The challenge of photographing the miniature
Open collections require high-quality collections photography. This not only means high resolution images that meet research standards, but also images that can be enjoyed by artists, school students, and members of the public. As part of Auckland Museum’s three-year Collection Imaging project (running November 2015 until November 2018 and published to Collections Online), our goal is not only to photograph as much of the collection as we can, but also to inspire these different groups with really great images of objects, artefacts and specimens.
In this new series of #MuseTech blogs, I will share some of the tips, tricks we’ve learned in the photography studio. There is never a dull moment — where apparently ‘simple’ jobs turn out to be complex, and apparently difficult jobs turn out to be easy. Let’s start with something small…
Capturing the fine details of tiny, ancient shells
One of the natural science areas we are working in is the marine fossil collection, a project so large that, until further cataloguing work is done, it’s not clear exactly how many thousands of specimens there are to photograph. When we start on a new collection group like this, we consult with the curator and collection manager, and the goal for the first set of fossils – tiny, ancient shells, some less than 5mm in length – was to capture four to six images per object displaying the fine details of their form and surface.
When we placed the first fossils on the perspex still-life photographic table, their small size became an immediate issue, as depth of field is tricky to manage in macro photography. We just couldn’t get the whole visible fossil surface in focus at close range. When we adjusted the lens aperture control to gain depth of field, we lost optical sharpness in the image through diffraction.
We ran tests to check the effect wasn’t being made worse by flare from backlighting, and we also ran through all five of our macro lenses to see if different working distances and lenses would help – but all five lenses displayed the same issues. After exhausting our options at this close, tight-in range, we had to rethink.
We decided to move the lenses physically further away from the specimens to gain depth of field and return the lens apertures to the sweet spot around f/8 or f/11. The only issue with this was we had to accept that the fossil would sit in the middle of a big white space as, for digital preservation reasons, we don’t do any cropping or post-production on the files. But with one image requiring the colour chart and scale in shot anyway (the other with just the fossil), the white space appears to carry a practical function, if somewhat larger than is typical. When researchers and members of the public access the full resolution image they can zoom into the image at a pixel-to-pixel level and still see all the minute detail.
The perfectionist’s solution to this problem is a technique called focus stacking, and we have the gear and expertise to do it in-house, but as it is a time-consuming process, with many more steps, it would blow our productivity goals.
Lighting the fossils
In macro photography, any light falling onto the surface of the photographic paper reveals its texture — which is why we used a still-life table instead. Backlighting the white Perspex surface produced too much flare, but with just an overhead light on the surface it was luminous enough to provide a similar effect. We used one light, positioned slightly off-centre, to cast shadows and define shape. It’s quite common with a lot of pure reprographic work in the GLAM sector to look for even lighting, but because the Auckland Museum collections are often three-dimensional, flat lighting can be deceptive: it can potentially reduce the visual interpretation of the photo and, at its worst, portray the object unrealistically.
We use flash studio lighting for everything, and favour Broncolor equipment primarily for its reliability and because its output maintains colour accuracy across the power range. Flash lighting gives us a bit more control than constant lights, and it is less harmful to the collections, as it doesn’t give off constant UV and heat while we’re setting up.
As we progress through the imaging of the marine fossil collection, we see a staggering variety of specimens, and there are rumours we have a few fossils coming which demonstrate the evolution of fish in a way not seen before. But what the team and I are really looking forward to is when we get the crystals into the studio — so keep an eye on Collections Online as we’ll be posting those shots as soon as we’ve photographed them.
We use a range of macro lenses at the Museum, primarily from Canon, though we also have a range of Mitutoyo microscope objectives used in imaging before we get into actual microscopes. The Canon lenses range from 50mm, through two types of 100mm, to a 180mm. Our last special lens is the MP-E 65, a 1-5x life-size lens, and we also use extension tubes when needed.
We save multiple file types: CR2, DNG, an uncompressed ‘vanilla’ 8-bit TIFF, and full-size JPEGs.
For storage the Museum follows quite a complex system which is currently undergoing significant changes. For smaller institutions or smaller community organisations — even home users try to use the 3:2:1 principle – keep at least three copies of everything in at least two locations, always with at least one off-site.
Get in touch
If you’ve got any questions or suggestions, you’re more than welcome to get in touch with me.
See where the fossil images are published at Collections Online. We also have our own API if you want to pull collections data to your website.
Post by: Dave Sanderson
Dave Sanderson is the Project Leader Collection Imaging. He is a career imaging professional and an advocate for digital archiving and preservation as well as Open GLAM.