 10 tips to fight image noise
If you are experiencing image noise problems with your compact camera you are not alone.
In today's compact camera arena there is a prevalent disease: image noise. This is a clear disadvantage for this category of cameras. In some cases, like the the high-end G9, even at ISO 100 there is noticeable luminance noise in shadow areas in well lit scenes. Take a look at the following two crops: both were shot at noon with the lowest ISO sensitivity allowed (ISO 80) by the G9 .
 
The problem lies in the imaging sensors and it is unavoidable because of physical limitations. The equation is simple: try to fit millions of pixels in a sensor smaller than your pinkie fingernail and you'll get noise.
Obviously the problem is aggravated if you pump up the ISO levels. It is pretty much the way a microphone works. If you try to record with a microphone really close to your mouth, you won't need too much amplification to obtain a good recording; but if you set the microphone in the other side of the room, you'll have to crank up the volume to register your voice. Obviously other sounds will be amplified as well, and there will be audible noise. The ISO settings amplify the signal of the sensor and you'll get random noise.The luminance noise are luminosity aberrations that show as irregular particles across the image. The irregular color variations (color aberrations) are known as chroma noise.
The first option to deal with noise is to leave the pixels untouched using a RAW file to process the image later with software or you can decide to shoot JPG files and leave the camera's processor in command to apply a noise reducing algorithm. That's only possible with the G9, since this is the only Canon's compact digital camera to feature RAW files.
Testing the noise performance
First, we shot the scene at the right in very low light, so the noise would show up even at the lowest ISO levels. We made a set with the G9 with RAW then JPG to test the in-camera noise reduction approach of the Digic III sensor. We compared these files with two other high-end compacts: the Canon Powershot G7 and the Canon PowerShot S5 IS to analyze the typical noise performance of a compact digital camera. |
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There are several conclusions from the images above:
1. Although noise begins to show at ISO 100 it becomes a real problem at ISO 400
2. Noise gets much worse at ISO 800 and ISO 1600 and these settings are unusable. Why does canon provide such futile setting? It remains an enigma.
3. In JPG, the G9 handles the noise better than the G7
4. The G9 noise is equally bad compared to the G7 or the S5. It's worth to mention than the G9 showed less noise with 12 mega pixels than the S5 with 8 mega pixels. The difference is that the G7/G9 have a bigger sensor (1/1.7") and the S5 has a smaller one (1/2.5").
Software improvement
There are several noise reduction programs such as Neat Image, Noisware, Grain Surgery, Picture Cooler, Noise Ninja and -obviously- Adobe's omnipresent set of imaging software. We have used extensively Lightroom and Noise Ninja.
For the following test we tried to reduce the noise with Adobe Lightroom 1.3 and Noise Ninja. Lightroom's approach is pretty straightforward with a slider for each kind of noise (luminance and chroma). The results are pretty good and the approach is not overly aggressive but you can't fine tune the settings.
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G9 - RAW file |
Filtered with Adobe LightRoom |
Filtered with Noise Ninja |
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ISO 100 |
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ISO 200 |
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ISO 400 |
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ISO 800 |
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ISO 1600 |
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The noise levels were so high with this sample at ISO 1600 that Noise Ninja was unable to profile the image. |
Noise Ninja produced comparable results with Lightroom at default settings, but it is more advanced when you want to fine-tune your image. Although it is good to have more control, don't expect miracles. The good news is that you have much more control over the different causes of noise and you can decide how to treat them.
The G9 vs dSLRs
We made a set of shots of the same scene with dSLRS (40D and a 5D). Take a look to the comparison shots. The difference is spectacular.
The performance of both dSLRs is just impressive. At ISO 1600 they produced as much noise as the G9 at ISO 100. The size of the sensor makes a huge difference in quality image. Although we tested two high end dSLRs, you can obtain excellent results even with entry level cameras such as the Rebel XT or Rebel XTi.
10 tips for fighting image noise
Compact cameras have real problems with image noise at any sensitivity level under low light conditions and it gets worse with every step up of the ISO setting. This problem is inherent to all compact digital cameras. Here are several ways to deal with image noise:
1. Stay on the light. Try to avoid low light conditions whenever possible.
2. Maintain low ISO levels. Stick to ISO 80, 100 and 200. Set the ISO 400 as the last resort.
3. For emergencies only. Use the ISO 800 only if you have no option. ISO 1600 is hopeless.
4. Don't sweat the small stuff. Decide what you will do with your images: are you going to print a 4x6 or a huge poster? Do you want to share them via e-mail or in a photo share web site but they won't ever be printed? If you pixel-peep your images you may suffer unnecessarily.
5. Know your limits. Experiment and try to see your camera performance at different ISO levels when printing or when the image is displayed at a normal size in your screen. Try to find your camera's limit and don't force things unnecessarily.
6. Use the software (or plug-in) of your choice . But expect no miracles: if you have an IS0 400 noise problem you will typically improve the image as if the photo had been shot at ISO 200 but it is very rare to reach a quality of ISO 100 without seriously degrading the original image.
7. Don't lose detail. Apply the exact noise reduction to avoid loss in detail. Most software solutions will reduce dramatically the detail in your photos. If you overdo your photos with noise reduction the images will seem airbrushed and with a plasticky look.
8. Maybe it's time for a dSLR. If your compact camera noise performance is causing you a major trouble, then you must seriously consider a dSLR. The Rebel XT and XTi are really light and small and both provide great performance at high ISO levels and under low light conditions.
9. Use the luminance noise creatively. Film photographers take advantage of the grain in high ASA films. Sometimes you may find that the noise can create some interesting effects. Just remember to use an effect intentionally, not to cover a defect: this technique should not be hiding the dirt under the carpet.
| 10. For sentimental reasons. A friend had a meeting with his idol Michael Dell. Someone took a picture but the light was terrible, the flash didn't fire, the shot had strong hand-shake blur and everyone looked like posing in the Tunnel of Love. The image was horrible, but the content was very important: the lifetime opportunity to have a picture with a legend. The final result has questionable quality: everybody ended looking as if they paid a visit to a bad plastic surgeon; the chroma noise was unbearable and the image ended converted to gray scale. But our friend was incredibly happy: "You are an artist!" he said, and he didn't truly cared about the terrible imperfections of the "enhancement". Sometimes even the worst noise in the world won't really matter if the content of the image is truly important for you. |
 Original image |
 Final image
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