Feature in Professional Engineering Magazine

    The Professional Engineering Magazine or PE as it brands itself is the magazine of the Institution of Mechanical Engineers of which I have been a Member for many years. There is a section in PE for articles about hobbies, careers, ideas, etc called Engineering Extras, and in this section under the banner of “My engineering hobby…” this month there is a piece about my macro photography of insects and the focus stacking rig that I built to take the images. The article is titled Putting Insects in Focus, and was based on information I sent them about my focus stacking project; the article  is very nicely written as if it were an interview. I am well pleased!

    article

    Focus Stacking with a Raspberry Pi – One year On

    It is more or less a year since I got my focus stacker working, and there have been many developments and changes to the set-up during this time.

    What’s good?

    • Interfacing with the RPi using a laptop running MobaXterm is straightforward and the built in editor is really handy
    • The concept of moving the specimen and not the camera works well – the moving parts are very light weight with hardly any inertia, and vibration is not an issue.
    • The Componon 28mm lens is a dream – so sharp
    • Continuous lighting using a light box lit from below is a simple solution to provide even diffused lighting
    • The whole focus stacker rig works, and produces very acceptable extreme macro images
    • It has kindled an interest in entomology and insect anatomy

    What’s not so good?

    • Getting real time into the RPi automatically – should be easy!
    • Setting up the specimen is still fiddly – but not as difficult as it was before the jack and the rack
    • Cleaning and mounting the specimens – and there is nothing that can be done about that other than doing it!

    What next?

    • Fix RPi real time – somehow DONE
    • Build a bigger light box to give more room around the specimen for adjustment DONE
    • Take more stacks
    • Improve my insect identification and understanding of  insect anatomy

    And then? 

    • A  3-axis (of spin) specimen mount – motorized – remote controlled – ha ha!

    Focus Stacking with a Raspberry Pi – Design Refinements

    focus stackerThe parts for making the lighting control box arrived and I was spurred into action before Christmas to modify the rig to accommodate the revised lighting controls and to build the light control box itself. In the end it took a whole day as I decided to take the opportunity to remove some redundant wiring and to reallocate the push buttons on the sledge mounted control box. I also updated the wiring diagrams to keep track of what I had done.

    Focus stacker light control box
    The focus stacker light control box and the “STOP” remote

    So now I have a lighting control box that sits behind and below the camera; there is also a momentary switch to operate the camera shutter so that I can make a blank exposure between stacks very easily.

    The remote camera shutter is now a remote stop button for the stage which makes it much easier to control the set up of near and far focus points, eyes on the camera and remote in hand.

    focus stacker electrical connections
    Focus stacker electrical connections

    The lights are plug and socket connected to the sledge as is the control box, for easy dismantling and storage. When I need to work on the main module I can quickly disconnect it from everything, and there are no trailing wires getting in the way.

    The redundant 6v lights switch on the sledge mounted control box has been replaced by a push button to operate the camera shutter – mainly to put something useful there instead of having a hole!

    Focus Stacker
    The light diffusion box – now with removable top and back – much better.

    The light diffusion box has also been modified to enable the top and back to be taken off leaving the front and the camera/lens set-up undisturbed. This makes it much easier to tweak the specimen during set up and after successive stacks.

    I am still not totally satisfied with the light diffusion box and may make yet another one, even bigger. I am finding it fiddly to get at the lab jack even with the removable top and back, and the lights would ideally be sited a bit further away from the subject to allow for more diffusion and baffling.

    I have forgotten to manually enter the time and date on at least one occasion, and have given up on the software solution to updating Pi time as too difficult, and so I recently obtained an Adafruit real time battery operated clock module (RTC). It is very compact and is supplied with its battery. It sits neatly in the junction box under the rack where the two wires that need to connect it to the Pi are already present and unused having been taped back originally at the time of build “for a rainy day” – there was a stroke of good luck!  It also needs Pi 5v and GRND which were both there too. The assembly and installation was easy. Modifying the config files on the Pi was not difficult. Installing the drivers for the RTC was impossible………. why, because……..you need the Pi to be connected to the internet. If it was connected to the internet I wouldn’t need the RTC, would I?  The driver goes by the name of i2c and enables one chip to talk to another.  There is, apparently, no reliable way to download the correct version of i2c (there are many and various!) and install it without being connected to the internet, which is a bit daft. There are plenty of people wanting to do this judging by the forum talk on the web, but the experts issue dire warnings of workarounds messing up your PI configuration big time. Later versions of Debian whatever, have the drivers in the supplied library. But not mine. Back to square one for the time being.

    focus stacker
    Overall set-up
    focus stacker
    focus stacker- the new light control box handily located behind the camera.

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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