Category Archives: General

UV Macrophotography with a Zeiss Luminar 25mm f3.5

While pulling together parts for my microscope build, I also saw that the supplier I bought some of my lenses from (Best Scientific, Wiltshire UK), had a Zeiss Luminar 25mm f3.5 lens available. It was an early lens (version 1), but the price was good so I bought it.

The Zeiss Luminars are renowned as pretty special lenses for macro work, and cover a huge image circle, so are great for full frame sensor cameras (and much larger sensors too if you have deeper pockets).

I got to wondering whether it would be any good for UV work, so I ran a transmission test on it using my UV transmission rig, and was amazed to see it had great UV transmission, letting light through down to about 300nm.

Transmission of the Zeiss Luminar 25mm f3.5 from 280nm to 420nm

This type of transmission is fairly unusual without resorting to specialised UV lenses, and it made me wonder what UV images using this would be like. I attached the lens to my modified Nikon d810 (modified for UV imaging by ACS, UK), using an 80mm extension tube, resulting in a magnification of about 4x. The camera sensor has been modified to be sensitive to UV between 320nm and about 380nm. For lighting I used a Hamamatsu LC8 200w Xe lamp, about 12cm from the subject, in this case a Common Dandelion from the garden. Setup is shown below.

As you can see from the image above working distance is small. Very small. Of course depth of field is tiny too, although the Zeiss Luminar does have an adjustable aperture which is very handy.

How do the images look? I took some images of the middle part of the flower, and then whitebalanced them in Darktable, after also taking some images of a Labsphere diffuse reflectance standard under the same UV lighting. Examples below, taken with an aperture setting of about 8 on the lens.

Dandelion flower head in UV with Zeiss Luminar 25mm f3.5
Dandelion flower head in UV with Zeiss Luminar 25mm f3.5

Now you may be wondering why some parts of the flower look black. This is because they strongly absorb UV, hence they come out black. What isn’t obvious on the images at the resolution here, is that this type of macro work shows up every little bit of dirt on your sensor. The sensor is filthy, and needs a damn good clean……

The images above were reduced in resolution for sharing (the originals from the Nikon d810 are massive – 8674×5792). How about up close within the image at higher resolution? Below are some crops from the images above, shown at actual pixel resolution.

Actual pixel resolution with the Zeiss Luminar 25mm f3.5
Actual pixel resolution with the Zeiss Luminar 25mm f3.5
Actual pixel resolution with the Zeiss Luminar 25mm f3.5

The round features on the parts of the Dandelion are individual pollen grains. In the middle image of the above three, towards the left of the shot in the out of focus region, you can see small round dots. This is some of the dirt on the sensor.

Now you may think, “well those aren’t that sharp”. This was done with a camera on a tripod, on wooden floor boards, and the light source on the same bench as the subject (the light source has a massive fan in it to try and keep it from overheating), and the exposure times were about 2s. As you can imagine, at this level of magnification, trying to keep things from not moving is a huge problem. Every little bit of vibration is amplified. Also, these were single shots, no focus stacking, taken with the lens at about f8, so the depth of field is absolutely tiny. Focus stacking would help get more of the subject in focus, but that is something I have yet to play with.

Another thing to note is the 25mm Luminar exhibited virtually no focus shift between the visible and UV regions. I was able to focus it using the view finder, and then take the shot in UV, and the same parts of the flower were in focus.

Overall, I’m really impressed with the Zeiss Luminar 25mm f3.5 in UV, and it has huge potential for macro photography (I’m sure it’ll be great for visible light work too). If you want to know more about this or my other work, you can reach me here.

Project Beater – Olympus microscope teardown

I’ve bought myself an Olympus BHB microscope to learn a bit more about microscopy, and while the price was good it’s in pretty poor condition. The work has begun to get it operational again. Thankfully these older microscopes are fairly easy to dismantle, and after an hours work, it’s currently looking like this…..

Microscope teardown has begun….

For those born after 1980, those things on the left are electronic components from before the advent of integrated circuits.

So far, I haven’t identified too many more issues with it. Taking it to bits enabled me to get at various bits which needed cleaning and lubricating (and boy, did they need cleaning).

Thankfully the optics look to be in pretty good shape, so with a little bit of tender loving care I should be able to get it working again.

Now then, back to the cleaning…..

Olympus BHB Microscope refurbishment – Project ‘Beater’

So, what to do when work goes a bit quiet because of what’s going on with Covid-19? Learn a new skill of course. Given my interest in all things imaging, it is perhaps surprising that I have very little experience with optical microscopy. In previous jobs and projects there were always microscopy experts as part of the team, and I used to look on in awe when they’d create these amazing images.

A few days ago I thought it was time to jump into the world of optical microscopy, learn something new, and perhaps put together a system which I can use for UV imaging at the same time. Instead of buying a new, ‘plastic fantastic’ microscope, I decided to get an older one which would hopefully be simpler to work on. As I found out though, older microscopes still command quite high prices, presumably because they were so well made. After a quick search on eBay, I found an Olympus BHB from the 1970’s, with no lenses, and advertised as ‘not working’. The price however was low, so I contacted the vendor and we agreed on an even lower price. So begins the journey of discovery I’m calling ‘Project Beater’, and the name will become obvious later…..

Project Beater – the start point.

Surely, if it’s not perfect now, how hard can it be to get running again……. Oh, how ignorance is bliss.

The microscope arrived yesterday, well packaged, and pretty much as shown in the pictures in the advert (one of which is above). Once unwrapped, and on the bench, the areas that needed working on started to become apparent, and then more things became apparent, and more, and more. The snag list so far stands at;

  1. There are no eyepiece lenses. This was mentioned in the advert, so some old 10x ones are on order.
  2. There are no objective lenses. Again this was in the advert, and isn’t a problem, as I have a few on order. Given my interest in UV imaging, I wanted to source some very specific objectives anyway, so this was actually a benefit as I wasn’t buying ones I didn’t need.
  3. The light source bulb has blown, so a new one will be sourced. Also, the cable for the light source has been modified to run from an external power supply, rather than the one in the microscope itself. So I need to either get an original plug for the cable, or just run it from an external power source. I’d like to get an LED source up and running for this at some point anyway, so this isn’t a huge issue.
  4. The light path selector in the observation tube was stuck, and wouldn’t slide freely. This has been fixed now after loosening off the mounting screws, and a bit of jiggling, as there was something blocking it.
  5. The high/low magnification light source selector was stuck, as the grease used in it had gone very sticky. All these bits are now out ready to be cleaned.
  6. The field iris diaphragm adjustment ring is extremely stiff. I haven’t figured out how to get this out yet to loosen it off (this could be tricky).
  7. While it has a trinocular head, I have no way of attaching a camera yet, although I have some ideas for that.
  8. Overall, it is filthy and in places some of the metal in the body is quite corroded. I get the feeling this has been dumped in the back of a cupboard for 20+ years, and has been generally neglected. So an overall clean and lube is needed.

Welcome to Project Beater, and given the snag list above, the name now becomes obvious. I hope over time to get this up and running again into a usable microscope. However if not, there is a fall back option. The focus block would make a good macro photography focus rail, so if the microscope proves to be beyond resurrection, the hacksaw will be coming out, and it’ll get cut up and reused. In the current climate where reuse and recycle are becoming more and more important, just trashing this is not an option.

Why bother doing this? Why not just buy a new microscope? Other than the obvious of not going with a new deice, these are valid questions. One of the reasons for me was to get something that required a bit of work, to get me to learn something new, as it’s only by learning how something works that you can figure out their limitations and where things can be improved. If I can get it working again even better.

At this point I would like to give a quick shout out (that’s such a corporate phrase) to Best Scientific in Wiltshire, UK. They didn’t supply me with the microscope itself, but they have been great regarding getting hold of the objectives I was after, and in general advice on all things microscopy.

If you’d like to know more about any aspect of my work on imaging and skin, you can reach me here.

Large format digital imaging with LargeSense backs

Some new photographic products have obvious uses and markets, others, well, other that come along, can be a little more difficult to categorise.  I came across this recently, a company in the US making a large format digital camera back, which to me falls in to that latter definition;

http://largesense.com/

What they are doing is taking the concept of a type of photography with its roots in wet plate gelatin and bringing it bang up to date.  Imagine being able to use those fantastic old plate camera lenses, and to be able to control the perspective and plane of focus through the use of manual controls, combined withe the convenience of digital imaging.

Of course you may well be asking, why bother?  For me the key thing is pixel size, and the increase in the signal to noise ratio that goes along with that.   Add to that the fact that they are making monochrome cameras with no Bayer filter or microlenses, and this is getting very close to a digital emulsion layer.  The monochrome camera should be great for IR and even UV (depending on the cover glass they end up using for the sensor), making this a tool with huge potential.

So, taking all that into account, very much a purists camera.  However if the purist wants one, they will need to be well funded, as they are not cameras that will be made in huge numbers or be cheap to buy.

To be honest I find the concept amazing – to see someone push the boundaries of what can be developed like this gives me hope in the future of the art.  I wish LargeSense LLC all the success in the world, and I hope they continue to push at the edges of what is possible.

#LargeSense

New optical transmission measurement service

Need a rapid and cost effective measurement of the optical transmission properties of something?  Maybe a camera filter for a graph to provide data for a paper you’re writing, or do you want to know whether your product you’re interested in marketing which is supposed to block UV is actually doing so?  I now offer a light transmission measurement service.  Read more about it here, along with some examples of the type of things I can measure.  Contact me to find out more…..

Hasselblad Zeiss UV Sonnar 105mm – The Sonnar has landed

A very special lens has arrived in the lab, a Zeiss Hasselblad UV Sonnar 105mm f4.3.  Consisting of quartz and calcium fluoride lenses, this was one of the ones designed for space exploration work with NASA.  An amazing piece of history (manufacturing date shows this is one month younger than I am, so unfortunately it would have never made it to the moon), and now to be used for my UV imaging work.

Arrival of Asahi Ultra Achromatic Takumar 85mm f4.5 lens

I am very excited to have recently acquired an Asahi Pentax Ultra Achromatic Takumar 85mm f4.5 lens.  A bit of a legend in the imaging world, this extremely rare lens was made in the late 1960s using Calcium fluoride and Quartz elements, and is chromatically corrected for imaging in UV, visible and IR regions. Look out for a more detailed review in my ‘Techniques’ section soon.