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!



    Focus Stacking with a Raspberry Pi – test stack of 148 images of a fly

    Today I made another test run with a stack of 148 images at 40 micron intervals using the Otamat 20mm lens, this time on a 42mm extension tube. The subject was another of my old insects forraged last year for trial purposes. I have been waiting to see how these tests go before getting hold of various bits of entomological equipment – forceps and the like – as well as acquiring the necessary chemicals for relaxing the insects, stilling, drying etc, and plastic/glass tubes and containers for processing the specimens and keeping them clean. The work by Johan J Ingles-Le Nobel on his website – Extreme Macro – has been an inspiration and a huge help in working out what to do.

    test specimen - not in the best of conditioning - no prep other than mounting for the stack
    Test specimen – not in the best of conditioning – no prep other than mounting for the stack

    So this specimen is a bit ugly in many respects, is missing some key components with many bristles broken off, and it could do with a wash and brush up!  But it has served its purpose. I am satisfied that if I can prepare a passable specimen, then I can make a passable macro image. After a number of test stacks I am now sure that the kit works as envisaged, and that the lenses are OK; we are good to go to the next stage.

    There are some minor software changes to be implemented to make things a little easier; I am accumulating a list and at some point will do an integrated update. I intend to make another light box, much larger, to accommodate larger specimens in a diorama form for 1:1 macro work; for this I will need to improve the method of positioning and lighting the backdrops as the current arrangement doesn’t really do what is required – back to the drawing board here.

    Finally I need to decide on my stacking software. At the moment I am using a trial version of Zerene. I am quite happy with the results so far but will probably have a look at Helicon Focus too.

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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