August 29, 2022

Fluorite from Tombstone, Arizona

A specimen from near the gate below the Goodenough tour level
This is my specimen xxx, an actual micromount from my collection.

I used the MPE-65 set at 5x and f/2.8. I set exposure to manual and 1/6 of a second.

Lighting is a single Jansjo lamp with no diffuser. I left my flurorscent room lights on during the shoot because I am lazy. I set my color balance to 3600K as a wild guess.

I am using a 20 micron (0.020 mm) step size, which is 12 motor steps for my rail. I set the bottom focus to 98800 and the top to 100500, which yielded 137 exposures. I took a few manual exposures to check things, then deleted those.

I had lightroom directly capture the images, which it saved as DNG files. When it finished, I used Ctrl-A to select them all, then used the lightroom export to generate TIF files, putting them back into the same directory without resizing or renaming.

Then I launched Zerene and used File -- Add Files to bring the TIF files into Zerene. Once they were in, I used "Stack, Pmax" to do the stacking, which took about 7 minutes. When it was done, I saved the result directly to the 2022_minerals folder.

When this was done, I went to lightroom, found the final TIF image in the 2022_minerals folder and imported it into lightroom. I did not yet delete all the "pieces", which is good because there is a bright streak on the image and I want to explore the Zerene retouching features to get rid of it. When I am finished, I intend to delete all of the parts and pieces in the working folder and just keep the final TIF for any stacked photo I take.

I am using my Canon 1D mark III with the APS_H sensor. This is 3888 by 2592 pixels and 28.1 by 18.7 mm in size. I cropped my exports to be square, and with the 5x setting on the lens, this should be 3.74 mm on a side.

Here is the image with the streak:

Retouch on linux

This will be the first time I have used Zerene on linux! I pull all the TIF images into the linux copy and stack first with Pmax, and then with Dmap. The stacking goes faster than on my Windows machine, I think because the files are on local disk on the linux machine, but accessed via a network mount on the windows machine. Pmax takes 7 minutes rather than 10.

Pmax requires a "contrast threshold" to be set. This is new to me. I pick a value of 14 rather than the default 20, but need to learn about this.

I have used two of the original images and the brush to get rid of the light streak. And I rather like the Dmap image better, but brushed in the shadowed areas from the Pmax image because Dmap was doing weird stuff with out of focus shadow areas. I was able to get rid of the big light streak (and another I didn't originally notice) by finding a source image without it and with the area in focus and brushing it in. It really works well and is much easier than I thought it would be. In less than a minute I have made major improvements to the image without really knowing what I am doing yet.

Disk space

This project has 286 files, 143 are CR2 files and 143 are TIF files. The CR2 are each 11M and the TIF are each 60M. This totals to over 10G of disk space. Clearly I need to discard all of these files once I am satisfied with the final stack.


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Tom's Computer Info / tom@mmto.org