choose the best.

Remark: longer lenses are tend to use at lower distances manually focused, so their inifinity performance is not that important. Wider lenses are tend to use at hyperfocal distances with everything is sharp. So, their infinity performance is not that important as well.

Edited on Nov 18, 2013 at 03:17 PM · View previous versions



Nov 18, 2013 at 02:06 PM
michaelwatkins
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p.1 #2 · p.1 #2 · A7/A7r testing procedure with RF lenses


A good number of the wide angle lenses tested are symmetrical designs without floating elements; in these, the rear lens element moves farther away from the sensor as focus approaches maximum (infinity) distance.

Even on APS-C cameras, edges can sometimes be a problem, but often they perform well enough at/near infinity to be tolerable, and perform much better closer in since a) the lens elements move forward, away from the sensor and b) often edges don't matter as much with subjects close in.

Your point is important - be aware of lens design when testing and evaluating.



Nov 18, 2013 at 02:46 PM
philber
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p.1 #3 · p.1 #3 · A7/A7r testing procedure with RF lenses


Emacs , in another thread, you called the A7 camera "bad" for a number of reasons like the lack of touch screen and no tilt EVF.
Now you add that published tests of this bad camera + lenses are all incorrect.
Yet you want more, no doubt to add more negativity.
That is called being a troll.
Why can't you leave this "bad" camera and its dollowers alone?



Nov 18, 2013 at 06:12 PM
rscheffler
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p.1 #4 · p.1 #4 · A7/A7r testing procedure with RF lenses


Emacs: looking forward to your controlled test with a properly shimmed adapter (if it turns out the 50 Lux ASPH does not correctly infinity focus with your a7/7R), preferably with samples from several copies of cameras and lenses to rule out variables. I think the only one on the forum possibly equipped to do so is Roger at Lens Rentals. Not that he'll do it, considering how busy he is..

#2 assumes infinity focus was simply setting the lens at the infinity hard stop and leaving it there. In the tests I did, I refocused each lens at maximum EVF magnification at a specific distant target. In the Shanghai skyline series on Flickr that many are questioning, the photographer states in his blog that he did the same (though his results do look strange at wider aperture on the faster lenses).

'Infinity' was chosen for the reason you point out about the angle of incidence, intending to show the 'worst case' scenario for a given lens... whether or not it's relevant to real world applications depends on each photographer.

In your proposition, do you mean to shoot at the infinity hard stop, then several series backing off infinity slightly each time? I don't see the point in using the hard stop if it focuses past infinity, unless the lens has severe field curvature back towards the camera at the edges. Backing off correct infinity focus could make sense with a lens with the opposite kind of field curvature, which many RF lenses have. By doing so, the averaged result once stopped down a bit to compensate for the loss of central sharpness, might be an overall improvement - testing will need to be done.

#3: 'Real world scenario is photographer owns one or two adapters for a number of lenses. It's a compromise. Not all combinations (or any) will have correct infinity focus at the hard stop. Not everyone will dedicate an adapter to each lens and shim it accordingly. But, if tests (which we're waiting for someone to do) prove that the floating element lenses require critical shimming and alignment for infinity focus, then that will be the only solution if one wants the best results... one more consideration when debating the merits of adapting lenses vs. buying the native offerings.

Since I feel these comments were somewhat directed at my results and methodology, I would like to reiterate that given the time and weather constraints at the time of testing, I did my best to be as consistent as possible to establish a 'first look' impression of what the camera and lens combinations promised to offer. I'm looking forward to the fine-tuned results from others now that the cameras are shipping...



Nov 18, 2013 at 09:12 PM
RustyBug
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p.1 #5 · p.1 #5 · A7/A7r testing procedure with RF lenses


Emacs wrote:
Wider lenses are tend to use at hyperfocal distances with everything is sharp. So, their infinity performance is not that important as well.


Says who ...

While hyperfocal focusing is a technique that is commonly associated with WA/UWA as it renders greater dof than with longer counterparts ... it in no way negates the significance of using WA/UWA at the actual infinity (near infinity/distant) end of the focal spectrum. If the primary subject matter is at greater distances, the use of hyperfocal focusing technique is somewhat less than ideal or at least less than necessary.

Ironically, the use of hyperfocal technique also warrants stopping down more for a greater utility of increased dof. The smaller focal length of WA/UWA means that the physical aperture is also going to be even smaller than a longer lens counterpart and thus stopping down more for hyperfocal dof warrants an increase in diffraction. For optimal sharpness at distances, stopping down to generate hyperfocal dof technique is not exactly what I consider ideal for sharpness, but a technique for modest compromise in exchange for the dof increase. Effective strategy/technique for some images, not so much for others.

Not all wide shooters use hyperfocal technique only. Accordingly, testing at infinity/distant is just as valid as testing @ mfd or mid-range distances.

My .02



Nov 18, 2013 at 09:49 PM
LightShow
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p.1 #6 · p.1 #6 · A7/A7r testing procedure with RF lenses


michaelwatkins wrote:
A good number of the wide angle lenses tested are symmetrical designs without floating elements; in these, the rear lens element moves farther away from the sensor as focus approaches maximum (infinity) distance.

Hi Michael, you may want to double check that. as I'm quite sure that infinity will have the lens at it's closest position.



Nov 19, 2013 at 12:37 AM
michaelwatkins
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p.1 #7 · p.1 #7 · A7/A7r testing procedure with RF lenses


LightShow wrote:
Hi Michael, you may want to double check that. as I'm quite sure that infinity will have the lens at it's closest position.


Ooops, reverse all that, of course. Fingers typing while brain disconnected.





Nov 19, 2013 at 12:39 AM
michaelwatkins
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p.1 #8 · p.1 #8 · A7/A7r testing procedure with RF lenses


rscheffler wrote:
Since I feel these comments were somewhat directed at my results and methodology, I would like to reiterate that given the time and weather constraints at the time of testing, I did my best to be as consistent as possible to establish a 'first look' impression of what the camera and lens combinations promised to offer. I'm looking forward to the fine-tuned results from others now that the cameras are shipping...


I'd like to thank you Ron, again, for taking the time to shoot, organize, and publish that series and also the follow up with your M9 in comparison. I found the ability to look at the three different views very helpful, particularly since the closer in shots put the at times disappointing infinity performances in context ... all is not necessarily bad. I doubt we are going to learn radically new truths now that units are shipping.





Nov 19, 2013 at 01:34 AM
Olaf G
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p.1 #9 · p.1 #9 · A7/A7r testing procedure with RF lenses


Re #1: set the lens to infinity and focus with a helical mount.
That should solve the FLE problem (only for infinity shots, of course).



Nov 19, 2013 at 01:59 AM





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