Archived posting to the Leica Users Group, 2011/06/23
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]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 >