Gain Collaboration
Prepared 2007-12-01 by Bill Claff
Revised 2012-01-29
The purpose of the collaboration is to collect gain information on all Nikon DSLR models.
Gain can be used to estimate Full Well Capacity (FWC) as
well as relative Quantum Efficiency (QE).
It is also used to convert values such as Read Noise from ADUs to electrons.
A rigorous approach requires numerous pairs of exposures
taken at different light intensities.
However, this expedited procedure uses
a smaller number of pairs to produce reasonable results.
You need to be
running a Windows system and to get the following from my web site:
(You should be able to right‑click and save from these links.)
Choose your fastest
lens that can take images of your computer monitor at a comfortable distance.
Use a 50mm f/1.8D AF-Nikkor if it is available as this is what I used to
collect my data.
Use default noise
reduction settings. In particular do not use long exposure noise reduction.
Do not use ISO Auto.
Use RAW or RAW+JPG.
If your camera does
both 14‑bit and 12‑bit then use 14‑bit.
You will be using
Manual mode and Manual focus. Be certain Exposure Compensation is set to 0.
Put any solid white
image on the screen, such as an empty notepad.
All readings and
images are taken wide open in manual focus with the lens set to infinity and
touching the computer screen.
(If your screen curves a lot then be sure to use a lens with a recessed from
element.)
Take a set of 14
images at each full ISO such as 100, 200, 400, 800, 1600, 3200, etc. using the
steps as outlined.
Including any Lo or Hi ISO that your camera may have such as Lo 1.0 or Hi 1.0.
If you can, do any intermediate Lo ISO values as they are often of interest.
As you increase ISO you can either decreasing shutter duration or stopping
down.
Transfer the images
into the directory with the downloaded programs and batch file using your usual
procedure (although a card reader is preferred to Nikon Transfer).
Using a ‘DOS box’ in
the directory with the images run NefUtil as follows:
NefUtil . +CGAIN +M
+S +H>CGain.txt
This may take some
time.
The program will create a C_Gain.txt file and a CGAIN.txt file.
Simply e‑mail
the two .txt files to me at BClaff@comcast.net
and I’ll add your data to the collection.