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Ultraviolet

dudler

Time for an update: I still use film, though. Not vast quantities, but I have a darkroom, and I'm not afraid to use it.

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Ultraviolet

24 Jul 2021 10:05AM   Views : 324 Unique : 248

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The title of a British TV series about vampire hunting – vampires are allergic to UV being the basis for the whole thing. Subsequently used elsewhere as a title…

My full spectrum Sony will record UV, but it needs two filters to do it – one to exclude visible light, and another to block IR wavelengths. I’ve finally bought a pair, after wondering what to put them in front of: the problem being that glass tends to block UV light, so one needs either a monstrously expensive UV-Nikkor, or a lens with three elements or less.

Even with an old Ludwig Meritar (50mm f/2.9, three elements and undoubtedly the worst standard lens ever available for an Exakta) and bright sunlight, exposures were not within normal ranges – 6400 ISO gave me 1/40 at f/8… Put the filters in front of an ordinary camera, and you’ll be looking at several seconds. The trick of using an unconverted sensor and a filter just about works for IR, but it’s a dead loss for UV, I think.

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The bit of a portrait (it has to be a bit, as the overall result’s awful, technically, and unflattering) shows the reverse of the IR effect on dark glasses. The shades in this shot are actually clear glass for very short sight, with not the faintest tint. On a sunny day, two layers of window were allowing so little UV indoors that I was working at ˝ second and 102k ISO. Yes – over 100,000 ISO…

Early days yet. I’m told some flowers have enticing UV-visible patterns to lure bees to the pollen, and that male portraits can be very craggy indeed. We shall see…

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Comments


dudler Plus
18 1.7k 1876 England
24 Jul 2021 10:06AM
I wonder if there's a way to get false colours from UV? Any thoughts welcome, as always.
24 Jul 2021 11:27AM
Never had a converted IR camera body but have spent what sometimes appears to be a small fortune on IR Filters in various thread sizes from 37mm to 77mm diameter and various strengths but have always had what I consider poor results. Using Lightroom seems to give good conversions to IR but nothing like some of the results I see on here. Will continue to persevere. Paul.
altitude50 17 21.7k United Kingdom
24 Jul 2021 11:51AM
I do not know aboutUV. have had two cameras converted to IR The first one was a Sigma SD15 in which there is an easily removeable IR filter behind the lens - just slip it out and add an appropriate filter on the lens.
My current camera is a converted (830nm) Panasonic Lumix GX-7. I have three lenses for it, the best lens being a Leica 15mm. I have had a few reasonable results from both cameras, and a lot of not so good. The problem being to get the contrast looking right. I only use Elements and NIK.
I do not dabble in colour IR mainly due to lack of knowledge and patience. I think that 830 nm would make it difficult if not impossible anyway.

Incidentally, I genuinely have seen two ghosts, both in daylight and whilst I was sober. Try to tell anyone and they take the p*ss! So I keep quiet.
These TV programmes about ghost hunting usually send 'investigators' into old buildings at night. Plenty of opportunities to scare yourself.
dudler Plus
18 1.7k 1876 England
24 Jul 2021 2:33PM
Paul, the crucial thing about shooting IR images is that all cameras come with a very effective filter to block IR in front of the sensor. This means that exposures using an IR filter will be very long. A converted camera allows perfectly normal exposure settings.

So it's worth the money to have a camera converted - and while you're at it, you might as well have a full spectrum conversion done, as it allows the whole range of different IR sensitivities

Lightroom applies a heavy red filter, giving a sort of semi-IR effect, but rather diluted. Pictorially, though, this is often all you need - the equivalent of using Rollei 80S film. Not true IR, but looks good! According to the website of the firm that did my full spectrum conversion, you need something around a 580nm filter for colour, possibly 620nm.
25 Jul 2021 2:52PM
Just read the article about Full Spectrum and IR conversions, will contact the company to see if the Lumix GF2 I have might be suitable to convert. Thank you for the comment above. Paul.

PS. Just read that he doesn't appear to do lumix but does have some converted possibles the Canon EOS M might be OK for what I want with the 18-55 Lens option.

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