Last night on Facebook I posted one picture from Saturday’s trip to New York City. It was one of the first ones I looked at and among the last I shot. In case you’re interested I’ll tell you how this shot came to be.
First, it is not really one shot. It is nine shots! Each was exactly the same–shot from a locked down tripod. The only difference was how long the shutter was open. The fastest was 1/8 second. The slowest was 32 seconds!
That’s a 256:1 ratio between longest and shortest which is easily seen as brightness.
Shooting a wide range of exposures is a workaround for a weakness of cameras and the human eye. In both cases (though worse with the camera) we can see a large range of light levels, just not at the same time! To get an image bright enough to see detail in the shadows, we must also ‘blow out’ detail where it’s bright.
I ended up with lots of detail in bright and dark spots, but in nine separate images. Enter Photoshop. It is programmed to combine those images, preserving the most detail from each. There are other standalone programs (including Luminance (free) and Photomatix, the standard for this kind of work) which will do the same job.
The technique is called HDR for high dynamic range. When done judiciously the result is pleasing and looks more like reality than any single photo. When done poorly it looks like Elvis painted on velvet!
The images were shot with a Canon 7d DSLR using a Tamron 17-50mm f/2.8 lens wide open. ISO was set to 100.
Many thanks to the development team at Magic Lantern who have produced ‘firmware’ for my camera to allow it to do things it was never designed to do! The process for getting the nine separate photos, all with different shutter speeds, was automated by Magic Lantern which is free! HDR automation is just one tiny feature of Magic Lantern.
More pics to come.