Re: 35mm lenses compared?(tech/optics)

[Erwin Puts <imxputs@knoware.nl>]

Well Andrew, this will be a long answer to a complicated problem.
First of all: why the change from two to one aspheric lens. Any aspheric 
introduces two problems and splves a number of other ones. While 
correcting some aberrations (Spherical aberration in particular and also 
com.(the recent article about the 35mm Asperics erroneously only mentions 
coma) it generates other faults. These however are quite difficult to 
correct. The more aspherisc the more problems. Aspherics need very small 
tolerances during the production stage. So more aspherics mean more 
control at the production. 
So it is quite sensible to try to reduce the number of aspherics.  From 
the optical and production view the first version is more 'difficilt'than 
the current one. 
Your kind of testing must be quite inconclusive. Colour neg material is 
totally unsuitable for lens testing (with the exception of the Ektar 25, 
BUT then a high performance enlarger lens is imperative)
Your 4x6 prints are too small to see the details, even with a magnifier. 
And what you see is the result of the enlarger lens of the lab, And these 
are notoriously off margin quite often. 
And hand held shots can be misleading. See the two pictures in the 
Viewfinder article referred to. Both pictures show elongated light 
sources all over the field. From center to corner. The authors attribute 
it to coma. BUT: coma is an off axis aberration and is only seen in out 
of center areas. Therefore their 'coma' is presumably shaking of the 
camera while shooting handheld. 
The remark in that article that at f/5,6 both aspherics work fine is true 
but totally uninformative. Every lens in the Leica stable, gives very 
good to suberb results at f/5,6. The critical opening would be f/2,8 or 
f/2,0. That separates the good from the bad. 
Now to the performance of the 35mm ASPH. At 1,4 you are in Nirwana land: 
the lens then exhibits a high contrast, very fine detailed image with no 
traces of flare and extremely good suppression of halo around light 
sources. This performance is a quantum leap above the old Summilux 
1,4/35. At f/2.0 the performance of the ASPH is slightly better than at 
1,4. In comparison the Summicron-M 35mm ( 7 element version) at f/2,0 is 
the equal of the f/2,0 performance of the ASPH. From then on both lenses 
are the same performance wise. 
So if the maximum aperture is not absolutely needed the current Summicron 
35mm is certainly the equal of the ASPH at apertures from 2,0. Remember: 
apherics are needed to enhance performance in situations where high 
apertures and/or large fields of view must be covered. 
I really am eager to see what the announced 35mm Summicron ASPH will do. 
Erwin Puts
>All in all, the second version of the 35mm f1.4 aspheric won't get you to 
>photographic Nirvana. Consequently, setting the steep price of the 35 asph 
>aside, I and perhaps other LUGgers are currently undecided between the f1.4 
>asph,f2 Summicron or the forthcoming f2 Summicron asph(if very low light 
>performance is not a top priority). Mr. Puts and other experts can you help?
>
>
>                Andrew Jordan
>                Clark,NJ 
>