Lichen images stacks

Do not use/reproduce without permission.
Remco Brand - 2023

Lichen image stacks

With this technique you combine the sharpest / in focus part of many images into one. In small items where you might have a depth of field (DOF) of fractions of a millimetre only a small part of the overall image is in focus. This technique can take that one sharp area from a stack of photos and combine it to one sharp image.

Hardware used is an old Canon EOS 50D with a 100mm macro lens and a 15-85mm lens (locked at 15mm) with reverse macro ring for extreme close-ups. This is combined with a macro rail that can take micrometre (μm) steps if needed. For this magnification I used 250μm and 50μm steps.

This is handled by Helicon Focus which has 3 techniques for this. Which is the best mostly depends on the subject, all 3 are included here to compare. You will recognize the method (A/B/C) in the file-name. Summary of the methods:

Method A computes the weight for each pixel based on its contrast and then forms the weighted average of all pixels from all source images. This method works better for short stacks and preserves contrast and colour.
Method B selects the source image containing the sharpest pixel and uses this information to form the "depth map". This method imposes strict requirements on the order of images - it should always be consecutive. Perfectly renders textures on smooth surfaces.
Method C uses pyramid approach to image processing dividing image signals into high and low frequencies. Gives good results in complex cases (intersecting objects, deep stacks), though increases contrast and glare.

I included zip-files (big!) with the original images as well. Don't download on your phone.

2023.02.16_001	26 images, 100mm macro lens, 250 μm steps.	download 120mb
2023.02.16_002	49 images, 15mm lens reversed , 50 μm steps.	download 218mb
2023.02.16_003	55 images, 15mm lens reversed , 50 μm steps.	download 239mb
2023.02.16_004	34 images, 15mm lens reversed , 50 μm steps.	download 108mb
2023.02.16_005	26 images, 15mm lens reversed , 50 μm steps.	download 78mb
2023.02.16_006	31 images, 15mm lens reversed , 50 μm steps.	download 92mb

Click on below image to load the original file which will be between 6-9mb.

001

2023-02-16_001_(A,Radius8,Smoothing4).jpg

2023-02-16_001_(B,Radius8,Smoothing4).jpg

2023-02-16_001_(C,Smoothing4).jpg

002

2023-02-16_002_(A,Radius8,Smoothing4).jpg

2023-02-16_002_(B,Radius8,Smoothing4).jpg

2023-02-16_002_(C,Smoothing4).jpg

003

2023-02-16_003_(A,Radius8,Smoothing4).jpg

2023-02-16_003_(B,Radius8,Smoothing4).jpg

2023-02-16_003_(C,Smoothing4).jpg

004

2023-02-16_004_(A,Radius8,Smoothing4).jpg

2023-02-16_004_(B,Radius8,Smoothing4).jpg

2023-02-16_004_(C,Smoothing4).jpg

005

2023-02-16_005_(A,Radius8,Smoothing4).jpg

2023-02-16_005_(B,Radius8,Smoothing4).jpg

2023-02-16_005_(C,Smoothing4).jpg

006

2023-02-16_006_(A,Radius8,Smoothing4).jpg

2023-02-16_006_(B,Radius8,Smoothing4).jpg

2023-02-16_006_(C,Smoothing4).jpg