[Leica] Monster High-tech 50mm 1.4 from Sigma and everyone else

[henningw at archiphoto.com (Henning Wulff)]

At 11:30 AM -0500 2/5/09, David Rodgers wrote:
>Marty,
>
>Thanks for your excellent and very informative post. I have a few
>questions that perhaps you, or someone else, can answer. First, how
>important is distortion for photography outside of architecture?
>Secondly, is there much sample variation in modern lenses (my assumption
>would be less than in the past, but sometimes I wonderA)? Finally, are
>lenses today really any better overall than lenses from say 25 years ago
>-- or are they just better in some ways, at the expense of other ways?
>
>I don't shoot any architecture anymore, though at one time I did. I know
>that for me to notice distortion now, a lens has to be pretty bad. I can
>also live with a little barrel or pincushion, because in a critical
>situation I can fix it with software. But the moustache distortion found
>in some multi-asph consumer grade zooms (I haven't seen it in primes,
>but I haven't bought any new primes in a long time) is impossible to
>correct.
>
>DaveR


The importance of distortion is: if it bothers you, it's important.

If the distortion is of the pure barrel type, it's both the least 
objectionable (within reason) and the easiest to correct. Also, it 
some instances it can be helpful. The reason for that is that wide 
angle lenses distort three dimensional objects placed in the corners 
of the field, so that spheres become ellipses. If you have barrel 
distortion, this effect gets reduced. So if your subject has 
significant three-dimensional objects in the corners of the field, 
and no straight lines near the edges, the picture will look less 
'distorted' taken with a lens that exhibits barrel distortion than 
one that has no distortion.

Barrel distortion is also easy to fix in software now, and if left is 
usually less objectionable than pincushion distortion or 'moustache' 
distortion.

Software exists to correct all types of distortion. Panorama tools 
developed by Helmut Dersch allows setting all the parameters to fix 
distortion, although his software was as much a mathematical exercise 
as a practical tool. Others have taken his work and put a more 
pleasant front end on them, such as kekus.com with their LensFix and 
PS plugins on the Mac, and epaperpress has PTlens for Windows.
Moustache distortion is typically found in retrofocus designs, 
whether in zooms or in prime lenses; some of the ugliest is in primes 
that are even marketed to architectural photographers, such as the 
18mm lenses from Nikon (all three versions).

DxO also has good software, but it costs waaaay more and is neither 
as customizable nor available for as many camera/lens combinations. 
It does other things as well, though.

Overall optical quality has definitely increased, with both basic mtf 
improving and even more so, coatings improving. Sample variations are 
also way down, but high volume consumer lenses are still problematic 
in that area, and the higher priced stuff is also worthwhile checking 
because you don't necessarily want the one disaster in 20 or 100 that 
even the best manufacturers produce.

Right now Leica seems very good in all areas of quality; in design, 
materials and general quality control. The prices are not out of line 
because of that; the last 10% of the quality is responsible 90% of 
the price, or something like that. Even so, duds will find their way 
into the hands of buyers.

-- 

    *            Henning J. Wulff
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