Luminous Landscape Forum

Raw & Post Processing, Printing => Adobe Camera Raw Q&A => Topic started by: jvora on March 20, 2011, 12:55:56 pm

Title: ACR Lens Correction Question
Post by: jvora on March 20, 2011, 12:55:56 pm: Hello :

Wondering if the Lens Correction feature in Adobe Camera Raw is able to correct lens aberrations ( distortion & CA ) at all focal lengths of a lens ?

For example, if one was using the 14-24mm lens and a particular image was shot at an odd 17mm or 17.5m focal length - With the exif data noted, does the software correct the image for that particular focal length or finds the closet "known" focal length ( say 18mm for this example ) and uses this data for correction ?

Any ideas how this works ?

Thanks,

Jai
Title: Re: ACR Lens Correction Question
Post by: Schewe on March 20, 2011, 02:34:15 pm: As long as the lens profile contains multiple focal length samples when the profile was created (and all of Adobe's supplied profiles do) then yes, the corrections will apply to intermediate focal lengths of a zoom. The more samples the better...and in the event of an interim focal length that doesn't exactly match the length in the original profile, then the settings are interpolated.
Title: Re: ACR Lens Correction Question
Post by: jvora on March 20, 2011, 03:56:25 pm: Thanks for the confirmation, Jeff - Good to know !

As long as the lens profile contains multiple focal length samples when the profile was created (and all of Adobe's supplied profiles do) then yes, the corrections will apply to intermediate focal lengths of a zoom. The more samples the better...and in the event of an interim focal length that doesn't exactly match the length in the original profile, then the settings are interpolated.
Title: Re: ACR Lens Correction Question
Post by: ternst on March 20, 2011, 07:13:25 pm: Hey Jeff, any chance that ACR/LR will ever be able to do LCC corrections? I can't stand c1, but am forced to use it with tech camera files. I miss ACR!
Title: Re: ACR Lens Correction Question
Post by: Schewe on March 20, 2011, 07:39:46 pm: Quote from: ternst on March 20, 2011, 07:13:25 pm
Hey Jeff, any chance that ACR/LR will ever be able to do LCC corrections?

Don't know...it's an issue that the engineers know about. It's less of an issue with DSLR captures than MFDBs so it's kinda an edge case.
Title: Re: ACR Lens Correction Question
Post by: madmanchan on April 18, 2011, 06:06:55 pm: We currently don't have a UI workflow built around it, but it is technically supported in ACR/LR today, via the DNG opcode architecture.

(I tested this by writing a tool to perform flat-fielding, i.e., taking a LCC target and removing the color cast and (optionally) light falloff that it captures.)
Title: Re: ACR Lens Correction Question
Post by: ternst on April 18, 2011, 07:18:28 pm: Thanks Eric - is that anything that a mere mortal could do, and if so, how does one go about it? Thanks...
Title: Re: ACR Lens Correction Question
Post by: sandymc on April 19, 2011, 01:04:07 am: Quote from: madmanchan on April 18, 2011, 06:06:55 pm
We currently don't have a UI workflow built around it, but it is technically supported in ACR/LR today, via the DNG opcode architecture.

(I tested this by writing a tool to perform flat-fielding, i.e., taking a LCC target and removing the color cast and (optionally) light falloff that it captures.)

The problem is though, the way ACR/LR works today, you can only embed opcodes in DNG files, not in profiles. If that could be changed, then tools such as e.g., CornerFix, could easily generate profiles, as opposed to having to modify DNGs.......

Sandy
Title: Re: ACR Lens Correction Question
Post by: madmanchan on April 19, 2011, 01:13:10 pm: Correct; that's what I meant when I said it was a workflow issue. The current lens profile model is not great for this type of correction, because this type of correction can be rather dependent on the illumination (hence the need to capture the target in the field, instead of in the lab).