Monday, December 15, 2008
- image above from Lensbaby website
I've been considering a Lensbaby for some time and a recent cold snap was the final impetus to go out and purchase one. It seemed sensible to pick up the latest (and presumably best) Lensbaby, the Composer model.
The original Lensbaby came with a plastic corrugated tube which could be flexed and stretched and shortened as desired. Another model added Sputnik like appendages to the outside to control the positioning of the tube. The most recent Lensbaby Composer uses a ball and socket arrangement to rotate the lens, while beyond the ball and socket is a standard rotating focusing mechanism that moves the lens in and out, much more like a traditional lens.
I had understood that one could swing the lens to align plane of focus as needed but that's not quite accurate. In reality, there is no plane of focus, rather a central sweet spot with surrounding and ever increasing blur and stretch of the image. The degree to which this happens is a function of depth of field but of course if you stop down to increase the size of the sweet spot, you reduce the blurring at the edges of the image.
What really happens as you tilt the lens is that the sweet spot moves from the centre of the image to the outside and possibly beyond the image so that nothing is sharp. It's a little more complicated though. At least some of the blurring off centre is due to a change in the plane of focus (this with the lens all squared up - by eye, there are no marks or centre detent). This change in focus means that things nearer the camera are sharp and the closer to the edges of the image, the nearer is the plane of focus. It mght be more accurate to describe it as a cone of focus, or perhaps even better a bowl of focus.
In theory this sharpness of nearer things should allow you to tilt the lens to get two things sharp at the same time which are not equidistant, but in fact the way the lens is built (unlike a regular tilt and shift lens) is that as the lens is tilted, nothing is sharp at any distance as you move away from the now off centre sweet spot. All this has to do with the fact that the centre of rotation of the ball and socket is in fact well forward of the sensor and tilting the lens puts you well into the periphery of the lens' coverage. A normal tilt and shift lens doesn't pivot around anything, rather it slides over a curved surface designed so that the curve would be centred on the sensor - thus maintaining lens maximum resolution when tilting.
Now, none of the above is necessarily a disadvantage, just a bit of a surprise to me and not quite what I had expected. It would be better to think of lens tilt in this case controlling the amount of blurring and the placement of same rather than trying to control a plane of sharpness. After all, you buy the lens for it's blurring capabilities, not its off axis sharpness.
I haven't had much chance to explore the lens capabilities but look forward to doing so and you can be sure you are going to be subjected to anything I find interesting.
I welcome comments from those who have made more use of their Lensbabies. Before purchasing it I did spend some time searching the net for images which make good use of the Lensbaby. Unfortunately there are far more bad examples than good and even most of the images on the Lensbaby site leave something to be desired. It isn't a digital Holga, but I am still hopeful it can be used effectively.