Autofocus Microadjustment Adjustment

A Brief Review Of Reikan FoCal Software

By now it's an old story that lenses and cameras can't be expected to be manufactured to tolerances that ensure perfect focus. If it's not an old story to you, I would strongly recommend a read of "This Lens Is Soft And Other Myths" by Roger Cicala as well as the update to that article "This Lens Is Soft And Other Facts". Oh, and this one by Cicala is good too! Inaccuracies of focus may be caused by a problem with the lens or camera, but more often than not, it's caused by mismatch of the microtolerances in manufacturing. Meaning that the lens that doesn't focus perfectly on YOUR otherwise functioning camera might focus perfectly on another of the exact same model of camera body. And vice versa, that lens that provides a perfectly sharp image on your camera body might be a bit soft when focusing with your backup body of the same model.

But what about autofocus? Of course the ability to obtain sharp images using autofocus entails all the issues discussed above, but with other added potential sources of error. Of course, that's why camera manufacturers introduced the 'autofocus microadjustment' option....and more recently have introduced the ability to input a microadjustment for both the short and long ends of zoom lenses.

For those that are unaware of this feature, it consists of the ability to 'register' a specific lens to the camera and instruct the camera to change the point of focus by a very small but specific amount compared to what it thinks is perfect when that lens is mounted and autofocus is turned on.

So what's a photographer to do? While most of my work is done with manual focusing, there are times when I walk around town or when on vacation and I want to handhold the camera looking for interesting shots using autofocus. And I never got anywhere near perfect results with my Canon 5D MK II and Canon 24-105 f4.0 IS lens even though it was pretty sharp when focused manually. In fact, some years ago I had tried using the older solution of utilizing LensAlign for manual determination of the microfocus adjustment. The keyword there is tried. It seemed tedious and I was always questioning and comparing the results of different microadjustment settings. Ultimately, I just gave up on it. (I should mention that I recently discovered that LensAlign now has automated software as well, which I have not tried).

When I received my new Canon 5D MK IV I did a brief test of tripod mounted autofocus vs manual focus with several lenses and, though the differences were small, they were nonetheless consistent. The shot I picked as sharpest (admittedly by only a small degree when viewed at 100% in Lightroom; pixel peeping at its best) was always the manually focused photo. 

So I was excited when I learned that there was software that could do the microadjustment electronically and with no human decision making involved (unless you want there to be some). I wanted to give such software a try and put it to use with my new 5D MK IV.  I discovered and purchased FoCal by Reikan and really couldn't be more pleased!

So how does it all work? First, you purchase the software via download (I am not associated with Reikan in any way other than being a very satisfied customer). Once the download is extracted there is a folder than contains the manual, another that contains the installer for the software itself, and a folder that contains printable targets. Personally I just bought one of their hard copy targets that could be mounted on the wall. Since Reikan is located in the UK I purchased their target from B&H.

You mount the target on a wall, illuminate it (instructions on minimum brightness levels etc are in the instruction manual), and connect your camera to your computer by means of the USB cord that came with the camera. OK, so there is  little 'gotcha' here. That cord isn't long enough! The manual does mention that could be the case, but that a USB cord extender could be used if the total length of the connection is kept under about 15 feet.  I got an extension cord from Amazon for under $5 and it worked just fine.

From there on in the entire process is essentially all automated. In short, you aim the camera at the target keeping it parallel (this is probably a shortcoming as there is no verification of the 'parrallelness' of the target and camera unless it is way off) and click on a target verification button in the software. This provides a direct Live View image from you camera to your computer screen with a grid for you to center the target in. Then you click on a button to check the target position. If the software senses that the camera and target are positioned correctly in relation to each other you are good to go and the software gives you a nice green checkmark over the target and, if not, a red X with an indicator of what the problem is. Once you get your green checkmark just click on the 'start test' button.

The software takes control and autofocuses the camera via the USB cable, looks at the image results after it trips the shutter (which it automatically does with mirror lockup), and then compares the results internally at multiple autofocus microadjustment settings. It is suggested that for zoom lenses the test be run at both the widest and longest focal lengths, as both Canon and Nikon allow you to enter a separate microadjustment calibration for both ends of the lens's focal length.

In some camera models the manufacturer does not allow the microadjustment to be changed via the USB cable (the models are listed on their website). The Canon 5D MK IV is one of those models, which initially put me off. It shouldn't have. In these cases the software talks to you and says "please change the telephoto autofocus microadjustment setting to -20" which you do manually and then click OK to continue the test. During the course of the testing it will ask you to do this five or six times. Then, when the test is over the software has you set the adjustment to the correct setting. The entire process takes maybe five  or six minutes per lens. Frankly, it took me much longer to get the target mounted and illuminated with the camera set up on a tripod connected to the computer than it did to run the test.

So how did it all turn out? I tested several lenses; the ones that I am most likely to shoot with handheld. They all 'required' microadjustment calibration. The one with the biggest adjustment was that 24-105 I started this story with. When I reran some tests shooting newsprint before and after the calibration there were definite differences.  Pre-adjustmet I could always pick out a difference in sharpness that was consistent when viewed at 100% and it was always the autofocused shot that was softer. After the microadjustment both the autofocused and manually focused images (examined at 100%) were most often indistinguishable to my eye and, if there was a discernible difference, it seemed to be both minimal and randomly distributed between the autofocused and the manually focused versions.

Overall, I found the software simple to use and was very pleased with the results. I recommend it highly if you are interested in making these sorts of adjustments to your camera!

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