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Archive 2013 · Zeiss Distagon 55mm 1.4 Defect

  
 
Toothwalker
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p.3 #1 · p.3 #1 · Zeiss Distagon 55mm 1.4 Defect


AhamB wrote:
Actually, Erwin Puts was talking specifically about the correction of the Apo-Summicron for 435nm blue, which is identical to the Distagon in the diagram he published. http://www.imx.nl/photo/leica/apo-summicron-m-250-mm-asph.html

So redisburning took Puts' sentence "As a comparison, note that the new Distagon is equally well corrected." out of context.


Reading the article again, I think that you are right.

It is funny though that Erwin does not mention the overall better correction of the Distagon.






Aug 02, 2013 at 02:30 PM
JohnJ
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p.3 #2 · p.3 #2 · Zeiss Distagon 55mm 1.4 Defect


Toothwalker wrote:
I would extend this specification as follows "corrected for SA in two points (wavelengths of light) and three zero-crossings in the LoCA line within in the visible part of the spectrum.

That is what I had in mind with the strict definition, and my answer to JohnJ as to what the ASCR50 is not.

I agree of course that compliance with the strict definition of apochromatic does not imply superior image quality, and that the characteristics of the secondary spectrum are more important. It is new to me that the letter sequence APO could mean something different than apochromatic. Leica uses
...Show more

Thanks to both. I'm curious about this 'strict definition' for apo. Where does come from?



Aug 02, 2013 at 06:09 PM
MaxBerlin
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p.3 #3 · p.3 #3 · Zeiss Distagon 55mm 1.4 Defect


I think the term APO is loosely used by many. It implies a better correction for ACA and LCA. I can only speak for the Zeiss 135 APO which seems to have for the most part limited CA to where it leaves no artifacts when it can be forced to occur by shooting very high contrast situations at wide open. From other places I've read, Leica and Sigma and others APO designated lenses are less capable of this. The tradeoff is this 'replication', double line, or nisen bokeh. I have seen others comment on seeing it in some 135 images.

There is some in the left side of this frame but those are twigs in the foreground so I'm not sure it's exactly the same issue.

http://www.flickr.com/photos/zeissgeist/9258420220/in/set-72157634501030325

With a distant background the bokeh with the 135 is among the best I've seen.


Cropped Goose by Zeissgeist

Some say the Zeiss 25mm should be designated an APO but I didn't think much of it or the Zeiss 100 Makro. The 135 is amazing.



Aug 02, 2013 at 06:51 PM
Toothwalker
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p.3 #4 · p.3 #4 · Zeiss Distagon 55mm 1.4 Defect


JohnJ wrote:
Thanks to both. I'm curious about this 'strict definition' for apo. Where does come from?


The original meaning of apochromatic goes back to the microscope lens design of Ernst Abbe. Apo comes from Greek and means something like "free from". Apochromatic = free from chromatic aberration.



Aug 03, 2013 at 07:24 AM
JohnJ
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p.3 #5 · p.3 #5 · Zeiss Distagon 55mm 1.4 Defect


Toothwalker wrote:
The original meaning of apochromatic goes back to the microscope lens design of Ernst Abbe. Apo comes from Greek and means something like "free from". Apochromatic = free from chromatic aberration.


Thanks but that wasn't what I meant. I was curios about the specific definition you and Suede referred to which went further than the typical definition for apo:

theSuede wrote:
...The original specification for apochromatic is "corrected for SA in two points (wavelengths of light) and has three zero-crossings in the LoCA line".....


and

Toothwalker wrote:
...I would extend this specification as follows "corrected for SA in two points (wavelengths of light) and three zero-crossings in the LoCA line within in the visible part of the spectrum.
...


TBH, this is so off topic, it really doesn't matter.



Aug 03, 2013 at 07:49 AM
Toothwalker
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p.3 #6 · p.3 #6 · Zeiss Distagon 55mm 1.4 Defect


JohnJ wrote:
Thanks but that wasn't what I meant. I was curios about the specific definition you and Suede referred to which went further than the typical definition for apo:

and

TBH, this is so off topic, it really doesn't matter.


Well, that specific definition simply refers to the level of correction that Abbe achieved.

What is the "typical definition for apo" that you refer to?




Aug 03, 2013 at 10:37 AM
eosfun
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p.3 #7 · p.3 #7 · Zeiss Distagon 55mm 1.4 Defect


MaxBerlin wrote:
Thanks Edward, yes. I noticed the same with my 135APO in some situations. Is there a name for it?



The name of this optical defect in optical engineering terms is called 'diplopia'.



Aug 03, 2013 at 11:34 AM
wayne seltzer
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p.3 #8 · p.3 #8 · Zeiss Distagon 55mm 1.4 Defect


Not fair to compare the bokeh of a f2 lens to a f1.4 as the faster lens has to be designed to correct more SA.
Whether the lens has slightly undercorrected SA or slightly overcorrected SA or neither over or under corrected has an impact on the bokeh rendering as shown in zeiss white paper on bokeh shows. More contrast and sharper resolution wide open means you are not going the slightly undercorrected SA soft bokeh route like Z* 35/1.4.
I have seen plenty of Z* 100/2 MP shots with nervous /double edging type bokeh. The bokeh rendering of the 100MP is strongly drawn/high contrast style bokeh rather than the 50P which has the less strongly drawn type of bokeh. The leica R 90AA is perfect example of a very sharp lens with nervous bokeh.



Aug 03, 2013 at 12:43 PM
theSuede
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p.3 #9 · p.3 #9 · Zeiss Distagon 55mm 1.4 Defect


The blur in a sharp lens can't be "soft" in all circumstances. One of the requirements on "sharp" is that all light from a point in reality is concentrated to a perfect point on the image plane (sensor) when it is in focus.

If you want this to happen, then you also get "flat" background blur discs. If you have a point light somewhere far back behind focus, it will become a plate with equal brightness all over the surface - if you want a soft blur blob you have to introduce lots and lots of spherical aberration, and then you don't get a sharp image in focus any more.

The flat blur disc is modeled with a box filter. When you have a repetitive pattern in the target, you will at some certain frequency get overlap between two pattern lines. With a box filter, that overlap will be BRIGHTER than the blur disc - since it's flat. A Gaussian blur would gradually fade into each other, and at some blur radius it would just be a flat surface.



So if you want sharp images at large apertures, you get flat blur discs in the background. Lenses like Nikon's 105 and 135F2.0 DC lenses have adjustable amounts of spherical aberration, that's basically what the "DC" does. The only way to avoid flat blur AND have sharp images at the same time is apodization, like Sony/Minolta's 135STF lenses.



Aug 03, 2013 at 12:51 PM
carlitos
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p.3 #10 · p.3 #10 · Zeiss Distagon 55mm 1.4 Defect


Nice illustration and explanation. Thanks!


Aug 03, 2013 at 03:25 PM
carlitos
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p.3 #11 · p.3 #11 · Zeiss Distagon 55mm 1.4 Defect


To simplify unnecessarily, the upper box blur is the Zeiss ZF 35/2, and the lower Gaussian blur is the Zeiss ZF 35/1.4?


Aug 03, 2013 at 03:28 PM
jcolwell
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p.3 #12 · p.3 #12 · Zeiss Distagon 55mm 1.4 Defect


redisburning wrote
....because I think the future of dSLRs is going to be....


Emacs wrote:
DSLRs have no future. Period.


Wrong thread. Also, wrong conclusion. Period.

Maybe...



Aug 03, 2013 at 08:32 PM
JohnJ
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p.3 #13 · p.3 #13 · Zeiss Distagon 55mm 1.4 Defect


Toothwalker wrote:
Well, that specific definition simply refers to the level of correction that Abbe achieved.

What is the "typical definition for apo" that you refer to?



In short, that 3 colors are focused at the same point at the focal plane, but with little concern for what happens elsewhere.



Aug 04, 2013 at 10:11 PM
TSY87
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p.3 #14 · p.3 #14 · Zeiss Distagon 55mm 1.4 Defect


loooks good to me... i for one, cannot wait to get my hands on this lens... the 135/2 apo has been nothing but a pleasure.. i am very confident that the 55 will also deliver.

As much as i liked the 100/2 makro... it did not wow me as much as the 135 has...



Aug 05, 2013 at 07:28 AM
tccin3d
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p.3 #15 · p.3 #15 · Zeiss Distagon 55mm 1.4 Defect


All of this is based on pre production model sample image...
One thing is very possible - they will have great 3d separation and pop. Better build quality. 'Great' price tag



Sep 09, 2013 at 03:27 PM
Krosavcheg
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p.3 #16 · p.3 #16 · Zeiss Distagon 55mm 1.4 Defect


edwardkaraa wrote:
I'm not very familiar with Japanese language, but I believe "ni" means two or double. I don't know what "sen" means, but in my aikido background we use it often to describe defense strategies, as in "go no sen" and "sen no sen".


depending on the kanji it might mean "line". So nisen could be "two lines" or "two thousand"...take a pick..



Sep 09, 2013 at 08:49 PM
RustyBug
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p.3 #17 · p.3 #17 · Zeiss Distagon 55mm 1.4 Defect


Optics are always a series of compromises. Even in a "no compromise" design. There are plenty of lenses that exhibit great sharpness with nervous bokeh. The distances for which "no compromise" were optimized for may not be capable of being optimized the same for mfd as infinity ... i.e. always compromises.

Imo, it is unreasonable to actually expect any lens to be perfect in every situation. A great lens is well corrected for a vast majority of the inherent issues with optics, but I don't know of too many lenses that could qualify as being perfectly corrected for all optical aberrations, under all situations, at all distances. As to the image shown ... that seems to be a small amount of compromise, rather than what I would call a defect.

Defect seems to infer that the lens should be perfect. It may indeed be the very best 55/1.4 on the planet, but that doesn't mean that it is in fact perfect. Imo, every lens has its tradeoff(s)/poison(s) ... you just pick how much (and they can get pretty small) of which ones (and few) you are willing to tolerate in your design/application.

Like Joakim points out, some things just can't be both ways simultaneously, so a compromise is a often times a necessity. Hence, "no compromise" is an excellent marketing slogan, but in optics, it is always a series of compromises somewhere ... to some degree of refinement. Reminds me of knife making @ holds an edge longer = harder to sharpen, carbon content (iirc) = brittle vs. sharp so you have to decide how you want to design the tradeoffs.

Imo, expecting anything less is delusional.



Sep 09, 2013 at 10:46 PM
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