Archived posting to the Leica Users Group, 2011/06/23
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Thanks, I couldn't find where I'd gotten them again.
>And there's a good explanation of MTF as a starter here:
>http://www.luminous-landscape.com/tutorials/understanding-series/lens-contrast.shtml
>
>The Zeiss brochures Henning mentioned are:
>http://www.zeiss.de/C12567A8003B8B6F/EmbedTitelIntern/CLN_30_MTF_en/$File/CLN_MTF_Kurven_EN.pdf
>and
>http://www.zeiss.de/C12567A8003B8B6F/EmbedTitelIntern/CLN_31_MTF_en/$File/CLN_MTF_Kurven_2_en.pdf
>
>Marty
>
>On Fri, Jun 24, 2011 at 3:10 AM, Henning Wulff
><henningw at archiphoto.com> wrote:
>> Hi Frank,
>>
>> The MTF curves give some indication of the relative performance, but
>> certainly not all. Zeiss put out a couple of brochures that give a very
>> good
>> general explanation of MTF curves. If you want me to send them to you,
>> send
>> me a note off-list.
>>
>> The MTF curves give an indication of the point transfer function of the
>> lenses, so if the solid lines (for sagittal structures) and dashed lines
>> (tangential structures) overlap, a point light source will be imaged as a
>> slightly diffuse circle. If both lines are at 100%, the point will be
>> imaged
>> as a point. The lower the contrast value (%), the larger the diffuse
>> circle;
>> the more the two lines diverge, the more elongated the now oval diffuse
>> circle becomes. This leads to flare and 'bleeding'.
>>
>> All of this only applies at the plane of focus. Little about the out of
>> focus imaging qualities can be deduced from these graphs. Also, testing
>> protocols can vary quite a bit and still be 'accurate', so graphs from
>> different manufacturers, or even different testers from the same
>> manufacturer can't be compared reasonably.
>>
>> There's a lot more to optics than these graphs can show, so they always
>> have
>> to be taken with a grain (kilo) of salt.
>>
>> The Summilux at f/1.4 has the weakest performance (surprise, surprise!),
>> but
>> by f/2.8 is quite respectable and very close overall to that of the
>> Elmarit
>> ASPH. Especially the larger and medium details are rendered very well
>> across
>> the field, and if anything are rendered a bit better further out in the
>> field by the Summilux than the Elmarit. Extremely fine detail has pretty
>> good resolution but lower contrast than the Elmarit.
>>
>> All the lenses are very good in the central 15mm at all apertures, with
>> very
>> fine detail rendered at high contrast; only the Summilux at the widest
>> apertures falls off a bit here.
>>
>> At f/4 there are actually only two categories in performance: the
>> Super-Elmar and the others. The other three each have their strong points
>> and their weak points (relatively), but the Super-Elmar is best. The
>> Super
>> Elmar has a very slight increase in performance at the edges at f/5.6,
>> but
>> for the most actually loses performance as it is stopped down.
>>
>> So from the graphs the Super-Elmar is definitely the best, but the others
>> are all outstanding lenses. The Summilux, for example, is a fair bit
>> better
>> at f/1.4 than the non-ASPH Elmarit was at f/2.8.
>>
>> The Tri-Elmar is quite interesting in that at f/4 it's performance is
>> quite
>> similar to that of the f/3.4 Super Angulon at f/5.6, except the far
>> corners
>> of the T-E are better than those of the SA. The old f/4 SA was noticeably
>> worse than the f/3.4, and closer to the non-ASPH Elmarit in performance.
>>
>> At present I have a number of 21's; the Summilux, the Elmarit-ASPH, the
>> Tri-Elmar, the f/3.4 SA and the CV f/4. The CV is decent, but lacks the
>> clarity of the Leica lenses and all samples I've tried of the CV have had
>> some decentering, which I've not had with the Leica lenses. The CV is not
>> bad, but it's just not as good. The SA isn't useable on the digital M's,
>> so
>> it's hard for me to really compare it. On B&W film I still like it, but
>> it
>> clearly is not a modern optic. The other three I use pretty much
>> interchangeably. The Summilux has a bit more distortion than the others,
>> and
>> the distortion on the Tri-Elmar is a bit more strongly mustache-shaped,
>> so
>> the Elmarit wins here. At medium apertures they are largely equivalent
>> for
>> practical purposes, and I tend to carry one or the other depending on
>> their
>> other attributes. Since distortion can be corrected in software when
>> necessary, it's not as big a deal anymore as it was in film days, and the
>> other qualities are reasonably given priority.
>>
>>
>>
>>
>>
>>
>> At 7:38 AM -0700 6/22/11, Frank Filippone wrote:
>>>
>>> Henning... you are among the few LUGgites that can read and make sense
>>> of
>>> MTF charts.
>>>
>>> Can you give a quickie review of the MTF charts for the 4 x 21mm lenses?
>>> 21
>>> ASPH Elmarit, WATE, Summilux, and Super Elmar.
>>>
>>> I have always wondered their relative merits....
>>>
>>>
>>>
>>> Frank Filippone
>>> Red735i at earthlink.net
>>>
>>>
>>> From the MTF graphs the new 21 looks as good as anything ever made at
>>> that
>>> focal length, but it's not perfect :-). Still has distortion, the
>>> sagittal
>>> and tangential curves don't cover each other, they're not all above 95
>>> at
>>> 40lp/mm, and there is significant light falloff.
>>> When will they ever make a perfect lens??? :-)
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> Leica Users Group.
>>> See http://leica-users.org/mailman/listinfo/lug for more information
>>
>> --
>>
>> Henning J. Wulff
>> Wulff Photography & Design
>> mailto:henningw at archiphoto.com
>> http://www.archiphoto.com
>>
>> _______________________________________________
>> Leica Users Group.
>> See http://leica-users.org/mailman/listinfo/lug for more information
>>
>
>_______________________________________________
>Leica Users Group.
>See http://leica-users.org/mailman/listinfo/lug for more information
--
Henning J. Wulff
Wulff Photography & Design
mailto:henningw at archiphoto.com
http://www.archiphoto.com