Exercise 7: YOUR TOLERANCE FOR NOISE
Noise has always been the troublemaker. In the world of film cameras, it was known as grain and the digital world, calls it noise. I have faced the noise problem myself. I knew that mainly higher ISO or long exposure triggers the noise problem. However, I had never gone in-depth to find out, what is the cause for the noise. This exercise was a good opportunity to learn more.
During the exposure, one of the task that camera sensor performs is, to count the number of photon (of one particular color) that are being received by photoreceptor. Sometimes there is a sampling error that occurs during this process and that results into the image with noise. In simple language when you set the camera on high ISO the sensor of your camera works at higher sensitivity. Very little light is falling, hence pixels (sensor particles) start heating up more. Modern sensors are highly filled with the pixels. Due to proximity when the heating process is going on pixels can disturb the adjacent pixels. This can introduce noise in photos. New cameras are coming up with better technology to handle this issue. To know more about this topic “Click here”.
On many occasions (like sports photography, low light photography) photographers have to select between two bad choices available. Go for Low ISO and settle for blurry picture or boost up to the ISO and compromise with the noise. Nowadays editing software can help in bringing the noise levels down, however, at times that is quite inadequate. While doing the noise reduction, we are surely compromising the quality.
I try to shoot all my images with as low ISO as possible (without compromising the shutter speed), as this gives me the flexibility to use the image for whichever media I want. If the image has very small amount of grain, then maybe I can ignore it. Provided image is going to be used for smaller print or web sizes. This is very important, because if one tries to enlarge the image that has noise then surely the quality will not be satisfying. I am using Nikon D300s, I have observed that in low light condition, after ISO-1600 I start getting visible noise problems.
Now lets begin with the exercise. I have shot these images with natural light. However, it was close to sunset hence the light was quite low. Camera was fixed on the tripod and the Aperture was set on f/8. The ISO range is 100 – 6400.
Image clicked at ISO 100 exposure was 2 seconds. The quality of the image is very good, and there is no noise at this point.
Frankly speaking till ISO 800 images have the clarity and they are quite useable. At the ISO 1600 noise has been introduced and it is noticeable. However, at the ISO 3200 the image looks unworkable. This is when one can see the power of software. See the image below.
In LR3, I made a virtual copy of the image that had ISO 3200, and applied noise reduction. I have also increased the sharpness and modified the curves little bit to balance the loss of detail. See the comparison between the images. If required, even the images with very high noise levels can be recovered and used. This is especially a blessing for situations where noise cannot be avoided.