The image controls appear almost exactly in the order in which they are
applied to the image.
First appears the raw data histogram. I find this histogram
as it shows that even in well exposed photos, most of the pixels
have very small luminosity.
On this histogram you can also
see the red, green and blue curves that show how the raw data will be
converted to the final image. These curves can be thick, since a single
raw value can be translated to a range of values, depending on the
value of the other RGB channels in the same pixel.
Right clicking on the raw histogram pops up a menu that gives you
control over the scaling and size of the histogram.
If you select a spot area in the preview image
(this can only be done when you are on the
white balance page), its average RGB values are shown
in the display color space. The next value is the luminosity - the Y of
the linear XYZ space (between 0 and 1).
The last number is the Adams' zone.
Adams' zone is the log of the luminosity (base 2) normalized so that middle
gray (18% gray) is mapped to zone 5.
You can digitally change the original photo exposure.
Increasing the exposure is very simple, the only downside is that at
the same time you are also increasing the noise in the image.
Decreasing the exposure is more tricky, since it is impossible to
recover clipped highlights.
When setting the exposure you can control the way highlight restoration
restores highlights in LCH space. This means that luminosity is restored
while chrominance and hue are preserved. This results in soft natural
highlight details (symbolized by a bulb lighting the object directly).
More information about this feature can be found
restores highlights in HSV space. In this case value (which corresponds
to luminosity) is taken as the average of the clipped and unclipped
values, resulting in sharp details (symbolized by a bulb lighting
the object from the side).
clips the highlights completely, this guarantees that there will be
no artifacts from the highlight restoration.
These options are only relevant when applying negative EV.
You can also control how positive exposure correction is applied.
emulates the linear response of the digital sensor.
This is mathematically correct, but can result in harsh cutoffs.
adds a "shoulder" to the response curve, emulating the soft behavior
applied together with white balance, and before color management.
is calculated according to the white balance and color management settings.
Therefore, every time you change one of these settings the auto exposure
The rest of the image conversion settings are separated into several groups.
White balance are settings UFRaw must apply during the raw conversion.
UFRaw uses the camera white balance if it can, still I think that this is
the setting that would most probably require adjustment.
The reset of the settings on the other hand can usually be simply set to
no corrections, and this is the default.
The WB settings control the ratio between the three color channels.
Here you can set
the color Temperature, making your picture warmer or
Going into technical terms, we are using the correlated color temperature
of CIE daylight illuminant, which is not exactly the same as black body
radiation. CIE daylight illuminant are not defined below 4000K, therefore
in the range 2000K to 4000K we use black body radiation.
We also use the color matrices (discussed later) to convert to the
camera color space.
You can learn more about color science at the excellent homepage of
Setting the ratio between the three color channels requires
Since the Temperature adjustment mostly controls the
between the red and the blue channels, it is natural that the second
will control the intensity of the Green channel.
In addition you can set the white balance to the Camera
WB, Auto WB and a list of preset WB.
The preset values are camera dependent, and there is also fine tuning
for cameras that have this feature.
If your camera is not supported, go to the
Contribute page to read how to
get it supported.
have a neutral gray color in your picture, then instead of fiddling
with the above controls, you can simply use spot white balance.
Click anywhere on the image (and drag the mouse to change the spot size)
to get the output color of that area, and press
to make this area neutral gray.
The reset white balance button
behaves a bit differently from all the
other reset buttons. It resets the white balance to the initial value
with which the image was loaded as opposed to the other reset buttons, which
reset their controls to UFRaw's default values.
The channels multiplier show the actual numbers by which the different
camera channels would be multiplied as a result of the other settings.
You can change them directly, but usually this should not be needed.
Notice that the lowest value is always normalized to 1.00.
After setting the white balance UFRaw interpolates the Bayer pattern.
- AHD interpolation is the Adaptive Homogeneity-Directed
interpolation. It is the default interpolation.
- VNG interpolation uses
threshold-based Variable Number of Gradients interpolation.
This used to be the default interpolation and it is still
- VNG four color interpolation
should be used if you get Bayer pattern artifacts in your photo (see
DCRaw's FAQ for
- PPG interpolation stands for Patterned Pixel
Grouping interpolation. It is almost as good as all of the above
and much faster.
- Bilinear interpolation is a very basic interpolation
but it is much faster.
After the interpolation you can apply
color smoothing. Color smoothing can reduce color artifacts
such as noise and chromatic aberration without loss of detail.
(The EAHD interpolation option in previous version of UFRaw was just
AHD interpolation with color smoothing enabled.)
The Threshold controls the amount of noise reduction
applied to the image. The default of 0 (zero) stands for no denoising
Dark frame subtraction
Many cameras apply dark frame subtraction for long exposures to reduce
noise and remove hot pixels. The downside of this procedure is that
it makes the exposure twice as long, since the dark frame exposure time
has to be the same as that of the real image.
You can make your own dark frame by putting on the lens cover and
load the created raw file in this entry.
It is useful if your camera does not have the dark frame subtraction
feature or if you decide to disable it to save time.
For best results the dark frame should be taken in similar conditions
to the original frame.
When a grayscale output is selected, only one channel per pixel
is written to the output file instead of three.
Therefore the output file should be much smaller.
There are sevral modes for generating the grayscale image
- Lightness takes the average beween the maximum and
- Luminance sets the saturation of each pixel to 0,
while preserving Luminance.
- Value uses the channel with the maximum value.
- Channel mixer mixes the channel according to the
user choice in the channel mixer adjustments.
Base curve imitates the functionality of Nikon's tone curves.
For Nikon NEF files you can choose Custom curve
if you want to use the curve that is embedded in the raw file.
Choosing Camera curve will enable the embedded curve
only if it was enabled in camera.
All camera users can load curves to apply custom curves to their images.
The famous white wedding curve (V3.5) from
was applied to the image on the right. Move the mouse over the image
to see the original image with a linear curve.
A +0.5EV was applied to the original image to equalize the luminosity
of both images.
The white wedding curve adds some details to the dress.
UFRaw can directly apply
The curve from Fotogenetic
to your images.
The base curve is applied directly to every color channel.
It is applied after the exposure and white balance setting so that
it will effect each channel equally.
It is applied before the gamma correction, meaning that it is
applied on the linear data.
You can also create curves of your own using the curve editor.
The curve editor can be fully controlled using either the mouse or
the keyboard. When using the keyboard the relevant keys are
INSERT, DELETE, HOME, END, PAGE-UP, PAGE-DOWN and the arrow keys.
I'll let you discover yourself what each key does or how to use
Color profiles and color management are explained on the
Color management page.
The Saturation adjustment changes the saturation
in Lch(ab) space, meaning that hue and luminosity are preserved.
Use a value larger than 1 to increase the saturation and a value less
than 1 to desaturate the photo. A value of 0 will give a black and
The curve in the Corrections settings is applied
to the luminosity channel in Lch(ab) space.
The controls on the left of the curve editor are for controlling
the black point. You will notice that they simply control the leftmost
point of the curve.
If your picture looks foggy, the auto black button
might fix it.
The auto curve button
on the right tries to set a curve that flattens the histogram.
It can add lots of contrast to your photo
but sometimes the results look very artificial.
Crop and Rotate
On this page you can crop your image, shrink and rotate it.
Notice that you can change the crop area by clicking the mouse on the
edges of the crop area.
For aspect ratio, you can choose any of the presets or enter you own
value in decimal notation (1.273) or as a ratio of two numbers (14:11).
the aspect ratio allows you to change the image cropping
without changing the aspect ratio.
When setting the shrink factor, you should take into account the fact
that for values of 2 or heigher, no interpolation needs to be applied
to the image. This means that the image conversion would finish
The name of the output image is split to a path and a filename.
By default, the output path is the same as the input path.
If you want to save a batch of images to a non-default path,
use the Remember output path option.
The JPEG compression level setting, also controls the
sampling factor. For compression level 90 or less, 2x2 sampling is used.
For compression level 91, 2x1 sampling is used.
For compression level 92 or above, 1x1 sampling is used.
EXIF data can be written to JPEG or PNG images. EXIF data can also
be written to TIFF file when using Exiv2-0.18 or newer.
UFRaw ID files have the same name as the output file on with a
ID files contain all the settings for generating the output file.
Choosing Create ID file Also is useful
for keeping track of the setting used, or for making future changes
on top of the saved settings. The only option is useful
if one doesn't want to wait while the output file is being generated.
The output file can be generated in the background using the command:
Here you cannot make any setting, you can only view some very basic
UFRaw can save the EXIF data to JPEG output for a few supported formats.
These formats include Canon (CRW, CR2), Nikon (NEF), Pentax (PEF),
Samsung (PEF), Sony (SR2, ARW), Minolta (MRW), Fuji (RAF) and Adobe's DNG.
UFRaw relies on Exiv2 for the EXIF
support, therefore if you want to add support for your camera you should
help the Exiv2 developers in this respect.
Meanwhile, for unsupported formats it is recommended to use
ExifTool by Phil Harvey.
To copy all the EXIF information, use the command:
exiftool -TagsFromFile RAWFILE -x Orientation OUTPUTFILE
This will copy all the EXIF data except for Orientation.
UFRaw already rotates the image as needed, therefore copying this field
could cause a double rotation.
This is the histogram of the preview image, it is updated as
you change the settings. Below it you can get some statistics.
Notice that the histogram bins for the extreme values (0 and 255) might be
clipped, so if you have many over or under exposed pixels, this fact will not
appear in the histogram but only in the statistics below it.
Right clicking on the raw histogram pops up a menu that gives you
control over the type, scaling and size of the histogram.
The are two modes in which you can Indicate
Overexposure and Indicate Underexposure on
If you enable them in the appropriate check boxes, then pixels
with at least one overexposed channel will be colored black
while pixels with at least one underexposed channel will become white.
Press the appropriate button to see which channel is over or under
Like the histogram, this option adds up the colors, so if more than one
channel in a pixel is overexposed, when you press the indicate
Overexposure button, you will see the
where white means that all three channels are overexposed.
For underexposure this is a bit counter intuitive.
When pressing the indicate Underexposure button,
if all three channels are underexposed you will get black as expected,
but if only one channel
is underexposed you will get the complementary color (for example, if
the blue channel is underexposed it will show up as yellow which is
red + green).
Controls under the preview image
This option is obvious. Zooming is limited to 50%.
Hopefully 100% zooming will be added in the near future.
All settings which are not directly related to image editing are
hidden in the Options dialog.
In the first page you can delete profiles and curves that you loaded
In the options dialog you can also see the
configuration data that will be written to UFRaw's ID files
and the resource file
which is created in your home directory. Here you can also tell UFRaw
to save the current configuration now. Otherwise, the data is
saved only after you convert the image.
Notice that if you press Cancel,
the configuration data is not saved.
The Save image defaults is explained
in the Taming UFRaw's configuration section.
The log information is a bit technical and mostly not interesting.
Pressing delete will pop-up a window with the raw file and all other
files with the same name but different ending.
You can decide which files to delete, if any.
Send to Gimp
Hopefully, this option will work correctly out of the box.
Otherwise you might have to go to the options window to set the
gimp-remote command to match your environment.
Saving the image
In the plug-in version, you just press OK to send
the image to the Gimp.
In the stand-alone version you can Save the image
or send it to Gimp
Hovering with the mouse over the Save button,
pops up a tool-tip with a summary of where and how the image will
Taming UFRaw's configuration
I believe that generally using UFRaw is straightforward and that
its behavior is mostly predictable.
Still, if you are converting lots of images and want to minimize the
number of key strokes, or if you are using batch mode, then you might
find a few useful tips in this place.
UFRaw's configuration options can be divided into three groups:
- Image manipulation options that control how the raw image will
be converted. These are the options which are controlled from the
- Save options that control how the image will be saved. These are the options
which are controlled from the
- GUI settings that control how the preview window looks.
There are several sources for these options. The possible sources
are listed in the order in which they are applied.
- First, the options are set to UFRaw's default settings.
All subsequent sources will override these settings.
Still, it is very simple to return to these settings using the
buttons. These buttons are grayed out
when their appropriate settings
are already set to default. This allows one to quickly see which options
were changed. The one exception to this rule is the reset white
balance button, whose behavior was explained earlier.
- Next, UFRaw reads the options from the resource file
.ufrawrc located in the user's home directory.
This file is created every time you save an image. Notice that
this file is not saved if you exit the preview window with
ufraw-batch also reads this file but does not write
to this file.
- If you open an image using an ID file:
the information in the ID file is used at this point.
ID files are created by setting the Create ID file
page to Also or only.
- These ID files can also be used as configuration files using
the command line option
You can use these file to hold different sets of configurations for
- Next, all the options specified in the command line are applied.
If you are using
ufraw-batch then these options will
be the decisive options. For example,
ufraw-batch --temperature=5000, will always create
output with the color temperature set to 5000K, no matter what
the other configurations contain.
- In interactive mode, the options you see in the user interface
are naturally the options that will be used.
By default UFRaw saves all the settings to the resource file.
This is the expected behavior by new users.
If you start using UFRaw on a regular basis, you will probably
discover that you have your preferred settings.
At this point you would like to set Save image defaults
to never again. This way you can
fix your default settings, and if a certain image requires special
settings it won't affect the defaults for subsequent images.
In batch mode the save options from the resource file are ignored.
This is to prevent a scenario where you converted a big batch of images
only to discover that JPEG compression, for example, was set to 20.
If you want to be sure that other setting from the resource file
.ufrawrc do not affect your batch conversion, you can
create an ID file with your default configurations and batch
ufraw-batch --conf=default.ufraw [...].
The ID file is in XML format. This means that you can read and write to
this file with any text editor. Writing to this file is not recommended,
even if you know what you are doing, since UFRaw assumes that this file
was written using UFRaw and therefore there are very few consistency
checks on it.
The resource file uses the same format, but you should not go around
switching between these files, since different data is saved to
each of them.
Examining these files could be instructive. They only contain
settings which are different from the default ones.
Therefore, all the information in the ID files has at least some relevance
to the image conversion, and all lines in the resource files are related
to a change you made in UFRaw at some point. It is safe to delete
the resource file if you want to return UFRaw to its default behavior.
The ID file also contains the log of the conversion.
UFRaw has three auto adjust
buttons. When they are pressed in
you can click on them to release them. This has no effect on the
image you are converting, but the information of whether these
keys are pressed or not is written to the configuration files.
Therefore, if for example the auto exposure button is pressed,
UFRaw will auto expose the next image also. Otherwise the next
image will use the same exposure as the current one.
There are some subtle differences between the behavior of the three
auto adjust keys.
Auto exposure and auto black are active as long as their button is pressed in.
This means that changing the white balance could simultaneously change
the exposure and the black point.
Auto curve is never kept pressed in. The reason is that auto
curve behavior is unpredictable and can lead to very strange outputs.
It therefore does not make sense to apply it blindfolded.
Batch processing workflow
There are two reasons to use batch processing.
One reason is if you know exactly the parameters you want
to apply to your images.
The other reason is you don't have the patience to wait for UFRaw to
process your images after you make your settings.
For the first scenario, you need to prepare an ID file with all the settings.
Then you can convert the images using
You can also use the command line options, but beware that settings
from the resource file
.ufrawrc might affect your
For the second scenario, use UFRaw's interactive interface and in the
page set the option
Create ID file to only.
With this setting UFRaw finishes the save procedure immediately since it
does not need to convert the raw file.
Later you should use the command
to do the actual conversion.
UFRaw is a GTK+2.0 application and as such its theme can be changed by
changing the GTK theme. Still, you might want to use a specific theme
for UFRaw. This can be done by putting a GTK theme file in the
home directory with the name
A good starting point is this sample