Photographers can use perspective control tools to get the most lifelike imagery of buildings and other open spaces. Here we will cover tilt-shift lenses for beginners in 2 parts. In part 2, we go over the tilt function. In part 1, we covered how to shift.
How to Use the Tilt Function in Tilt-Shift Lenses
We’ve all seen photos where the subjects (usually views from high-up of cars, buildings, people, etc.) appear to be miniaturized versions of reality. This is perhaps the most the most often-seen result from using tilt-capable lenses like the Nikon 85mm PC-E.
Here is how this effect is achieved with tilt-shift lenses. Below, the camera is pointing downwards at the railroad tracks, with the tilt element swung upwards.
The reason this scene looks like a miniature is because the plane of focus is so narrow and both the foreground and the background are out of focus. That’s not something the human eye is used to seeing and we interpret images like this differently. This is known as the “diorama effect“.
In order to get that effect, you have to swing the front part of your tilt-shift lens up so that it is either as perpendicular as possible to your subject, or is at an obtuse angle to your subject, as shown below.
Doing so “minimizes” the depth of field in your image, resulting in a very narrow slice of the subject actually being in focus. Swinging the lens away from your subject, in other words, “miniaturizes” it.
Note, however, that tilting the front element doesn’t actually increase/decrease your depth of field (DoF). It changes the angle of your DoF. You effectively gain the benefits of an increased DoF but only for the plane that your subject is on. The technique takes some practice to get right. I’ve found that it’s easier if you try and shoot from a pretty high place and eliminate as much of the sky from your shot as possible.
Perspective control lenses swing the other way, too (no pun intended). Landscape photographers (and some product shooters) may already be familiar with this technique and it’s extremely handy to “maximize” your DoF. To do this, swing the lens so that it’s at a more acute angle to your subject’s plane, as shown below.
Practical Example of Tilt Function and Depth of Field
What you’re looking at below is a device called a LensAlign Pro. It’s used to test autofocus accuracy for cameras and lenses. We use these to test our lenses between rentals.
In this shot, the LensAlign Pro is shot at f/2.8 with a Nikon D800 and an 85mm PC-E lens. The lens is not tilted, as shown below.
If you look back at the LensAlign, you’ll notice there’s a sort-of ruler on the right that I’ve laid back at a pretty steep angle to demonstrate the effect of tilting the lens on DoF. Here’s a 100% crop from that shot:
Only the ‘0’ and part of the ‘8’ above and below the ‘0’ are in sharp focus. That’s to be expected at f/2.8 – the wider your aperture, the narrower your DoF.
Now, let’s tilt the lens down:
Let’s take a look at the LenAlign’s ruler. Remember, we’ve not changed the aperture, which is the way most lenses control DoF.
The change is pretty drastic. We’ve gained a lot of depth of field without changing aperture.
Use the Tilt Function to Increase Your Depth of Field Options
This technique of using the tilt mechanism is often ignored, which is why I spent some time on it. The first question people ask when I explain this function is, “Why don’t you just make your aperture smaller?”
Indeed, making your aperture smaller is a valid way to increase depth of field, but there are also many reasons why you would not want to do that.
Let’s say you’re shooting a field of wildflowers and want a pretty deep depth of field. You stop down to f/8 or f/11, which is where many lenses perform best. You could go all the way to f/22, but beyond f/16, other factors come into play that can hurt your image. Lens diffraction, for example. Luminous Landscape has a nice piece that explains what this means but, basically, beyond a certain point, your image actually begins to lose detail as you make the aperture smaller.
Exposure is another reason why making your aperture smaller may not work. The smaller your aperture, the slower your shutter speed and/or the higher your ISO needs to be to compensate, both of which bring their own pitfalls. If you’re shooting handheld, slow shutter speeds would result in motion blur, whereas kicking your ISO up to compensate would increase noise.
While it is true that in many cases there are ways to gain that depth of field through other means, knowing about these features of PC-E lenses is one more thing you can add to your arsenal!
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