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Multiple Image Techniques
Published in Brian E. Dalrymple, E. Jill Smith, Forensic Digital Image Processing, 2018
Brian E. Dalrymple, E. Jill Smith
Focus stacking is also known as focus blending or focal plane merging. The camera, subject, and lighting are positioned to best record the impression, bearing in mind the measures listed earlier in this chapter. The aperture is set at F8, and the focus is in manual mode. The focus is set on a point slightly behind the furthest plane of the recorded impression. This is the first exposure and ensures that the portion of the impression most distant from the camera is captured in sharp focus.The focus ring is then adjusted slightly to bring the plane of focus slightly closer to the camera, and the second exposure is recorded.This process is repeated (perhaps 15–20 exposures) until the plane of focus is just slightly in front of the nearest portion of the impression to the camera. This results in the entire impression being out of focus, ensuring that all planes of the impression have been recorded in focus. The greater the depth of field requirement, the more exposures need be captured.The camera card is then connected to Photoshop.Select File > Scripts > Load Files into Stack.In the open window, select Browse, and highlight the source images for the stacking process.Check the box Attempt to Automatically Align Source Images, and press OK. It may take several minutes for Photoshop to complete this task, depending on the number of exposures.When the alignment process is complete, select the Layers tab to the right of the working window. Using the Shift key and cursor, highlight the layers of all source images.At the top of the Photoshop display, select Edit > Auto-Blend Layers > Stack Images. Photoshop then selects the areas of sharp focus from each of the source images and blends them into one seamless image. Again, this process may take several minutes, depending on the number of source images and the abilities of the computer.
Application of 3D imaging and analysis techniques for the study of food plant cellular deformations during drying
Published in Drying Technology, 2018
C. M. Rathnayaka, H. C. P. Karunasena, W. Senadeera, Y. T. Gu
The microstructure of the TB stained fresh samples were observed under the Leica (Wetzlar, Germany) DM6000M digital light microscope before and throughout the dehydration process. Staining of the sample with TB enhances the clarity of the microscopic image through making cell wall membranes more distinct. It has no impact on z-directional stacking or corresponding 3D effects created during image analysis due to the one-time staining. There was no further requirement to stain the image during or after dehydration. This microscope could be used for observations under both the incident and transmitted light with an automated contrast and light management. In each case, images were taken at a resolution of 1352 × 1000 pixels using z-stacked acquisition for better focus and clarity. z-Stacking (or focus stacking) is a digital image processing technique where multiple images taken at different focal lengths are combined together to eventually generate a composite image with a greater depth of field.[41,42] Due to the z direction stacking of the images, the 3D aspect of the obtained images were enhanced and it was helpful in making a better analysis on the experimental findings. The process of generating an image with 3D effects has been visually represented in Fig. 1. It outlines how the images taken at different focal lengths are combined through focus stacking (or z-stacking) to generate the final image with 3D effects. The real number of images taken at different focal lengths are usually larger than 30. However, in Fig. 1, only a few have been shown for the sake of simplicity.