My thoughts on HDR

When it first gained popularity a few years ago, image sharing sites like Flickr were awash with heavily processed, ultra-high contrast images with halos around trees and clouds.  They were fascinating pictures, because they were some of the first easily created photos that allowed you to see the detail of both dark and light areas of the image.  The novelty of these images quickly wore off, but the software that processes them has been refined and, although I’ll still go for a slightly over-processed look sometimes, I use HDR to try to recreate what I saw when I was there.  As much as technology has moved on, the human eye is still slightly ahead, and the brain makes a pretty good job of adapting quickly to give you an overall view that captures as much detail as possible.

Bracketed exposures of Canterbury Cathedral

Bracketed exposures of Canterbury Cathedral

Even phones will now take HDR photos for you, automating the processing to give an overall result of detail in areas that would ‘struggle’ otherwise.  Think of the photo you’ve taken out of a window somewhere, the outside looked lovely, but it basically had a black border.  Or the other way, where you just get a bright white window and a nicely lit room.  I’m aiming for a more subtle effect, and so my first requirement is as many exposures to work with as is practical.  The more exposures you have, the more choice whatever software you use will have to choose an exposure that is closest to what you want in every part of the image.  I generally take 7 exposures, from -3 to +3 stops.  That’s probably overkill, but I actually like the process.  5 (-2 to +2 in single stops) is usually plenty, and in most cases 3 exposures will get you fair results.  You can judge how much to bracket your own photos, but I’d generally go for +/-1.5 stops.

To go that step further and aim for your best photos, the points I stick to are:

  • Use a tripod (and don’t forget to switch the image stabiliser off).
    Using a tripod is the biggest step change you will see in the sharpness of your photos.  However, leaving the image stabilisation on will actually introduce tiny movements in the mechanism, thus introducing ‘softness’.
  • Focus manually.  If your camera has a live view and zoom mode, use it.
    Unless you have a camera with tens of focal points, and you’ve chosen exactly which one you want, then you want to be zooming in on exactly what you want to see and focusing manually on that.  Actually, never trust the auto-focus, it’ll end in tears.
  • Use a shutter release cable, or the short timer.
    As careful as you try to be, pressing the shutter button will introduce movement to the camera.  The timer can help with this but, especially if your tripod is set high, small vibrations can continue for several seconds.
  • Use the mirror lock up facility if your camera has it.
    We’re getting down to the slightly obsessive level now, but in an SLR camera, just before the photo is taken, the camera has to move the mirror out of the way.  That’s a solid lump getting thrown around in your camera and, yes, you guessed it, that’s movement right there.  The mirror lock up facility will add a button press to your process.  The first will move the mirror out of the way, with the second taking the photo.
  • Keep an eye out for gross movements in or out of your shot between exposures.
    While you’re concentrating on your camera, trying to remember whether you just did -1 or +1 stops of exposure, people are moving around.  People are generally very inconsiderate when it comes to your photography 😉  Make sure if there’s anything in the frame that you want it to be there.  If not, wait for it to move.  This is particularly relevant with fisheye shots.
  • Bracket using shutter speed, not aperture.
    My camera won’t automatically shoot 7 bracketed shots (it will do 3) so I switch the camera to manual and change the exposure myself.  When I haven’t been concentrating, I have been known to change the exposure by altering the aperture rather than the shutter speed.  On the back of your camera, the result will look like what you want, but the depths of field will be sufficiently different to cause unwanted results later on.

I think you should probably go and take some bracketed photos.  There’s lots of software out there to process HDR images for you, but come back in a bit and I’ll show you what I used to transform this photo.

Chris Geatch

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