The Lens Calibration Machine at LensRentals HQ Is Amazing

A one-of-a-kind way to measure lens sharpness

lensrentals adjustment

lensrentals adjustment

Usually, making microadjustments to a lens is a slow and exacting process. It involves taking a photos, making a tweak, and repeating ad infinitum until you have it looking as good as you can. But the folks at LensRentals have to adjust lenses more than most, with the huge volume of glass that they rent out on a daily basis, and have commissioned a custom built device for figuring out lens sharpness, and adjusting it on the fly.

The rig doesn't yet have a name, but was specially designed and built by a company called Optikos. Here's how they describe what it can do:

Basically, we are shining collimated (infinity) light through 5-micron pinhole reticles so we can see how the lens renders tiny points of light. Nothing shows aberrations like a pinhole light. The three collimators let us look at three positions, one in the center and two off-axis. The angle of the outer two collimators can be adjusted so we can see different distances away from the center. The lens mount can be rotated so we can look at the lens through a full 360 degrees.

In lay terms, it shines a miniscule beam of light, one smaller than a pixel for many cameras, at the lens, and then you can analyze the refraction at multiple (and adjustable) points on the lens' surface. In some cases, what it shows might not be noticeable by the naked eye, but in others, it allows substantial improvement through adjustments. In one of the examples, the MTF improves by more than 200 points on the lens' edges after adjustments. You can see a before and after below from a 24-105mm lens.

LensRentals is going to use this to improve their in house testing and adjustments. In a recent AMA on Reddit, the LensRentals team said there was a chance in the future they might open up their lab to letting people send in their own lenses for adjustment—and if that ever happens, you just know there will be a huge queue of people wanting their glass to take a spin on this machine.