Fred Miranda wrote: chiron wrote: Fred Miranda wrote:
Regarding lateral CA.
When editing Sony FE 24/1.4 GM raw files in Lightroom, lateral chromatic aberration is automatically corrected with a built-in profile even if CA correction is turned off "in-camera" and unchecked in Lightroom. (See Lightroom alert message below)
I don't see any way to turn this off.
I brought a RAW file to Capture One, which does not correct CA automatically and as suspected LaCA is more pronounced. See below:
What is the practical significance of the LaCA, given how effectively it seems to be corrected by software?
Increasingly, software is so much a part of how a lens functions. I would imagine that is going to continue to increase, as with software implementation of bokeh characteristics. And I assume that lens designers might permit flaws that they know will be well-corrected by software in order to achieve useful design characteristics (like large apertures), or they might create designs that tolerate software-correctable flaws in order to reduce other flaws that are not so easily correctable by software.
Is it the case that the software-correction damages the image or the file in a significant way?
The higher the lateral CA, the lower resolution will be towards the corners. In other words, less 'edge' definition. I think the discrepancy between the sag and meridional lines in the MTF graph is a combination of LaCA and astigmatism.
Yes, it can be masked in software but instead of having a visible color aberration, we get a grayish correction patch in its place. Vignetting can also be correctable in software but there is an increased in noise and a dynamic range drop in the area affected.
No free lunch.
With lateral CA sometimes the correction is truly lossless with no grey border and little resolution loss.
Why?
Lateral CA is caused by the magnification being different for different colour channels. Correction works by resizing one or more so that they perfectly align. When it works well there should be no gray border and only the tiny loss of resolution due to
The slight resizing. LoCA correction is different: just looks for edges and desaturates them.
This also means that sometimes, when the MTF shows what looks like astigmatism but is lateral CA, the resolution after good lateral CA correction can be, amazingly: *better* than the published MTF!
Edit: thanks to an alert forumer I corrected LaCA to LoCA in line 7!
Fred Miranda wrote: chiron wrote: Fred Miranda wrote:
Regarding lateral CA.
When editing Sony FE 24/1.4 GM raw files in Lightroom, lateral chromatic aberration is automatically corrected with a built-in profile even if CA correction is turned off "in-camera" and unchecked in Lightroom. (See Lightroom alert message below)
I don't see any way to turn this off.
I brought a RAW file to Capture One, which does not correct CA automatically and as suspected LaCA is more pronounced. See below:
What is the practical significance of the LaCA, given how effectively it seems to be corrected by software?
Increasingly, software is so much a part of how a lens functions. I would imagine that is going to continue to increase, as with software implementation of bokeh characteristics. And I assume that lens designers might permit flaws that they know will be well-corrected by software in order to achieve useful design characteristics (like large apertures), or they might create designs that tolerate software-correctable flaws in order to reduce other flaws that are not so easily correctable by software.
Is it the case that the software-correction damages the image or the file in a significant way?
The higher the lateral CA, the lower resolution will be towards the corners. In other words, less 'edge' definition. I think the discrepancy between the sag and meridional lines in the MTF graph is a combination of LaCA and astigmatism.
Yes, it can be masked in software but instead of having a visible color aberration, we get a grayish correction patch in its place. Vignetting can also be correctable in software but there is an increased in noise and a dynamic range drop in the area affected.
No free lunch.
With lateral CA sometimes the correction is truly lossless with no grey border and little resolution loss.
Why?
Lateral CA is caused by the magnification being different for different colour channels. Correction works by resizing one or more so that they perfectly align. When it works well there should be no gray border and only the tiny loss of resolution due to
The slight resizing. LoCA correction is different: just looks for edges and desaturates them.
This also means that sometimes, when the MTF shows what looks like astigmatism but is lateral CA, the resolution after good lateral CA correction can be, amazingly: *better* than the published MTF!
Edit: thanks to an alert former I corrected LaCA to LoCA in line 7!
Fred Miranda wrote: chiron wrote: Fred Miranda wrote:
Regarding lateral CA.
When editing Sony FE 24/1.4 GM raw files in Lightroom, lateral chromatic aberration is automatically corrected with a built-in profile even if CA correction is turned off "in-camera" and unchecked in Lightroom. (See Lightroom alert message below)
I don't see any way to turn this off.
I brought a RAW file to Capture One, which does not correct CA automatically and as suspected LaCA is more pronounced. See below:
What is the practical significance of the LaCA, given how effectively it seems to be corrected by software?
Increasingly, software is so much a part of how a lens functions. I would imagine that is going to continue to increase, as with software implementation of bokeh characteristics. And I assume that lens designers might permit flaws that they know will be well-corrected by software in order to achieve useful design characteristics (like large apertures), or they might create designs that tolerate software-correctable flaws in order to reduce other flaws that are not so easily correctable by software.
Is it the case that the software-correction damages the image or the file in a significant way?
The higher the lateral CA, the lower resolution will be towards the corners. In other words, less 'edge' definition. I think the discrepancy between the sag and meridional lines in the MTF graph is a combination of LaCA and astigmatism.
Yes, it can be masked in software but instead of having a visible color aberration, we get a grayish correction patch in its place. Vignetting can also be correctable in software but there is an increased in noise and a dynamic range drop in the area affected.
No free lunch.
With lateral CA sometimes the correction is truly lossless with no grey border and little resolution loss.
Why?
Lateral CA is caused by the magnification being different for different colour channels. Correction works by resizing one or more so that they perfectly align. When it works well there should be no gray border and only the tiny loss of resolution due to
The slight resizing. LaCA correction is different: just looks for edges and desaturates them.
This also means that sometimes, when the MTF shows what looks like astigmatism but is lateral CA, the resolution after good lateral CA correction can be, amazingly: *better* than the published MTF!
Nov 02, 2018 at 04:19 PM
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