Images (c) Dilip Krishnan & Rob Fergus

I was reading through the proceedings of this year’s SIGGRAPH (Special Interest Group on GRAPHics and Interactive Techniques) conference - as I’m sure we have all done at some point in our lives - when I came across a very interesting paper.

The conference generally concerns computer graphics and image analysis however the following title has a very practical application in photography: Dark Flash Photography. No we’re not talking about Joey Lawrence’s promotional images for the film Twilight, but instead a way to take flash photographs without people objecting, or even noticing!

The gist is that you can ‘hide’ the pulse of light outside the visible spectrum thus making it appear as much as 200 times dimmer than a regular flash. This requires an IR enabled camera and suitably modified flashgun. The use of flash for photography can range from an mild annoyance to a dangerous distraction in certain circumstances, which leads to the use of shutter speeds far slower than would be ideal. The dark flash solves this problem but creates a new one.

left to right, IR image, natural light image, combined image, long exposure natural light (for reference)

Capturing light in the IR part of the spectrum doesn’t allow natural looking colours to be recorded. Dilip Krishnan and Rob Fergus solved this problem by taking two exposures, one with the dark flash and one high ISO natural light photo immediately after it. The clever part is that the dark flash image can be used to guide to de-noise the high ISO image far more effectively that any other noise reduction technique. Simply put if you see an edge or spike in the natural light image and there isn’t a corresponding edge in the IR image then the point is probably the result of noise. The actual process is a little more involved, I’d recommend anyone technically minded to have a look at the original paper.

The result is a clean image with natural looking colours. The post processing required is complex, and there times when the approach wont work well if the subject moves between the two exposures (shooting fast paced sports for example). However if you have an IR enabled camera and like black and white images I can see this being a very valuable technique when in many circumstances, and indeed the only real solution to the problem of dazzling people with flash.

MG

Conventional wisdom states your money is better spent on a good quality lens than on the camera body. And for the most part it’s a very good piece of advice - something like the Canon 85mm f/1.2L will produce stunning images mounted on a 1000D body, whereas even a Nikon D3x will struggle to take decent shots with the 18-55 kit lens in anything other than favourable conditions. There is, however an curious anomaly in this trend that occurs at precisely fifty millimetres.

By and large telephoto lenses are easy to design, optically but require some very large [read expensive] elements if you want a fairly wide maximum aperture. In contrast wide angle lenses have to bend light much further and apertures can only be so large without the use of sophisticated [read expensive] optical corrections.

The humble 50mm, once the standard ‘kit lens’ bundled with new SLRs happens to sit at the crossover point. The focal length is long enough to employ a simpler non-retrofocus design, which is tried and tested, with inexpensive elements keeping the manufacturing and assembly cost down. As a result you get a very large maximum aperture and good optical performance for what is relatively little money.

And mounted on a full frame 35mm body the selective focus is sublime…

MG

Here’s to the photograph of 2009, may there be many more to follow! This year I had the pleasure of being official photographer at Bobo Lobo’s red carpet new years eve party in York. Read on to see some more photos from the night (all taken with the Orbis ring light adaptor). A very happy new year to all.

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I’m going to start this with a quick recap for people who might be unsure of what a ring light/flash is or why they should care, those of you who came here for the review may skip straight to the “read the rest…” link at the bottom!

A ring light surrounds the lens and produces images with an intense glowing look and faint ‘halo’ like shadow around the subject. They have been very popular with fashion photographers for a while although opinions on their use tend to differ…

Until recently the only commercially available ring flashes were either the AC powered studio variety or the hotshoe mount macro ring lights. Neither of these are particularly well suited to shooting people on the go - the big lights require an even bigger battery or long extension chord and the macro version simply isn’t powerful enough. Now there is a third alternative in the form of adaptors that take an existing hotshoe flash and turn it into a ring flash through a series of special reflectors inside a ring shaped diffuser.

As an events photographer who strongly dislikes on camera direct flash this option is extremely attractive I preorded the Orbis as soon as shipping was announced. Read on to find out what it’s like to shoot with under real world conditions and more importantly what it does for your images!

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