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Author Topic: New Leica Summilux-M 35mm ASPH  (Read 4596 times)

Nemo

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New Leica Summilux-M 35mm ASPH
« on: April 23, 2010, 04:05:46 am »

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Rob C

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New Leica Summilux-M 35mm ASPH
« Reply #1 on: April 23, 2010, 08:56:43 am »

I don't know if the link comes up in Spanish for other viewers, but anyway, it was a bit of an eye-opener to discover that Leica M lenses were know to demonstrate focus shift which had to be compensated for by guesstimation;  I had always imagined them to be better controlled, particularly since the range of different focal lengths is so much more limited than for slr systems.

Would still love an M9, though, if anybody feels stupidly generous.

Rob C

250swb

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New Leica Summilux-M 35mm ASPH
« Reply #2 on: April 23, 2010, 12:41:15 pm »

Rob, I can't read Spanish, so I don't know what the article says, but using the word 'lenses' sort of implies focus shift is common amongst all Leica lenses, which it isn't. Thats why its such a big deal a new version is being released that has solved the design issues. Out of the rest of the range of lenses I don't think you'd find another that has the problem.

Steve

fdisilvestro

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New Leica Summilux-M 35mm ASPH
« Reply #3 on: April 23, 2010, 01:07:55 pm »

According to the article, it is not confirmed yet. Anyway, the improvements should be the use of floating element or elements, and an improved coating to reduce possible reflections from the sensor.
From the article it seems that the "focus shift" was specific to the previous version of this lens and not a widespread problem in Leica lenses

Nemo

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New Leica Summilux-M 35mm ASPH
« Reply #4 on: April 23, 2010, 02:41:13 pm »

Quote from: Rob C
I don't know if the link comes up in Spanish for other viewers, but anyway, it was a bit of an eye-opener to discover that Leica M lenses were know to demonstrate focus shift which had to be compensated for by guesstimation;  I had always imagined them to be better controlled, particularly since the range of different focal lengths is so much more limited than for slr systems.

Would still love an M9, though, if anybody feels stupidly generous.

Rob C

Rob,

it is in Spanish just because it's the only on-line source at this moment.

The current 35mm Summilux 35mm ASPH has strong focus shift, and you are right: I also expected those dangerous aberrations to be better controlled. It is common problem in old designs for fast lenses (the previous Noctilux also had focus shift problems), specially when used on digital sensors. The focus has to be guesstimated and it is a pain in the ass. This lens costs 3.300 euros (taxes included), this is, more than $4,000.

Digital cameras made the focus shift problem (uncorrected spherical aberration) worse because:

1) we magnify the images much more than in the film days for focus inspection.

2) filters on the sensor may introduce additional spherical aberration and other problems (chromatic aberrations, etc.)

3) film has more thickness than the photosensitive surface of sensors

The new design seems to be based on the previous one but with several improvements: the floating element and new optical formula correct the focus shift problem to tolerable (invisible) limits; improved coatings will reduce flare; and a smaller sun hood. The price will be more than $4,500.

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Rob C

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New Leica Summilux-M 35mm ASPH
« Reply #5 on: April 24, 2010, 04:32:54 am »

Re-reading the artiocle, the two writers above who commented on the focus-shift problem being particular to one focal length and not all of them are probably quite right - I took the 'floating element' application introduced to most new lenses (post Photokina) within the family to indicate it was being employed as a solution to the problem in all the lenses - maybe not! I certainly hope it didn't exist in them all! Funny thing: though a well-known phenomenon, I can't remember ever coming across it in practice with other systems (I never owned Leicas), although as I seldom stopped down that much beyond, say, f8 or f11 on any lens, maybe I just didn't work within the range where it might show.

Actually, floating elements are supposed to be there to improve performace at all focussing distances which isn't the same thing as being a compensation for focus shift; I remember when Nikon first introduced it into some wides to make them perform better close up.

Oh well, just another throw of the cards in the biggest poker game in town.

Rob C
« Last Edit: April 24, 2010, 04:34:33 am by Rob C »
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Nemo

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New Leica Summilux-M 35mm ASPH
« Reply #6 on: April 27, 2010, 08:36:28 am »

Quote from: Rob C
Re-reading the artiocle, the two writers above who commented on the focus-shift problem being particular to one focal length and not all of them are probably quite right - I took the 'floating element' application introduced to most new lenses (post Photokina) within the family to indicate it was being employed as a solution to the problem in all the lenses - maybe not! I certainly hope it didn't exist in them all! Funny thing: though a well-known phenomenon, I can't remember ever coming across it in practice with other systems (I never owned Leicas), although as I seldom stopped down that much beyond, say, f8 or f11 on any lens, maybe I just didn't work within the range where it might show.

Actually, floating elements are supposed to be there to improve performace at all focussing distances which isn't the same thing as being a compensation for focus shift; I remember when Nikon first introduced it into some wides to make them perform better close up.

Oh well, just another throw of the cards in the biggest poker game in town.

Rob C

Uncorrected spherical aberration explains focus shift. Spherical aberration depends on aperture (in a exponential cubic manner!), so super fast lenses tend to have more potential focus shift problems. Leica employs floating elements in fast lenses. Lenses with moderate maximum aperture values may control focus shift without special measures.
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