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Leica T performs digital lens correction , a claim by dpreview.com


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I'm a little surprised that people are very forgiving to Leica for this revelation.

 

The reason that many people ponied up to buy Leica lenses is that the quality is top notch, supposedly. Usually this means that the lens has high resolution across the frame, high contrast, and well corrected, ie. low distortion, vignetting, flaring and color aberrations. Well, if the software can do a lot of the correction for the lens, which it seems like Leica is doing (the uncorrected barrel distortion is hideous!), then they have no reasons to charge so much money for the lenses.

 

For me, the T series is really starting to look like a lower quality Leica that the company is trying to tart up to sell for a lot of money.

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Patek Philippe in most of their ads use the slogan You never actually own a Patek Philippe. You merely look after it for the next generation."

 

They also make quartz watches that may not last a generation.

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After some Web search, here is the resolution whom I was referring to. It was Hermann von Helmholtz* (1821-1894) who once stated:

 

"Wenn mir ein Optiker ein Instrument verkaufen wollte, welches solche Fehler (wie das Auge; ergänzt) hätte, so ist es nicht zuviel gesagt, daß ich mich vollkommen berechtigt glauben würde, die härtesten Ausdrücke über die Nachlässigkeit seiner Arbeit zu gebrauchen, und ihm sein Instrument mit Protest zurückzugeben."

(If an optician wanted to sell me an instrument, which had such errors (like the human eye - added by me), it is not too much to say that I would feel perfectly justified to use the harshest expressions of the negligence of his work and return his instrument to him with protest. -- Originally translated by Google, adapted)

 

* German physicist and psychologist in the 19th century

 

Best regards, Gerd

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(I mean, even M lenses are corrected and Leica has never claimed otherwise.)

 

It is not the same.

 

M lenses are corrected for vignetting on digital sensors, and we all know why is it.

 

The problem with the T lenses is different: this is a zoom lens with modest specifications and a very, very high price. Leica is risking their reputation here.

 

The distortion of this lens at the wide end is astounding.

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It is not the same.

 

M lenses are corrected for vignetting on digital sensors, and we all know why is it.

 

The problem with the T lenses is different: this is a zoom lens with modest specifications and a very, very high price. Leica is risking their reputation here.

 

The distortion of this lens at the wide end is astounding.

 

That is correct. Leica M lenses are corrected only for vignetting and color shading.

 

The correction can be turned off by the user.

 

The Leica T lenses are corrected for vignetting, CA, distortion. But the correction can also be turned off by the user.

 

Both M and T corrections are permanently embedded in the file, if selected.

 

So if someone (like myself) who does not like the in-camera corrections and likes to deal with them separately, then it is very easy to turn off the correction.

 

Not defending the camera, I don't like it. Just stating the facts.

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Both M and T corrections are permanently embedded in the file, if selected.

But while the M applies corrections to the raw image data, the T does not. Rather it stores the corrections to be applied by the raw converter as opcodes, i.e. as metadata. As far as I know, the image data are not affected. This has to do with the nature of the corrections: the corrections applied by the M can be quite complex so they are not easily mapped to parametrised opcodes, still there is no problem applying the corrections to the raw data. On the other hand the corrections applied by the T can be expressed as a set of parameters for an opcode, but require demosaiced RGB data to be performed.

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No doubt this looks like another tricky marketing situation if not an engineering one.

 

There is an element of learning from history here. Olympus likewise with their 4/3 DSLR system made similar claims and the lenses where indeed superb. However many of them where as big and heavy as inferior lenses made for systems with the larger sensor format so this played badly with the buying public. The E3/E5 and any of their top and middle range lenses being prime examples. Practicalities of combining digital sensors and highly corrected lenses has resulted in this same physics problem for all manufacturers. I think we can all understand and agree that highly corrected built to last lenses on this sensor would result in substantially bigger and heavier lenses than the mirror less competition the result being a system no one would buy in too.

 

Like all these things the proof in the pudding will be where Leica have struck the balance between software based correction and optical correction at the source, for that we will have to wait and decide based on comparative test results.

 

On this last point I will add my own opinion from my previous experience of 4/3 and m4/3, I bought 6 or 7 different lenses in the end for m4/3 but none of them outshines the one copy of the mid range 14-54 zoom I still have on loan to my brother. I think that says something about the balance between optical correction and software correction as I think the consumer end of mirrorless there has been too much reliance on software correction.

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It is not the same.

 

The distortion of this lens at the wide end is astounding.

 

That is not necessarily a bad thing. Group photos or when there is just a single person near the edge of the frame will look better without correcting the barrel distortion.

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That is not necessarily a bad thing. Group photos or when there is just a single person near the edge of the frame will look better without correcting the barrel distortion.

 

so it is a feature, not a bug?

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But while the M applies corrections to the raw image data, the T does not. Rather it stores the corrections to be applied by the raw converter as opcodes, i.e. as metadata. As far as I know, the image data are not affected. This has to do with the nature of the corrections: the corrections applied by the M can be quite complex so they are not easily mapped to parametrised opcodes, still there is no problem applying the corrections to the raw data. On the other hand the corrections applied by the T can be expressed as a set of parameters for an opcode, but require demosaiced RGB data to be performed.

 

Which means there is an option to use an uncorrected image in postprocessing?

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so it is a feature, not a bug?

 

Yeah. Unless you are shooting architecture or repro, distortion correction may detract, not enhance the image. DXO Optics has ways to add distortion back into shots that is particularly beneficial to some kinds of photos of people when using wide angle lenses.

 

The real issue is if either the corrected or uncorrected result is only a little better than the 16-50 on a Nex 6, then why spend 8 times as much on the T?

 

http:// http://www.dxo.com/intl/photography/dxo-optics-pro/features/optical-corrections/volume-anamorphosis

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This is not something I'm familiar with so would you very kindly show an example of this distortion please, Reuben?

 

Pete.

 

Its on DPReview Pete - Leica T (Typ 701) First Impressions Review: Digital Photography Review

 

Interesting apart from the extreme distortion is how much image area is lost in the corrected version - so at 18mm what are you actually getting? 24mm?

 

How does the I corrected image compare to say a 28mm M lens?

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This is not something I'm familiar with so would you very kindly show an example of this distortion please, Reuben?

 

Pete.

 

Here it is...

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Yeah. Unless you are shooting architecture or repro, distortion correction may detract, not enhance the image. DXO Optics has ways to add distortion back into shots that is particularly beneficial to some kinds of photos of people when using wide angle lenses.

 

The real issue is if either the corrected or uncorrected result is only a little better than the 16-50 on a Nex 6, then why spend 8 times as much on the T?

 

http:// Volume anamorphosis | www.dxo.com

 

Indeed full frame fish eyes are the best wides to shoot people, because there is no rectilinear stretching in the borders/corners, as long as there are no straight architechtural elements in the frame.

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Its on DPReview Pete - Leica T (Typ 701) First Impressions Review: Digital Photography Review

 

Interesting apart from the extreme distortion is how much image area is lost in the corrected version - so at 18mm what are you actually getting? 24mm?

 

How does the I corrected image compare to say a 28mm M lens?

 

I guess it would be interesting to know (from Leica maybe) if the 18mm FL is calculated before or after the correction. Maybe it is actually a 16mm before :)

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Which means there is an option to use an uncorrected image in postprocessing?

 

I assumed in my post there must be, and if there isn't, Leica should add it. It doesn't cost them anything. Or you can use a raw converter that doesn't read the code.

 

The Sony A7 gives you the choice to select which corrections you want to apply (vignetting, CA, distortion) per each lens individually.

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I am sure the 18mm designation is before correcting and cropping.

 

BTW, many zoom lenses are not equivalent to a prime in terms of magnification at the long end...except at infinity. When focused closer they give the field of view of a slightly shorter lens.

 

I guess this zoom has comparable trade-offs to other similar compact zooms. I chose the Nex 6 solely because its 16-50 is light and collapses. Yes, when the w/a distortion is corrected maybe it is more like 18mm. It does make for a more compact package. I can accept the resulting consequences and if a larger package is a little better it would not appeal to me for the purposes I use this camera.

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