Hi to all the experts here, i'm interested in buying a new 18x zoom panasonic prosumer cam. the cam comes with 8 megapixel and 1/2.5" CCD sensor size. i have read that with 8megapizel, 1/2.5" sensor size is too small, which will cause image to be noisy.
my question is, if i want a clear and sharp noiseless pic, other than manually set (or force) the ISO at 100, will it help if i take pictures at lower picture size? that is to say instead of taking pic at full 8mega pizxel, i take the picture at probably 1024x960 size only.
Thanks for viewing..
The amount of Noise is inversely proportional not to sensor size per se but proportionally to pixel density (i.e. how closely packed the photosites are physically within the CCD sensor) and individual photosite size (which determines how much light signal is collected per photosite. The more light is collected, the lower the noise to light signal ratio which determines how apparent the noise will be.).
In most situations, all the photosites (i.e. 8 MP in this case) are still used even if you choose a lower picture resolution (this is evident in that the 35mm equivalent focal length remains the same regardless of the picture resolution you choose. In some cameras, only a part of the CCD sensor is used and therefore the angle of view is narrower, resulting in higher 35mm equivalent focal length for those lower resolution pictures even though the actual focal length remains the same). (This part requires some understanding of angle of view, focal length vs sensor size).
In the usual Bayer Array arrangement, each pixel in the picture resolution does not correspond exactly to one photosite but is a calculated value using the values collected by a number of adjacent photosites (each of them collecting only a value for Red, Green or Blue).
So at the raw level, you're going to get the same amount of noise regardless of the picture resolution chosen.
A lower resolution picture is usually just a downsizing of resolution from original picture in a way similar to what downsizing does in post-processing software (such as in photoshop).
At lower resolution, noise will be less apparent to the eyes. However, it also means that at high ISO where there is a high level of noise at the raw level, there is going to be a much more severe loss of details in lower resolution pictures.
In the case of the FZ18, I don't know how the camera handles the downsizing and jpeg compression in its algorithm. Only someone with the camera can try out and show us the result. Theoretically, since noise will definitely be high at the raw level due to a high pixel density and small photosites on the small 1/2.5" CCD sensor, you still cannot run away from the effects of high noise at high ISO at the raw level even if a low resolution is chosen and it is basically still the same trade off between noise and details at various picture resolution.
