For “hit-the-wall” and “spike” types of highlight structures, it is the spike itself. The conservative approach is to consider the value that starts the overexposure “structure” to be the maximum, as the higher values are mostly pattern and processing noise. Which value should be considered as practical maximum? Color channels preconditioning zoomed in. This is because of how the preconditioning is implemented – it is digital multiplication of data in red and blue channels by a number slightly higher than 1, applied before the data is written into a raw file.įigure 25. Zoom to blown out highlights - maximums are different for different channelsĬameras where color channel preconditioning is used are recognizable by the regular one-pixel gaps in the histograms of red and blue channels (sometimes, additionally, they have different clipping points for red, blue, and both green channels, as on fig.24). In our case, it is what we want as we will be analyzing how the clipping exhibits itself on the shots like these from Imaging Resource:įigure 24. Here we will try to demonstrate the typical “looks” of the histogram of the clipping zone.Īny curved metal or glass surface is a good source of specular highlights.
It is important to recognize the look and calculate the practical clipping point, which is not always the same as the maximum raw value.
#Fastrawviewer dynamic range for specific camera iso how to
It is useful to know how to determine practical clipping point for at least two reasons: the most common is that we need to know clipping point to determine the headroom in highlights and tune the camera settings to provide more reliable overexposure warning (“blinkies”) another one is dynamic range analysis (signal-to-noise ratio, SNR), and measurements of utilized well capacity (full well capacity, FWC, is seldom used in modern cameras).ĭifferent cameras, even if based on the same sensor, may render extreme highlights around the clipping point differently and differently, even with different values of clipping points, depending on ISO setting. Study of the highlight clipping using RawDigger histogram
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