Lens Distortion Correction and DNG files

[DavidFriedman]

From Peter's latest blog entry:

"...new functionality has been added to the DNG specification (and to the latest version of Camera Raw) that can do new tricks to the pictures.  For instance, there is now a way for Adobe (and others) to remove lens distortion from the image.  Since this is a new function, it’s necessary to make a new version of the spec that details how to save and apply the instructions."

Is this simply in the specification for future use, or is there software that actually does this now and saves the adjustment data in DNG files? Is this a soft announcement/confirmation of a feature for Lightroom 3?

David

[peterkrogh]

David,
It's not a Lightroom 3 announcement, and I still don't have clarification as to which cameras and features are included here.

One thing I can talk about is the use of Opcodes in the DNG spec and lens distortion.  The Opcodes that are now supported are basically chunks of code from manufacturers.  One of these is  from Panasonic/Leica for the camera LX3. There is a lot of lens correction that is done to fix barrel distortion. Part of the condition set by the manufacturer to use the Opcodes is that the files are never displayed *without* the lens correction.

The new DNG spec allows for this, since it incorporates the Opcode in the decoding of the LX3 file. The problem is that older DNG software does not know what to do with the Opcode, so saving the DNG as a regular DNG would violate the agreement with Panasonic. What backward compatibility does, in this case, is to linearize the DNG, with the lens correction built into the source image data included in the DNG.  Now older software will only see the image with correction applied.

Unfortunately, this also means that some of the rawness is gone from the file.

Does that help to clear it up?

You can make any guesses you wish about future features of ACR.
Peter

[DavidFriedman]

Thanks for the explanation.

David

[WaltSorensen]

wow, scary thought that camera manufactures are pulling some of the rawness from raw files pushing only automatic lens corrections.

makes you wonder if we'll see this translate to lens manufactures requiring lens corrections on all images shot with their lenses. Will we see less expensive, lower quality lenses with mandatory lens corrections flood the market?

~Walt

[peterkrogh]

>makes you wonder if we'll see this translate to lens manufactures requiring lens corrections on all images shot with their lenses

No, not something to worry about.

And the restrictions by camera makers on use of the correction only applies if the corrections are done with software they make available by SDK.  So Adobe could make its own geometrical correction algorithms, and would not to have to abide by any manufacturer's wishes about how the image must be displayed.  The camera manufacturer only has leverage to demand this if it attaches that demand as a condition of using code it also distributes.

Make you feel better?
Peter

[WaltSorensen]

It does make me feel better. I would guess that forced lens corrections will mostly apply to some point and shoot digital cameras.

overall I think this announcment is a big step in the right direction towards the much requested Lens correction feature being added to ACR and LR