Focus stacking

I bought a new camera the other week, and reports of a good snowfall up in the mountains had me itching to use it. So today I packed myself a lunch, grabbed a book, and hit the road, heading for my favourite spot again.

There was less snow on the road this time so I was able to park just around the corner. I opened up the laptop and started picking up some ATCS transmissions. Soon I had a pretty clear picture what was happening out there... nothing. Never mind, I had my book to keep me company and knew that in an hour or so the regular Glacier Express passenger train would be coming through.

Sure enough, a couple of hours later I saw the track occupancy circuits on the ATCS lighting up, so I headed out and set up for my shot. Unfortunately with no other traffic on the line there would be no crossings or breaks here, and hence I'd only get the one shot.

With my shot in hand I headed back home. As I approached the grain elevator near home I heard some scanner chatter from SLRG #115. Great! I stepped on it and set up an intercept course at the railway crossing. It was making good time and I only had time to get a grab shot in the field next to the tracks. Never mind.

About the photos

These photos are made using a technique called "focus stacking". This is a method that combines many photos, each shot at a different focal length, into one crisp result.  As an example, here is first frame from the above scene:

... you can see why I like to use focus stacking now!

To take them, I used my new camera and activated a custom "DOF stacker" script. Then I entered the start and end focal lengths, and number of steps in between, and hit RUN. A minute later and I had all my shots. I then used Zerene Stacker to combine and align all shots and automatically produce the final result. It's a pretty cool process, and doesn't take too long when this way.

About the camera

And what kind of expensive camera do I use to make these? A $130 (delivered, inc GST) Canon point-and-shoot! Thanks to an open-source project called CHDK, it is trivial to replace the original code in the camera with a modified system, allowing all sorts of fancy new features, like manual focus, RAW output, ultra-slow shutter speeds, and even remote shutter triggers; all features you would normally only expect on cameras costing $1000 or more.

I ordered one of these last week and it arrived on Thursday, however I was shocked to find that while all the other cameras in this range had CHDK versions available for them, no one had made one for the a2400IS! So I downloaded the code and started porting CHDK to the A2400 IS. After 3.5 days of staring at disassembler dumps and tweaking the code, I had a working version!

So today I decided to see what it was like at focus stacking. The good news is it is very good. With a macro focus range of just 1cm in front of the lens, I can take very very close up photos. On the shot above I didn't set the start-distance close enough which is why the foreground is blurry. Once the weather here improves and the sun comes out, I'll repeat the shot and see if I can't get a better result.