LWN: Comments on "Working with raw images on Linux"

Working with raw images on Linux

moxfyre — Mon, 10 Dec 2007 18:56:00 +0000

Just another reason to buy Canon. :-)

... Or Pentax, which actually has adopted the Adobe DNG standard raw image format, for its latest K10D digital SLR!

Dave Coffin, author of dcraw, has high regard for DNG as a standard format: interview

12-bit JPEG

roelofs — Wed, 04 Apr 2007 00:37:56 +0000

For people who like to play with HDR techniques there is an additional advantage: the camera typically record 12 to 16 bits of data for each channel - rather more than fits into a JPEG file.

Technically, that's not entirely true: JPEG/JFIF supports a 12-bit-per-sample mode, and libjpeg can even be compiled to support it (albeit as an all-or-nothing option--i.e., if you do that, you don't get 8-bit support anymore, at least not without third-party patches).

That said, I've never heard of a camera that can record 12bps JPEG, so it's sort of academic.

Greg

Many manufacturers obfuscate their RAW data, including Canon.

pizza — Mon, 02 Apr 2007 21:33:03 +0000

To quote Dave Coffin (of dcraw fame)"

A firestorm of controversy recently erupted when Thomas Knoll of Adobe accused Nikon of encrypting the white balance data in the D2X and D2Hs cameras, thus preventing Adobe from fully supporting these cameras.
I cracked this encryption on April 15, and updated dcraw.c and parse.c on April 17. So "dcraw -w" now works correctly with all Nikon cameras.
This is not a new problem. Phase One, Sony, Foveon, and Canon all apply some form of encryption to their RAW files. Dcraw decodes them all -- you can easily find decryption code by searching for the ^ operator.
Compression is not encryption. Phase One and Sony do encryption only. Kodak does compression only. Canon, Nikon, and Foveon compress the image data and encrypt some of the metadata.

Working with raw images on Linux

pointwood — Fri, 30 Mar 2007 15:59:07 +0000

I completely agree and this is probably the only major gripe I have about my Nikon D80. Nikon makes some great cameras, it is sad that they do something like this :(

Dynamic range and file formats

corbet — Fri, 30 Mar 2007 13:06:28 +0000

I think we disagree slightly about what "dynamic range" means. It's not the difference between the upper and lower ends, instead, it's the ratio between the highest value and the smallest possible change you can represent. If you take 12-bit output from your sensor and cram it into an 8-bit file format (compressed or not) you've lost dynamic range.

In other words, the "more data between the top and bottom of the dynamic range" you mention is the dynamic range. It's what lets you record a bit more information about what's in the shadows without overexposing the image as a whole.

Dynamic range and file formats

StuHerbert — Fri, 30 Mar 2007 12:29:08 +0000

Just a quick correction ... the dynamic range of an image is limited by the capabilities of the sensor, first and foremost. It isn't that RAW images have a *higher* dynamic range - the top and bottom of the range isn't different between RAW and JPEG. It's just that, having more bits per channel, RAW images have more data between the top and bottom of the dynamic range than an 8-bit JPEG image can hold.

You need a better sensor to achieve a higher (or, strictly speaking, a *wider*) dynamic range. One such sensor is the specialist sensor used in the Fuji S5 Pro.

Best regards,
Stu

Working with raw images on Linux

vondo — Thu, 29 Mar 2007 20:34:24 +0000

From what I understand in the Nikon situation they are contemplating (or trying) to deny the user access to the white balance data, not the actual sensor data. I guess Nikon could try to argue that those correction curves are their proprietary property.

Just another reason to buy Canon. :-)

dcraw, Raw Therapee

vondo — Thu, 29 Mar 2007 20:26:06 +0000

There is also RawStudio which appears to handle multiple images.

I keep finding myself using the crappy Canon software for windows since it allows me to adjust sharpness, saturation, etc, and work in batches easily. (Pull up 100 images, tweak WB and exposure on a few, and then start a convert.) The user interface of this software leaves much to be desired, though.

I'd love to have a Linux replacement. I'll try these other two soon, but UFRaw just doesn't cut it.

Working with raw images on Linux

leoc — Thu, 29 Mar 2007 20:25:15 +0000

Especially considering that the image file is NOT owned by the company that sold the camera, but by the person taking the picture, so why do they think they have a right to deny the photographer access to the data?

It seems to me that the lack of interest that the general public has shown about the increasing problems around intellectual property has emboldened corporations to push even further into claiming ownership of things that people have usually taken for granted. Sooner or later people will wake up to this, and there will be reckoning.

dcraw, Raw Therapee

maderik — Thu, 29 Mar 2007 16:06:08 +0000

missing feature from dcraw like meta-data decoding and easy thumbnail extraction

Actually dcraw has thumbnail extraction ("-e" option) and support for the most common Exif fields. Another free (as in beer) program based on dcraw that runs under Linux (and Windows) is Raw Therapee.

dcraw is updated frequently (16 times since the beginning of the year). Keeping up with the changes is a major challenge for projects that do not just call the executable.

libopenraw

paravoid — Thu, 29 Mar 2007 15:25:17 +0000

I think libopenraw[1] is worth mentioning.
"libopenraw is an ongoing project to provide a free software implementation for camera RAW files decoding. One of the main reason is that [WWW]dcraw is not suited for easy integration into applications, and there is a need for an easy to use API to build free software digital image processing application.

It also has the goal to address missing feature from [WWW]dcraw like meta-data decoding and easy thumbnail extraction."

Author's blog[2] seems also interesting.

1: http://libopenraw.freedesktop.org/
2: http://www.figuiere.net/hub/blog/?Libopenraw

Working with raw images on Linux

jospoortvliet — Thu, 29 Mar 2007 11:47:56 +0000

Sad world indeed... It seems, in many cases, there aren't even real good reasons to keep ppl out of these files, except the thought that 'closed is better than open' from the companies...

Anyway, I just read a blog about creating HDR pictures which you might find interesting: http://cyrilleberger.blogspot.com/2007/03/creating-hdr-im...

Working with raw images on Linux

nix — Thu, 29 Mar 2007 09:51:30 +0000

It's a sad, sad world we live in where *reading an image file* could be described as `breaking in' to anything :(

How about a fork in the Grumpy Editor series?

felixfix — Thu, 29 Mar 2007 01:22:43 +0000

And the fork would be, obviously, the Foolish Editor series!