Variable gain - variable noise
Posted: Sun Feb 05, 2006 9:39 pm
Video cameras contain an automatic gain control. In low-light conditions the gain becomes very high, and the noise usually becomes visible. NV is capable of removing, or at least reducing the noise considerably. This is possible if the calibration is made using the same gain as the processed clip.
But how NV handles the case where the lightning conditions vary a lot during the video clip? Is the Noise level setting useful in Noise filter settings? I studied this by recording a video clip that started from my room's corner and ended to a clear blue sky seen through the window. I also made a single video frame that contained calibration targets recorded at variable lightning (=gain) conditions.
My goal here is to find settings for NV that:
Next I left the Noise level settings in their default positions and processed my video clip. The result was satisfactory. Some details were lost in the low-gain part, and the noise in the high-gain part was reduced a lot, but is still a bit annoying.
The Noise level setting is probably useful in processing photographs where the noise levels are quite low. But the situation is quite different when we talk about videos taken with digicams and home camcorders. I wonder if the inverted Noise level setting could help in filtering home videos. That is, the noise below a certain level is preserved, and only the higher elements are reduced.
But how NV handles the case where the lightning conditions vary a lot during the video clip? Is the Noise level setting useful in Noise filter settings? I studied this by recording a video clip that started from my room's corner and ended to a clear blue sky seen through the window. I also made a single video frame that contained calibration targets recorded at variable lightning (=gain) conditions.
My goal here is to find settings for NV that:
- - leave the frames that are taken in good lightning (low gain) untouched
- reduce considerable the noise in frames taken in low light (high gain)
Next I left the Noise level settings in their default positions and processed my video clip. The result was satisfactory. Some details were lost in the low-gain part, and the noise in the high-gain part was reduced a lot, but is still a bit annoying.
The Noise level setting is probably useful in processing photographs where the noise levels are quite low. But the situation is quite different when we talk about videos taken with digicams and home camcorders. I wonder if the inverted Noise level setting could help in filtering home videos. That is, the noise below a certain level is preserved, and only the higher elements are reduced.