Stereoscopic Snow

Camera	Sony DSC-F828
Exposure Mode	auto
Focal Length	7mm
Aperture	f/2
Exposure	1/30 sec.
ISO Speed	100
Flash	off

In Penistone it snowed quite heavily for much of the 20th of December 2009. In fact it snowed so much that all our guests who had been staying for the weekend left early as they knew it would take longer than usual to get home. Around four o'clock the light was fading fast but the snow had temporarily stopped failing allowing me to take a few clear shots of the snow covered garden.

Whilst the photos are nice I don't think that on their own they are particularly special. However, I took a few photos from view points about 8cm apart and this allowed me to experiment with stereoscopic photography to produce a 3D view of the garden.

I've always had an interest in 3D images and films but have never previously tried to create a 3D photo myself. Until recently when I thought of 3D images I always thought of the red-green images that require tinted glasses to view properly or projection systems using polarized light which require expensive pairs of projectors and glasses. Both of these approaches have their problems; the red-green images never look great as small differences in the printed ink and the tinted glasses tend to distort the colours and while the polarized light images always look good they aren't really an option for most of us given the associated costs. The answer to producing good 3D photos is to forget modern technology and use a good old fashioned Victorian approach to making and viewing 3D photos.

Not long after the advent of photography people started experimenting with taking 3D photographs. This was achieved by taking the first photo, shifting the camera slightly and then taking a second photo. When the photos were then printed side by side they could be viewed through a stereoscope which would present a different image to each eye tricking the brain into seeing the scene in 3D (anybody who has ever used a ViewMaster should understand what I'm talking about).

The idea of trying to replicate the Victorian way of making 3D photos only took hold when I recently bought a fascinating book called A Village Lost and Found. I wrote a blurb for the book on my book blog but that description really doesn't do the book justice. The book reproduces a full set of 59 3D photos taken by a true 3D pioneer, T. R. Williams, during the 1850's. The photos show everyday village life and are fascinating when viewed in 2D but when viewed with the accompanying stereoscope they really spring to life. Unfortunately the book had a rather limited print run and I believe that it is now out-of-print. Hopefully there will be a second printing soon for those of you who would like your own copy of this fantastic book.

The OWL stereoscope supplied with the book is a brilliant little device. It folds flat for easy storage in the slipcase with the book but can be assembled in seconds. What makes it really useful is that is can be used to view any 3D photos not just those in the book (it actually works only with parallel 3D images, where the image for the left eye is on the left and the right on the right but as this is the common format...). Given how useful the stereoscope is it is nice to see that they are on sale separately from the book, so if you are interested in 3D photography I'd certainly recommend buying one. So given that I own a stereoscope and enjoy experimenting with different photo techniques it was only a matter of time until I tried taking my own 3D photos.

The first step is obviously taking the two photographs. I took the right hand image first by resting the camera against the right hand side of the back door. I then tried to keep the camera as level as possible and moved it about 8cm to the left before taking the second photo. This is known as a sequential 3D photo as the two images are taken in sequence and not at the same time. In my case there are a few seconds between shots, whereas T. R. Williams has a gap of minutes between the two images. This approach means that you can only take 3D photos of static scenes. Anything that moves between the time of the first and second photo will ruin the effect.

Once I had uploaded the photos to the computer I then had to process them to get the best 3D effect. The first thing to ensure is that the two photos are level -- i.e. the horizon is perfectly horizontal in both images. I didn't have an obvious horizon but I corrected the images so that the top of the low wall was horizontal in both. The second step was to then line up the images vertically. Our eyes are in the same horizontal plane so the only difference in the two photos should be a slight shift of horizontal viewpoint. In this case I ensured that the now horizontal wall top was at the same vertical position to line the two images up. I then cropped the top and bottom of the images so that they were the same height. Unfortunately there were a few snowflakes in each photo that didn't appear in the other one and these spoiled the 3D effect quite badly, so the final step was a little re-touching (the clone tool in Paint Shop Pro) to remove the snowflakes.

Now you can use the OWL stereoscope to view the image on the computer monitor but it isn't easy, especially as I was worried about scratching my new LCD screen! Fortunately it is possible to see the 3D effect without the stereoscope (although it can give you a headache if you do it for too long) using a technique known as freeviewing. If you can see Magic-Eye pictures then you already know how to freeview and the same approach will allow you to see the snowy garden scene in 3D. If you don't know how to freeview then the trick (with parallel) 3D images is to stare at the screen but focus on a infinitely far away point behind the screen. The two images should overlap presenting a third 3D image in the middle. If you need more instructions or help then this page is really useful.

Viewing on the screen is limiting though (with parallel images there is a limit on the image size) and so the best effect is achieved by printing the image and using a stereoscope. For this I've produced a large high-res version of the image. If you have this printed as a 7x5 photo (it cost me 45p at the local pharmacy) you should be able to slot it straight into an OWL and get the full 3D effect.

As a first attempt at taking 3D photos I'm quite happy. You can see multiple levels of trees at the back of the image, the washing line comes right out at you and the swing and bird feeder stand out from the slope. Having said that there is definitely room for improvement both in composition and technique -- as the objects were all distant from the camera I could have had a bit more horizontal movement to make the difference between the layers in the image more obvious.

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