Lesson Videos:
Introduction
In this lesson, you will learn to calibrate your camera to capture the highest quality images. Calibration is the key to capturing high quality images, making it one of the most important skills you will learn for capturing historical records.
See the DCam User Guide section titled “Color Calibration (Nikon)” for more detailed instructions.
The processes in this lesson apply to Nikon cameras. When the camera has been plugged in to the computer and the DCam program has started, the software automatically identifies which camera you are using.
You decide when recalibration is needed. At a minimum, the camera should be calibrated at the following times:
- Each day when you are ready to start capturing images
- When the camera height has changed
- When the height of the copy board has changed
- When the lighting has changed
- If you change the type of document you are capturing, such as changing from a single page to a book
- After lunch or another long break
The device calibration tab in the footer bar shows if the camera has already been calibrated. Even if this tab shows that the camera has been calibrated, you may need to recalibrate the camera for any of the reasons noted above.
For Nikon cameras, calibration requires the following processes:
- Exposure calibration
- White balance calibration
- Focus calibration
- Capturing the color target
Single-step calibration is the default calibration mode and combines all calibration tasks into a single step. You will likely use single-step calibration most of the time. There may be occasions, however, when you need to calibrate the camera manually.
When calibrating the camera manually, the DCam program guides you through each calibration step sequentially. While not as simple as single-step calibration, manual calibration is very straightforward.
The following sections explain everything you need to know about single-step calibration and manual, or multi-step, calibration.
The following processes should be completed before you begin calibration:
- If you are going to capture a folder, find the largest document, and place it directly beneath the camera lens.
- If you are going to capture a book, open it and place it directly beneath the camera lens. To make the image display on the screen, click Refresh Image.
- Adjust the camera height to the level that captures the entire document, including a border of black copy board around it. The border should be at least several inches.
- If the whole document with its border cannot be viewed completely, move the camera and diving board higher on the center post of the workstation.
- If the whole document and its border does not fill the viewing area, move the camera down.
Note: After each adjustment, continue to click Refresh Image so you can see your progress.
- A best practice is that the camera should never be closer than 22 inches (about 56 centimeters) from the copy board.
- If a document in a folder is larger than the camera can capture, even at the highest camera position, set the camera height to capture the size of most of the documents and capture the large page separately.
To set up your device, perform the following steps:
Step 1: Click Preferences.
Step 2: Click the Device Setup tab.
Step 3: Verify that single step calibration is selected.
For Nikon cameras, verify that the orientation is set to 180°.
Getting to the calibration screen depends on whether you are practicing or getting ready to capture images. If you are practicing, perform the following steps:
Step 1: From the home page, select Practice Configuring Imaging Device.
Step 2: At the bottom of the left control panel, click Calibrate.
Step 3: Create a new folder if you are getting ready to capture images. See the “Projects, Listings, and Folders” lesson for more information.
Step 4: From the bottom of the folder screen, select Save and Capture.
Single-step Calibration
Single-step calibration performs camera calibration in 1 step. To begin single-step calibration, perform the following steps:
Step 1: Place the calibration targets on the copy board.
Note: Do not touch the surface of the calibration cards with your fingers. The oil from your skin can affect how color, light, and shadow are interpreted by the software.
There are 3 calibration targets:
- Grayscale
- Color
- Focus
Step 2: Make sure the targets are completely within the camera’s view. Single-step calibration requires that all 3 calibration targets be placed on the copy board surface. If the targets can be seen by the camera, their placement on the copy board does not matter.
Step 3: If you are capturing a book, open the book to the center pages with wedges under the front and back covers to make it as level as possible. Place the calibration targets on top of the book.
Step 4: If the targets in the current reference target window on the left side of your screen do not match the targets you placed on the copy board, you need to change the targets that do not match. Normally, the only time you will have to do this is the first time you use single-step calibration.
Step 5: There are several different grayscale and color calibration targets that you may find with your workstation. To change the targets, click the expand arrow located next to the phrase “choose a different reference target.” Cap Choose if it is capped in program here.
Step 6: 2 buttons display: 1 for changing the Grayscale target and 1 for changing the Color target. Click a selection to view choices for the target.
Example: Click Grayscale and you see a set of choices. Match one of the choices to your target, and click OK to return to the calibration screen.
Step 7: Click Start for DCam to automatically move through the following calibration steps:
- Focus
- Locate targets
Note: If this step fails, choose a different grayscale or color target.
- Exposure adjustment
- White balance adjustment
- Color target capture
During these steps, the adjustment progress bar indicates which step is occurring.
Step 8: When complete, the adjustment progress bar indicates complete.
Step 9: To begin capturing images, click Next.
Note: The first time you run calibration, it can take up to 1 minute. Subsequent calibrations take less time and depend on how long it has been since the last calibration and whether lighting conditions have changed.
Step 10: To troubleshoot any problems that arise, complete the following:
- Verify that the targets on the copy board are within the camera view.
- Verify that the correct grayscale and color targets are selected in DCam.
- Complete the calibration steps manually.
Step 11: Verify that the focus meets quality standards by using the mouse scroll wheel to zoom to 2,300%. Position the screen to view the horizontal and vertical lines on the focus card at 1.0.
Note: Rotate the mouse wheel away from you to make the pixels bigger. Rotate the mouse wheel toward you to make the pixels smaller.
Note: If the lines on the card are horizontal and vertical, the edges should be crisp with no more than 2 transitional pixels on either side of the fully blocked, or darkest, pixels.
Step 12: If the settings are correct, your equipment is ready to capture images.
Manual or Multi-Step Calibration
Begin manual or multi-step calibration by completing the following steps:
Step 1: In Preferences, verify that single step calibration is not selected.
Note: Remember that single step calibration is the default setting.
Step 2: If you are going to capture a folder, find the largest document, and place it directly beneath the camera lens.
Step 3: If you are going to capture a book, open it up, and place it directly beneath the camera lens. To make the image display on the screen, click Refresh Image.
Step 4: Adjust the camera height to the level where you capture the whole document, and include a border of black copy board around it.
Note: A best practice is that the camera should never be closer than 22 inches (about 56 centimeters) from the copy board.
Step 5: Exposure calibration uses a grayscale card that consists of 255 values from the brightest white to the darkest black to calibrate the tonal range of an image.
Note: DCam identifies the A, M, and B patches of the grayscale card to calibrate the values. The software then ensures that all values fall between 23 and 242. If values fall outside this tonal range, information on the documents being captured can be lost.
Step 6: Place the grayscale card on the copy board vertically in the center of the viewing area so light can wash across it evenly.
Step 7: If you are capturing a book, open the book to the center pages with wedges under the front and back covers to make it as level as possible.
Step 8: Place the grayscale card on top of the book.
Note: Do not touch the surface of the cards with your fingers. The oil from your skin can affect how color, light, and shadow are interpreted by the software.
Step 9: Verify that the radio button Automatically Locate Grayscale Card is selected.
Step 10: Check the autofocus during calibration.
Note: The type of card being used should be shown in the top of the calibration panel. If the card being used is not displayed, click Choose a different card. Select the correct card from the options, and click OK.
Step 11: To begin calibration, click Start.
Step 12: DCam automatically locates the grayscale card patches. When the grayscale patches are found, the camera’s exposure and other settings are established.
There are situations where it is necessary to locate the grayscale card patches manually. But before locating the patches manually, check the following:
- Verify that the card is correct and that it is centered.
- Verify that there is no extra glare or darkness on the copy board.
Note: You may need to adjust the room or the workstation lighting.
- Verify that there is no excess clutter on the copy board.
- Verify that the F-stop is set at F-8.
Manually Locating Grayscale Patches
If DCam still has trouble locating the grayscale card, you will need to manually locate the grayscale patches by following these steps:
Step 1: On the exposure screen, click Manually Locate Grayscale Patches. The 3 sampler targets and labels display.
Step 2: With the mouse, click and drag the targets onto their associated grayscale patches.
Note: The sampling tool displays orange when the pixel values are inconsistent.
Example: When placed partially between 2 patches, the sampler will have an inconsistent value. Make sure the sampler is correctly positioned.
Step 3: Click Start. The camera takes several snapshots, so make sure not to move the grayscale card. Red boxes display on the screen around the A, M, and B patches on the grayscale card. Keep the following information in mind:
- If DCam cannot identify the A, M, and B patches on the card during calibration, you are reminded to check to ensure that the correct grayscale card has been selected.
- If a bad sample is indicated, check the grayscale card for damage.
- If the relative position of the samplers does not appear correct, DCam will display the following warning prompt.
- The sampler values should follow the rule: A > M > B
This means white is larger than gray is larger than black. If the sampler readings do not meet this rule, DCam displays a warning.
Step 4: If the exposure calibration is successful, a green circle with a check mark appears with the text “grayscale passes” below it. Cap Grayscale here if it is capped in the text that appears
Step 5: After grayscale calibration is complete, check the adjusted grayscale values. The values should be in the following ranges:
- A-patch (White): 243 or less
- M-patch (Gray): between 104 and 108
- B-patch (Black): greater than 23
Note: If the grayscale calibration does not pass, or if the values are not correct, adjust the lighting, and start the calibration over again.
Step 6: The calibration panel also displays the DPI (dots per inch or pixels per inch). DCam uses the known size of the grayscale card and determines how many DPI are being captured. This value is stored with every captured image.
Note: DPI changes with the height of the camera. DPI can be increased by lowering the camera or decreased by raising the camera. Some archives may require images to be captured with a minimum DPI.
Step 7: To go to white balance calibration, click Next.
White Balance Calibration
During white balance calibration, a white piece of paper provides DCam with a reference point for the color white. Complete white balance calibration by doing the following:
Step 1: Remove the grayscale card used during exposure calibration.
Step 2: Place a clean white piece of paper on the copy board.
Step 3: Click Start.
Step 4: When white balance has been calibrated, the Next button briefly flashes.
Step 5: Click Next.
Calibrate Focus
When calibration begins, the first screen that appears is the focus camera screen. To calibrate focus, complete the following:
Step 1: Place the largest document in the folder on the copy board. If capturing a book, open the book to a center page, and place wedges under the front and back covers to make it as level as possible.
Step 2: The entire document should be filling as much of the DCam capture frame as possible. If needed, turn the document so it fits in the frame with the longest side of the document to the longest side of the camera array, always leaving a black border along all 4 sides of the document or book.
Note: A best practice is that the camera should never be closer than 22 inches (about 56 centimeters) from the copy board.
Step 3: Place the focusing target on the copy board.
Step 4: Click Autofocus.
Note: To check the focus, find the 1.0 lines on the focus card. Using the mouse scroll wheel, zoom to 2,300%, and position the screen to see the 1.0 vertical and horizontal lines on the focus card. Rotate the scroll wheel away from you to make the pixels bigger. Rotate the scroll wheel toward you to make the pixels smaller.
Note: If the lines on the card are horizontal and vertical, the edges should be crisp with no more than 2 transitional pixels on either side of the fully blocked pixels.
The darkest pixels are called fully blocked pixels. They may have a slight variance in darkness because of the ink of the target. The transitional pixels are pixels that transition from the darkest black to the lightest background.
Step 5: If needed, manually adjust the focus by using the arrow buttons in the panel until the maximum focus score is achieved with no more than 2 transitional pixels on either side of the fully blocked pixels.
Step 6: When using the manual focus controls, first adjust to the left until slightly out of focus, and then adjust to the right until the best focus is achieved.
Note: The best focus is represented by the maximum level of green and the highest score.
Step 7: To make slight focus adjustments, click the left and right single arrow buttons.
Step 8: To make greater focus adjustments, click the left and right double or triple arrow buttons.
Step 9: Once the target is focused, click Next.
Capturing the Color Target
To capture the color target, complete the following:
Step 1: Place the color target so that it is centered in the viewing area.
Note: If you are capturing a book, open the book to the center pages with wedges under the front and back covers to make it as level as possible. Place the color target or clamshell on top of the book.
Step 2: DCam locates the target, and a green rectangle appears around the color target.
Step 3: After the green rectangle appears, click Next.
Step 4: If the color target is not recognized, make sure the color target is placed on the copy board directly under the camera, and start the color capture over again.
Note: If things still are not working as they should, you can find further troubleshooting tips in the Dcam User Guide section titled “Troubleshooting Calibration and Troubleshooting Whiteboard Calibration.”
Learning Experiences
Activity 1: Check Your Understanding
- At minimum, when should you calibrate a Nikon Camera?
- For Nikon cameras, calibration requires the following what processes?
- Nikon cameras capture what type of images?
- Grayscale
- Color