Old dogs

23 05 2013

They say you can’t teach old dogs new tricks. I don’t know why they say that. It doesn’t strike me as particularly well based in scientific research.

I’m feeling a bit of an old dog today – I just clocked up 49 circuits of the sun. Give or take a partial spin of the Earth for emigrating from the UK and immigrating into Canada. That’s more of a rounding error in the grand scheme of things. I also flew clockwise all the way around, so I’m not sure what that means in ABSOLUTE age, either. But I do like a new trick every now and then. I can be obsessive in my interests. To the point of annoying Mrs E. My most recent obsession is a newly refreshed interest in photography. I did all the usual mid-life male pseudo-crisis stuff and bought a new camera and lenses. Convinced myself I now took better photos. The usual.

It’s not surprising therefore that when pushed to state preferences for potential presents by offspring and assorted rellies, I came up with an assortment of camera and photography related items. It was a bit tough, as being reasonably affluent and of the male persuasion, I’m not shy of splurging out whenever I feel the desire for a new gizmo or trinket. Nevertheless, I was indeed pressed to name items I might not be averse to receiving, and so duly received even more baubles with which to play.

One such item is an Infra-red filter for my camera. More expensive than I’d have expected, so I’m even more grateful to my father-in-law for sending it.

I attempted to snap a few photos this morning before work. Nada. The images barely registered. I’d watched a video that had explained how hard it was to compose your shot because the IR filter blocks all visible light… kind of makes the through-the-lens viewfinder a bit useless for the non-bionic amongst us!

So I wasn’t looking to get any super photos, just something to see the promised ethereal effect of an IR spectrum shot. The video had mentioned that IR focuses slightly shorter to visible light, and that your focus ring needs to compensate, or you need a deep enough depth of field to handle the difference. Again, I wasn’t looking for super sharp images at this stage… just SOMETHING. The video had gone on to mention setting a small aperture to give that extra depth of field, but had just vaguely mentioned “the appropriate exposure time”. Thinking I was being smart, I set my fancy schmancy camera to aperture priority, slapped on the auto-focus, set ISO100 to try and get a low-noise image, set a small aperture for good DoF and let the camera do the rest. It selected a relatively short exposure (1/50s I think) and snap.

As I said… nada!

Time to leave for work, and a frustrating day pondering the puzzle.

I read more, and discovered that the camera’s sensor is confused by the narrow band of light reaching it through the filter and assumes there’s more light than there actually is. Exposures in the 10s range are more appropriate. Ah! So, once back home, I took care of the other little issue I’d read about – setting the custom white balance of the camera to deal with the strong red/magenta cast of using the filter – and then went about putting my camera on a tripod and having another go.

Here’s where I learnt one last new trick. It turns out that because of the aforementioned difference in IR wavelengths and the band of visible light, the IR light bounces around inside your lens a bit differently before it hits the camera’s sensor to be recorded. Depending on the design of the elements in the lens it may be prone to producing “hot spots” in the centre of the image. The good ol’ Interwebs provides a few sites listing various lenses and their suitability for IR photography. Guess what? My lenses are all on the “bad” list. All except my 100mm Macro.

Oh well – that’s a good excuse to buy more toys. 🙂

There’s a few tricks left in the old dog yet, it seems…

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