Eventually even your favorite lens might misbehave. Is a particular lens and camera body combination consistently missing focus? The lens might need some adjustment, but first you need to test.
The lens could be focusing a bit too far forward or backward. One of my favorite portrait lenses is a Canon EF 135mm f/2.0. A few months ago I used this lens with my Canon 5D Mark III, specifically for the bokeh at f/2. To my shock almost none of the photographs were sharp enough for me. The shutter speed plus the DigiBee 800 flash unit really should have been adequate for what I had in mind. The Vello LENS-2020 Lens Calibration Tool is an inexpensive way to find out for sure.
The Vello LENS-2020 Lens Calibration Tool is about the size of a paperback novel. It’s essentially three parts: One vertical panel with a focus target, a bright ruler that stands at an angle and a plastic horizontal base. Two bubble levels are on the base to help you set it up just right. The kit also comes with a gray card which is usually pretty handy to set color temperature.
The idea is to set up your camera level with the tool, then autofocus on the target. If the lens is calibrated then the “0” on the ruler will be in tightest focus. If it’s out of calibration then some other mark on the ruler will be in focus, either backward or forward. That all seems pretty simple, right?
For this tool to be effective it must be setup level. You can see in the photo above that I placed it on a light stand for this particular demo. I’m not sure if my light stand is at a slant or if my floor is, either way I had to shore up one leg with a couple of pamphlets.
The camera must be level and pointed directly at the target. Use a tripod to get the camera lined up right. This can take a few minutes but it’s worth it.
Take the picture
Open your aperture to the widest setting — for me that was f/2.0. Autofocus on the target. Take the picture. Zoom in on the ruler to see focus accuracy. In the photograph below you’ll see that the “0” line is in tight focus. This was both a relief and a surprise to me because this lens/camera combination is calibrated fine. At least now I could rule out a gear problem.
What I discovered was how very delicate this lens is when wide-open and handheld. The rule of thumb for acceptable focus is for the shutter speed to be the inverse of the focal length (assuming full frame). By that logic, a shutter speed of 1/200s should have been adequate. Add my strobe to the equation and it should have been more than enough. It turns out that 1/250s gets better results for me, but now I’m at my max sync speed with my strobe.
Fun fact: I did a series of bokehrific (it’s a word) portraits with my amazing friend Danielle Crook using this same lens/body combination except on a tripod at 1/200s. Focus on Danielle was perfect. The same shutter speed handheld for Corey was a bit softer than I’d like. I’m also kind of a perfectionist.
Why this was important
I discovered was there was nothing wrong with my gear. My problem was how I was using it. The Canon 135mm f/2 doesn’t have image stabilization — something I usually don’t mind. Stabilizing the camera with the tripod resulted in a better photograph.
By checking the calibration using the Vello LENS-2020 Lens Calibration Tool, I decided on a better way to use one of my favorite lenses.
Vello LENS-2020 Lens Calibration Tool
The Vello LENS-2020 Lens Calibration Tool sets up quickly onto a tripod through its 1/4″-20 tripod mounting socket and can level out using the two-way bubble level at the base of the target. With this tool, you can test your camera’s auto focus accuracy and then calibrate the focus system to correct for any front-or back-focusing issues. After the adjustment is saved within the camera as a lens profile, it can be used for future photo sessions. The included gray card helps you to set custom white balance for true colors, and the target folds flat for easy storage and portability.