How To Use RawDigger

Establishing the in-camera exposure meter calibration point is the way to extract more dynamic range from your camera

RawDigger. Determining the middle grey value

“My camera has not enough dynamic range”

“The numbers on that and that review site suggest that many stops of the dynamic range, but I do not see it, my highlights are blown out, my shadows are noisy and blotchy”

Part of the problem is in how one sets the exposure. To set the exposure correctly it is good to know how the in-camera light meter works, and how it is calibrated. So, what is exposure meter calibration and why is it important?

Understanding of the exposure meter calibration determines the outcome of the exposure.

What does this mean? Well, let’s take a closer look.

Digital camera light meter calibration

RawDigger. Exposure meter calibration

Unlike film sensitivity, which can be measured using a standard procedure, the sensitivity of a digital camera is somewhat a fuzzy concept.

Moreover, the sensitivity of the camera turns out to be a pretty random variable, and the camera manufacturers do not make it easier for the user, adding quirks of their own.

Further on we will discuss a simple method, which allows us to calibrate the exposure meter in such a way that on different cameras (or on different sensitivity settings of the same camera) the results are predictable.

Determining pixel charge capacity and amplification gains for a digital camera

Unlike its film-using predecessors, modern digital cameras present us with a challenge of a non-replaceable sensor. Due to this, the given amount of light, which falls on an element of the sensor (pixel), creates the same charge irrespective of ISO sensitivity setting resulting in an identical output signal. The response of the sensor itself depends only on the light, and not on the digital camera sensitivity (ISO) setting.

It would seem that this contradicts everyday photographic practices: if there is not much light, you have to set the sensitivity (ISO value) higher, and the picture will come out right, but if you set the sensitivity low, then it won t come out right. Lets have a closer look.


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