DxO Labs suggests shortcomings of Adobe's Lens Profile Creator
Adobe's image processing rival DxO Labs has highlighted potential pitfalls in allowing users to profile their own lenses using Adobe's recently announced Lens Profile Creator utility. The company has expressed concerns about the accuracy and number of measurements taken to achieve an accurate profile. In response, Adobe has explained the reasoning behind encouraging users to profile their own lenses and says it has tried to mitigate the potential errors.
'We do not know how Adobe generates its own profiles, but the documentation and the tools provided by Adobe for users to generate their own profiles raises some issues on distortion and vignetting.' says Cyrille de La Chesnais, Sales and Marketing Director - Photography at DxO Labs. 'Distortion estimation requires a perfectly flat target (or a very precise process),' he explains: 'a 1% target curvature yields strongly visible distortions on a wide angle camera.' Correct illumination is also important, he stresses: 'Light uniformity is key for vignetting estimation: all engineers know the difficulty of achieving less than 10% light non-uniformity using only two light sources, as suggested by Adobe.'
DxO Labs conducts its own tests to create its profiles, he explains: 'DxO profiles (called Lens Modules) are created from shots taken in a very controlled environment with no wall reflections, calibrated lighting equipment and glass targets to ensure flatness.' To check the effect, the company tested the Adobe utility using the provided instructions and concluded that it 'clearly under-corrects distortion and vignetting in some situations.'
In addition to concerns about the dependability of home-testing, he also highlights the amount of work involved in profiling the behavior across its zoom, aperture and focusing range: 'typically for a wide range zoom, we may use dozens of different focal lengths, dozens of focusing distances, dozens of apertures, etc. This generates a lot of configurations to be calibrated and verified. We of course do not know which sampling policy has been used for profiles generated by Adobe but from the documentation, we understand that Adobe recommends users to sample just three focal lengths, three focusing distances and four apertures to generate 'advanced' profiles.'
He also mentions that DxO Lens Modules do more than correcting the geometric distortion, vignetting and chromatic aberration addressed by Adobe, also aiming to resolve volume anamorphosis and uneven sharpness.
Adobe responds that it has designed its system to mitigate the potential errors. It's all about photographer empowerment say Adobe senior product manager Tom Hogarty and the Camera Raw team.
'The photographer can decide the accuracy level of the calibration they want to achieve utilizing the Adobe Lens Profile Creator. By empowering photographers they can put as much or as little into their profile creation as they feel is necessary for their workflow. An advantage of Adobe’s lens calibration setup,' they say: 'is that it does not require a strict studio setup to achieve good results.'
'For vignette estimation, Adobe’s method does not require the calibration target to be uniformly lit, it just requires the lighting to be constant from one shot to the other. The utility applies advanced math to eliminate the uniformity requirement, thus allowing accessibility of the technology to a wider audience, allowing regular photographers to calibrate their own lens with their own camera.
'Photoshop, Lightroom and Camera Raw also have advanced lens profile interpolation and retargeting systems, which enable us to provide high-quality results even with a few samples and map profiles created with a larger sensor to images shot on a smaller sensor.'
Adobe also points put that the its current setup for sharing profiles is based a rating system that enables users to search, preview and download the lens profile that is compatible their target image. Based on the feedback the company will aim to improve the sharing features further.
Commenting on the profiles that are currently being shipped with the software itself Hogarty and the team explain: "the lens profile creation process is taken quite seriously by Adobe and, in the case of Sigma, we were able to work directly with the lens manufacturer with the goal of achieving the highest possible quality in lens characterization."