issue143:darktable
Différences
Ci-dessous, les différences entre deux révisions de la page.
Prochaine révision | Révision précédente | ||
issue143:darktable [2019/03/31 15:30] – créée auntiee | issue143:darktable [2019/04/12 14:13] (Version actuelle) – andre_domenech | ||
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- | Welcome back to another issue packed with open source goodness. This time we will be looking at noise reduction. If you have ever taken a picture in low light, or at night, you know what I am talking about. It is that - ‘picture of your best friend’s going-away party before they moved to China, and you will not get another photo like that, as you will only see her in 4 years’. Now let me just say, Darktable has some really powerful algorithms when it comes to noise reduction. For me, they are more powerful than those of other photo manipulation programs, even the commercial ones! | + | **Welcome back to another issue packed with open source goodness. This time we will be looking at noise reduction. If you have ever taken a picture in low light, or at night, you know what I am talking about. It is that - ‘picture of your best friend’s going-away party before they moved to China, and you will not get another photo like that, as you will only see her in 4 years’. Now let me just say, Darktable has some really powerful algorithms when it comes to noise reduction. For me, they are more powerful than those of other photo manipulation programs, even the commercial ones! |
- | Okay, let’s fire up Darktable and pick a photo with noise to edit. This time, I will choose a picture you can download and follow along: https:// | + | Okay, let’s fire up Darktable and pick a photo with noise to edit. This time, I will choose a picture you can download and follow along: https:// |
- | It is difficult to find grainy pictures on the internet as people put forward only their best photography. Steal this one from the Pentax forum. It is not really stealing, it’s ‘borrowing’. We are substituting the random kid for our friend - for educational purposes. | + | Bienvenue dans ce nouveau numéro rempli des bontés de l'Open Source. Cette fois-ci, nous regarderons la réduction du bruit. Si vous avez déjà pris une photo avec une lumière faible, ou de nuit, vous savez ce dont je parle. C'est ça - « image de la fête chez votre meilleure amie, sur le départ pour la Chine, et dont il n' |
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+ | Bon, démarrons Darktable et choisissons une photo avec du bruit à modifier. Cette fois, je choisirai une image que vous pouvez télécharger et suivre : https:// | ||
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+ | **It is difficult to find grainy pictures on the internet as people put forward only their best photography. Steal this one from the Pentax forum. It is not really stealing, it’s ‘borrowing’. We are substituting the random kid for our friend - for educational purposes. | ||
Once you have the random kid on screen, I need you to click on more modules on the right. Click on everything from “denoise” to “exposure”, | Once you have the random kid on screen, I need you to click on more modules on the right. Click on everything from “denoise” to “exposure”, | ||
- | Our goal is to get the maximum SNR (Signal-to-Noise Ratio), that is the maximum detail possible. We want to have a picture as a keepsake of (some random kid) before she moved to China. | + | Our goal is to get the maximum SNR (Signal-to-Noise Ratio), that is the maximum detail possible. We want to have a picture as a keepsake of (some random kid) before she moved to China. ** |
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+ | Il est difficile de trouver des images avec du grain sur Internet, car les gens ne diffusent que leurs meilleures photos. Volez celle-ci dans le forum de Pentax. Ce n'est pas vraiment du vol, c'est un « emprunt ». Nous remplaçons notre amie par cet enfant pris au hasard à des fins éducatives. | ||
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+ | Une fois que vous avez l' | ||
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+ | Notre objectif est d' | ||
- | As you can see the ‘power’ icon is greyed out on each of the modules. This means they are switched off. If you hover over each icon, you should see a tooltip. Now the profiled de-noise is the easiest. It will profile your lens and speed and work back from there. This is great if you used your camera to shoot the picture. This does not work so well with unknown cameras, like mobile phones. I want you to turn it off and on, and look to the right of the kid’s face at the window in the background. Where it is lighter, this tool does a very good job, but it does not do so well in the dark areas. You have two settings: non-local means and wavelets. You can read up about these methods on the Darktable website, but, for now, we are sticking to the practical so you can get to learning by doing. Turning these modules on and off takes some computing power, so if there is a pause, or your CPU fan spins up, this is normal, unless you have the top-of-the-range CPU. | + | **As you can see the ‘power’ icon is greyed out on each of the modules. This means they are switched off. If you hover over each icon, you should see a tooltip. Now the profiled de-noise is the easiest. It will profile your lens and speed and work back from there. This is great if you used your camera to shoot the picture. This does not work so well with unknown cameras, like mobile phones. I want you to turn it off and on, and look to the right of the kid’s face at the window in the background. Where it is lighter, this tool does a very good job, but it does not do so well in the dark areas. You have two settings: non-local means and wavelets. You can read up about these methods on the Darktable website, but, for now, we are sticking to the practical so you can get to learning by doing. Turning these modules on and off takes some computing power, so if there is a pause, or your CPU fan spins up, this is normal, unless you have the top-of-the-range CPU. |
- | Your homework is to go through each of the “blend modes” to see what they do. | + | Your homework is to go through each of the “blend modes” to see what they do.** |
- | This is what you will use with your own camera and photos most of the time. Should your noise, however, be tiny colour spots, you would need to use “wavelets” with “color” blend mode. Lots of times, you will see that you get tiny red spots instead of white ones if you take pictures at night with a flash. This is where you fix it. You can Zoom in on the kid’s red cheek to play with this. This is the method you use to get rid of annoying color noise in pictures that are supposed to be black, like for instance, black clothing. | + | Comme vous pouvez le voir, l' |
- | Tip: Don’t be afraid to zoom in and get a better look at what is changing. | + | Comme travail personnel, essayez chacun des « modes de fusion » pour voir ce qu'ils font. |
- | Back to our stolen picture. One of the strengths of Darktable | + | **This |
- | This is, by no means, comprehensive or the only way! If you look at our second image, you will see that our few selected modules are under the star = favourites, however the ‘correction group’ is the second last icon with the ‘broken circle’. As you added modules to favourites, so you can add too under correction group. Double click your modules to add. | + | Tip: Don’t be afraid to zoom in and get a better look at what is changing.** |
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+ | C'est ce que vous utiliserez la plupart du temps avec votre propre appareil photo et vos photos. Cependant, si votre bruit se compose de petits points de couleur, vous devrez utiliser les ondelettes avec le mode de fusion « couleur ». Très souvent, vous verrez que vous obtiendrez des petits points rouges à la place des points blancs si vos images ont été prises de nuit avec un flash. C'est ici que vous les corrigez. Vous pouvez agrandir l' | ||
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+ | Astuce : N'ayez pas peur d' | ||
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+ | **Back to our stolen picture. One of the strengths of Darktable is the ability to ‘layer’ corrections. You will see a difference in the way you ‘layer’ your corrections. Should you do local means BEFORE you do wavelet correction, it will look different than if you did it the other way around. This, I cannot give you a recipe for, the only tutor is experience. In my humble experience, it is better to start with red, then green, then blue, then local means, but this does not work universally. Do what works for you. Do not be afraid to undo everything and try something different. Darktable does non-destructive editing. Now we want to layer the next round of corrections on our photo. To do so, simply click on the very last tiny icon in the row where the on / off switch was, and select ‘new instance’. (If your middle mouse button is clickable, that is your short-cut).** | ||
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+ | Revenons à notre image volée. Une des forces de Darktable est sa capacité à corriger par « strates ». Vous verrez la différence dans la façon dont vous « stratifierez » vos corrections. Si vous avez fait la correction par moyenne-locales AVANT celle par ondelettes, alors le résultat paraîtra différent que si vous l' | ||
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+ | **This is, by no means, comprehensive or the only way! If you look at our second image, you will see that our few selected modules are under the star = favourites, however the ‘correction group’ is the second last icon with the ‘broken circle’. As you added modules to favourites, so you can add too under correction group. Double click your modules to add. | ||
Tip: For some reason, mousing over some drop-down options does nothing, but hovering your mouse over them, and rolling your mouse wheel to move the list below your mouse pointer, does then apply the effects on-the-fly so you can preview them. | Tip: For some reason, mousing over some drop-down options does nothing, but hovering your mouse over them, and rolling your mouse wheel to move the list below your mouse pointer, does then apply the effects on-the-fly so you can preview them. | ||
- | Before you go charging off, I want to say that not all noise is bad. When you make prints, minimal noise will disappear and if you overdo denoising, you will lose detail. | + | Before you go charging off, I want to say that not all noise is bad. When you make prints, minimal noise will disappear and if you overdo denoising, you will lose detail.** |
- | Tip: After denoising, it is a good idea to ‘up’ your sharpness on a picture to get back any edges that denoising softened. | + | Ce n'est en aucune façon ni exhaustif, ni le seul moyen ! Si vous regardez la seconde image, vous verrez que nos quelques modules sélectionnés sont sous l' |
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+ | Astuce : pour une quelconque raison, passer la souris sur certaines options en liste déroulante ne fait rien ; mais, passer la souris au-dessus d' | ||
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+ | Avant que vous ne me quittiez, je veux vous dire que tout bruit n'est pas nécessairement mauvais. Quand vous imprimez les photos, le bruit minime disparaîtra et si vous allez trop loin dans la réduction du bruit, vous perdrez des détails. | ||
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+ | **Tip: After denoising, it is a good idea to ‘up’ your sharpness on a picture to get back any edges that denoising softened. | ||
Tip: If you have a picture with a lot of dark areas, ‘up’ your exposure very slightly to expose the noise. (Low light photos too). | Tip: If you have a picture with a lot of dark areas, ‘up’ your exposure very slightly to expose the noise. (Low light photos too). | ||
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Tip: Adjusting by slider, is also not the only way. Right-click the number to be able to enter your own values as in the last picture. | Tip: Adjusting by slider, is also not the only way. Right-click the number to be able to enter your own values as in the last picture. | ||
- | Next issue: we will continue with more Darktable. We will be using the same picture so do not discard it yet! | + | Next issue: we will continue with more Darktable. We will be using the same picture so do not discard it yet!** |
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+ | Astuce : Après la réduction du bruit, c'est une bonne idée de remonter la netteté de votre image pour retrouver les lignes nettes qui ont été émoussées par la réduction de bruit. | ||
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+ | Astuce : Si vous avez une image avec beaucoup de zones sombres, monter l' | ||
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+ | Astuce : L' | ||
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+ | Dans le prochain numéro, nous continuerons plus avant dans Darktable. Nous utiliserons la même image ; aussi, ne la jetez pas encore | ||
issue143/darktable.1554039007.txt.gz · Dernière modification : 2019/03/31 15:30 de auntiee