RawTherapee, another alternative

After the Open Source RawStudio, after seeing that LightZone is no longer available for Linux, there is another workflow oriented RAW processing software available for Linux: RawTherapee (web). Although it is not Open Source, it is available for free – but donation for its development is encouraged. RawTherapee is available for Linux, Windows and Mac, but there is no 64bits version.

Although RawTherapee is a one-man work, it offers high quality 16bits / channel processing and is color managed, so well suited for high quality RAW processing. Pretty amazing. Let’s see what it has to offer.

Opening RawTherapee

This is what it looks on opening:

Nothing fancy here: your main picture, thumbnails, a directory navigator, plenty of tools on the right and a histogram. There is also a “history” browser which I don’t show here and can be used as an undo mechanism.

At the top of the main image region, you have a couple of “most often used” function: white balance picker, cropping, rotation (same tool as RawStudio), orientation and high / low light warning.

At the bottom, you find the zoom function as well as a magnifier which allows you to check a part of the image at 100%:

The toolbox – basic tools

Now this is the part that interests us most. Plenty of things to play with here – so I will not detail each of them. Refer to RawTherapee’s users manual for all details. So here is a screenshot of the toolbox:

We find here the ususal white balance and exposure (with curves) tools.

One interesting bit is the Highlight Recovery which allows to retrieve some detail in near white burnt clipped zones of an image.

The Shadows/Highlight tool allows to selectively adjust the dark or light zones of an image without touching the rest.

Sharpening is a classic Unsharp Mask Tool.

Color boost (according to the manual) amplifies the A and B channels of the CIELAB profile – well, well… play with it: it boosts your colors nicely but don’t over use it.

The Color Shift allows color correction on the green-magenta and blue-yellow axis – I would say that this type of correction should be done in the white balance tool, so I find very little use for this tool.

The Luminance Curve is very similar to the exposure correction, but it modifies the luminance channel of the CIELAB space rather than working directly in RGB – thanks to the manual again. If I ever manage to turn a bad picture into a masterpiece via Luminance Curve rather than Exposure Curve, I’ll blog about it. Promise.

Denoising allows to separate chroma noise (patches of the wrong colors) from luminance noise (dark / light pixels). This is very good, since the chroma noise looks very unnatural and needs a rather energetic denoising, while the luminance noise is more natural (film-like, I for one, like it more than an over-denoised image) and you can leave quite a bit of it on your image. This allows to keep more detail as well.

The toolbox – transform tools

We find here the Crop, Rotate, Distortion and Chromatic Aberration correction tools:

Distortion allows to correct optical default in some lenses (usually at their widest focal) – it appears when shooting marines: the see is curved rather than flat at the bottom of your image. Playing with this tool will help, although it is no near as powerful as something like DXO (which offers a database of all the optical default for each lens at each focal and aperture for every camera; it makes automatic corrections from there)

Chromatic Aberration (wiki) are the little color fringes (generally purple) that appear in very high contrasted areas. I haven’t done extensive testing about this tool. As said, the problem affects only some lenses in high contrasted areas and will prove a handicap when you print your images in big size (A3 onwards).

The toolbox: ICM

The ICM is where you chose your color management settings: color profile, editing profile and so on. What you would expect from any color managed application.

Saving images

Obviously, RawTherapee keeps your settings for each picture. You can either “save as…” which will allow you to chose where to save your picture and then process and save your picture or click “save” in which case your image will be processed in the background while you carry on working with your next image. Nifty.

RawTherapee: conclusion

RawTherapee is very complete when it comes to RAW images processing. There are every tool you can think of available, some could even be omitted as far as I am concerned (fortunately each tool can be disabled). The processed output is of very high quality, so RawTherapee does its job, and does it really well.

However, this comes at a cost. Or I would say at two costs:

• Firstly, I find the interface confusing: too many sliders everywhere which effects aren’t always clear to figure out from their name. OK, I guess RAW processing isn’t an easy task and giving the user power means adding some complexity. I don’t mind messing around with sliders to see their effects, but…
• Secondly, the program is quite slow. So when you make a change to one setting, you need 10-15 seconds to see the result on screen – that is painful especially when trying to evaluate what one of these sliders do.

So this, to me, makes RawTherapee not so easy to use, in spite of its completeness.

Lastly, RawTherapee doesn’t has a batch feature yet, so while you can define standard processing profiles and apply them to your images, you still have to save each image separately. Batch will probably come in the next version.

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