In order to prevent the analysis software from rejecting your test images, you need to correctly align the camera to the poster, check the cameras settings and follow the instructions series shooting.
This part of the manual covers:
Camera adjustments
1. Use a stable tripod to prevent blurring caused by camera shaking. Deactivate, if existing, the picture stabilization of lens or camera. Please avoid hand-held shooting!
For analyses, the poster should cover the whole picture field. Define the working distance for your camera.
2. If possible, activate the camera intern grid lines and change into Live View Mode.
3. Adjust your camera to be centered and parallel to the test chart.
4. Correct horizontal and vertical camera position and make sure the poster fills the camera format completely.
Aspect ratio: The test chart has an aspect ratio of 3:2. When using a camera whose sensor has the same aspect ratio, the test chart covers the image field completely.
The test chart also can be recorded in 4:3 or 16:9 format. Capture the test chart format-filling. Depending on the sensor aspect ratio, free spaces arise on the sides.
Camera settings
Ensure correct white balance through either automatic white balance or manual adjustment.
1. Place a memory card into the camera slot and format the card. Select JPEG high quality. RAW-data cannot be calculated. Before analysis, you have to change it into TIFF-Files.
For analyses, the poster should cover the whole picture field. Define the working distance for your camera.
2. Choose the manual mode to set the aperture, exposure time and the sensitivity manually.
3. For your system-test activate the camera internal vignetting correction and deactivate the flash. Set the basic sensitivity und choose an aperture (depending on your measurement series).
Use the camera default settings. Reset your settings for color, sharpness, contrast, saturation and other parameters.
4. Use the camera side histogram display to get the required exposure time setting. Choose an exposure time by which the histogram holds all brightness values while the peak lays in the midtones, according to the grey background of the test chart.
5. Choose manual focus mode for very accurate focusing. Focus on the target marker of the central siemens star.
Use the live View Mode for assistance. If possible, scale up the live view and start focusing.
To avoid discrepancies that could appear through the manual focus setting, we recommend to shoot a focus range. Take about 10 pictures of the test chart and refocus for every single shoot. This allows for choosing the sharpest image for later analysis.
Series shooting
1. Autofocus: Set the sensitivity to low value, for example basic ISO and choose an open aperture. Change to the autofocus mode and choose the central focus field.
Make a total of 10 pictures to acquire a good result for the autofocus accuracy. After every single shot the focus should be set to infinity.
At a very small focus-area, the Siemens star could not offer enough contrast for accurate automatic focusing.
In this case, we recommend to select a higher contrast image area for the focus field. For example, the black and white outer rings of the Siemens star. Manually place or choose a suitable autofocus field.
2. ISO: For comparing the resolution at various ISO settings, focal length and aperture should not change. Use for example aperture f/5.6 and keep one focal length, for example.
3. Focal length-Comparison: For a good comparison, the test photos should have the same aperture und sensitivity.
4. Aperture: If you are shooting pictures with different apertures, the sensitivity and the focal length should be constant. Set the sensitivity to the basic sensitivity.
For the individual measurement series we recommend appropriate settings, to receive meaningful and comparable results.
Download our guide for recommended settings (german version).