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UltravioletPhotography

A beginner's trials and tribulations


DaveO

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I started trying to get into UV about last March, just as winter was looming on the horizon here down under. Yesterday was the first good sunny day for a few weeks so I ran around like a headless chook (Aussie for chicken) and now to display my ignorance to the world. I had read all about lenses not transmitting into the UV so went looking on-line for something that looked vaguely affordable and found a quartz 105 mm lens from Universe Kogaku (America) at about one fifth of the price of a Coastal Optics lens. The manufacturer clearly warned that it was NOT colour corrected but it did have good transmission right down to 266 nm. My standard visible macro lens is a 100 mm Zeiss Macro Planar which used to be available in a Pentax K fitting when I bought mine (for only one arm and leg) about 3 years ago!

 

Here's a shot through the quartz lens from my broad band modified Pentax K-5 (same sensor as Nikon D7000) in RAW (the camera gives me DNG files) before any manipulation

post-28-0-28259300-1377583546.jpg

Exposure 0.2s @ f/8

 

After White Balance in Photninja on the square of uncalibrated Spectralon

post-28-0-12323500-1377583752.jpg

 

From camera through Macro Planar lens

post-28-0-72516500-1377583834.jpg

Exposure 0.5s @ f/8

 

After White Balance

post-28-0-18988600-1377583894.jpg

 

I think you can see where this may be heading. I will post another set of macro shots to compare the two lenses but the basic question is - Am I losing UV information by using a "normal" lens which gives longer exposures and should I really be saving my pennies for something like to Coastal 105 or 60?

 

Cheers,

 

Dave

PS. A Bunyip is a mythical Aussie critter.

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The warm hues on the unbalanced quartz lens shot indeed indicates it'll pass a lot of UV also well below the 380 nm mark. The same cannot be said for the Zeiss Planar which of course just reflects the difference in optical design, glasses, and coatings applied.

 

The quartz lens being uncorrected for colours means it will show colour fringes because each colour has a slightly different wavelength. For visible-band work this will be a major issue and difficult to correct, so sharpness may suffer. However, when you attach an efficient UV bandpass filter to the lens, the more narrow passband alleviates the colour problem to a large extent so results should improve markedly and sharpness ought to benefit as well. This is a lens that in fact might be suited for true narrow-band use in UV.

 

With regard to the similarity in appearance of the quartz vs Planar when you do a colour balance, this is not really an indicator that the Planar can replace the former for UV shooting. Do remember that the Spectralon target may be fairly linear over a wide spectral range and that the Color Checker never was intended for UV use. This in turn means you will get more or less the same rendition whether the balancing is over a narrow window in upper UV-A, say 380 to 400 nm, as with a wider 300-400 nm range, because the CC has its "signature" in that upper window only. Put in a flower or two and the output will be clearly different.

 

Your Pentax appears to have a good reach into UV. I'm curious to see it applied on more exciting test subjects !

 

PS. Thanks for the clarification of the Bunyip - I was worried this was a coded message of some kind .. DS

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Thanks Bjorn,

 

Flowers are still a bit rare as Spring is just about to Sprung but here's a start

post-28-0-37527500-1377595032.jpg

A "daisy" of some sort (here in the garden when we moved here 2 years ago), Visible shot with Planar 1/000s @ f/8 WB in Photoninja preset on Spectralon

 

post-28-0-14858400-1377595181.jpg

Same lens, BaaderU, WB preset on Spectralon, 1s @ f/8

 

post-28-0-47302300-1377595270.jpg

Quartz lens visible (with B+W UV/IR cut filter) WB as above, 1/1600s @ f/8

 

post-28-0-41341100-1377595402.jpg

Quartz lens BaaderU, WB preset as above,1/5s @ f/8

 

You can see that the Planar loses a few stops as well as much of the warmth which is visible in the UV quartz result.

All focusing was done with Liveview and a loupe on the screen. I checked the histograms RGB of the captures to decide if the exposure was OK.

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Here are a few more shots of the type of flower I'm working towards (you knew we would get past all the boring stuff eventually)

 

A Grevillea hybrid Visible with the Planar, 1/1000s @f/8

post-28-0-83137200-1377596471.jpg

 

Same flower through BaaderU, Planar, 2.0s @ f/8

post-28-0-46565800-1377596611.jpg

 

Same flower, Quartz, visible, 1/500 @ f/8

post-28-0-94559500-1377596693.jpg

 

Same flower, Quartz, BaaderU, 0.5s @ f/8

post-28-0-47607700-1377596780.jpg

 

Cheers,

 

Dave

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Dave, good start.

 

After your intro post, I wrote how excited I was to see a converted Pentax in use. We have known of them in the past, but this is the first time I've seen any UV work with the newer K5.

 

Some observations --

 

You appear to have a light leak when shooting UV. For example, the very last posted photo shows a cyan cast in a lower right triangular area, a sure sign of light leak. This is probably happening through the Viewfinder. Close the Viewfinder before making your UV shot. Light leaks can also happen through misfitting adapters, filter holders, open port doors or lens windows. The visible and infrared light leaks through and contaminates the UV photo causing lighter areas and discolouration.

 

Your standardized colour balance with the Spectralon is pretty good. You are definitely in the ballpark. In the white balanced shot of the Spectralon, that pesky light leak is contaminating things, so I cannot determine whether your WB needs a little more work.

 

When posting a UV shot for evaluation, please mention all three exposure variables - aperture, shutter speed and ISO setting. It is also useful to know whether sunlight or UV-flash is the source of illumination.

 

I see you have made use of Photo Ninja. We have found it a truly useful app for UV work.

I usually set PN's colour correction tab to Plain for UV because UV shots tend to oversaturate.

 

About lenses for UV work: Please look in our Gear lists and in the UV Lens Sticky for information about many, many lenses useful for UV which do not cost an arm and a leg. I'm just about to add a few more to the Sticky.

LINK: http://www.ultraviol...ography-lenses/

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Thanks Andrea,

 

Yes, I sort of tried to ignore what I was sure was a light leak after some of your earlier comments. It's not so obvious with the BaaderU/Planar combinations, perhaps that's just because the Planar is only pretending to pass UV and there's only a tiny little bit actually getting through. When I saw the leak/flare earlier I did what anyone who remembers real photography would do, I dug out an old black cloth I used to use to peer at focus screens (probably not a particularly good one, very home made but very useful these days when looking at Liveview screens - what goes around comes around) and sort of threw it over the back of the camera. I did use the somewhat pathetic plastic Pentax viewfinder cover as well. I didn't have a lens hood on the quartz lens but did on the Planar.

 

Sorry I forgot to say all the shots were on ISO 200.

 

Way back in my film days (where I had to develop the film to see I had a problem) I was driven crazy on several occasions, with different camera/lens combinations with flare on the film, often caused by bright highlights which were outside the viewfinder area but actually visible to the lens. The WORST offender was the Mamiya 7 rangefinder with the 47 (?) mm wide angle lens!!! So, I will try to find the problem. I solved that one by getting rid of that camera, it was never a problem with the wonderful Hasselblad SWC.

 

I'll post some more shots. You've probably all guessed by now that I'm well on the NERD side of the spectrum, that's probably what happens when you train as a Chemist.

 

Cheers,

 

Dave

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I think your problem isn't a light leak per se, but ghosting caused by the lens itself. Your quartz lens likely is not designed for daylight use and/or has insufficiently effective coating. You absolutely need the longest possible lens shade for it. Covering the camera itself with a black focusing cloth (which I remember fondly from my view camera days - does your cloth have those nifty lead-filled seams so it'll stay put?) will help cut down on any leakage coming from the viewfinder of the camera or the lens adapter (itself often a point of leakage). However this will not suffice to remove stray light and ghosts if these issues arise at the lens front end.
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First off, let me say that it's probably a severe case of pigs ear into silk purse with my quartz lens which was probably intended to be used on surveillance CCTV or some such, it only has three elements with a magnesium fluoride single coat and is apparently optimised for 266 nm (whatever that means). But, hey I wanted to see how a lens with better than 80% flat transmission down to 260 nm or so would perform. The Baader U filter only transmits 320 - 380 nm after all.

 

However I think I have nailed the leak/flare:

post-28-0-09132500-1377670869.jpg

 

This was the quartz lens with the metal lens cap screwed in and using a 31 mm extension tube which I sort of suspected might be the problem. As far as Pentax is concerned, extension tubes went out with button-up boots so I had to get what are politely called "after market" ones. Two shorter ones seemed OK (perhaps). So, Plan B, use my Novoflex Bellows - problem solved

 

post-28-0-77107600-1377671131.jpg

 

I know it's not sharp, the breeze was blowing and I welcomed it with some Anglo-Saxon phrases and it was hot under the black cloth etc...

 

Cheers,

 

Dave

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Glad you tracked down the problem. However, be aware that many bellows do leak IR and for a modified camera with the UV bandpass filter set in front of the bellows that is a potential problem.

 

You can test for IR leakage by adding a layer of aluminium foil around your bellows unit to learn if this makes any difference when you shoot in direct sunlight (50% IR).

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I should have said that the exposure I used for the leakage tests, with full sun on the back of the camera, was 1 second ISO 200. My quartz lens shots had been typically 0.5 s @ f/8 ISO 200.

 

Here's the result with the bellows racked out full

post-28-0-20399500-1377682124.jpg

 

On the original the levels histogram just moves away from the left edge, but when I repeated the test with the black cloth thrown over the bellows it didn't move away from the left edge.

 

Of course, the "elephant in the room" as you will well know, for shooting macro of delicate flowers in the bush is wind induced movement. I do have a white "tent" that I use as a wind break with visual macro shots and Metz ring flash (off-camera for better modelling) so I suspect I will be using the 365 nm LED that I got from Don McLeish. Here's a result of the Spectralon

 

post-28-0-78144600-1377682462.jpg

 

I'll try some LED/Flower shots soon.

 

Cheers,

 

Dave

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Good work, Dave, in tracking down that light leak. I am relieved to know it had nothing to do with the Pentax body. I didn't think it did, but we get surprised sometimes.

 

So you have a MacLeish !! I have two of his "Haiku" models - one with a 365 Nichia-LED and the other with a 385nm LED. Aside from being the most elegant torches ever designed, the 365 is very useful for shining on the flower in order to focus via Live View.

 

Shooting in the wind is a pita. I was just out yesterday for a Lobelia, and it tried my patience. Any flower in a park here in the US is not collectible, so I had to zen it out and wait for the intervals between the breezes. Eventually I got it.

 

We all employ various tricks to shoot in situ. I have some garden flower stakes with a ring on the end that help stabilize a flower stalk. You can cut open the tube of a plastic straw and wrap that around the stem. Sometimes I resort to tucking stems under a bag strap or similar if I think the stem will not break. If the flower grows by the roadside and is not endangered, I simply pick it to bring home and shoot under windless conditions. Sometimes I make Michael hold a flower for me if he is in a patient mood.

 

But good strong UV illumination is the only real help. The 365nm LEDs are too narrow to use as UV illumination. Eventually you will want to use some kind of UV flash. We have flash pointers in the Stickies in the UV Gear section.

 

Helpful hint for posing picked flowers: Put them in a little vase. Or, get a rock with a nice flat bottom and drill a hole in it for the stem. Some of my best UV shots have been made with my rock vase. Here is an early example: http://www.ultravioletphotography.com/content/index.php?/topic/55-coreopsis-verticillata-zagreb-threadleaf-tickseed/page__fromsearch__1

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My MacLeish is a "Sundrop" which he recommended when I told him what I wanted to do with it. This afternoon was rainy so I picked a few flowers of 'Ironbark' Eucalyptus sideroxylon (growing in our garden, we have the same prohibitions as you in the bush) I set up a shot of the same flowers last May as shown here

 

Planar, UV/IR cut filter, 1/640s @ f/8 200 ISO

post-28-0-07543900-1377769791.jpg

 

The UV shot was a bit of a surprise, Planar, BaaderU, WB from black patch on Color checker, 5.0s @ f/8 200 ISO

post-28-0-38265300-1377769965.jpg

It was as black as the proverbial Ace of Spades - there's a fortune to be made by extracting the UV absorber as a natural sun screen - You saw it here first.

 

Here's one from today with the Quartz lens, 365 nm UV LED, 1.0s @ f/8 200 ISO

post-28-0-73205800-1377770210.jpg

 

Exposure through the Planar for an equivalent shot with the 365 LED was 30s @ f/8 800 ISO Hmmm...

 

Have you taken any images of eucalypts, I gather they are common in California.

 

Cheers,

 

Dave

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The blackness of anther filaments is widespread. The occurrence of UV-dark flowers in general is related to presence of conical cells on the surface to make the entire flower shimmer from pin-point specular reflections. You need pretty good detail of magnification in order to document this, though. A reproduction scale of 1:2 or better usually is required.

 

The very long exposure for your Planar when the UV LED is used clearly indicated its UV response drops like a stone below 380 nm or so. Like I said in an earlier post and you now provided the evidence.

 

As for your quartz lens it evidently works as expected. Due to the simple optical design it probably is best to stop it down even beyond f/8, you might actually find f/11 or even f/16 to render details better. All of this presumes a stationary object of course which in the field isn't always that easy. So, the next step should be getting a UV-capable flash?

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What a cool flower in both Visible and UV. I've never seen any eucalyptus blooms before. Yes, they are grown in California and Arizona. I walked through a small Eucalyptus forest at the Boyce-Thompson Arboretum outside of Phoenix. I should have said that he forest was small -- the trees were enormous.

 

When you write your exposure info, please put a little more for the lens than just "Planar".

There are a host of Planars out there and I can't keep track of who is using which one!!

Thanks.

Example: Zeiss 60/4.0 UV-Planar

Yours: Zeiss 100/?? Makro-Planar

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Yes, sorry I should have said Zeiss 100/2.0 Makro-Planar (in the now rare Pentax-K fitting). I did also wonder if part of the long Planar exposures might have been that I was using the 48 mm diameter Baader U filter on the 67 mm Planar front element by means of a 67 - 48 set of step down rings making a sort of Waterhouse stop in front of the lens. An academic point perhaps, I was a bit surprised the first time I tried the Baader U on the Planar to be able to see anything through the Liveview but the Pentax K-5 did that OK. I got very similar exposures on a Macro-Takumar 100/2.8.

 

How can I tell if a flash gun would have a good UV component if the plastic shield in front of the flash tube was removed? The current biggest in the Metz range, for example, is the 76MZ-5 (with lots of auto functions you would never use). It seems impossible these days to buy a flash gun which just puts out light when you connect a synchronising cord.

 

Cheers,

 

Dave

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Look for the tell-tale cast of yellow - is it the cover "glass" or on the flash tube itself. The cover can be removed (at the risk of getting into trouble if the flash blows up). The flash tube coating can be removed by polishing it off, but do leave a thin strip along its length intact as otherwise the flash may not fire.

 

UVP member Shane is well versed in making UV flashes so shoot him a PM. He might even have stuff for sale so won't hurt to ask for advice.

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