Saturdays Sunset

Sunset November 5th, 2009

I don’t know about where you live, but here the sun sets pretty much every day. Granted it sometimes does so behind a veil of grey or in the total absence of cloud it just disappears without the slightest hint of pomp and ceremony.

We are blessed, however, here in Canterbury with a reasonable number of stunning sunsets, along with the one at the beginning of the day. What’s the name of that one? Sunlift? Sunclimb? Not sure. I’m not really a morning person, but I’m sure you know what I’m on about.

I’m a sucker for a good sunset as much as the next bloke, although in truth it’s the cloud scape I’m after when I venture off into the setting sun. The way our house faces the first indication I get of a good sunset is the red glow out to the east towards Banks Peninsula.

If I see the landscape getting that surreal golden look about it I’ll grab the camera and do a 5 minute photo recon of the back yard and check out what mother nature has thrown on. This is what I got on Saturday night when the wind had calmed itself from a furious day, and the number one daughter asked “Why is the sky a funny colour?”.

I blasted off some initial cloud-shots and chimped the RGB histogram on the camera to see what sort of light range I’d be competing with. Things were still a fraction too bright on the horizon for my liking, but the clouds looked great.

As the sun drops lower the light shears across the cloud base, creating the textures and effects that define and paint the sky. The closer it gets to the horizon the less contrast there is in the light and the more modelling you get of the clouds.

It’s a bit like playing chicken with mother nature. The sky changes quickly, shifting hues of red, orange and blue right, shards of light spreading further outwards as the sun gets under the base of the lowest clouds. If you wait too long the show is over, packed up it’s bags and moved on to another time zone.

This shows the problem with the light, even though this is two different exposures from one raw file, with a bit of doding on the shadows thrown in for good measure, I was still struggling to get enough detail in the shed and grass to be compelling, and the hot-spot from the sun is still too large and distracting for my liking.

After playing chicken for about 5 minutes things were looking about right. I couldn’t decide what exactly to take the photo of, so I opted for a sweeping 270 degree panorama shot vertically to get enough of the sky in the frame.

The shed is just off to the left of this, I decided it was too ‘heavy’ to leave in the frame, while the gate and fence balanced out the bright spot where the sun was sneaking out of site quite nicely.

Click thumbnail for larger view

Again this image is created from two raw conversions of each image, 16 in total without the shed on the right. The sky is as-shot, and the exposure for below the horizon was bumped up 2 stops and then blended in the GIMP before assembling the panorama.

There are two things that make a panorama successful, apart from the obvious need for something interesting to take a photo of. Exposure and overlap of images. The software for creating panoramas has come ahead by leaps and bounds over the last few years, but there’s no substitute for good source images.

If you take a set of mediocre images and try to stick them together you’re going to get an equally mediocre result. I’m a great fan of digital photography but many people seem to focused on the digital bit, and ignore the photography.

Setting exposure for a panorama is more problematic than a single-frame photo as you are potentially covering a far wider dynamic range. In this case I shot some frames of the brightest spot, adjusting the exposure until an acceptably small patch was showing the blinking over-exposure highlight. I then used AE-lock to fix the exposure for all 10 frames.

Using AE lock fixes the exposure and means that the tone-blending part of the panorama process is so much easier for the software to sort out. I use Hugin on Linux, but all of the current tools are very similar in function. They don’t cope well if you’ve got a two stop difference in exposure between frames, and you get bands of light and dark areas in the finished image.

Along the lines of keeping the job simple for the computer is having the images overlap in a sensible way, and having plenty of overlap to work with. On the left is one of the images from the panorama, full frame.

Keeping the horizon through the middle of the frame makes the job of stitching the images far easier, and having at least 1/3rd of the frame as overlap ensures the software will have enough points to create a seamless version of what you saw.