Friday, July 28, 2017

Apple’s Photos App and Lens Correction

Kirk McElhearn:

If you shoot RAW files, many apps that process these files can also apply lens correction, using metadata stored with the files, to create better images. In some cases, this can even be using a huge database of information about lenses and cameras.

It’s interesting to know that Apple’s Photos app also applies lens correction, yet doesn’t tell you anything about it. This lens correction is not only applied in the Photos app, but also within macOS; if you have a RAW file and view it using Quick Look (select the file and press the space bar), lens correction is applied.


Here is a good explanation of these types of distortion, with a number of images showing how each one presents in photos.

Update (2017-07-31): Nick Heer:

For what it’s worth, I’ve found that the automatic preprocessing done in Photos is less visually pleasing than that in Lightroom.

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Worth pointing out that digital lens correction is part of the Micro Four Thirds specification (this is the camera type used in Kirk's example) - almost all m4/3 RAW converters will do this. It's critically important in m43, as Olympus/Panasonic lenses rarely bother using expensive optical techniques in the lens to fix barrel/pin cushion distortions, as they know this can be fixed using lens correction software. This is largely because M43 lenses are digital only - there is no way to mount them on a film body, so no need to really worry about these optical distortions in the same way Nikon or Canon engineers have to do.

All M43 cameras apply the distortion correction in realtime to the viewfinder and live view displays too. Some M43 lenses, even high end ones, produce truly terrible results without this correction.

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