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Figure 7. Setting the f/stop on the Camera. F/16 is the preferred value by the imaging specialists onboard. Darker cores may need a larger f/stop of F/22.
a) Calibration Check using Image Correction
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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Figure 12. Image Correction command selection.
NOTE: The Image Correction screen has been updated as of . We are in discussion with Lab Working Group on utilizing the new user interface. The main difference is that we can use colors other than the Whitewhite, shades of grey and Black black to make any determine corrections. For now, continue to select the the white, shades of greys and black for image correction calibrations. This user guide needs to be updated to reflect the new user interface. In progress.
The main Image Correction window displays three main areas (Figure 13):
A. Graph panel: Main graphical viewing area on the left side of the screen.
Uncorrected Image Tab: Shows the measured Redred, green, and blue values of the gray scale color squares.
Applied Corrections Tab: Applies polynomial fit corrections to the RGB lines.
Compare: Shows a visual and RGB values of the Original color square before corrections, the Xrite Color checker standard and the Color after corrections are applied.
B. Image Viewing Panels: Area in upper right portion of the screen that displays the original and corrected test image and Xrite color checker with RGB values.
Original: Displays the uploaded tiff.
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Color Checker: Displays the known values of the MacBeth Xrite Color Checker values.
C. Correction Panel: Panel in the lower right portion of the screen that allows user to apply corrections to the image
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JPEG Correction: Shows brightness, contrast, and gamma settings.
Instructions: Shows instructions to follow in this
Figure 13: Image Correction window.
7. Select Open Test Image and select the image you just took (Figure 13-1), located in C:/DATA/IN/IMAGE. The On opening of the Image correction window the program prompts you to select the TIFF file as soon as the Image Correction window opensof the color standard you took. The image loads into both the Original and Corrected windows.
8. Draw a ROI box loosely around the color checker in the Original box (Figure 1314-21)
9. Click Crop (Figure 1314-32).
10. Draw another ROI box around the Color Checker squares and this time making sure to only have XRite MacBeth color checker in the box. White squares will appear inside each square. Adjust the box to get those white squares close to the center of the color squares. Do not click Crop again.
11. Click the colors you want to sue for the correction curve.
As of use only the white, shades of grey and the black.
Figure 14Figure 13. Image Correction Window. Steps are indicated in the figure. (New image correction window vi to be ADDED).
Check TIFF and JPEG Corrections
Here we check and adjust, if needed, our TIFF and JPEG Corrections. You may find you only need to slightly tweak the values and the calibration is good. With the new lights we have found that no adjustments have been needed. However if the image appears streaky, a physical change has happened to the Camera or lights, the RGB values between corrected and expected are far off (>10), or the graphs of either the tiff or jpeg don't look good, you will need to re-calibrate following the full calibration discussed below.
TIFF Correction Check
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1. Click TIFF Correction Mode tab (Figure 1315-21).
2. Click Uncorrected Image tab (Figure 13-3). This graph shows the measured red, green, and blue values of the color squares.
3. Click TIFF Correction tab to adjust the shape of the graph (Figure 13-4). The goal is to have line as straight as possible.4. In the Tiff Correction tab adjust the LUT polynomial order values for the Red, Green, and Blue channels (Figure 1315-51). Adjust these values to create the lowest residual error with the smoothest curve in the Uncorrected Image tab. Poly Polynomial values should be about 3. Make sure that the curve does not wave about too much. If it does, the values need to be lowered. Also check that the corrected ROI and Xrite color checker values are very close. Make sure that the white does not exceed the Xrite values (RGB = 242, 242, 236). If you are unable to produce a reasonable correction curve, it is necessary to redo your white balance correction in the Calibration section below.
Figure 15. Tiff Correction Figure 13. Steps for Tiff Correction illustrated on image. 1. Redraw box on color squares. 2. Select Tiff Correction Mode. 3. Put graph on Uncorrected Image. 4. Select Tiff Correction to view polynomial order. 5. Adjust polynomial order. 6. Check graph for linear relationship. (INSERT NEW FIGUREHERE)
Note: the TIFF correction is applied to both the TIFF and JPEG image but for the JPEG image you can also apply a Brightness, Contrast and Gamma (BCG) correction (See JPEG Correction section below). This is done at the photographer’s discretion. With better balanced LEDs on the new light system you may not have to use the BCG corrections (leave the values at their mid-points. Figure 14-4).17).
4. Compare the original, the color checker RGB values and the Corrected RGB values for each color square. (Figure 16). There is also a visual so you can see the difference in color for the color checker and the corrected. The RGB values for the corrected should be very close (<5) in value to the RGB of the Color checker RGB values.
JPEG Correction Check
In JPEG correction you will check and adjust, if necessary, the brightness, contrast and gamma (BCG) of the image. Situations may also arise where a JPEG correction should be applied. In the instance of very white or very dark cores, the TIFF images may look good but the JPEG images may look washed out or too dark to view details. JPEG corrections do not alter TIFF image settings. As mentioned above, with the new lights the BCG values may not need to be adjusted and to be kept at the mid values (Figure 14-417).
1. Click JPEG Correction Mode (Figure 1417-1)
2. Click Applied Corrections tab (Figure14Figure17-2)
3. Click JPEG Corrections tab (Figure 1417-3). Adjust the Brightness, Contrast, and Gamma levels (Figure 5417-4) to achieve a straight line in the Applied Corrections tab and the ROI Corrected box should have values near 242 for the white square and near 50 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. The Applied Corrections Graph should be a straight line and the ROI Corrected Box should have values near the RGB values of 242, 242, 236. 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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Note: this section follows the same steps as listed in the Calibration Check section above. This needs to be completed after a Calibration. An enhance method (utilizing more colors in the write color cehecker) is being implemented , and the following steps are being updated (in progress).
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