Prism in the light path!

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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Prism in the light path!

7 Jul 2020 8:21AM   Views : 236 Unique : 161

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This blog owes a lot to mistere, who not only suggested the topic, but has made a suggestion on a one-day workshop into a bit of a personal specialism. The pictures of models are his. But here goes with some thoughts on using prisms and other bits of plastic in front of your camera…

The model on that workshop, Jenni JJ, had some marvellous images in her portfolio that had been shot through a prism, so I duly ordered some ‘Ring Chandelier Glass Crystals Lamp Prisms Parts Drops Pendant 50mm ‘ from Amazon, and worked out some basic ideas. The description’s misleading, as they’re actually made of plastic, by the way – that’s not a problem, but it’s worth knowing. By the way, they’re three times the price they were last year.

With a large prism and a small lens, you can shoot entirely through the prism: otherwise, the image will be partly through the prism, and partly in plain sight. This can put a premium on compact, fixed focal length lenses. Almost always, it will be best to shoot without a lenshood, as this allows the prism to be really close to the front element of the lens.

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Many prisms, such as the chandelier rings, are too small to cover the front element of most lenses, and holding one in front of the lens from the side will distort shapes and focus, and maybe introduce some rainbow highlights. Follow the Julia Margaret Cameron line (the Victorian portraitist said that she focussed until the image was beautiful, rather than sharp), and move your prism around ‘until it looks beautiful’ (or, at least, interesting).

The leading image tied me up for a while, working out how to shoot it… I think Pink Floyd cheated with the cover of Dark Side of the Moon. I shot it with a prism that I bought several years ago: just like the ones I remember for the physics lab at school. It was remarkably cheap on eBay: it’s also rather slender. This image is unusual, in prism terms, as the arrangement could be very static and stable – not so many variables to juggle.

Prisms come is all shapes and sizes: from those made for use with cameras, such as the Seventies Cokin effects filters to Lensballs and even the bottom of a beer glass. Handholding is probably the best approach, though it will be annoying to see some lovely effects slip away as you move in a way htat you hadn’t planned. Think of it as a form of juggling, and be grateful you’re not doing it while riding a unicycle!

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If your AF system is up to the challenge, make sure that you select a single AF point, and that you position it precisely – the nearer eye is the optimum place for almost anything involving a face. If you have the luxury of a mirrorless camera, magnify a small part of the frame, as this gives more precise results than focus peaking. (DSLR owners – think of this as improved live view, in the viewfinder, all the time.)
But as prisms of all kinds simply present too much complex and anomalous information, so that most AF systems will be confused, and you will end up resorting to manual focus almost whatever you do. You may find that back button focus helps, if you really want to stick to AF (or if you’re running out of hands to hold camera, filter, focus ring…)

Stopping the lens down makes a big difference to the results, and so using the depth of field preview button is important. Too small an aperture may the structure of the prism apparent in the finished image, and lose the delicate effects that are possible. Always, with prisms, the best advice is to play.

You may find that you hit it off with a particular combination of lens and prism, and that other combinations don’t work very well for you. It’s highly individual, though – Dave has achieved lovely results with the simple ring, and I’ve struggled.

To sum up:

1. 50mm or longer seems to work best.
2. Manuel or aperture priority.
3. Single point auto focus, or manual focus. Or the camera gets confused.
4. Bottles and cling film work for different effects.
5. The lens from an old magnifying glass gets interesting results.
6. You need a decent strong light. Continuous light (or strong sunlight) is easier to work with than a flash, though a studio unit with modelling lamp can work well.
7. Good luck!

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Comments


dudler Plus
17 1.2k 1682 England
7 Jul 2020 8:22AM
From top to bottom, models are Black Beauty, Jenni JJ and Amethyst. All model pictures copyright Dave Edkins.

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GGAB Plus
4 31 1 United States
7 Jul 2020 1:12PM
Why not use a tripod to provide a "third hand"?
Really cool images
mistere Plus
7 6 3 England
7 Jul 2020 1:19PM
And practise. The results can be very unpredictable and it's difficult to replicate the same effect twice. Especially with the camera in one hand and the prism in the other Smile
Dave,
dudler Plus
17 1.2k 1682 England
7 Jul 2020 2:21PM
The idea of using a tripod makes absolute sense for static subjects. Working with models in the way that both Dave and I do, that would be as limiting as trying to run a marathon with one shoe, or play rugby with your arms tied behind your back.

You need to be able to make tiny adjustments of angle and distance to get any given shot - that's why the idea of remote shoots hasn't appealed to me at all. It would lose all the flow of the session to have to work with a rigidly static camera.

Gaffer tape and Blue Tak to hold the prism in front of the lens are options - but, again, you actually want the fluidity of constant adjustment of the position of the prism...
mistere Plus
7 6 3 England
7 Jul 2020 2:36PM
As John already mentioned. Shallow depth of field works best. I get best results by focusing on the subject before putting the prism in front of the lens. Then it's up to the photography gods.😱😂🙂,

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