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UltravioletPhotography

Macro UV with the Zeiss Luminar 25mm f3.5


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I recently got a Zeiss Luminar 25mm f3.5 lens and wondered what it would be like in UV. Turns out the transmission in the UV is very good, starting to transmit at around 300nm.

 

I took some images of a Common Dandelion, using the lens on about 80mm extension, on my UV modified Nikon d810. I think the magnification is about x4. Light source was a Hamamatsu 200W Xe lamp, and the images were whitebalanced in Darktable.

 

Here are a couple of the images (one full frame, and the other cropped slightly).

 

post-148-0-36655900-1587815077.jpg

 

post-148-0-54023700-1587815081.jpg

 

These were just done using a tripod and exposure was 2s so they aren't as sharp as I'd like (I so need to build a proper macro setup).

 

Lens exhibited virtually no focus shift between visible and UV - I was able to focus fine with the view finder.

 

Link to my full write up here; https://jmcscientificconsulting.com/uv-macrophotography-with-zeiss-luminar-25mm/

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Did this lens come on your microscope?

If so then you got a cheap microscope with a steal of a lens. Those are still collectable items.

 

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enricosavazzi

There are already reports that the Luminar 63 mm f/4.5 is good for UV imaging. It is not strange that it transmits UV well, since it uses an optical formula with 3 elements in 3 groups, i.e. no cemented elements. See for example the optical schemes at http://www.marcocavina.com/articoli_fotografici/Zeiss_Luminar/00_pag.htm (the text is in Italian). I think Klaus also reported using it reversed for general-purpose NUV imaging.

 

The Luminar 40 mm f/4.5 also uses a 3 element/3 groups formula, and should be about as good in NUV transmission (although whether it is also good for UV imaging needs testing).

 

The Luminar 25 mm f/3.5 uses 4 elements/3 groups, so it has one cemented group. Excellent to know that this does not seem to matter.

 

The Luminar 16 mm f/2.5 uses 5 elements/4 groups, so it might absorb a bit too much NUV. It is also the most difficult to use among the Luminars.

 

The emphasis in photomacrography today is the use of modern infinity-corrected microscope objectives with complex optical schemes and long working distances, which are not likely to perform well in UV imaging except when specifically designed to do so . The best known example is the Mitutoyo M Plan Apo NUV series, optimized for 355 and 532 nm (note that the Mitutoyo M Plan Apo UV series is completely different and not designed for NUV imaging, only for 266 and 532 nm although it might happen to be usable also for NUV). Nonetheless, it should not be forgotten that legacy lenses like the Luminars still have niches for specialized uses not intended by their designers.

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David, no the microscope came with no lenses, but I found the Luminar with a UK based microscope dealer when I was looking for lenses, and the price was good compared to what I normally see them going for.

 

Enrico, yes I saw about the 63mm one, but haven't seen anything reported on UV with the 25mm lens. Yes, I was surprised the UV transmission was so good given the cemented group. It'd be interesting the measure the transmission through the 40mm and 63mm ones, and see how they compare.

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Jonathan your dandelion bits have round balls, whereas mine look to have spikes. Although now thinking about, maybe I knocked off all the pollen into the slide as you can see it in the background.

 

I captured these today using my Swift microscope and its 4x and 10x objectives. A convoy 365nm flashlight was held by my hand shinning down on the dandelion bits placed on a slide. This is needed as the microscope LED diffuser and the 1.25x NA condenser both fully block UV. UV is not blocked by the eye piece, or the internal focusing lenses.

 

EM1 full spectrum camera connected to the triocular head of the scope, with U330WB80 improved filter on Camera. Light was Convoy 365nm flashlight with U340 2mm filter.

4x objective:

post-188-0-12549900-1587883923.jpg

 

10x objective:

post-188-0-70753500-1587883941.jpg

 

Alternative area with 10x objective:

post-188-0-42421400-1587883955.jpg

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The "spikes" are conical cells on the outer side of the style. The receptive surface (stigma) is disclosed when the style splits and curls backwards as it pushes through the [fused] anther tube. A bit like the chimney sweeper in action, done the dandelion way.

 

Not all dandelion microspecies have pollen although most at least have some vestiges. Thus the styles and stigmata are usually densely set with attached pollen grains, as can be seen in Jonathan's nice pictures. Dave's microscope photos complements these in an excellent manner.

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Bit of an update. I found a 100mm f6.3 Luminar for sale in the UK, thankfully for not much money, and it arrived today.

 

Despite being a simple triplet (simpler design than the 25mm version), it does not have good UV transmission. See below for the comparison.

 

post-148-0-30648900-1588248571.jpg

 

Just goes to show you can not assume anything when it comes to UV transmission through lenses....

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  • 1 month later...

Bit of an update on the Luminar. I've been playing with microscopy recently, with the eventual aim of building a UV microscope. I got myself a couple of beaten up old Olympus BH microscopes with the aim of rebuilding them and learning how they work at the same time. Turned out one of them was a lot more beaten up than I thought, but could still make the basis for a good macro setup. After sourcing various bits from different countries, I pulled together the parts for making an M42 to RMS adapter with a build in dovetail for the microscope, so I can mount the camera vertically into the microscope stand, and then use the microscope focusing setup to move the subject.

 

Photos of the setup - hastily put together to get a sample photo.

post-148-0-59962500-1591875908.jpg

 

post-148-0-52953900-1591875905.jpg

 

Using the Hamamatsu xenon lamp, I got a quick shot of the center of a Buttercup, with the Luminar stopped down all the way. Single shot, no stacking, and whitebalanced in Darktable. Overall magnification about 4x based on the extensions used.

 

First is a full frame image, reduced in resolution for sharing.

post-148-0-80474500-1591876042.jpg

 

And then a cropped section, which was also reduced in resolution for sharing here.

post-148-0-37912200-1591876039.jpg

 

Amazed how the UV yellow from the petals is reflected in the black parts of the flower. This was not stacked, and was definitely stopped down too far. In fact it was stopped down all the way. The goal eventually will be to use the microscope mechanism for some stacking. I did play with Zerene stacker and it is working well for my pictures of microscope slides, but the free usage period has expired so I need to bite the bullet and buy it.

 

I had a lot of problem with flare and loss of contrast while trying to image the Buttercup, and it seemed to be drive by specular reflections from the flower itself. With this setup, I should be able to do cross polarised (or partially polarised) imaging as well.

 

As always, sharing in case it is of interest.

 

Edit - Doh, I just realised one of the big sources of flare. I used some white paper to supposedly diffuse the light, but it's just bounced it around too much.......

 

2nd edit - also the petals themselves causing too much reflection....

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The old photomacrographic lenses are not good in dealing with flare. Come to think about it they probably have very simple coating and/or were only calculated for artificial light not spectral white. Thus some judiciously arranged shielding off light sources can often be required for best results.

 

A Zerene license is not very cheap especially for the Pro version. On the other hand, you have effectively life-long support of the software. I have had Zerene for 10-15 years and there are still upgrades for free. Plus I appreciate it runs natively under Linux as well as under Windows. In fact, one of my dedicated stacking boxes runs Linux with Zerene (it also runs Photo Ninja, RawTherapee, Darktable, and Monochrome2DNG).

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It seems that a number of us are also into microscopy, which is not at all surprising.

Anybody know of a good forum, of similar superb quality to this one, for discussions on that subject?

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It seems that a number of us are also into microscopy, which is not at all surprising.

Anybody know of a good forum, of similar superb quality to this one, for discussions on that subject?

 

Photomacrography.net

 

Some pretty amazing images on there, and I've seen one or two familiar names as well :)

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An annoying fact of modern life and repeated moving homes is that I know there was a specimen of the Zeiss Luminar in my possession. Now, after the last and final move, it is impossible to locate .... Even more unfortunaterly it's not the only item gone astray.
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