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.

     

    Focus Stacking with a Raspberry Pi – initial trials

     

    Green Bottle Fly
    Green Bottle Fly

    I have had some time to play with my macro focus stacker recently, having accumulated some specimens to practice on. And so I have found that I need to acquire a new set of skills besides those of macro photography, namely the mounting and preparation of the insect specimens, and the cleaning thereof. They aren’t exactly dirty per-se, but they have microscopic particles on their eyes and in their hairs that catch the light and/or are noticeable in the image and can be a distraction – awfully difficult to remove, even in Photoshop!

    And it can take ages to get everything lined up exactly as you want, bearing in mind that one is dealing in fractions of a millimeter.  The whole business of mounting and arranging is very fiddly, time consuming and frustrating. If you want a nice clean symmetrical head on image you will have to do some work for it!

    This shot is of a green bottle fly (not a blue bottle). It was taken with a Nikon 50mm f2.8 enlarging lens reversed onto a Minolta MD 135mm lens with adapter on a Sony NEX7 camera. This gives a magnification of about 2.5.  The stacking increment was 100 micrometers. I used Zerene Stacker for processing.

    I have realised I need to do a lot more work on the lighting, as my light box is giving too much back lighting and not enough front lighting. Also I need a better way of providing a coloured back drop. I have an old pc monitor that I may experiment with, by using it as a back drop driven from a pc running photoshop or something like that, and displaying a suitably coloured screen. I am not sure if it will be bright enough, but we will see!

     

     

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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