PLEASE NOTE THAT THIS POST IS NO LONGER FULLY UP TO DATE. A new post was made on 18-August-2017 updating this blog with my latest lens calibration methods and techniques. It is best to go here to read the new post.

A key part to ensuring that your camera gear performs the best it can is by calibrating the auto-focus of each of your lenses with your camera body. Many people are either not familiar with this aspect and/or may not realize how important it is. But it can make all the difference between a photo being in focus where you want it to be and it not, especially when and if you are shooting using a shallow depth of field.

In a nutshell, the calibration between the auto-focus system of most lenses and camera bodies is just slightly off. The bigger problem is that we often don’t notice or realize this at first or at all. In fact, we simply expect when we buy a camera and a lens from the same manufacturer that they will work together seamlessly without ever giving it a second thought. The sad reality though is that things don’t work that way and camera manufacturers fail to inform us about this as well as they should. And if you don’t calibrate each lens individually with each of the camera bodies you shoot with, then you might eventually find that all of your images are slightly soft or are completely out of sharp focus.

The technique of calibrating your lenses and correcting this problem is something known as making Micro-Adjustments to the settings of your camera body and many of the newer DSLR bodies that have been released within the last 5 years have a function to do this. The settings are typically found within the camera’s Custom Function settings. And what these micro-adjustment settings do is force your camera to offset and correct what the auto-focus reading should be for each lens. The result is that the camera compensates for the imprecision of the auto focus synchronization and is then able to focus the lens more precisely.

The two big questions now are how do we calibrate our lenses and how do we know how to set the micro-adjustment settings on our cameras to align everything properly?

There is a process for this and tools to do it with. So here in Part 1 of this post I am going to help you to understand more about what is involved with calibration. Then, next week in Part 2 of this post, I will actually walk you though each step of the 20 step process of calibrating a lens with a camera body from start to finish.

For starters, a lens calibration tool will be required. I am using the one made by Michael Tapes called the LensAlign MkII Focus Calibration System, which sells online for $85 with free shipping here. This one seems to be the most popular one out there, but there are other brands and models too of the same type of a calibration tool. They all work relatively the same and the Datacolor SpyderLENSCAL made by a German company is another good one and a slightly lower cost option, which you can order here online for $65 with free shipping.

Before writing this article, I had used the LensAlign tool myself to calibrate 8 of my Canon lenses together with my Canon 5D Mark II DSLR camera body. You can also use this same calibration tool with Nikon cameras and lenses or any other brand of camera that offers a method of making micro-adjustments to the camera body for their own respective brand of lenses.

Understanding more about the general process of calibrating a lens:

First off, it takes about half an hour to test each lens once you have setup the LensAlign tool and everything else needed for the calibration process. The initial setup of all needed equipment itself takes about an hour to get everything in place. So you can expect to spend about 2.5 hours time in total to calibrate say 3 lenses.

What you will need in terms of actual equipment is the LensAlign tool, two tripods (or one tripod and one studio light stand), a room with good ambient light, a tape measure, a flash light, a hot-shoe spirit level, and a remote shutter release. Ideally an empty room to work in that is at least 15 feet long is best in terms of a work space.

One important note is that the standard screw head on most light stands and tripod heads is 3/8″, but the screw mounting hole on the bottom of the LensAlign tool is unfortunately only 1/4″. So you may need to buy a 3/8″ to 1/4″ screw adapter to mount the LensAlign tool onto your second tripod or studio light stand. I am using Manfrotto light stands which have 3/8″ screws, but you can buy Manfrotto 015 3/8″ Female to 1/4″ Male brass thread adapters from your Manfrotto dealer. You can also find Chinese made copies of these adapters on eBay and they can be used with either a light stand or a tripod head to reduce the thread size from 3/8″ to 1/4″. The adapters sell for approximately US$5 each.

Next, you will need to set the height of your LensAlign tool and your camera to the same height. I usually set them both to about 60 inches in height from the floor since I am about 72 inches tall. But you can use any height that is comfortable for you at your own eye-level.

Once you have both your camera and the LensAlign tool mounted on their respective stands, you can place the spirit level into the hot shoe of your camera. The spirit level helps ensure your camera body is mounted level on the tripod.

In terms of the distance that you need to place between your camera and the LensAlign tool, it actually depends on the focal length of each individual lens you will be testing. There is a table on the link here you can use. Click on the Distance Tool tab to determine the distance needed for each lens.

You also will need to have a computer close by to view your alignment test shots in real time while you are carrying out your calibration testing. This is because the process of calibrating involves taking test shots using the subject camera body together with each of the lenses you are planning to test. Then, using your test shot results, you will make the micro-adjustments to your camera body for each of your lenses tested as needed.

Before you start the whole process though you should place a fully charged battery in your camera, insert a blank memory card into the camera itself, and set the camera to capture images in JPG at the highest resolution that the camera is capable of.

If you have a live view mode on your camera this will make things a lot easier in terms of workflow. And if you are working in a space which doesn’t have so much light then you will need to set your camera to a higher ISO setting of either 800 or 1,250 in order to be able to see what you are doing on the camera preview screen when using the live view mode. You can also do everything without live view. So having live view is not essential or critical.

What was most surprising to me from the test results I got from my 8 lenses was that all of my lenses needed some micro-adjustment. Some more so than others. But 7 out of my 8 lenses had some back focus problems and 1 of the lenses had a front focus problem.

This means in simple terms that all of my lenses were not focusing correctly, even when the auto-focus would beep on my camera to indicate that the lens is focused correctly on the intended focus point.

Then, once you have finished testing a lens, and have your test shot results from your lens alignment tool, there are lens compensation settings within the custom function settings of your camera. As I mentioned earlier, these are known as Micro-Adjustments. Following are what the micro-adjustment menu settings look like on my Canon 5D Mark II DSLR camera body:

As you may see in the second image above, this is where you can set micro-adjustments to offset the amount of misaligned focus for each lens by setting a level of focus compensation. The compensation settings allow for 20 incremental micro-adjustments going either forward or backward to compensate for either front focusing or back focusing problems that might be occurring with each particular lens.

The compensation settings that you make are then stored permanently in your camera (unless you choose to change or erase them later) and are reapplied by the camera body to each particular lens automatically whenever it is mounted to the camera. Most cameras are capable of storing alignment compensation data for up to at least 20 different lenses, which is normally enough to cover one’s lens arsenal.

The result of the calibration tests that I performed, in the most extreme case, reported that one of my lenses was off by about 3.5″ in focal distance. That’s considered a lot and very much worth being concerned about.

I never actually thought too much about the whole calibration issue in the past. But I realized about a year ago, as a result of this exercise, that my pictures should really be sharper than they were at present. Especially since the lens that was most out of auto-focus alignment was my Canon 135mm prime lens, which is a telephoto lens that is known to be tack sharp. I often shoot this lens handheld, at a wide aperture setting, and with a shallow depth of field of about F/2. And it is during precarious shooting conditions like these where focus accuracy is most critical. So now that I have calibrated all my lenses, my pictures will now be sharper in the future.

Also worth noting though is that, if and when you change DSLR camera bodies, you will need to retest all of your lenses together with your new body using the LensAlign tool and then set the micro-adjustment settings in your new camera body for each lens again. And if you have a second DSLR camera body, even if both your bodies are the same make and model, you will need to conduct the same tests with each of your lenses and bodies together. This is because the results will differ from body to body, regardless of the fact they might be the very same make and model.

Conducting these calibration tests can also help you to discover any internal mechanical lens element alignment problems which might be occurring within your lenses as a result of lens elements physically being misaligned. As a result of my testing, I also discovered that 2 out of my 8 lenses were not sharp at all. And this had nothing to do with calibration. So, had I not done these tests, then I most probably would have never known that 2 of my lenses were not operating properly. Internal lens alignment problems are not something that involves the auto-focus system or the camera body itself and therefore cannot be corrected by making micro-adjustments. I had discovered these problems because, during the lens tests, 2 of my lenses were not able to focus sharply anywhere at all on the LensAdjust tool. So eventually I had these 2 problematic lenses serviced by Canon and Canon realigned the lens elements internally in order to correct the internal lens problems I discovered.

Lastly, bear in mind, if you do mostly manual focusing then this whole issue won’t be critical for you since the calibration is all based solely upon the auto-focus system of the camera. But if you are like me, and your eyesight might not be as good as it used to be, then the correct operation of the auto-focus system of the camera could be a critical element to the success of your photography.

I am going to end the first part of this article here. Click here to continue reading Part 2 of this article.