#Silverfast hdr raw file software

Look at the histogram of crop of a very small portion of the image near the center of the image. Some at high exposure, some at moderate exposure and some at low exposure. You might even consider taking the lens off altogether.

It will also help if you will defocus the lens to make sure there's no small-scale variability in the image. Find a perfectly uniform object to photograph, like a blank wall. I'm not talking about your regular photos but rather photos generated specifically for the purpose of testing this. Now to the question of t-max 100: here is one way you can investigate this experimentally using your own scanner and your own photographs. I don't know if this applies to 8 bit scanners.

#Silverfast hdr raw file software

However, I understand that in some signal processing systems when a high-bit word is converted to lower bits the software may add pseudo-random noise in order to make sure that dithering is present. I am told that when a scanner saves in 8 bit mode there may be a non-linear transformation, and I can't say to much about that possibility. If so then it is possible that the effective dithering effect might go away due to roundoff error. Things get a little more complicated if a non-linear transformation is applied to the signal somewhere in the signal chain. This means that if there is effective dithering taking place at low signal levels it will also be there at high signal levels. They become proportionally less important compared to the signal level if the signal level is high, but from the point of view of how it relates to the effective dithering effect the important comparison is not the comparison to the absolute signal level but rather the comparison to the step size of the analog to digital converter. None of the noise sources mentioned above go away at high signal levels. This probably comes mostly from some combination of sensor noise and shot noise. Anyway, a lot of scanner reviews talk about the existence of noise in the shadows. There is also something called flicker noise.

For example, there is something called thermal noise, which comes from the random thermal motion of electrons. This can come from various sources, primarily electronic in nature. Sensor noise (as distinct from shot noise) is very likely at low signal levels. For example, if a high signal level were equivalent to detecting 10,000 photons the standard deviation would be 100, so if the step size were 10 photons it would be more than enough to produce effective dithering. It would also apply at high signal levels. In that case shot noise would be more than enough to produce effective dithering. Suppose that the analog to digital step size at low signal levels is equivalent to ten photons. For example, if 100 photons are detected then the standard deviation is 10 photons.

To give you an idea of how the statistics work, the standard deviation is equal to the square root of the number of photons. I don't know if shot noise is a factor in scanners, but I would not be surprised if it is. Shot noise comes from the quantized nature of light in combination with the statistics of photon detection, and in theory it can show up at low signal levels. The other sources could include (but not limited to) sensor noise or even shot noise. The noise could come from a combination of film grain and other sources. Click to expand.The important thing is whether there is noise in the scan.