or How to create better images
Why combine?
How many frames?
Calibration: how to use dark, flat and bias frames
Which ISO speed?
The Calibration Process
The answer is simple: only to increase the Signal to Noise Ratio (SNR).
Is the resulting image more luminous? No.
Is the resulting image more colorful? No.
The goal of combing many images into one is only to increase the SNR. The
resulting images are neither more luminous or more colorful but they contain
much less noise which will let you stretch the histogram a lot more which will
give you more freedom to bring back colors and details.
The example on the right shows the result of stacking a single image.
No calibration was done and some hot pixels are visible in some cases (no dark and bias subtraction, no flat division).
Mouse over the text to see the result of the stack for 1 image 2 images 4 images 16 images 32 imagesYou can see that the resulting image is not lighter or more colorful when the number of stacked light frames is increasing but is much smoother.