Thursday, June 21, 2012

Adobe Lens Correction Profiles compared

Adobe Lens Profile Downloader profile info window Version 4.0.9 was released of the raw photo process raw Therapee, which has the ability to use Adobe's Lens Correction Profiles (LCPs). LCPs can correct light falloff (vignetting), lens geometry (distortion) and chromatic aberration. Raw Therapee itself doesn't have any correction profiles built-in, but one can acquire most of the by installing Adobe's Camera Raw with Photoshop or DNG Converter. Not all lenses have correction profiles, for example the Tokina 11-16mm f2.8 lens wasn't included so it had to be downloaded separately using the Lens Profile downloader, a small AIR applet. Funnily though, Samyang's 8mm fisheye lens didn't have a correction profile at all.

Care must be taken when downloading the profiles. Most user-supplied profiles only have vignetting correction measured for only one small aperture. For example profile that has light falloff correction only for aperture f/11 can't be used to remove vignetting at larger apertures. It's a good idea to take a look at the calibrated apertures and focal length before applying or downloading the profile, see the screen capture on the right-hand side of the page for example of a quite thorough profile.

Below is a mouseover image with a lackluster profile that has the light falloff correction only for aperture f/11. Even though there seems to be some extrapolation of vignetting correction values, it is just not enough to rid of all of the vignetting.


Move mouse over the image to see the LCP corrected image, flat field corrected image acts as a reference. Image taken with the Tokina 11-16mm f2.8 lens with wide open aperture and at the lenses widest setting.

Below is another example image pair with a better profile, that corrects most of the vignetting. Do note however, that the corner color shift can't be corrected, hence the greenish cast in the extreme corners.


Move mouse over the image to see the LCP corrected image, flat field corrected image acts as a reference.

For example, there's user submitted profile for the old Nikon 50mm f1.8D AF lens that's been calibrated twice for each aperture at different focusing distances. Focusing distance can affect the vignetting and most probably the distortion of the image. However even that profile can't correct for the hot spot problem the lens has; at smaller apertures (f/5.6 and onwards) a round, brighter area appears in the center of the image. It's cause by the aperture blades reflecting light back from the sensor.

Below is a mouseover image pair, flat field corrected photo is used as a reference.


Move mouse over the image to see the LCP corrected image, flat field corrected image acts as a reference.

Both Sigma and Tamron offer 'official' profiles straight from the manufacturer, Nikon and Canon seem to want to keep the users on their own respective pieces of software.

This post originally appeared on Pallopanoraamablogi as "Adoben korjausprofiilit" at 2012-05-12

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