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"Aperture chameleons"
Old 07-07-2011   #1
Robin Harrison
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"Aperture chameleons"

Perhaps this is the wrong term, but it's the one I'm using. I'm using it to refer to a lens whose character changes over the aperture range in an unpredictable, non-linear, but beneficial fashion.

A lens is expected to be softer wide open and sharper near an optimum pre-diffraction effect aperture. But what I'm talking about are lenses whose 'character' changes through the aperture range, meaning one might choose to shoot, for example, wide open not for reasons of speed or depth of field, but for reasons of aesthetics of rendering.

Lenses that come to mind in the RF world:
Voigtlander 75mm f1.8
Leica Thambar 90mm f2.2

And one I'd like to suggest:
Leica pre-asph 35mm summilux

Any others? Any from the SLR/MF/LF world?

Just something I was thinking about after looking closely of the rendering on my 35mm pre-asph summilux:
http://www.cronbi.com/2011/07/06/aut...ure-chameleon/
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Old 07-07-2011   #2
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I think I get it. So, I throw my 35mm Canon Serenar into the mix. It has an irritating flare at some apertures while seems fine at others, I know I could reduce with a lens hood, but I to lazy to make one.

from same roll but different apertures:



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Old 07-07-2011   #3
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Ah yes, the ZM Sonnar, forgot about that one. And I note that in an uncanny piece of timing there's a short article on LL just published about that very lens. The phrase "two lenses in one" is used, which is a good way of describing what I'm talking about.

http://www.luminous-landscape.com/re...nar_50mm.shtml
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Old 07-07-2011   #4
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I believe that any of the Zeiss Sonnars are "two lenses in 1". Lower contrast wide-open, much higher contrast by F4.

The Summarit5cm F1.5 sharpens up dramatically, and Bokeh settles down by F2.8. At F4, hard to tell from a Summicron.

So- Classic Summarit gets my vote.
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Old 07-07-2011   #5
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And of course, the Jupiter-3.

At F1.5, on the M8:



And at F4:

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Old 07-07-2011   #6
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Ah, perfect illustration, Brian. The style of bokeh remains similar to my eyes (style, not force/amount), but it's the tones of the branch and leaves that really show the difference.

I have a Jupiter-3 on my *bay watch list right now. If I win it I think it might replace my CV 50 f1.5. I do like that lens, but it's a tad large and fails to offer much appeal over my Hexanon other than a stop of speed when needed. I think a Jupiter-3/Hexanon pairing has less cross-over than a Nokton/Hexanon pairing.
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Old 07-12-2011   #7
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Quote:
Originally Posted by Robin Harrison View Post
... refer to a lens whose character changes over the aperture range in an unpredictable, non-linear, but beneficial fashion.
Such a lens doesn't exist. Sure, there are lenses which change their character with aperture—but never in an unpredictable fashion. It's always more aberrations at wide apertures and less at smaller apertures, as simple as that. Of course, for any given lens, the particular pictoral effect of its own aberrations are unpredictable until you try it out ... you need to know your lens. From then on it will be predictable for that lens—at the same aperture, you'll get the same effects.


Quote:
Originally Posted by Robin Harrison View Post
A lens is expected to be softer wide open and sharper near an optimum pre-diffraction-effect aperture. But what I'm talking about are lenses whose 'character' changes through the aperture range ...
There is no 'but'. That's exactly what's happening: softer wide open and sharper when stopped down. Only the kind of softness will vary between lenses. Some are simply not sharp (less 'character'), others add all kinds of funny artifacts to the pictures ... mostly flares, 'glow', field curvature, and/or swirly bokeh (more 'character'). In this context, 'character' basically is just a friendly euphemism for obvious artifact created from aberration. Sometimes it adds to the picture, sometimes not.

In some lenses, the 'aperture chameleon' effect is just a side effect of the lens designer being unable to create a better lens. In others, it's built in on purpose ... the Rodenstock Imagon, the Leitz Thambar 90 mm 1:2.2, the Zeiss C-Sonnar T* 50 mm 1:1.5 ZM, or the Minolta MC Rokkor 85 mm 1:1.7 come to mind.


Quote:
Originally Posted by charjohncarter View Post
So, I throw my Canon Serenar 35 mm into the mix. It has an irritating flare at some apertures while seems fine at others, I know I could reduce with a lens hood, but I'm too lazy to make one.

From same roll but different apertures ...
The reason for the flares being different is not different apertures but different lighting conditions. More back-light, more brightness, and more contrast will result in more flare at a given aperture. On the other hand, for a given subject in given light, flare will be stronger the wider the aperture is.

So there are two parameters affecting the result, but you are falsely attributing it to just one.
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Old 07-12-2011   #8
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Canon 50mm f1.2L for dslr.

Wide open has a really specific 'look' which I've never seen from another lens, and stopped down it just becomes a normal 50.
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Old 07-12-2011   #9
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Noctilux 50/1.0 (the real one ). At f/1.0 it renders like only the Noctilux can and stopped down to f/5.6 or f/8.0 it is similar to a Summicron.
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Old 07-12-2011   #10
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I concur with ka7197 that in the end, what you call "chameleon" is just the sum of the lens' inherent optical shortcomings being more visible at one aperture than at another. Still, it is true that some lenses gain from their faults, while others (the Noktor 50/0.95 comes to mind) are simply unusable.

An example for a lens with loads of character would be the Cosmicar/Pentax 25mm f/1.4 TV lens in C-mount, which I am using on an Olympus E-P1. Wide open, it provides low contrast, crazy swirly bokeh, soft rendering and great possibilities of subject separation with its .3 meters minimum focusing distance. Stopped down to, say, f/2.8 or f/4, it sharpens up considerably and gets a lot more contrasty. While I prefer shooting wide open (for its dreamy rendering obviously), sometimes stopping it down will give the images an even more surreal look: sharp and contrasty in the center, with blurry edges and strong vignetting due to its image circle being smaller than the Micro Four Thirds sensor format.
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Old 07-18-2011   #11
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Has the Nikkor-S.C 1.4 5cm been mentioned yet?

@f1.4 it reminds me of the defects, a pre ASPH 35 Lux does with specular highlights (flaring them out wildly), but it can be a razor blade stopped down to f4 or so.

Stopping it down just a bit from wide open entirely tames the strange flaring and coma, which is impressive.

I treat it as a less contrasty, nice tone and background 50/2 with the special effect of 1.4, when wanted.
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Old 07-18-2011   #12
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Zuiko 85/2, but I think it was designed to be different 2 lenses..
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Old 07-18-2011   #13
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My pet theory about these surprises is that, dismissing the flare and spherical aberration, they are more likely to happen with lenses that vignette heavily at full aperture. It's a fact that the placement of aperture influences the bokeh but wherever it is, when you open it up you are gradually giving its function away to the edges of the first lens and the rearmost lens. The aperture of a Jupiter-3, at f/1.5, even slightly off axis, consists of two arcs at the extreme edges of the lens, while at f/8 it's a nice round hole in the center. No wonder the bokeh is very different, too.

Last edited by t6un : 07-18-2011 at 06:19.
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Old 07-18-2011   #14
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Definitely the Summitar as well...
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Old 07-24-2011   #15
Brian Sweeney
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The 1955 KMZ J-3 at F4, on the M8 at ISO 160.



The J-3 is a "different lens" in terms of color saturation and sharpness at F4.
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Old 07-24-2011   #16
Doug
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Not in the "RF world" here... But as has been alluded to, some makers including Minolta and Pentax have made "soft" lenses for special purposes, deliberately soft and dreamy wide open, gradually sharpening up as it's stopped down, so the user can control the degree of softness.

I have the 120mm f/3.5 SMC Pentax-67 Soft, and this came to mind with the OP. It has a 4-element 3-group construction. With some focus shift, it should be focused at the taking aperture. From about f/8 and smaller apertures it's reached a "normal" level of sharpness, but retains a gentle bokeh.

Pentax also made a similar lens for 35mm SLRs in 85mm focal length.
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Old 08-02-2011   #17
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I just picked a Nikkor 135/2 DC lens with the "defocus control", which shifts optical elements, to achieve a unique control about back and foreground rendering.
The lens has completely different renderings from modern, crisp, sharp and contrasty with neutral setting to very dreamy, soft looking (but amazingly retaining fine detail).

I love that lens and wish, there would be other focal lengths apart from the rather big and heavy 135/2 and 105/2 - a 50mm and a 90mm superfast RF lens in LTM mount and "defocus control" would be dream (droooooool)!
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Old 08-25-2011   #18
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The legendary (?) Leitz Summar goes from smeary and veiled at f/2 to be competitive - virtually indistinguishable, in fact - with a Summicron DR by f/4, based on my tests. Basically the glasses and coatings weren't really available to make a good f/2 lens in the 1930s.

The Summar does have much better bokeh than the 'cron; the sharpest lenses rarely have the best bokeh.
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