Raw picture format
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The raw picture format is a file format used by some digital cameras to save photos.
While every modern digital camera is able to save photos in the jpeg file format,
many but not all of them are also able to save raw photos.
What is the difference between jpegs and raw images ?
In short, JPEG is a lossy format, RAW is and leads to a lossless format.
When high quality digital photos without the so called JPEG artefacts are needed,
saving raw image files is the solution.
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JPEG photos
JPEG is a lossy format, that means that a part of the original information of the camera is lost.
Moreover, if you enhance your jpegs or manipulate them through a photo software in anyway,
additional information will be lost each time you save the jpeg.
A commonly known problem of jpeg images is the jpeg artefact
-some blurry zones with wrong colored pixels, specially around strong contrast lines-.
This effect will be more visible, the more a jpeg image is compressed.
RAW picture files
The raw picture format contains all the information available at the time the photo was taken.
It can be converted into a lossless image format like tiff or png.
Therefore you need a software.
Converting RAW picture files
At first, the raw picture information is available in every camera.
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When the camera saves jpeg images, it is the software inside the camera that did convert the raw information into a jpeg.
When the camera saves a raw picture, it will be a software on your computer that converts the raw information into a tiff or whatever.
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The biggest difference between camera internal conversion and outside conversion of the raw picture file,
is the fact that the camera internal conversion will be performed without a possible influence of the photographer.
When performing an outside conversion of raw pictures,
you will be able to highly influence the result through the usage of a software of your choice that let you select among several parameters.
Example: Raw pictures that are very near to over-exposure can mostly be recovered if you convert the raw picture yourself.
If converted internally by the camera software and saved as a jpeg,
it will ALWAYS be over-exposed and the data of the over-exposed zone will be definitely lost.
Raw picture conversion software
Since digital camera manufacturers could not yet find a common way to go,
there are presently more than 100 different raw picture file formats around.
A big challenge for software developers who write conversion tools and would like to master ALL RAW picture formats.
Digital camera manufacturers
Each digital camera manufacturer proposes a raw picture conversion software.
Unfortunately, most of them do work the same way the camera internal conversion works:
the user can not influence the result. No settings to choose.
Command line tool
The first camera manufacturer independent raw picture conversion software I did found was Dcraw.
Dcraw
is a command line tool that is able to convert more than 100 different RAW picture formats.
It works on Linux (console), Mac and Windows (DOS box).
You can download the
dcraw source
from the author, David Coffin and compile it yourself on any platform.
You can download a
dcraw MacOS X build
or a
dcraw Windows exe
from the
insflug.org website.
Plugin GUI tools
(graphical user interface tools)
Three plugins for The Gimp, based on dcraw are available.
Rawphoto
is a plugin for the Gimp I did try out and got good results with it.
You can download the Rawphoto source and compile it on Linux.
It should also be possible to compile it on Windows.
Ufraw
is a plugin for the Gimp, but it is also able to run as a stand alone program.
Personally I found it more convenient to use than the one above.
I did specially like the way that it shows over-exposed and under-exposed areas.
With some raw pictures the results looked better with Ufraw while with some others it was with Rawphoto.
You can download the
Ufraw plugin's source code to compile yourself,
you can download packages for Debian, Mandrake, Fedora, NetBSD, Gentop,
and a Windows install file from the same page.
For the later, look far down on the
Ufraw plugin page.
RougePhoto
is also a plugin for the Gimp.
Unfortunately, I could not yet find the time to try it out.
It needs a special version of dcraw to work with.
You can download
RougePhoto's source code and compile it yourself.
Stand-alone GUI tools
Above, we mentioned that Ufraw is also able to run as a stand alone program as opposed to a plugin.
There is another stand alone software I did use a lot these days: S7raw.
S7raw handles only Fujifilm raw picture files, so it is not an universal raw picture converter.
But in my opinion the results with Fujifilm raw pictures are far better than with the Rawphoto and Ufraw plugins above.
Colors are very similar to the jpegs the camera would store.
This was hardly the case with the plugins above.
Settings possibilities are numerous, but very intuitive.
The user interface is well thought-out.
S7raw is a Windows software that works perfectly on Linux through the Wine.
On an AMD 1.6 GHz, 1GB ram with SuSE 9.3 it works very fine and converts a 12 Megapixel raw picture in about 28 seconds.
The
download page of S7raw is bilingual, Japanese and English.
So don't be afraid if you cannot read everything.
Just look for a link that says "Download".
There is no install procedure.
Unpack the downloaded ZIP file and copy its content to a (new) folder in your "program files" tree.
Then run s7raw.exe. Make a shortcut for later usage.
The finest thing with s7raw is that you can save the settings for each raw picture in a small file.
This lets you retrieve the exact settings you did use to convert a given raw picture months later,
eventually modify them slightly and convert your raw photo again at any time.
Another advantage of the saved settings: let's say you have 50 raw pictures to convert.
Instead of converting them one by one and waiting for the approx 30 s each time,
you can choose the settings for each picture with the help of the preview and just save the settings.
No waiting time to do this.
After saving all the settings, you can run a batch job that will do the conversions using the individual settings you predefined.
Fine isn't it ?
Best of all: s7raw is the only one among the converters described that will save the EXIF data in the resulting jpeg or tiff file.
With the other converters, additional software and handling is necessary to get the EXIF data in your jpegs or tiffs.
