I’ve recently bought a new camera (Canon 70D) and, since I want to exploit its full potential, I’ve just started shooting in RAW, and I needed an editing program (I use Linux).
I tried Rawtherapee (currently using version 4.2.0) and it has this very annoying pre-processing feature that I can’t seem to disable. I can only switch it from “Default” to “Neutral” but I don’t like the results anyway. I mean, if I’m shooting in RAW, it means that I don’t feel comfortable about my equipment making decisions… moreover the results are kind of disappointing (I’d show you but I don’t know how to embed pictures).
So. How so I disable the automatic preprocessing feature?
thanks in advance!
How is it annoying?
Auto CA correction isn’t something your equipment decides, it’s an algorithmic routine that measures the offsets and cancels them out prior to demosaicing, for maximum quality. Unless it’s actually acting up (very uncommon, in my experience), you almost never can correct it better manually.
It also doesn’t assume that the CA is radially symmetrical, so it better handles lenses with image stabilization or slight decentering.
But if you do want to disable it, it’s in the raw tab.
Embedding photos is trivial: just drag and drop into the text box.
Do you mean to say that using the “Default” or “Neutral” profiles you find that you don’t like the results?
If so, I’d say that sound about right. The Neutral profile does very little at all to your image and will require you to do all of the processing yourself to get results that are halfway decent…
I didn’t know you could drag and drop pictures! Boy, it has been a while since I’ve last posted in a forum. 
So, here’s how the picture looks like before I open it in Rawtherapee.
On the left, there’s the result of the “Default” preprocessing. It looks way too noisy. And on the right, we have the “Neutral” one. Too dull and dark.
Now, of course pic n.1 is not perfect, it’s a RAW and it still needs a lot of work but I’d like that as a starting point instead of n.2/n3.
That’s all I can see in RAW > preprocessing. Am I looking in the wrong place?
Double click on an image to go into the real editor mode, and then open up the collapsed things in the raw tab and you should find the checkbox. I don’t remember where it is offhand.
Regardless, you really should leave auto CA correct on.
If the left is too noisy, use the Default (high ISO) preset.
That’s not actually “how the picture looks before you open in RT”, I suspect that it’s the embedded JPG from your camera that you’re seeing. It’s what your camera thinks will look good for you…
The “Default” processing has Auto-Levels enabled so it will attempt to normalize the levels of the raw file as best it can, which often results in noisy results. The “Neutral” on the right looks much better to me as a starting point, as I don’t think anything is applied to the raw file at this point (adjustment-wise).
Now all of the processing is entirely up to you and your taste. 
Is it that necessary? I’ve tried other softwares (Lightroom and Photivo) and none of them had a preprocessing thing going on. (don’t get me wrong - I’m not doubting the validity of what you’re saying, I’m just curious and completely new to this stuff).
Anyway, I don’t mean to disable it for good, maybe it will look better on other photos.
I opened up all of the collapsed items in the tab, and I disabled the CA autocorrection:
Autocorrection off, slightly changes the colors; but it’s still not similar to what I saw in the thumbnail; does this mean that the CA autocorrection is the only aspect of the preprocessing that I can change? :
And this is what I get with the High ISO setting, but it’s still pretty noisy 
<img src="/uploads/default/original/2X/c/c120ff931f61121fa657d3e1344aa9cde3c61e76.png" width=“629” height=“440”
If they don’t have the pre-demosaic CA correction, they are inferior in this regard.
The 18-55 STM is pretty good, but you’ll still benefit from enabling the CA correction. It won’t be very visible unless you zoom in on the corners.
Yep I know the program uses the .JPG as a thumbnail. But other programs (I’ve tried Lightroom but I don’t wanna buy it, and Photivo, but it’s way too difficult) don’t pre-process the picture before, so I assumed I would be able to do that with Rawtherapee too. I think I’ll work on the Neutral. Thanks 
But the immediate results look kinda worse. I mean, why should I work on eliminating noise that wasn’t even there before?
You asked how to disable it and I showed you how to. I don’t think it’s necessary to disable it.
The immediate results of what are worse than what else? Please be specific.
If you lighten an image, it will be noisier. That’s why you see the noise more strongly. Match the brightness, and the noise should be similar (but the LMMSE demosaicing reduces color noise).
The camera does its own noise reduction, which is why you don’t see it in the thumbnail: the noise is there in the first place (because this is ISO 4000).
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I didn’t ask if disabling was necessary: I came here trying to disable it in the first place.
What I meant was: since I’ve used other programs that didn’t pre-process the file before letting you work on it, is this feature necessary?
Necessary in the sense of “does the software need it to function?”
No.
However, it’s better on than off, with at least 95% of lenses. (I have one lens that doesn’t like it)
I meant that the immediate results of the preprocessing (picture n.2/n3) looked worse than what I thought was the starting point.
That feature is not necessary for all files, but very often you have ca, which usually will be corrected very well using raw auto ca correction. If there’s no ca in your file, auto ca correction also works fine (in 99.99 % of cases) and does not correct it.
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CarVac, I’m insterested in an example file from this lens. Maybe there’s room for improvements