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- Note which version of standard you are using. Each color standard values vary based on the version and the manufacturer of the standard. The X-Rite Colorchecker (MacBeth standard) 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). White is 243 and Black is 15 (Figure 21). For the QP 101 v4 card, the RGB values are 235, 111, and 80 (Figure 21). All SHIL calibration standards are found in drawer PP-2B.
- Obtain the 3D standard (Figure 20), the gray silicone mat standardand the lens cap from PP-2B.
- Set camera f/stop to either F/16 or F/22 (Figure 22). The manufacturer suggested F/22 as the preferred for standard scanning with the current light set up however we have found F/16 work well and is the most used F/stop for calibration. For hard rock cruises, where 360° whole round scanning is required, a larger F/stop number is 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.
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Figure 20: 3D standard with Xrite Color checker (MacBeth Color) standard.
Figure 21: QP card 101 v4 grey scale standard.
Figure 22: Setting the F Stop on the Camera. Note that F/22 was recommended by the camera manufacturer but this is debated. F/16 is the preferred value by the imaging specialists onboard.
Calibration Check
The following calibration check is designed for technicians to check the SHIL’s calibration. The calibration check is required to be done at the start of every expedition prior to receiving the first core. If adjustments to the calibration are needed, please see the Calibration section below.
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3. Compare the current scan rate (Speed) to the requested rate. The Speed (Figure 23) of the camera will be in the first box. If the values need to be changed to match the requested values by the science party, please proceed to the calibration section below as you will need to do a full calibration. If the values match, close the ‘Image Scan Setup’ window and proceed with the following checks. Speed of 8 to 10 is the most common value.
Figure 23: Checking the Image Scan Speed.
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4. Check that the Max Image Scan Speed is equal to, or slightly more than the designated scan rate (Speed). The Max Image Scan Speed is usually between 8 to 10.
5. Again, if the values need to be changed to match the requested values by the science party, please proceed to the calibration section below. If the values match, close the JAI Camera Set-up window and proceed.
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3. Click JPEG Corrections tab (Figure 30-3). Adjust the Brightness, Contrast, and Gamma levels (Figure 54-4) to achieve a straight line in the Applied Corrections tab and the ROI Corrected box should have values near 250 243 for the white square (is this correct or should they be 243). We and 15 for the black. We want a linear relationship between the measured and given values. Each BCG setting adjusts the line in different ways and there are many different ways to adjust the values to achieve a linear relationship. You want to achieve a good image with good brightness, where the image has good saturation and not too washed out. (see JPEG corrections cheat sheet in SHIL lab notebook, to be added). The Applied Corrections Graph should be a straight line and the ROI Corrected Box should have values near 250. 243 These may change depending on the instance of extreme colors, extremely white or extremely dark cores, in which the settings may have be tweaked more to get a user friendly consumer image.
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Figure 30: Steps for JPEG Correction illustrated on image. 1. Select JPEG Correction Mode. 2. Select Applied Corrections tab on graph. 3. Select JPEG Correction to see Brightness, Contrast, and Gamma Corrections. 4. Adjust Brightness, Contrast, and Gamma corrections. 6. Check graph for Linear Relationship. 7. Check the boxes in the Color Checker and compare to RGB values in corrected image.
4. If the values all look are good and there are no streaking issues in the images or other unwanted artifacts, you can click Save and no further adjustments are needed. However if you have determined the doesn't look good, click Cancel and you can proceed to the following section and complete the calibration instructions listed in the Calibration section below.
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