Focus Stacking with a Raspberry Pi – New Light Box and Backlight Display
I have made great strides in the last week, having devoted a serious amount of time to fine tuning the set up. And now I have been able to produce an image of a green bottle fly that I am reasonably happy with. (see picture on left).
This was taken using a Nikkor 50mm f2.8 enlarger lens reversed onto a Minolta 135mm MD lens using an NEX7 camera with the new light box and display.
I am really pleased with backdrop arrangement that I now have operational. It was much easier than I thought. I have had this old PC monitor lying around for some time and now it has a purpose in life!
I have made a series of colour jpeg images in Photoshop – some flat and some grads. These are in a folder on the desktop and when opened using the windows photo viewer, I have it set up to provide a backdrop of roughly the right size. I can scroll through them to see what gives the best effect and adjust the size of the displayed window to suit the magnification I am using and get the gradient where it needs to be.
The new light box was constructed and tested over an afternoon earlier this week week. It is about half as big again as the original one and is doing a much better job at diffusing the light. Inside there are some removable baffles to limit the back lighting.
The light box extends further forward than the original one, and so can throw more light on the front of the subject. There are still a few hot spots and I am thinking about an inner diffuser made of white tissue paper like a tunnel over the specimen, to give more diffusion. This is also likely to demand a longer exposure so it will require some compromise.
Also on my list was to play around with different focus increments on the same subject with the same lens configuration. The jury is still out on that, as it is quite a lengthy process to take the images, then process them and try to evaluate sharpness etc. I am getting there.
I think that the rig is now 95% of where it needs to be – There are some minor changes required to the software for the Raspberry Pi that would help to speed things up a bit between shots and deal with a few bugs (software variety!) – nothing serious and a job for a rainy winter day.
What now needs sorting out is my ability to prepare the specimens – particularly cleaning, and arranging the legs but there are other things too which I will cover at a later date. I am also looking at optical jacks that come in very small sizes for making minute adjustments to the height of the specimen when on the rig, for accurate framing. There are some relatively inexpensive ones available in the USA (of course) but the required postage to the UK is prohibitive.