noise problem
- Thread starter qap15
- Start date
You don't have enough light. It's not a coincidence that your brightest shooting has the least noise.
This isn't something that camera settings are going to solve for you -- you simply need more light.
dvx100a pal
David, how are the clips in dark streets shot--just wondering?You don't have enough light. It's not a coincidence that your brightest shooting has the least noise.
This isn't something that camera settings are going to solve for you -- you simply need more light.
jambredz
Veteran
Well many scenes in films u think are dark,are in many cases very well lit. In post they reduce the brightness and do colour grading to make it seem darker or more moody than it really is. Now if ur just talking about footage on vimeo that's shot under streetlights and they say its something like test footy or they state its shot under street lights alone...and u don't have noise then I guess the settings I gave u will help alleviate but def not eliminate.
Oh and if I'm not mistaken the 100a is the noisest of the dvx series.
Oh and if I'm not mistaken the 100a is the noisest of the dvx series.
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Thanks for that info, it means it can be reduced but not eliminated in those street footages thanks.
They don't rely on the lights which are there. They use powerful instruments to provide plenty of light, yet make it SEEM that the light is coming from street lights.
Then, they leave dark elements in the scene to convey the idea of night.
Otis Grapsas
Carbonite Member
Visibility of noise = signal/noise = different for each of the three color channels.
1) A camera at zero gain, without white balance gets minimum noise on all three channels. Lets assume a true 500:1 S/N for a camera on all three color channels. But it should look rather green or red at that setting, depending on lighting. So we need white balance. See next paragraph.
2) Typical digital (the common type) white balance for daylight is (r,g,b)=(1.8,1.0.1.5). Which means red gets an 1.8x gain and blue gets an 1.5x gain. These amplify noise. It's just like applying gain to the overall camera, but it gets at different level on each channel. At the daylight white balance mentioned, the S/N becomes:
500/1.8 for red, 500/1.0 for green, 500/1.5 for blue. So, it's 278, 500, 333 for r,g,b.
But we could put the right optical white balancing in front of the lens, and avoid the increase of noise. If we can find an optical white balance filter that fits the daylight response, the noise can usually approach 500,500,500 for r,g,b. But we have lost almost one stop by optcally attenuating the stronger channels. Which is not really important in daylight.
3) Now, lets see what incadescent white balance can be. A typical setting for digital white balance gains is (r,g,b)=(1.1,1.0,2.7). 2.7x gain on blue due to the warm lighting, that's equivalet to about 9dB of gain on blue, and that's on the camera 0dB gain setting. This is what makes shots under warm light noisy. The S/n becomes 500/1.1 for red 500/1.0 for green and 500/2.7 for blue. Which is 455 for R, 500 for G and only 185 for blue.
But we could put an appropriate optical white balance filter in front of the lens and reduce the required gain in blue or even get close to eliminating it. Then the S/N would be 500 for all colors. But since this filter would attenuate the strong colors (red and green), we have lost sensitivity, 9dB of sensitivity. Our ISO300 becomes an ISO180.
If we increase gain to get the sensitivity back, we will have 2.7x gain on all three channels, so the S/N would be 185 for all three channels. Instead of heavy noise in the blue, we have heavy noise in all channels. It doesn't make sense. So we do something else, we increase the lighting by 2.7x. So we get the original exposure, identical to the one with digital white balancing gains, but now the blue is as clean as everything else. All channels have a S/N of 500 when the camera is at 0dB.
4) So, we either live with digital white balance and increase noise in some channels, or use optical white balance and increase light.
5) If we keep using digital white balance and increase light, there is no adventage, the blue channel is still under 2.7x gain. We just have to stop down and the S/N will be identical. So, more light cannot solve the noisy blue channel of the typical camcorders under warm lighting. But carefully prescribed optical white balance can do it combined with the increase in light to cover the sensitivity loss.
6) An alternative is to change the color of the light we are using. A color filter in front of the light, allows white balancing on a different setting, such as daylight, which typically does not involve heavy gain. So the results will be cleaner. But the light will still have to be increased, just like with the optical white balance in front of the camera lens.
7) We can also do the same by choosing daylight white temperature lights. Or slightly lower than daylight. It will be a lot better than 2700K light bubls or 3200K.
8) Everything mentioned above refers to the 0dB setting on the camera. A camera under gain affects S/N also. If the camera has a S/n of 455,500,185 for r,g,b as mentioned above under 2700k incadescent at 0dB, it will be 227,250,92 at 6dB, 113, 125, 48 at 12dB and 56,62,24 under 18dB and your blue will be a patchwork of noise. A 24 S/N ratio on blue means the blue part of whites approaching clipping is only 24 times higher in level compared to the blue channel noise. So your greys could be only 5 times greater than the noise, and the deep greys will be a noisy mess, invisible under the noise floor.
Hope this answers some questions on why the results could look inferior to what others are getting and helps reduce noise a little
1) A camera at zero gain, without white balance gets minimum noise on all three channels. Lets assume a true 500:1 S/N for a camera on all three color channels. But it should look rather green or red at that setting, depending on lighting. So we need white balance. See next paragraph.
2) Typical digital (the common type) white balance for daylight is (r,g,b)=(1.8,1.0.1.5). Which means red gets an 1.8x gain and blue gets an 1.5x gain. These amplify noise. It's just like applying gain to the overall camera, but it gets at different level on each channel. At the daylight white balance mentioned, the S/N becomes:
500/1.8 for red, 500/1.0 for green, 500/1.5 for blue. So, it's 278, 500, 333 for r,g,b.
But we could put the right optical white balancing in front of the lens, and avoid the increase of noise. If we can find an optical white balance filter that fits the daylight response, the noise can usually approach 500,500,500 for r,g,b. But we have lost almost one stop by optcally attenuating the stronger channels. Which is not really important in daylight.
3) Now, lets see what incadescent white balance can be. A typical setting for digital white balance gains is (r,g,b)=(1.1,1.0,2.7). 2.7x gain on blue due to the warm lighting, that's equivalet to about 9dB of gain on blue, and that's on the camera 0dB gain setting. This is what makes shots under warm light noisy. The S/n becomes 500/1.1 for red 500/1.0 for green and 500/2.7 for blue. Which is 455 for R, 500 for G and only 185 for blue.
But we could put an appropriate optical white balance filter in front of the lens and reduce the required gain in blue or even get close to eliminating it. Then the S/N would be 500 for all colors. But since this filter would attenuate the strong colors (red and green), we have lost sensitivity, 9dB of sensitivity. Our ISO300 becomes an ISO180.
If we increase gain to get the sensitivity back, we will have 2.7x gain on all three channels, so the S/N would be 185 for all three channels. Instead of heavy noise in the blue, we have heavy noise in all channels. It doesn't make sense. So we do something else, we increase the lighting by 2.7x. So we get the original exposure, identical to the one with digital white balancing gains, but now the blue is as clean as everything else. All channels have a S/N of 500 when the camera is at 0dB.
4) So, we either live with digital white balance and increase noise in some channels, or use optical white balance and increase light.
5) If we keep using digital white balance and increase light, there is no adventage, the blue channel is still under 2.7x gain. We just have to stop down and the S/N will be identical. So, more light cannot solve the noisy blue channel of the typical camcorders under warm lighting. But carefully prescribed optical white balance can do it combined with the increase in light to cover the sensitivity loss.
6) An alternative is to change the color of the light we are using. A color filter in front of the light, allows white balancing on a different setting, such as daylight, which typically does not involve heavy gain. So the results will be cleaner. But the light will still have to be increased, just like with the optical white balance in front of the camera lens.
7) We can also do the same by choosing daylight white temperature lights. Or slightly lower than daylight. It will be a lot better than 2700K light bubls or 3200K.
8) Everything mentioned above refers to the 0dB setting on the camera. A camera under gain affects S/N also. If the camera has a S/n of 455,500,185 for r,g,b as mentioned above under 2700k incadescent at 0dB, it will be 227,250,92 at 6dB, 113, 125, 48 at 12dB and 56,62,24 under 18dB and your blue will be a patchwork of noise. A 24 S/N ratio on blue means the blue part of whites approaching clipping is only 24 times higher in level compared to the blue channel noise. So your greys could be only 5 times greater than the noise, and the deep greys will be a noisy mess, invisible under the noise floor.
Hope this answers some questions on why the results could look inferior to what others are getting and helps reduce noise a little
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Otis Grapsas
Carbonite Member
Btw, exposure is king. Make the most of your exposure range Using the same camera settings, if you only get a grey level of 64 instead of 128, your noise is doubled so your S/N is reduced to half, it's no different than using 6dB of gain. When you bring it up in the post, it will look bad. Watch highlights from overexposure but keep in mind grey levels need proper exposure.