07 July 2013

Taming the Sweet Spot on a Composer

Lensbaby optics became famous for their 'sweet spot', a circular focal area which can be moved around the frame. Ideally, the photographer aligns the sweet spot with the subject, pulls focus accordingly and gets a perfectly sharp subject surrounded by gorgeous silky soft blur. So much for the theory.
In practice, it's really hard for beginners to master the sweet spot. Either it's not on the subject, or it's backfocused, which causes a ring of sharpness around the blurred center, or it's not focused very well. 

Of course you have to adjust your viewfinder to your eyesight to get acceptable results, but there are still some more issues dealing with the sweet spot properly. Today you'll learn a neat trick which works with pretty much all Nikon bodies I'm aware of. The optics used was the Sweet35 which I think is the hardest challenge whatsoever. The same principles can be used with Double Glass, Single Glass and Plastic Optic. These four are the Lensbaby optics which feature that circular sweet spot. 


Shift the focus field to the center of the blurred sweet spot and lock it


Let's get dirty

Focusing the optics on some pattern (here: a meadow) shows the sweet spot quite well. For starters, you do not look for the sharpness but you focus beyond the subject. At this point you will see a sharp ring around a blurred center. That center is the sweet spot. Shift the blurred center where you want your sweet spot to sit for your framing, then lock the Composer to have the tilting lens out of the equation. Once the composer is locked you can safely assume the position of the sweet spot, and here is where Nikon's focus indicator comes into play.


Lock the Focus Field

Pull focus to have a rather small blurred center surrounded by the ring of sharpness. Then move the focus field in the view finder to the center of the blurred ring. Once you got it, use the twisting 'lock' switch on the back of your camera to lock the focus field. Now you're set to go. As long as you don't use aperture discs smaller than f/5.6, the focus field in the view finder will guide you to the sweet spot  properly. When you use f/8 or smaller, the focus indicator will start flashing, telling you it's being to dark to use the camera's AF system.


Additional Benefit

With Nikons, the focus field gets stored in the raw file and when enlarging the picture on the view finder, most Nikon cameras will show the area around the focus indicator first. Having the focus field in synch with the sweet spot pays when you chimp to check how well you put the focus. Despite some opinions I suggest: chimp plenty -- that's what displays were made for. Focusing manually is a story by itself, but focusing a moving sweet spot is even tougher. So make use of whatever your camera has to offer to get exactly the pictures you intend. 


With Composer and focus field locked, getting crisp sharp subjects becomes less demanding.
Of course you're locked to a single position of the sweet spot -- but then it's all about practicing. And somehow pictures look best if the sweet spot is not dead center, so locking the sweet spot on one third of your frame will help your composition as well. Now compare the backfocused and the focused pictures: the blur is much smoother on the latter. Whenever you occur a rather rough bokeh, you may have backfocused your baby.


Summary

To get super nice pictures with tad sharp subjects and soft blur around it, begin by adjusting your diopter at the viewfinder. Then move the sweet spot to where you want it to be for the next shot(s), and lock the composer. Backfocus on some narrow pattern, like meadows, asphalt, brick walls, or even your computer's LED screen. Move the focus field to the center of that circle of blur. Lock the focus field into place and start shooting. The focus indicator of your Nikon will tell you when you are sweet spot on. 


Norbert Fürst
Happy lensbabying.