[Leica] Are Leica lenses muliticoated?

[hoppyman at bigpond.net.au (Geoff Hopkinson)]

Henning I always respect your expertise and experience. I don't understand
how you can achieve outstanding resolution without good contrast, nor
outstanding contrast without much resolution. I was thinking of
micro-contrast especially as part of achieving theoretical high resolution.
'Flare' that I would understand as veiling glare must certainly be a factor
in 'glow'. I would add aberration there. Personally I haven't seen anything
on my M8 that exceeded the sensor's dynamic range when shooting DNG's with
all modern, contrasty Leica lenses. I can make the images clip at both ends
of course in smaller colour spaces on conversion. I don't doubt what you say
there, only that it hasn't been a problem for me with my camera and amateur
use. 


Cheers
Geoff
http://www.pbase.com/hoppyman/e
http://gallery.leica-users.org/v/gh/
Pick up your camera and make the best photo you can.

-----Original Message-----
Sent: Monday, 24 November 2008 14:15
To: Leica Users Group
Subject: RE: [Leica] Are Leica lenses muliticoated?

You need good contrast along with good resolution to achieve 'sharpness',
ie, a perception of 'good resolution'.

You don't need a lot of contrast to achieve outstanding resolution, nor do
you need much resolution to achieve outstanding contrast.

The 'softness' or 'glow' or 'glamour' that is ascribed to older lenses is a
combination of low contrast and flare, both things that can be controlled by
using correct coatings, multi-coatings or whatever for the glass types and
curvatures of lenses. The latter also plays a part.

You can have low contrast without a lot of flare, but it's not easy. 
It's often proposed that to achieve a very high effective dynamic range a
low contrast lens is desirable, but that often leads to flare, which tends
to be localized and cannot be dealt with easily. 
Therefore, a lens that is chosen for its low contrast characteristics like
the DR Summicron often causes problems due to flare. Of course, when the
stars align the results can be outstanding, but a low contrast lens is not a
panacea for dealing with large dynamic ranges.

As I mentioned earlier in this thread, the earliest multi-layer coated lens
I know of is the 35/1.4 Summilux introduced around 1960; I'm sure there were
ealier examples but this lens was one of the very first commercially
produced lenses using this technology. Once designers were able to take
advantage of reducing the reflectance and therefore scatter of specific
spectral bands, it opened up a huge range of possibilities, especially in
marketing :-). Whether one uses 3, 7 or 20 layers is a bit like whether your
razor has 2, 3, or 5 cutting blades. Past a certain point it's mostly
marketing, especially if your lens is for general photographic use under
uncontrolled conditions.

Coatings for controlled conditions can be optimized to a much greater
degree; lenses for reproduction, especially three colour or even more so
monospectral reproduction could have highly optimized coatings that required
only a few layers, with slightly different thicknesses varying from the
center to the edges.

If you know a lens well, you can use it's flare characteristics to your
advantage, in particular to achieve an 'older' look, but if what you're
mainly concerned with is reducing contrast, there are usually other ways of
achieving that that are more controllable.

I've had a lot of different lenses over the last 50 years, and still have
quite a few. Among the latter are still a few low contrast lenses and a
couple that have very specific flare characteristics, but on the whole I
prefer lenses that medium to medium-high in contrast with as little flare as
possible. Those are the easiest to work with. If I wish, I can create most
types of flare after I take the picture. I can't remove it easily if it's in
the negative or digital file if at all.






>Steve you really need good contrast to achieve good resolution, the two 
>go hand in hand. The well recognised smooth look that you are 
>describing may be partly from moderate contrast, but also from the 
>degree of correction present. With more aberration present, the out of 
>focus blurs can retain their general shape and be smoother by being 
>more blurred! That is not meant to be a criticism of valid personal 
>preference. Of course my taste there is probably well established.
>
>Has anyone else noticed that this evolving thread is almost a digest of 
>perennial LUG topics?
>Lens coatings,
>Lens cleaning,
>Artistic vs. technical,
>Favourite lenses
>What great master photographers used etc etc Now I suppose I have 
>introduced the B word.
>
>
>Cheers
>Geoff
>http://www.pbase.com/hoppyman/e
>http://gallery.leica-users.org/v/gh/
>Pick up your camera and make the best photo you can.
>
>-----Original Message-----
>Subject: Re: [Leica] Are Leica lenses muliticoated?
>
>
>this same argument applies to some of the greatest and highest 
>resolution lenses of the past...for example  the Summicron 50/2 
>DR...low contrast combined with very high resolution allows a unique 
>smooth look...and you can always increase the contrast if desired...
>
>I am not sure how the coating impacts, or what the coating is for the DR...
>
>this look and behavior likely accounts for this lens being the desert 
>island favorite of so many individuals...
>
>
>Steve
>
>
>
>
>
>
>_______________________________________________
>Leica Users Group.
>See http://leica-users.org/mailman/listinfo/lug for more information

-- 
    *            Henning J. Wulff
   /|\      Wulff Photography & Design
  /###\   mailto:henningw@archiphoto.com
  |[ ]|     http://www.archiphoto.com

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