50 megapixel images from a point & shoot camera by Duncan Waldron

I’ve been dabbling lately with some stitching software (see this image, or this), mostly with sets of images that I’ve shot in the past, but never got around to joining together. Today I decided to have a serious attempt at a biggie. How big? Well, using my 5MP camera (Canon A460), which produces images 2592 × 1944 px, I have created a finished image that is 4812 × 7236 px – a whopping 33MP! The unedited original was 6615 × 8448 (53MP), but that had to be cropped to exclude ‘empty’ sections at the edge.

First, here’s an original image, taken at full zoom (probably around 135mm equivalent on full frame 35mm):

Now, here’s the ‘raw’ stitched image. You can see the black sections, where there was no image area available. As a raw image, it is pretty good. There is just a slight tonal problem around the edge of the top right ‘empty’ section (plus some JPEG artefacts, as this is a fairly compressed copy).

Finally, here’s the finished image. I have adjusted the exposure level, and corrected the verticals and perspective (and cloned out the umpteen copies of my dead pixel!), but very little has been done to the raw image.

In shooting the images, I set the camera to ‘continuous shooting’ mode, so that I could easily cover the whole area with lots of exposures, while keeping the camera as much in the same place as possible. The aim is to rotate the camera about the optical centre of the lens (or rather, the entrance pupil), but lacking any device to do this properly, I have to hand-hold and hope for the best; in practice, with a reasonably distant subject, there will be a bit of leeway before you have mismatch problems.

Another benefit from shooting ‘continuous’ is that the exposure will be identical for each image (at least, it is on my camera); this becomes important at the stitching stage. For a proper result when shooting panoramic images, it has always been advisable to use manual exposure settings, so that, for example, the sky tone does not vary between adjacent images. If you use automatic exposure, the camera will decide on the best exposure for each frame, and unless you are shooting a flat tone throughout (which would make for a pretty dull image…), you will most probably see variations from one image to the next.

Another set from this shoot is here. Possibly more interesting, photographically, I didn’t, however, shoot enough images over a wide area, so it was too narrow to correct the perspective without ending up with a severely cropped image.

BW image here

Overall, I’m very happy with this software (‘Autostitch’, developed by the University of British Columbia), which is both free, and very easy to use. If you want to try it out, you can download the demo here: http://cvlab.epfl.ch/~brown/autostitch/autostitch.html. I’m also happy with my new 50MP compact camera!