Gain Collaboration
Prepared 2007-12-01 by Bill Claff
Revised 2012-01-29

Introduction

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.

Required Program

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.)

Preparing your Camera to take the Images

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.

Taking the Images

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.)

  1. Determine the shutter speed for a “correct” exposure; eg. 1/160s.
  2. Make the shutter speed longer by one stop; eg. 1/80s.
  3. Take 7 pairs of two images at each shutter speed increasing shutter duration by 1/3 stop between each pair; eg. 1/80s, 1/60s, 1/50s, 1/40s, 1/30s, 1/25s, 1/20s.

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 your Images to the PC

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).

NefUtil

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.

Submit your Results

Simply e‑mail the two .txt files to me at BClaff@comcast.net and I’ll add your data to the collection.