Deflicker based on EV change
Of course (sigh), in our special case of a near-full Moon rising in a dark sky, a deflicker based on luminance is not effective. The change in brightness of the average of the image is quite low (luminance change from 0.066 to 0.065) for a 1/3 change in stop.
So in order to reduce the step function of a manual adjustment in brightness (typically 1/3 stop), it is important to deficker based on smoothing out the EV changes. Note that the smoothing is to be done on "Moon images", before compositing with a background.
Source: https://en.wikipedia.org/wiki/Exposure_value " it is common practice among photographic equipment manufacturers to express luminance in EV for ISO 100 speed"
The recommended f-number and exposure time for given lighting conditions and ISO speed are given by the exposure equation
where[5]
- N is the relative aperture (f-number)
- t is the exposure time (“shutter speed”) in seconds[2]
- L is the average scene luminance
- S is the ISO arithmetic speed
- K is the reflected-light meter calibration constant (usual value is K=12.5)
Flipping it around, L = K*N^2/(t*S) units of lux;
The concept of deflickering is to keep L near-constant or at worst so slowly changing it does not distract the viewer. For a typical night-time shot of an orange Moon low in the sky, the values are f/8 ISO 400,and 1/5s, hence L= 0.0024; at f/4
