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UltravioletPhotography

While waiting for the modified Z6


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I'm eagerly awaiting a new Nikon Z6 camera modified by Lifepixel. However, the camera seems to take forever reaching its destination. Nothing to do other than wait and hope for a spring to be sprung here in my high Nordic environments ...

 

Today however the first Tussilago farfara showed their cheerful little yellow heads along the road verges near to my house. Still just above the freezing point so getting pictures wasn't very enjoyable. This winter I've been housebound with bronchitis for such a long time now I had forgotten all about the outdoor life : D Hopefully weather improves and I can commence shooting again, with or without the new Z6.

 

I did capture some Tussilago flower heads by exotic lenses, in visible light by a Oude Delft 50mm f/0.75 on my existing Z6, and in UV by the Rodenstock XR-Heligon 100mm f/1.6 on my UV-modified Nikon D3200 (internal Baader u).

 

Both images done with a hand-held camera. Getting a compensation of the focus shift in UV without LiveView active was by trial and error and of course, at fairly slow shutter speeds no outstanding image sharpness is to be expected. However that's not my point by taking these captures. I could easily have set up UV shooting with the UV-Nikkor and a Broncolor studio flash to ensure razor-sharp images, but those have already been done many times before.

 

Rayxar 50mm ISO 100 1/2000 sec on the Z6 (image is slightly cropped to reduce vignetting artefacts)

 

_ZYY0737_spring_at_last_sprung_Z6v1.jpg

 

XR-Heligon, ISO 400 1/13 sec (hand-held) on D3200

 

T201903293691.jpg

 

Obviously the exotic Xray optic is not at all corrected for UV and introduces a lot of chromatic aberrations. Part of the fun, perhaps.

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Another view of the little Tussilago. This time though the Laowa 25mm f/2.8 Ultra-Macro lens at 2.5X magnification, on the UV-modified Nikon D3200 using a Broncolor 1600Ws studio flash (uncoated Xenon tube).

 

The lens is a modern optical design and being multicoated isn't expected to pass much in terms of UV. This experimental hookup at 2.5X magnification confirmed the predicted response, however also illustrates than one can "force" UV though most lenses. I shot at ISO 100 with the flash tube about 30 cm away from the flower head, running the flash on -1 EV output. The nominal aperture f/4 roughly corresponds to an effective aperture of ~ f/16. With the lens and camera on a Stackshot rail, it's easy to make a short stack of 10-13 exposures. More than this and the flower will wilt rapidly.

 

As the outcome material was pretty low in contrast and had virtually no "UV colour" apart from grey and black (both characteristics to be expected from the restricted UV transmission), I cast the stacked image in b/w. It shows the lens is very sharp (already confirmed with ordinary macro stuff) and that the step size of the stack is on the large side thus some stacking glitches remain.

 

Anyway, the pollen grains of the Tussilago are highly UV reflective and the anther tube and petals are UV dark. Both features have been documented on earlier occasions.

 

T201903313693.jpg

 

I have to repeat with a macro lens of better UV transmission to avoid overcooking the poor little flowers ...

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Interesting image Birna.

 

I wonder if the UV-reflectivity of pollen changes over time, when they mature or dries in some way.

In only image I have of the Tussilago, showing pollen, it is not at all highly UV-reflective:

post-150-0-25989300-1554092316.png

Daylight, Canon 60D full spectrum converted, ISO 360, 0.8s, Baader U, El-Nikkor 80/5.6 old metal @ 5.6

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I have gone though a lot of Tussilago UV close-ups to check, and apparently the pollen is bright when the flower is in an early stage of flowering, but might be dark later on. Perhaps a result of the grains drying out? Your photo shows late stage male flowering as the anthers have pushed through the anther tube.

 

I also thought of a fluorescence effect caused by intense UV light up close, but that would not explain why the pollen mass can be either bright or dark.

 

The Tussilago styles are almost always UV dark though. Female flowers are mainly ligulate and the centre of the head are male disc flowers.

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Redid the macro shooting of the Tussilago. This time at 2.4X using the combination of JML 50mm f/3.5 reverse-mounted on one of my UV-Nikkors. Same camera (D3200) and Broncolor 1600 Ws flash.

 

As expected this approach to getting greater than life-size magnification allows a lot more UV through and the "true" false colours emerge. The JML lens is a triplet only thus it adds some chromatic aberration, but results are more than just acceptable. The overall sharpness is good so one for example can identify spines on the pollen grain exine.

 

Here is the entire frame

 

I201904013705-2,4X.jpg

 

and a crop 100% to show better details.

 

I201904013705-100pct.jpg

 

We observe the pollen grains indeed are quite bright not dark. However, intentionally I included a male flower not fully opened and one can readily observe the anthers pushing through the anther tube being very UV dark. When the anthers dehisce the brighter appearance prevails, however.

 

Night temperatures are again dropping below the freezing point and thus spring still isn't here -- yet.

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Oh the tough little Tussilago !!! One of my favorite UV subjects thanks to Birna's work over the years. She always shows us how to make UV art as well as UV documentaries. :D

 

Birna, please do add the pollen macros to your Tussilago entry in the botanical section. http://www.ultravioletphotography.com/content/index.php/topic/354-tussilago-farfara-colts-foot/

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I took the broad-spectrum Nikon D600 out of its moth-bag today to combine it with a UV-Nikkor 105mm f/4.5 and various filters. This D600 is the DSLR cousin of the elusive modified Z6 (which Andrea now tells me is about to embark on its trans-Atlantic crossing -- yes!!). Both are 24 MPix models however Z6 should have the better ISO quality. Which a lens such as the UV-Nikkor one can comfortably do focusing through the optical viewfinder then just snap on the filter using a quick-release for the actual shooting. My hunch is that with the Z6, the same can be achieved using the EVF and the filter in place (or so I hope).

 

My endearing little Tussilago in my neighbourhood once again were pressed into service as test objects. To illustrate the quality of the UV-Nikkor, below is a 100% crop of a typical image. The crop also demonstrates the appearance of the flower heads when they are in the early female stage of flowering. Do note the circle of bifurcated styles at the base of the ray florets. The predominantly male disc flowers have not yet opened.

 

DSC_6888_Tussilago_UVNikkor105_BaaderU_D600_100pctv2.jpg

 

Considering the windy conditions and an exposure of f/11, 100 ISO at 2 sec, there is a surprising amount of detail to be seen. No flash was used.

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Shooting UV hand-held is a risky business. Here conducted with the EL-Nikkor 63mm f/3.5 on my modified Nikon D3200 (internal Baader U), a lens capable of focus to infinity by the way.

 

E201904043728_Birna_greets_Tussilago_BaaderU_63mmELNikkor_UV_D3200.jpg

 

The slight blur makes for interesting shapes if not the greatest of details.

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Going even slower, with the Tamron 21mm f/4.5 at 0.6 sec, f/16, 100 ISO. Still far from perfect of course, but what is to be expected with the hand-hand-held camera?

 

I201904043737_Tamron21mmf4,5_UV_D3200.jpg

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For this final attempt, I brought the heavy Piesker 400mm f/4.5 to bear on the little Tussilago. In this case, the lens is too heavy for me to give it adequate support unless the lens is put on a tripod.

 

Exposure 2.5 sec f/16, ISO 100. This exposure was on the rich side, though, but I kept it as the other tries were all blurred by persistent wind.

 

I201904043745_Piesker400mmf4,5_UV_D3200.jpg

 

The lens is decently sharp considering its vintage, but obviously cannot match a specialist like the UV-Nikkor 105mm. Much lower contrast, residual spherical aberration, and chromatic artefacts are all contributors to a reduced quality of the outcome.

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