I was still farting around with the Sigma 30mm f2.8 at that time and wanted to see if it would work for me (without my glasses) on the GF and automagically pick the right thing to focus on. Naturally I was shooting at f2.8 just to make it clear to me if it had picked focus where I wanted it.
Wondering if it was worth taking my Toho 4x5 out there I thought today I'd whack my 'tilt adapter' onto the Olympus OM28mm lens and take the GH1 instead. Well the sun has risen in the sky since the solstice (duh) and so I didn't get that same lovely light (drat), but the effect of the tilt is perhaps really quite clear
Now its important to note that both images were taken at f2.8, but note the totally different DoF that is visible here? This is actually why Large Format cameras employ tilts / swings and shifts, to allow such control over the focal plane.
So when the subject is at a slanted angle, you tilt the lens to alter the focal plane. This is called the Scheimpflug principle (if you didn't know that already) and is a cornerstone of Large Format photography.
The idea is not the same as Depth of Field, as it actually changes the plane of focus.
In a typical camera the focal plane is totally parallel with the sensor (film or CCD) and so the focus is exactly in a line across the picture more or less equal distance from the camera. When you tilt the lens you get to change that to any angle you like.
Looking closely at the segment from the Sigma lens (not tilted) ..
its pretty clear that only a very narrow portion of the image is in focus. Classically it becomes more blurry either side of that focal plain
But in the lens tilt example:
it is clear that the focus follows different rules. Look for instance at the metal hinge and the barbed wire. The hinge is clear further away from the wall in this image, but its base is blurry. Compare that to the image above where as its further away from the barbed wire (at an angle receding from the plane of focus) it gets blurrier (as does the wall).
The reason I bring this up (well aside from that its interesting) is that I get tired of the foaming at the mouth Kingdom of Wang people who are not even one-eyed, they're blind (you know, Wangers), who go on about how infinitesimally accurate lens adaptors need to be or the image will just be crap. You know, down to microns (Daddy, what's a micron? Well Son its smaller than a mites antennae), while this image was made quite with some mm of tilt. And yet this vintage 1976 OM28mm lens (taken hand held even) still gives sharpness like this (100% crop, right click to open in a new window as its scaled a little in blogger):
The problem with Wangers is they focus (hey that's a pun) on how lenses perform on test targets (where such alignment will make a difference because the board and the camera are square), not on how they render images. However for those of us who take photographs of "things" or people such issues are irrelevant.
The reason I love micro43 is because I can get creative lens choices that are simply not possible in Full Frame and for peanuts.
I don't know about you, but I'm into photography as a creative outlet .. not to brag about my lens test chart results. I leave that to the Wangers.
bottom linestart focusing on your creative juices not on the camera specs. Go grab any adapter you want on eBay and use it with the legacy lenses you want to help your creative vision and your enjoyment of photography ... and stop looking at charts.
I hope you've enjoyed this brief introduction into Lens Tilts ... I'll leave you with an image taken with my LF camera to demonstrate Tilt to a mate.
Lastly a very rough and ready video showing the effect as it happens. Sorry its rough and pardon my voice-over