Sunday 25 November 2012

I finally understand flash too late

I had a eureka moment earlier on today. Exciting for me, boring for you. Yes, I realised that I had finally cracked flash. Or perhaps just finally cracked? Anyhow, I have been jumping up and down very enthusiastically for most of the day - knowledge is power, as they say. Why it has taken this long, i.e. many many years, is anyone's guess, but I finally understand how it works and how to use it. Shame that this revelation only took place on the penultimate day of my holiday, and that I had already visited the rainforest - where let me tell you, that Blue-backed Manakin would have been toast - but such is life. The secret lies in manual everything. Manual flash, manual exposure. None of this fill-flash crap, manual all the way. The specific revelation was realising that if you reduce the power of the flash, what you're actually doing is reducing the duration of the flash - the actual light output remains the same. I just hadn't grasped that before. So if, say, you reduce your flash power to 1/32 of full power, it illuminates for a split second, a much faster split second than your camera shutter is capable of. Thus in a dark place, for instance a rainforest, the shutter speed you set on your camera is completely irrelevant, as the light that hits the sensor is all driven by the flash, and not from ambient light. So your shutter can be open for ages, say 1/200th of a second, but if your flash is set to 1/32nd of full power, then that lights up for only 1/20,000th of a second (or so), and the rest of the time it's just dark and nothing is recorded. With me so far? So you can safely set your camera to manual, dial in 1/200 or similar, set a nice small aperture that will ensure lots of stuff in focus, and fire away safe in the knowledge that in Aperture Priority mode you would get a black image and the flash does everything else. This also means you can handhold, and leave the pain-in-the-arse tripod at home for ever. As the distance changes between you and the bird, so the relative power of the flash increases, so you can keep your exposure constant by moving ISO down as you get closer(sensor less sensitive to light), up as you move further away (more sensitive), or your aperture down as you get closer (make hole smaller, less light hits sensor in available time), or up as you get further away (bigger hole, more light hits). The only issue with this is that, for me at least, at the beginning of this voyage of discovery, it's all a bit trial and error, with a high likelihood of either not enough or too much with the first attempt, after which the bird zooms off. Nonetheless it's a miracle, and I am really really dense for not discovering this earlier. This is how people freeze the wings of hummingbirds - by using 100% flash which gives bonkers shutter speeds far in excess of what the camera is capable of. Genius. All of the above came to me in a flash, so to speak, when I was wandering round the gardens of the hotel early this morning . There were plenty of birds, but they were impossible to photograph. I idly wondered whether the Hummingbird technique might not work on other birds, birds in dark places.....bugger me if it didn't. Look at this Barred Antshrike - perhaps not the natural-looking image we all strive for, but given the choice between impressionistic blur and pin-sharp albeit flash-lit, I'm going for the latter every time.


1/300s, f8, ISO 640, FLASH 1/32 power

  

6 comments:

  1. Great shot with the flash. I've been trying to get my head around flash using the Better Beamer. It's great when it works but pants when it doesn't :) I'll try out your settings and see how it goes for me using the BB. I should have used the BB yesterday when photographing the Waxwings in the gloaming which seemed to exist all day. Flash works!

    Mark

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  2. Hi Mark
    All these shots are with the Better Beamer - the Antshrike was 300 + 1.4x + BB. I never got round to trying flash photography without it, so I have no idea what any difference might be. I used the BB with the 800 as well, mounted higher than the lens, for the Hummingbirds a couple of posts down. It definitely gets light on the bird, not sure how! I'll plan a few posts on the other blog that go into what I've learned so far, including exposure details, as I've yet to get my head round how it works when in AV mode. Rubbish mostly.....

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    1. Great, I look forward to that. The exposure on the Antshrike looks spot on. The Hummer images are equisite.

      Mark

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  3. That's a simple enough explanation that even I understand. How swish a flash do you need to have that level of control?

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  4. Your flash need to have manual mode, that's it.

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  5. Off to Blue Waters Inn next week so making a note of all this advice to give it a try - thanks!!

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