Advanced RAW Photography Techniques

This section explains some advanced techniques for RAW photography based on image sensor characteristics.

Whiteout portions of RAW data cannot be restored even if the sensitivity is adjusted during development.
However, some cameras can record brighter areas than the white areas reproduced with zero exposure into RAW data.
If you conduct the following experiment using this software, you will be able to find out if your camera can record such bright areas.

Take a whiteout picture of something that contains details in a bright area.
Next, use this software to reduce the exposure. If the whiteout portion with zero exposure contains details, this means that your camera can record portions brighter than white.

If you conduct this experiment correctly, you will be able to find the maximum exposure where some details are not shown.
For example, details are shown at -1/2EV, but are not shown at higher EVs.
This means that your camera records RAW data at 1/2EV.
In other words, the top 1/2EV of the upper image sensor dynamic range is not used.

Some cameras have this function only when the ISO sensitivity is increased.

However, even if whiteout does not occur in bright portions at 1/2EV, it does not necessarily mean that you can take pictures using the full range.
This is because the range may already have lost linearity.
In order to use the full range, you must take some test photos to find how to reproduce the colors you want at that range.

If you can understand the above information, you may be able to create cleaner images with less noise by using 1/2EV overexposure.

Image sensors consist of either a CCD or CMOS and output signals according to the received light intensity.
However, the signal increase and stops at a certain light intensity. This is called saturation.
This causes RAW data to whiteout.
However, this does not mean that you can increase the light intensity to the image sensor up to just before the saturation point.
When the light intensity is outside of the range proportional with the output signal, color reproduction will be low.

Usually, cameras are designed to use only this proportional area for creating JPEG images.
However, this proportional area contains the tolerated area.
This tolerance area is determined by the camera maker, but it does not mean that you can tolerate it.

If you cannot accept the tolerated area, you can adjust the exposure to your tolerance level.
You can take underexposed pictures up to the tolerated area.
If you cannot accept your camera's tolerated area, you should think about getting a new camera.
When you take underexposed pictures, you may be able to avoid color reproduction loss, but noise may increase.
You must determine your balance between color reproduction and noise based on your camera sensor's performance.

In addition, you may be able to go over the tolerated area determined by your camera depending on the object being photographed.
In such cases, you can use overexposure according to the area mentioned in "Sensitivity Adjustment Potential" so that you can have clean images with less noise.