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At this point look at the intensity graph and determine which channel is the weakest (lower). 

1. Start with this channel and increase the exposure time until its value is between 240-245.  For the current lighting this is the red channel and well use this for these instructions but this could vary if the lights are changed. 
2. Adjust the green exposure until the red/green ratio is 1.000 +/-0.005. 
3. Adjust the blue exposure until the blue/green ratio is 1.000 +/-0.005. 

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Lets say in the above example you could not get the red to to 240 you have several options:

1. Open up the f-stop for more light
2. Increase the line rate (slower scan speeds) so that you can increase the exposure period
3. Use gains to amplify the signals.

Before Starting:

• Note which version of standard you are using. Each color standard values vary based on the version and the manufacturer of the standard. The XRite Colorchecker 2019 (MacBeth standard, Figure 5) is the preferred card to use for calibration. The program is set up to use the White and Black squares on the XRite Colorchecker (MacBeth standard). On the Xrite color checker standard the RGB values of White and Black are listed here for various illuminants. White RGBs are 242, 242 and 236 and and black RGBs are 49, 49, 50 (those values are calculated using illuminant D65), as of 01 Dec 2021 there is discussion that we will use RGBs calculated under illuminant A as it better matches our LED lights. Using illuminant A the RGBs for white is 240, 242, 235 and black is 50, 50, 50. For the QP 101 v4 card, the RGB values are 235, 235, 235 (light grey), 111, 111, 111 (medium grey), and 80, 80, 80 (dark grey) (Figure 6). All SHIL calibration standards are found in drawer PP-2B.
• Obtain the 3D standard (Figure 5) and the gray silicone mat standard from PP-2B.
• Set camera f/stop to either F/16 or F/22 (Figure 7). The camera manufacturer suggested F/22 as the preferred f/stop for scanning with the our light set up however we have found F/16 works well for our section halves and is the most used f/stop for calibration and scanning sections. For hard rock cruises, where 360° whole round scanning is required, a larger f/stop number maybe required.
• If you haven’t set the camera’s height, now is the time to do so!  See the section Camera Height Adjustment at the end of the calibration section. The camera height should not need to change between expeditions.

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