Neat Image user guide / Device noise profiles / Preparing a profile set for different device modes
To build a set of profiles for a certain camera or scanner, you have to identify different device parameters that affect the noise characteristics and that you will take into account during profiling. There may be many device parameters but not all of them influence image noise and those that do differ by the strength of their influence. Naturally, you are only interested in those parameters that appreciably affect noise. Different noise profiles should be prepared for different values of important parameters, so you have to identify these parameters in the first place.
In the tables below, those parameters are described that appreciably affect noise characteristics (from the most to the less important ones) for digital cameras and scanners:
| Digital camera parameters in the order of decreasing importance | ||
| ISO rate | 50, 100, 200, 400, etc.; depends on a camera | Higher ISO rate produces more noise. |
| Sharpness adjustment | Low, Normal, High, etc.; depends on a camera | Internal sharpness adjustment of a camera makes noise more intensive. Using no internal sharpness adjustment produces least noise. |
| Compression | 1:1 (or Uncompressed), 1:5 (or Fine), 1:10 (or Normal), 1:20 (or Basic), etc. or 2 bits/pixel, 4 bits/pixel, etc. depends on a camera | Strong JPEG compression typically produces more JPEG artifacts and destroys image elements including noise; weaker compression preserves more image elements including noise created by the image sensor. It is preferable to use the lowest amount of compression possible for the best results. |
| Resolution | 1:1 (original resolution, like 1600x1200), 1:2 (downsized in camera, e.g., 800x600), 2:1 (digital zoom, 2x), etc. | Camera's internal interpolation (both downsizing and upsizing, e.g., that of digital zoom) changes many characteristics of noise. |
| White balance | Sun, Cloudy, Incandescent, Fluorescent, etc.; depends on a camera | White balancing changes characteristics of noise (mainly of color noise) slightly. |
| Exposure | 1/16s, 1.0s, 16s; | Longer exposures produce more hot-pixel noise; also, some cameras switch on the automatic noise reduction when exposure is longer than a certain threshold - this may affect the noise levels. |
| Scanner / camera parameters in the order of decreasing importance | ||
| Film type | For example, Kodak Tmax 400, Kodak Tri-X Professional 320, Fuji Superia 200, etc. | Every film type produces specific grain pattern, which depend on film materials. Strength of the grain depends on ASA/ISO rate of the film. |
| Scanning resolution | For example, 300 dpi, 3200 dpi, 4000 dpi, etc. | Higher scanner resolution emphasized film grain and makes it more evident in the scanner image. |
| Number of scan passes | Single pass, 2x pass, 4x pass, etc. | Multi-pass scanning can potentially produce less grainy images. |
If two images were captured in the same or similar conditions (most of the above device mode parameters are the same) then the noise of these two images should be very similar. If you have built a device noise profile using one of these images, you can use this profile to filter both images with good results. If however, the shooting or scanning conditions were different then the noise in two images could be significantly different. In this case, cross-use of the noise profile is not recommended. Instead, two different profiles should be built and used to filter these two images.
Based on these considerations and tables above, identify the device mode parameters of your camera or scanner that (1) are important from the noise standpoint and (2) are changed in your imaging tasks. For example, if you never change the sharpness adjustment of your digital camera then there is no need to build profiles for different values of the sharpness adjustment parameter. On the other hand, if you do shoot with different ISO rates then you have to build profiles for every ISO rate you use. Some parameters are less important (for example, the White Balance or Exposure) and you may simply choose to ignore the difference in noise characteristics caused by such device mode parameters.
Identify the device mode parameters that, in your opinion, are important. For example, you could include the ISO rate: ISO 100, 200, 400; and JPEG compression level: HQ, SHQ. Then it is straightforward to write down all combinations of the selected parameters:
JPEG HQ, ISO 100
JPEG HQ, ISO 200
JPEG HQ, ISO 400
JPEG SHQ, ISO 100
JPEG SHQ, ISO 200
JPEG SHQ, ISO 400
Now you have to prepare a profile for each combination from this list. Please proceed to the Stage II to build profiles for all combinations.