Always nice to get an award for my imaging work, especially from such a distinguished organization as the Quekett Microscopical Club. I was awarded the 2025 “Barnard Certificate for Excellence in Photomicrography, Technical Category”, for my image of the diatom Pyrgodiscus armatus from a slide prepared by Michel Haak.

Quite a stunning looking (and rare) diatom from Brno, Tegl, Czech Republic. The image was taken on my modified Olympus BHB microscope, using 450nm slightly oblique illumination, and with a 63x Leitz Pl Apo NA 1.4 oil immersion lens. 145 images were stacked in Zerene (and yes I manually move the stage in between each image to build up the depth of field for the image), and I did final processing in Photoshop (mainly denoising and a little sharpening). The image above is a low resolution one, but the full sized one along with more details can be seen on my online museum (diatomimaging.com) website here.

If you are not familiar with the Quekett Microscopical Club, there’s more about them here. Founded in 1865 they are an amazing organization with over 150 years of microscopy history, and some of the most knowledgeable people I’ve met.

As always, thanks for reading, and if you’d like more information about my work I can be reached here.

Always fun to report a new article. At the end of last year I was asked to write a piece on the use of oblique lighting for the Postal Microscopical Society (an amazing group established in 1873). It was recently published in their journal, Balsam Post.

Oblique lighting helps to provide a more ‘3D’ appearance to microscope images, and can be very useful when looking at faint structures and features on subjects such as diatoms. For example, the image below – the diatom Triceratium robertsianum from King George’s Sound, on a slide by Samuel Henry Meakin, which was captured using oblique lighting from below.

The technique seems to have fallen by the wayside a bit these days, however it is a simple (and cheap) approach and can be done quite easily on all microscopes even if you don’t have an oblique condenser.

For anyone interested in microscopy and its history, I would strongly recommend joining the Postal Microscopical Society (see here). As well as being part of a really long running society with an immense wealth of knowledge, you have the option of signing up to receive slides from their collection on a regular basis to image.

As always, thanks for reading. My up to date publication list can be found here, and my contact details here. If you’re interested in seeing more of my diatom images, please checkout my online museum diatomimaging.com where I have thousands of high resolution photos, as well as background to the slides and techniques I use to capture the photos.

Being an avid microscopist of diatoms I come across some really beautiful slides. However occasionally I find one which is historically interesting as well. Today I’d like to share with you one of those slides. Here’s an image of the diatom – a fragment of Stictodiscus multiplex from Jérémie, Haiti.

The slide was one I bought at Microscopium, the annual sales meeting and get together of the Quekett Microscopical Club (more about that here). It is (incorrectly) labelled as Stictodiscus buryanus, and there is no makers name.

As I was looking to ID the diatom, I went through Schmidt’s Atlas – Atlas der Diatomaceenkunde. And specifically I came across a diatom fragment on Plate 75, Figure 1 which looked suspiciously like mine. This was a fragment of Triceratium multiplex. Also, later there is an image of Stictodiscus multiplex (Plate 451, Figure 10). I think S. multiplex is the newer name for T. multiplex.

The similarity to the fragment in Plate 75 got me wondering – is the diatom on my slide the one used to make this illustration? A couple of experiments, putting them side by side and then overlaying one on the other has got me convinced that this is indeed the one used to make that illustration based on the shape of it and the dot pattern.

The fact that algae have made these structures is amazing in itself. Factor in that some (like this one) are fossils that have been in the ground for millions of years, and the mind boggles. Then to think that I have a slide which was used to make such an important reference work as Schmidt’s Atlas, it is so cool (in a very geeky, nerdy way).

As always, thanks for reading and if you’d like to know more about my work I can be reached here.

Also, you can read more about this slide, and see a full high resolution image of the fragment, on my other site – the online diatom microscopy museum, Diatomimaging.com – here.

I was working on a client project recently which called for me to do some optical microscopy to image the droplets present in a skin cream. How you do microscopy has a huge impact on the nature of the images you get, and things like changing the wavelength of the light and direction the light comes from can have quite big effects on the final image and how it looks. I’ve seen various ‘qualities’ of images papers and scientific reports, and it has been my experience that many companies are losing technical experts from the their departments which means the experience of using things like microscopes is often disappearing. I thought I’d share some images of a topical oil in water emulsion using my modified Olympus BHB microscope and show the effect of changing the light source spectral distribution and lighting direction on the image, as well as going to high resolution to see what size features can be expected to be seen.

I’ll keep the product anonymized for now, but this is a topical skin cream with oil droplets in an aqueous matrix. A dot of cream was placed on a standard glass slide and a 0.17mm coverslip placed on top. This was gently pressed to flatten it out. The microscope is an Olympus BHB which has been modified to allow me to do UV work (although I am only using visible light here). Two objectives have been used, first a 20x Nikon Plan Apo NA 0.65 one, then a 63x Leitz Pl Apo NA 1.4 oil immersion one. Condenser was an Olympus Aplanat Achromat, used in brightfield and oblique configurations (and oiled to the underside of the slide when used with the 63x objective). 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. Light source was a white LED light which was left unfiltered, or filtered using a 450nm, 40nm FWHM bandpass filter from Thorlabs. The microscope was focused just below the underside of the coverslip. Single images were taken and processed in Photoshop (denoised, sharpened – unsharp mask, and auto contrast). They were then cropped to 1600×1200 and kept at original resolution.

Enough waffle. First two images – brightfield lighting, white light and 450nm light, and 20x Nikon Plan Apo NA 0.65 objective.

Both brightfield images look pretty good. The droplets can be seen. If you go in close the 450nm light image is slightly higher resolution than the white light image. This is simple physics – resolution of a microscope setup is highly dependent on wavelength. The shorter the wavelength the better the achievable resolution for a given setup. White light contains a mixture of light from 400nm to about 700nm. This spread will have an ‘average’ wavelength which is longer than the 450nm filtered light. Also, having a range of wavelengths puts greater stress on the optics being able to focus all those wavelengths to the same point. The objective is a Plan Apo (Plan – flat field, Apochromatic) and is a good one, but it will always be harder to correct for a wide range of wavelengths vs a small range.

Next oblique images. Oblique lighting, white light and 450nm light, and 20x Nikon Plan Apo NA 0.65 objective.

Changing the lighting to oblique (basically pulling the condenser slightly to the side) has the effect of creating a pseudo-3D image compared with brightfield, as it produces directional shadows. The effect is subtle here, and is easier to see when oblique and brightfield are put next to each other. Again, both the white light and 450nm light images look good, and the 450nm light one has slightly better resolution as before. I am a big fan of oblique lighting and use it a lot for my diatom photos. Brightfield images can be quite flat, but oblique lighting can make the structures in an image more tangible. Oblique lighting tends to be overlooked these days in favour of other approaches to improving contrast in images, which I think is a bit sad. It is such a simple technique and so much cheaper than something like Differential Interference Contrast (DIC). In fact oblique lighting has been called “poor man’s DIC” in the past.

While a 20x objective image is often good enough to see what is going on, sometimes higher magnifications and resolutions are needed. I also imaged this slide using a 63x Leitz Pl Apo NA 1.4 oil immersion objective, using 450nm light, and with brightfield and oblique lighting. Some people are scared of oil immersion, but it’s not that bad and enables the highest NA objectives to be used (and therefore the highest resolutions to be reached). These images are shown below.

Yet again, both images look good. However as expected the brightfield image is quite flat, while the oblique image has that pseudo-3D look about it, which can help with visualizing smaller features. For instance I picked on one of the small droplets in the image and used ImageJ to measure its diameter (which turned out to be 498nm).

Keep in mind with these 63x objective images that the depth of field is tiny – probably a few hundred nm, so very minor shifts in the stage will bring things in and out of focus, especially the smaller droplets. Sub micron resolution is not too hard with these high NA objectives, and it should be possible to see things down to about 4-500nm without too much difficulty. Below that things get a bit tricky without getting more complex in your approach.

Optical microscopy is a very powerful technique for the skin care formulator as it allows emulsion structure to be visualized which can impact everything from product stability to appearance and aesthetics on application. As with all imaging techniques the more you know the more you get out of it, and simple tweaks like choosing the right wavelength of light to use, and even how you illuminate your sample can have a marked effect on the image produced. While this can help with just seeing what is going on, if the images are to be used in marketing the product, getting the right ones can make the difference between a successful product and one which doesn’t live up to its potential.

As always, thanks for reading, and if you’d like to know more about my work, I can be reached here.

Most of my posts relate directly to my research in one form or another. However with some I just like to share information that I am unlikely to use myself, but may be of use to the work that someone else out there is doing. Today’s post falls into this second category.

There is a microscopy technique called Differential Interference Contrast (DIC) which many hail as being amazing and producing unique and fascinating images. There are various online resources which go more into the theory of this (such as the Leica site here). It’s quite complicated to do and requires some very expensive components, and as such this pushes it out of the realm of many microscopists (myself included). However given its complexity and my scientific curiosity I do keep an eye out for parts occasionally, and I recently managed to get a few prisms from an Olympus Epi NIC (Nomarski Interference Contrast, which is Olympus’s name for DIC) as I was wondering what the transmission through these looked like. I managed to get 4 prisms, one each for the 5x, 10x, 20x and 50x objectives. Unlike the usual astronomical prices which people often want for these, I get them for about £50 in total including one of the objectives. There are a bit beaten up, and will need re-gluing into their holders as the original glue has failed, however the filters themselves don’t look too bad. Below are the filters.

The transmission through the filters (as measured on my Ocean Optics FX spectrometer) is given below.

I had suspected that these filters would have good transmission down into the UV and indeed they do. So, they are not normal glass, but more exotic materials, presumably quartz. This undoubtedly contributes to the high prices for these items.

By the way, a technique called ‘oblique lighting’ can be used to produce pseudo 3D type images. While perhaps not as powerful as DIC, it’s results can be pretty spectacular, and it is much, much easier and cheaper to do. This is something I do for my diatom images (see my other website Diatom Imaging if you like microphotos of diatoms).

Anyway, a short post today just to share some info. If you have found this I hope it helps you with your work. As always, thanks for reading, and if you’d like to know more about my work, I can be reached here.

During my research into UV microscopy I’ve come across references to various different objectives. Some of these were refracting objectives, with quartz and sometimes other exotic lens elements. Other are reflecting objectives, which are based on the use of mirrors (and in some cases refracting elements as well). Today I’d like to share some findings on a recent acquisition – an American Optical 50x NA 0.56 reflecting objective. To start with some images of it.

It’s quite a tiny little thing. RMS threaded, and comes in its own box with a plastic push on cap to protect the front face. It is 50x and NA 0.56 and is designed to be used dry. It is marked ‘AO’ and ‘Spencer Made in USA 946485’. Mine is also engraved with ‘UC ZOO 66079’. This has been professionally done (not scratched on as these things are so often done), and presumably a University Zoology department. On the front of the objective there is a small opening and the 3 legged ‘spider’ that holds the small tiny mirror. Here is the entry for it from an AO catalogue.

Interestingly (and incorrectly) the catalogue entry states this is a catoptric objective. There is at least 1 refractive element to it and this can be seen in the image of the rear of the lens near to where it is threaded. It was designed to be used in spectrophotometric work from ultraviolet through to infra-red.

Next I measured the optical transmission through it in the UV (UV is more of my area than IR).

Transmission remains relatively flat between 280nm and 420nm, and I have no doubt this is a true UV capable objective (something with normal glass elements would not transmit down to 280nm). Overall % transmission is low as there is some clipping of the beam by the objective, and is nothing to worry about.

Next some tests on the microscope. I mounted it to my Olympus BHB microscope using a 8mm RMS spacer (just to get it approximately parfocal to my other objectives). Imaging was done with an Olympus Aplanat Achromat condenser, brightfield, optimized for each photo. Monochrome converted Nikon d850 camera. 450nm LED light.

First a Beck Optronics Silverpoint test slide, used to check alignment of reflecting objectives, which showed no obvious streaks which would indicate the mirrors weren’t aligned properly (thankfully).

Changing the focusing of the slide showed nice circular features as it went in and out of focus, with the 3 legs of the spider being visible.

Next a resolution test. Three images of a Newport test slide. The AO objective, and then 20x NA 0.65 and 10x NA 0.45 Nikon Plan Apo objectives.

The resolution for the AO reflecting objective (with its 0.56 NA) is certainly up there with the 20x Nikon NA 0.65. The AO image is more ghostly than the other two (which are Plan Apochromats) which I often see for reflecting objectives. In hindsight this was not the best test to do, as the image was so small with the 20x and 10x objectives, that the features were approaching the size of the pixel resolution on the camera. However it highlighted no major issues with the objective.

Finally some images of a diatom – Amphiplueria lindheimerii – single images using 450nm LED light. First image with the AO objective, with the condenser iris open.

Next a brightfield image with the 20x Nikon NA 0.65 Plan Apo objective. Compared with the Nikon, the AO objective shows some field curvature (seen as the ends of the diatom go out of focus), but it is not designed to be Plan so this is not a huge surprise. It could also to be due to my ‘hybrid’ microscope setup.

Final image, the AO objective with the condenser closed down to produce a darkground effect (this happens when the iris opening in the condenser is smaller than the front mirror of a reflecting objective).

Overall, the American Optical 50x NA 0.56 reflecting objective is a nice addition to my collection of quirky and ultraviolet objectives. It being RMS threaded makes it easy to use. As for finding one if you want to try it, I wish you good luck. As with many of these unusual objectives they were never made in large numbers, and rarely come up for sale. However, it is ‘rarely’, and not ‘never’, so keep your eyes out and you never know. I got mine on ebay.

As always, if you got this far, I thank you for your attention, and if you think I can help with your research I can be reached here.

Always nice to have a paper published. This one is in the area of Archaeology, which is somewhat outside of my day job area (Dermatology). My involvement was with the measurement of the spectral response of the camera used from the UV through to the IR, so that what was being imaged could be understood.

Funnily enough Archaeology is an area I’ve been interested since I was a young lad, so it is great to able to contribute to research in that area. This is one of the reasons I find the science of measurement an imaging a really interesting area to work, as the applications are endless.

The paper, “Seeing the Past in a New Light: LED Multi-Spectral Imaging as an Interpretative Aid for Archaeological Excavation” is available for download here.

At this time of year I try and do a bit of a reflection on what I’ve done over the last 12 months and what’s ahead for the coming year.

My dermatology work has carried on apace this year, both with existing clients and some new ones. I try and publish something each year, and 2024 saw two papers come out in a special edition of the International Journal of Cosmetic Science. These were on the use of In-vivo confocal Raman spectroscopy for looking at skin, a technique I was heavily involved with the development of. One looked at the development of the technique and the other how it was used in combination with a range of other skin measurement techniques to better understand how dry skin impact skin properties. This was a study I designed and ran back in 2006-7 but it was never published at the time. The techniques are still relevant today and I thought it was a good time to get this out there (take a look in my publications section for the two papers, they are free access so don’t require a subscription to download).

I’ve also been working with a couple of clients to characterize the spectral responses of their cameras. With this I measure the response of the camera between 280nm and 800nm, so can get an idea of how they behave in the UV, visible and IR regions, which is especially useful for people working outside of the visible spectrum. I love this type of research, and it is great to be involved with real imaging and measurement science.

My microscopy work has evolved somewhat, and I set up a new website to share my diatom images. This has the inventive name of Diatom Imaging and here’s the link (https://diatomimaging.com/). On that site I share high resolution optical microscope images from the range of slides I have, along with details on how they were taken and the slides themselves, and is a sort of on-line museum. Many of the diatoms are quite rare, and some I haven’t been able to find good images online, which is one of the reasons I wanted to set this up. An example image of one of the images is given below (this one won an award with the Quekett Microscopical Club).

Although the website has only been active for about 6 months, I have over a 1000 images on it already, and I am adding to it as and when I get the time to image new slides. I’ve already had people reach out to me to ask me to use images, and I hope in the future this will become a significant scientific and artistic resource.

So what does 2025 bring? More of the dermatology day work of course. I have been asked to give a key note talk at the 2025 Society of Cosmetic Scientists annual meeting, which will be a great opportunity to fly the flag for how skin measurements and imaging can be used to improve consumer lives and better understand dry skin.

On the microscopy/imaging side, I will continue to build and add to my Diatom Imaging site. I’m always on the look out for interesting slides to image, so feel free to contact me if you have collections that you are wanting imaging. I also need to return to my UV microscopy work, and do some work work for imaging with light below 300nm. In 2023 I published an article where I showed a new design for a darkground microscope condenser. That was a work in progress, and it would be great to get some time (and money) to finish that off. It needs some investment to buy a new optical lens, so I hope to be able to return to that one in the new year.

As always thanks for reading, have a great Christmas and New Year and all the best for 2025.

In my blog as well as presenting some serious science, I try and bring you interesting and quirky items I come across. Today’s post falls into the ‘interesting and quirky’ and is something I’ve been able to find out almost nothing about online. It is a Carl Zeiss Quarz Silberfilter (Quartz Silver filter) which I bought on ebay for the princely sum of £10 including delivery.

So what is this thing? It’s an optical filter with the markings “Carl Zeiss Jena” and “Quarz-Silberfilter x37” on it. It is a push fit filter with a diameter of 37mm (presumably that led to the x37 on the name). The optical part of the filter just looks like a mirror on both sides, and the mirror finish is sandwiched in the middle between two pieces of quartz, I am assuming to protect the mirror coating as much as possible. Overall, it is about 5mm thick and is held in with a threaded ring. Here’s some photos of it.

The filter does show some degradation around the edges, but this looks to be minor.

What is this filter, and why did it pique my interest? Often (but not always) Quartz or as it is spelt here ‘Quarz’ can mean that it is for a UV application. This got me wondering whether it was a filter designed to block visible light and let through part of the UV spectrum. Silver has an interesting property in the UV that it reflects most wavelengths, apart from around 310-320nm where it absorbs quite strongly. I have shown this effect before by imaging silver foil at different wavelengths in the UV here. After an online search I found one mention of Quartz Silver filter in translation of a 1920 document “The Palimpsest Photography
(Photography of the etched writings)” which talked about them being used to isolate the 313nm line. Aha I thought, it is using silver’s optical properties to not reflect light around 320nm-ish while reflecting other wavelengths. Digging bit more, I came across an article from 1911 in the Smithosonian Institution Annual report called “Recent experiments with invisible light” which talked about silvering of quartz lenses to isolate parts of the UV spectrum for imaging. In that article it states that “If we deposit chemically a thin film of metallic silver on the surface of a quartz lens, a certain amount of ultra-violet radiation between 3000 and 3200 [Angstroms, or 300-320nm] is able to struggle through and form an image on the plate”.

So, it seemed as though this is a filter for imaging in the low 300nm region, and that it would have low transmission even in the region of interest (given the light ‘struggles’ through. I love old science journals and their terminology). I was not able to find a transmission spectrum for the Zeiss filter online, so I measured it using my Ocean Optics FX spectrometer, the results of which are shown below.

Blimey they weren’t joking about light struggling through. It does indeed isolate the light around the 320nm region. However max transmission was only just over 2%. But it was very effective at blocking unwanted wavelengths. I guess if you had a nice powerful UV source (such a mercury xenon source) and you wanted to isolate the 313nm line, this type of filter could be used for that. Photographic paper could be made to be reasonably UV sensitive unlike normal digital camera sensors, so perhaps this was ‘good enough’ for imaging purposes.

As an aside, a Quarz Silberfilter is also mentioned in the brochure for the Zeiss 60mm f4 UV-Objectiv (a camera lens I have written about here). However this one is not designed to fit directly on to that lens – the filter ring on that lens is threaded and a larger diameter than this filter. So perhaps Zeiss designed one specifically for that lens as well.

Is it still useful? Probably not, given the low transmission. Nowadays dichroic filters can be made with relatively high transmission and good blocking of out of wavelength bands. However it is an interesting scientific curiosity, and a throwback to an early bandpass filter design for looking at the UV spectrum. Am I gutted I spent £10 on it? No, although I wouldn’t have wanted to spend any more on it. As I say, it’s a quirky piece of scientific history.

As always, thanks for reading, and if you’d like to know more about my work, I can be reached here.

It’s always nice to get some recognition for your work, and this year I managed to get an award for photomicrography from the Quekett Microscopical Club for one of my diatom pictures.

The slide was of Triceratium polycistinorum from Kamischev, Russia. Current name Entogoniopsis polycistinora. Single example on the slide. Described as ‘Rare’. Prepared by Sidney Chaffers. Olympus BHB microscope using 450nm LED light. 40x Leitz Pl Apo NA 1.00 oil immersion objective. Olympus Aplanat Achromat oil immersion condenser, brightfield. 2.5x Nikon CF PL photo-eyepiece. Monochrome-converted Nikon d850 camera. 43 images stacked in Zerene (Pmax). Imaging took about two hours including collection of the images, stacking and processing. Judge’s comment: Another amazingly detailed image of a diatom which indicates really extraordinary lighting and imaging and the fact that it has taken 43 separate photographs to achieve this is remarkable. The fact that this particular species is triangular with a circular centre gives it even more resonance as a photograph.

The image above has been reduced in resolution for sharing. The full sized image can be seen (along with many, many other diatom images) on my Diatom Imaging website here.

I can strongly recommend looking at joining a club such as the Quekett Microscopical Club or Postal Microscopical Society. Not only will you gain access to an amazing background of microscopy, putting your images in for judging or publishing gives you critique on your technique and how you can improve it.