- 1 Introduction
- 2 The Preview Panel
- 3 The Left Panel
- 4 The Right Panel
- 5 Editor Tab Modes
- 6 The Filmstrip
- 7 Monitor Profile and Soft-Proofing
The Image Editor tab is where you tweak your photos. By default RawTherapee is in "Single Editor Tab Mode, Vertical Tabs" (SETM/VT) which is more memory-efficient and lets you use the Filmstrip (described below). You can switch to "Multiple Editor Tabs Mode" (METM) by going to "Preferences > General > Layout", however each Editor tab will require a specific amount of RAM relative to the image size and the tools you use, and also the Filmstrip is hidden in this mode, so we recommend you first give SETM a try.
2 The Preview Panel
The central panel shows a preview of the image being edited. This preview is generated from raw data if such is available. It reflects the adjustments made by the tools in the Toolbox. Note that the effects of some tools are only accurately visible when you are zoomed in to 1:1 (100%) or more; these tools are marked in the interface with a "1:1" icon alongside the tool's name.
When opening an image, RawTherapee loads the tool settings from the sidecar file if one exists, else it applies a default sidecar file as specified in "Preferences > Image Processing > Default Processing Profile". When you close the image (which happens automatically if you open a different image or if you close RawTherapee) the current tool settings are automatically saved to a sidecar file as specified in "Preferences > Image Processing > Processing Profile Handling".
2.1 Eek! My Raw Photo Looks Different than the Camera JPEG
When opening a raw photo you may notice that it looks different from your camera's JPEG, or from what other software show when viewing the same raw photo. In some cases this difference is minute, but in other cases it could be significant - the image could be darker, lack contrast, be less sharp and more noisy. What gives?
There are three things you must know first to understand what is happening here:
- Your camera does not show you the real raw data when you shoot raw photos. It processes the raw image in many ways before presenting you with the histogram and the preview on your camera's display. Even if you set all the processing features which your camera's firmware allows you to tweak to their neutral, "0" positions, what you see is still not an unprocessed image. Exactly what gets applied depends on the choices made by your camera's engineers and company management, but usually this includes a custom tone curve, saturation boost, sharpening and noise reduction. Some cameras, particularly low-end ones and Micro Four-Thirds system, may also apply lens distortion correction to not only fix barrel and pincushion distortion but also to hide dark corners caused by severe vignetting or by the lens hood. Most cameras also underexpose every photo you take by anywhere from -0.3EV to -1.3EV or more, in order to gain headroom in the highlights. When your camera (or other raw editing software) processes the raw file it compensates for this by increasing exposure compensation by the same amount.
- When shooting a raw photo, most cameras embed within the raw file a full-resolution JPEG image with tone curves and other adjustments applied. Some raw files contain as many as three JPEG images differing only in resolution. Most cameras offer storing photos in one of three modes: "RAW", "JPEG", or "RAW+JPEG". The embedded JPEG image discussed here is stored within the raw file even in just "RAW" mode! When you open raw files in other software, what you are usually seeing is not the raw data, but the embedded, processed JPEG image! Examples of software which are either incapable of or which in their default settings do not show you the real raw data: IrfanView, XnView, Gwenview, Geeqie, Eye of GNOME, F-Spot, Shotwell, gThumb, etc. It is worth mentioning at this point that if you shoot in "RAW+JPEG" mode then you could in fact be wasting space on your memory card and gaining nothing for it, as your raw files most likely already contain an embedded JPEG identical to the external one saved in "RAW+JPEG" mode.
- Most raw development programs (programs which do read the real raw data instead of just reading the embedded JPEG) apply some processing to it, such as a base tone curve, even at their most neutral settings, thereby making it impossible for users to see the real, untouched contents of their raw photos. Adobe Lightroom is an example. Comparing RawTherapee's real neutral image to a pseudo-neutral one from these other programs will expose the differences.
RawTherapee, on the other hand, is capable of showing you the real raw image in the main preview, leaving the way you want this data processed up to you. When you use the "Neutral" processing profile you will see the demosaiced image with camera white balance in your working color space with no other modifications. You can even see the non-demosaiced image by setting the demosaicing method to "None".
To provide you with a more aesthetically pleasing starting point, RawTherapee by default uses the Auto-Matched Curve processing profile, which automatically generates a tone curve to make the tones of the raw image match those of the embedded JPEG, if one exists. If one does not exist, you can use the Standard Film Curve processing profile, which applies a curve which looks good in most cases. Choose the sub-type (ISO Low/Medium/High) depending on how noisy your image is.
2.2 Scrollable Toolbars
The toolbars above and below the main preview hold a certain number of buttons and other widgets which might not fit on lower resolution screens. If your screen's resolution is too low to fit the whole toolbar, some of the toolbar's contents (buttons, drop-downs, etc.) may become hidden. To see them, simply hover the cursor over the toolbar and use the mouse scroll-wheel to scroll the contents left and right.
2.3 Preview Background Color
The background color of the preview panel may be changed to allow you to better judge how the image tones will appear when the saved image is viewed on a website (or image viewer, or print) of a similar background color.
This choice also applies to the cropped-off area, if the image is cropped. See "Preferences > General > Appearance > Crop mask color".
2.4 Preview Channel
The preview can be toggled to show one of the following channels:
- luminosity, which is calculated as 0.299*R + 0.587*G + 0.114*B.
Preview of individual channels may be helpful when editing RGB curves, planning black/white conversion using the channel mixer, evaluating image noise, etc. Luminosity preview is helpful to instantly view the image in black and white without altering development parameters, to see which channel might be clipping or for aesthetic reasons.
2.5 Preview Mask
- Focus mask, which shows which areas are in focus (based on how sharp they appear),
- Sharpening contrast mask, which visualizes the mask which decides which areas are affected by sharpening. See Sharpening > Contrast Mask.
- Clipped shadow indication.
- Clipped highlight indication.
The clipped shadow and highlight indicators in the Editor allow you to easily see which areas of the image are too dark or too bright. Highlighted areas are shaded according to the much they transgress the thresholds.
The thresholds for these indicators are defined in Preferences > General.
The clipped shadow indicator will highlight areas where all three channels fall at or below the specified shadow threshold.
The clipped highlight indicator will highlight areas where at least one channel lies at or above the specified highlight threshold. If you want to see only where all channels are clipped, then enable the luminosity preview mode in addition to the clipped highlight indicator.
Clipping is calculated using data which depends on the state of the gamut button which you can toggle above the main preview in the Editor tab. When the gamut button is enabled the working profile is used, otherwise the gamma-corrected output profile is used.
The focus mask is designed to highlight areas of the image which are in focus. Naturally, focused areas are sharper, so the sharp areas are highlighted. The focus mask is more accurate on images with a shallow depth of field, low noise and at higher zoom levels. To improve detection accuracy for noisy images, evaluate at smaller zoom, around the 10-30% range. The current implementation analyzes the preview image, which is rescaled from the original captured size down to what you see on screen. When zoomed less than 100%, the preview image is downscaled, a side-effect of which is the apparent reduction of noise. You can take advantage of this to help identify truly sharp details, rather than noise itself which may introduce a false micro texture. At the same time, downscaling compresses larger scale details into a smaller size, and it may introduce aliasing artifacts, both of which could lead to false positives. You can increase your confidence by viewing the mask at various zoom levels. It is not always fault proof, but can be helpful in many cases. Due to these caveats, be sure to double-check your images if you decide to delete them based on the focus mask.
2.6 Detail Window
The "New detail window" button , situated below the main preview next to the zoom buttons, opens a new viewport over the main preview of an adjustable size and of adjustable zoom. This lets you work on the photo zoomed-to-fit while examining several areas of interest at a 100% zoom (or even more). The benefit of using this feature is particularly important to users with slower machines, though not only them, as the zoomed-out main preview takes a shorter amount of time to update than if you were to zoom it to 100% because working at a zoom level less than 100% excludes certain slow tools, such as Noise Reduction, while the little detail windows zoomed to 100% do include all tools and are fast to update because of their small size. This allows you can use the main preview for your general exposure tweaks where it is necessary to see the whole image, and one or more detail windows to get sharpening and/or noise reduction just right.
2.7 Preview Refresh Delay
Changing any tool's parameters sends a signal for the preview image to be updated accordingly. Imagine what would happen if there was no "delay period", and you dragged, for example, the exposure compensation slider from 0.00 to +0.60. A signal would be sent to update the preview for every single change of that value - for +0.01, +0.02, ... +0.59, +0.60. Updating the preview 60 times would be completely unnecessary and actually take longer than it takes you to move the slider. This is especially true for more complicated tools, such as noise reduction, where a preview update can take even a second (depending on your CPU and preview size). The solution is for RawTherapee to wait for a very short period from the moment you stop moving a slider (you don't have to let go of it, pausing movement is enough) until the moment it sends a signal for the preview to be refreshed.
We have introduced two parameters which control the length of this waiting period:
- Default value = 100ms.
- This is used for tools with a very fast response time, for example the exposure compensation slider.
- Default value = 200ms.
- This is used for tools with a slow response time, for example the CIECAM02 sliders.
You can adjust both of these values in the options file in the config folder.
3 The Left Panel
To the left is a panel which optionally shows the main histogram ("Preferences > General > Layout > Histogram in left panel"), and always shows the Navigator, History and Snapshots. You can hide this panel using the hide icon, or its keyboard shortcut.
3.1 Main Histogram
A histogram in photography is a graphical representation of the number of pixels of a given value. Typically the horizontal axis represents the range of possible values while the vertical axis represents the count of pixels with that value. The axes need not be linear - RawTherapee can also scale the histogram logarithmically.
Regardless of the photo's bit depth, the histogram itself has a precision of 256 sampling bins. To understand this, let us look at the example of a 16-bit image using integer precision. Its range of possible values spans from 0 to 65535 (2^16 = 65536 possible values, and since 0 is a possible minimum value then the maximum value is 65535). Drawing a histogram using 16-bit precision would mean that it would need to be 65535 pixels wide to faithfully represent the data, and no screen today is anywhere near that wide. Instead, all pixels with values from 0 to 255 (65535/256*1) are grouped into the first "bin". The second bin consists of a count of all pixels with values from 256 to 511 (65535/256*2). The third bin represents values 512 to 767 (65535/256*3). And so on until bin 256. This happens regardless of the input image's bit depth - and RawTherapee's engine uses 32-bit floating-point precision anyway.
The main histogram can simultaneously show one or more of the following:
- the red channel,
- the green channel,
- the blue channel,
- CIELab luminance,
- red, green and blue channels of the source raw image before demosaicing.
The histogram shows the channels listed above using the gamma-corrected output profile when the gamut button is disabled (default), or using the working profile when the button is enabled. The status of this button also affects the values shown in the Navigator panel, as well as the clipped shadow and highlight indicators. It does not affect the raw histogram.
Like water in a pipeline, image data flows through RawTherapee from the input file through various stages, most of which the user can control, to the output. The output could be the image saved in a file, or the image displayed on your screen. Each stage affects the color data. The histogram allows you to visualize this data at several stages. By default, the histogram shows color data as it will appear if you save the output image, including processing done at all intermediate stages. By enabling the gamut button you can peak at the data at the early stage where it gets converted into the working space. You can even look at the raw data before any transformations or demosaicing are applied.
Let's examine the large histogram example above. Though it actually shows four histograms (red, green, blue and luminance), focus on one histogram at a time. The horizontal axis represents the possible values of the histogram, where "A" are the darkest values possible, "C" the mid-tones, and "E" the brightest possible values. The position of the histogram line on the vertical axis represents how many pixels have that value. We can see that there are zero pixels in the red channel with values around "A" (from zero to very dark), because the histogram line lies right along the bottom. There is a significant number of pixels where the red channel is dark (between A and B), and a significant number where it is light (around D). Then, importantly, there is a spike at the right end of the histogram, at E - it tells us that a large number of pixels have maximal red values - they are clipped.
Generally speaking, you should care when clipping occurs on skin, and not care when it's due to specular highlights. If a histogram shows clipping, and if you care about the clipped regions, you should start by establishing where the clipping occurs. Check the raw histogram - are any channels clipped? If yes, then maybe highlight reconstruction can help. If the raw histograms are not clipped, then all the required information is intact, and it is some stage downstream in the pipeline which causes clipping. Ensure your working profile's gamut is large enough by enabling the gamut button to see histograms at the working profile stage of the pipeline. You might want to temporarily apply the Neutral profile to disable all the tools while checking, then revert. If your working space is not causing clipping (the default working space is ProPhoto and it's huge), then it's likely your adjustments which are causing clipping. Reduce exposure, go easy on the curves, use dynamic range compression if necessary.
Knowing how to read a histogram is a basic and very useful skill, as it can point out issues with your image regardless of how dim or miscalibrated your monitor may be.
To help you visualize the data, the histogram (as of RawTherapee 5.5) has three modes which scale the data in the x and y axes differently:
- Linear-linear mode. You find gridlines at halves, quarters, eighths and sixteenths, depending on the size of the histogram.
- Linear-log mode. The x-axis is linear, the y-axis and the horizontal gridlines are scaled logarithmically. The position of the gridlines still corresponds to the halves, quarters, etc.
- Log-log mode. Both the x- and y-axes are scaled logarithmically. The gridlines are not scaled logarithmically, but correspond to stops - with every gridline the value doubles, so there are lines for the values 1, 3, 7, 15, 31, 63, and 127 (
pow(2.0,i) - 1)).
When there is a disproportionately bright area relative to the rest of the image, it will show up as a spike in the histogram. If you want to show this on a histogram with a linear y axis, the spike may push the lesser values down the y-axis, making them difficult to see. Switch to one of the log modes to scale the data and help you get a better overview of all values.
The histogram can be moved to the left/right panel from "Preferences > General > Layout > Histogram in left panel".
3.1.1 Raw Histograms
Raw files contain a dump of data captured by the sensor and quantified by the analog-to-digital converter. The raw file as a container has a bit depth of its own, typically 16-bit, while the data it contains could have a lower bit depth - typically it is 12-bit (0-4096) or 14-bit (0-16384). To display the data from a raw file as an image, one of the several key bits of information required to process the data correctly are the black and white levels. The black level is not necessarily 0, as the sensor and camera electronics produce digital noise, so the noise floor may lie for instance at 512. The white level is also not necessarily 16384; it depends on various things, and may lie for instance at 16300. For more information, see the articles Demosaicing and Adding Support for New Raw Formats (especially the header of the
camconst.json file). The black and white level values used by RawTherapee are hierarchically set by looking in several places: in
dcraw.c, inside the raw file's metadata, and in
camconst.json (latter takes precedence). Furthermore, the user can tweak the raw black and white levels from within RawTherapee.
The raw histograms show data after black level subtraction. The right end of the histogram is anchored on the white level. The raw histograms are affected by the detected black and white levels as well as by the black and white level adjustments made by the user in RawTherapee.
When examining the raw histogram, you may also want to set the demosaicing method to "none". This will reveal the sensor pattern in the preview, and also cause the Navigator panel to show the raw RGB values of the pixel currently being hovered over. These values are affected by the detected black and white levels as well as by the black level adjustments made by the user in RawTherapee, but they are not affected by the white level adjustments ("white-point correction") made by the user in RawTherapee.
The Navigator panel shows a thumbnail of the currently opened image, and RGB, HSV and Lab values of the pixel your cursor is currently hovering over.
The values shown in the main histogram and Navigator panel are either those of the working profile or of the gamma-corrected output profile, depending on the state of the gamut button located in the toolbar above the main preview. When the gamut button is enabled the working profile is used, otherwise the gamma-corrected output profile is used.
By clicking on the values in the Navigator you can cycle between these three formats:
RawTherapee 5.1 onward can show the real raw photosite values. To see them, set the Navigator to use the [0-255] range, apply the Neutral processing profile, then set the Demosaicing method to "None". The Navigator will show the real raw photosite values after black level subtraction within the range of the original raw data.
The History panel contains a stack of entries which reflect each of your image editing actions. By clicking on the entries you can step back and forth through the different stages of your work.
An entry is added each time you adjust a different widget - multiple edits to the same widget are stored as one entry. For example, adjusting the exposure compensation slider from "0" to "0.3" and then to "0.6" will result in one entry being stored with a final value of "0.6". Likewise, when adjusting a curve, all individual control point adjustments are grouped into one history entry. Should you wish to store the adjustments as two (or more) history entries, you will have to split them by adjusting some other widget. For example, assuming a curve is in "Film-like" mode and you want to keep to that way: adjust several control points on the curve, then toggle the curve mode from "Film-like" to "Standard" and then back to "Film-like" to create a new history entry, and then continue adjusting the curve.
The history stack is not saved - it is lost as soon as you close the Editor tab. None of your adjustments are lost though, as the final state of all tools is saved in the sidecar file, ready to be used the next time you open that image.
Under the History panel is a panel called Snapshots. Its use is in that you can save a snapshot of the photo with all the adjustments up to that point in time, and then proceed to further modify your photo to give it a different appearance, saving new snapshots at every moment you feel you might have reached a version of your photo worth saving. Once you have two or more snapshots, you can just click on them to flip through the different versions and stick with whichever one you like best. In the future, the snapshots will be saved to the PP3 sidecar file. For now, the history and snapshots are lost when you load a new photo in the Image Editor or close RawTherapee.
4 The Right Panel
To the right is a panel which optionally shows the main histogram and Processing Profiles selector ("Preferences > General > Layout > Histogram in left panel"), and always shows the Toolbox. You can hide this panel using the hide icon, or its keyboard shortcut.
4.1 Processing Profile Selector
The Processing Profiles panel allows you to apply, save, load, copy and paste processing profiles, partially or in full.
Read the Sidecar Files / Processing Profiles page for more information.
The Toolbox, in the right panel, contains all the tools you use to tweak your photos. Each tool has its own RawPedia article.
5 Editor Tab Modes
RawTherapee allows you to work on photos in two modes:
- Single Editor Tab Mode (SETM), where you work only on one photo at a time, and each photo is opened in the same Editor tab. There is a horizontal panel called the Filmstrip at the top of the Editor tab showing the rest of the photos in that folder for easy access. There are Previous Image and Next Image buttons in the bottom toolbar (and keyboard shortcuts for them) to switch to the previous/next image.
- Multiple Editor Tabs Mode (METM), where each photo is opened in its own Editor tab. The Filmstrip is hidden in this mode and there are no previous/next buttons. Having multiple photos opened at the same time requires more RAM.
Try both modes and see which one suits you best. To do that, click on the Preferences icon in the bottom-left or top-right corner of the RT window, choose "General > Layout" and set Editor Layout to your preferred choice.
Use this Preferences window to select a different language for the user interface, to choose a different color theme, change the font size, etc.
It is also possible to start RawTherapee in no-File-Browser-mode (without the File Browser tab) by specifying RawTherapee to open an image from your operating system's file browser (in other words, right-click on a photo and select "Open With > RawTherapee"), or by using the image filename as an argument when starting RawTherapee from the command line (
rawtherapee /path/to/some/photo.raw). This mode was introduced for people with little RAM as not having a File Browser tab means RawTherapee uses a little less memory, however in practice the amount of memory saved is little and the usability cost outweighs the little benefit, so it is likely to be removed in the future (see issue 2254).
6 The Filmstrip
If you use Single Editor Tab Mode ("Preferences > General > Layout") you can display a horizontal panel above the preview, this is called the Filmstrip. It contains thumbnails of all images in the currently opened album, and is synchronized with the currently opened image so that you can use keyboard shortcuts or the previous and next image buttons to open the previous/next image without needing to go back to the File Browser tab.
As of RawTherapee version 4.2.10, you can hide the Filmstrip's toolbar to save screen space. There are two ways of doing this: one way just toggles the toolbar on/off without resizing the filmstrip to the new height, and the other way does the same but also automatically resizes the filmstrip's height. Both are invoked via keyboard shortcuts only. As resizing the filmstrip's height will trigger a refresh of the image preview and this might take a while if using CPU-hungry tools like noise reduction while zoomed in at 100%, the mode that doesn't resize has been implemented for users with slow machines. Users with fast machines will find the auto-resizing mode more helpful.
7 Monitor Profile and Soft-Proofing
The widgets under the main preview in RawTherapee 5 allow you to apply a monitor color profile to the preview image. This enables users who have calibrated and profiled their monitors to get an instant and accurate preview of their work, whether you're staying in sRGB or working in a wide gamut. Note: OS X users are limited to sRGB and will not get an accurate preview otherwise (see discussion), while users of Linux and Windows will get a correct wide-gamut preview.
Go to Preferences > Color Management and point the "Directory containing color profiles" to the folder into which you saved your monitor and printer ICC profile. Restart RawTherapee for the changes to take effect. Now you will be able to select your monitor's color profile in the combo-box under the preview. Use the "Relative Colorimetric" rendering intent unless you have a good reason otherwise.
One can also enable soft-proofing of the preview. This will show you what your image will look like once it gets transformed by the printer profile set in Preferences > Color Management. If you want to adjust an image for printing and you have an ICC profile for your printer-paper combination you could set that as your output profile, enable "Black point compensation" in Preferences so that the blackest black in your image will match the blackest black your printer-paper combination is capable of reproducing, then enable soft-proofing. You will see what your image will look like if you print it. This allows you to make adjustments and get an instant preview of the result, saving you time and ink on test prints.
The icon with exclamation mark next to the soft-proofing button will gray out areas that cannot be reproduced by your printer, i.e. areas where you will loose details.
You should have a calibrated and profiled monitor in order for the soft-proofing preview to be accurate.
The items you see in the monitor profile combo-box (under the main preview) and in the printer profile combobox (in Preferences > Color Management) are ICC files located in a folder which you can point RawTherapee to by going to "Preferences > Color Management > Directory containing color profiles".