Focus Stacking with a Raspberry Pi – Experimentation with 10x Microscope Objective

    Cluster fly proboscis
    Cluster fly proboscis

    My Nikon CFI Plan 10x 0.25 ∞/- WD 10.5 infinity microscope objective arrived a few days ago from the USA. I had first seen this lens on Johan J. Ingles-Le Nobel’s excellent Extreme Macro site and had been watching out for one on e-bay for a long time. While it was in transit I acquired on e-bay the necessary adapter rings to enable it to fit onto my Minolta 200 mm lens which is required to deliver the 10x magnification.

    The CFI Plan 10x 0.25 ∞/- is a lovely little lens. The dof, at 8.5 microns, is getting near to the limit of my focus-stacker but I have managed to produce a reasonable test image with it. If push comes to shove I can do a 2 micron focus increment which is one cycle of the stepper motor. The critical factors at this magnification seem to be vibration of the camera even though in my focus stacker system it is stationary; it means tiptoeing round the house while the focus stacker is busy stacking. Dust and contamination on the sensor is the other big issue, which now really shows up in spades. I had done a wet clean of the sensor a few weeks ago but that was the first one for several years and I think the sensor needs one more go at least, as the last clean has not done nearly a good enough job.

    The photograph above is the proboscis of a cluster fly – 197 images at 8 micron increments stacked and re-touched in Zerene Stacker and post-processed in Lightroom, Photoshop and Topaz Detail,  The proboscis is about 0.25 mm in diameter to give you an idea of the scale. The image required a lot of cleaning in Photoshop to remove the worst of the streaks and blobs caused by sensor contamination. None of these streaks and blobs show up in normal photography!

    Over the next few weeks it is my intention to carry out a series of tests with this microscope objective to establish the optimum focus increment and ideal aperture setting for the 200mm lens. I am suspecting that f8, which is what I determined was the optimum aperture for reversed enlarger lenses, may not be the best aperture for the Nikon CFI Plan 10x 0.25 ∞/- and that something wider open may be required. We will see. I will post the results when I have them.


What’s it all about?

Here are my jottings about my photographic projects and activities. I have been working on a focus stacking macro photography rig. There are quite a few posts about that. In addition I write about other photographic activities as and when!


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