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Author Topic: Leica Q2 clandestine distortion correction  (Read 1635 times)

Guillermo Luijk

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Leica Q2 clandestine distortion correction
« on: August 19, 2022, 05:44:34 am »

The Leica Q2 (FF compact camera with EVF and single lens 28mm Summilux f/1.7):



has been designed with distortion corrections in mind which cannot be disabled by the user. I have no problem with this approach but wanted to do a RAW exercise to find out the distortion correction applied by Adobe Camera RAW. I introduced a regular grid (100px spacing) in the RAW data, reduced exposure by 2EV in the overall image and compared a neutral RAW development (DCRAW) with a corrected one (ACR):

http://guillermoluijk.com/misc/correctionleicaq2.gif

Taking one grid element in the far upper right corner we have the worst case correction scenario:



Just by counting pixels this means a 44% interpolation rate, equivalent to a 120% upscaling in pixelcount:



Regards
« Last Edit: August 19, 2022, 05:54:40 am by Guillermo Luijk »
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fdisilvestro

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Re: Leica Q2 clandestine distortion correction
« Reply #1 on: August 19, 2022, 07:30:31 am »

... has been designed with distortion corrections in mind which cannot be disabled by the user.

This is true if you use ACR/LR. Capture One allows you to disable the correction. (Also opening the image in RawDigger will show you the uncorrected image).

Guillermo Luijk

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Re: Leica Q2 clandestine distortion correction
« Reply #2 on: August 19, 2022, 09:02:55 am »

This is true if you use ACR/LR. Capture One allows you to disable the correction. (Also opening the image in RawDigger will show you the uncorrected image).
I was talking about the maker (Leica), not about the RAW developers. The lens was designed that way, like some others (e.g. Zuiko 12mm f/2),...

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fdisilvestro

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Re: Leica Q2 clandestine distortion correction
« Reply #3 on: August 19, 2022, 05:20:33 pm »

I would say that they chose not to correct the distortions optically (expensive) because it is good enough to do them by software. That applies to a long list of lenses today, especially  wide angles and zooms.

Guillermo Luijk

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Re: Leica Q2 clandestine distortion correction
« Reply #4 on: August 19, 2022, 08:06:23 pm »

I would say that they chose not to correct the distortions optically (expensive) because it is good enough to do them by software. That applies to a long list of lenses today, especially  wide angles and zooms.
But not only expensive in price, also expensive in other regards such as size, CA, volume,... i.e. if you make a perfectly corrected lens you'll loose in other areas. Distortion correction is probably the most sucessful correction performed by software, so this approach of lens design with a fairly high amount of distortion makes a lot of sense in the digital era. This camera costs nearly $6000; I don't think Leica wanted just to save money.

The article: https://www.overfitting.net/2022/08/correccion-de-distorsion-geometrica-en.html

Regards
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