So I bought the LensAlign focus calibration system (minus the focus tune software) a few years ago. The idea was to get something reliable and precise that would allow me to check for AF issues on some of my Nikon lenses. Since LensAlign is the only product that I know of that uses a precise alignment system, I decided to get that one. I checked others like the Datacolor SpyderLensCal but since it only relies on the bubble level of both camera/lens and alignment tool to be level for proper setup, I disregarded it. On that system and others that I have seen, the camera/lens combination can be tilted (at an angle) in regards to the tool focus target plane itself which can skew the results and make them unreliable. The LensAlign system ensures that the camera lens and focus target are aligned as they should be.

I created this blog entry to help users who might be struggling to get the system set up to get reliable results. I will not explain in detail how to do the basic alignment setup. You can find a useful video that deals with the basics here. Other videos on the Michael Tapes channel deal with all the specific steps from setup to final test shots and analyzing the results. https://youtu.be/5R_-OasiULM

When I first experimented with the system (the MK II Gen 4 version), I found some of Michael Tapes explanation videos rather confusing so I searched on the web for further explanations either in video or in text form and I will share some of my findings. Hopefully they will help you get better and more reliable results and save you some time in the process.

Once initial alignment is done, make sure you turn off VR or IS on your lens if it has that feature. If your lens (most long lenses) has a focal length limiter, turn it off. Make sure that the distance between the lens and LensAlign is approximately the equivalent of 8.2 ft for every 100mm of focal length. So if your lens is a 50mm, the distance between lens and focus target should be about 4.1 ft. If your lens is 300mm, the distance between them should be about 24.6 ft.  

The height at center of the lens and LensAlign focusing target should be the same. I use a height of 55-60 inches on both and that allows me to stand comfortably when taking shots without having to crouch to see the camera view finder or LensAlign alignment ports. Whatever feels comfortable to you is OK as long as both are at the same height.

If you are testing a long and front heavy prime lens such as a 200mm f/2, 300mm f/2.8 or larger, I strongly suggest using some type of long lens support to brace the front end of your lens and negate any vibration produced by the shutter release mechanism. A sturdy tripod will also be a necessity for supporting fast long lenses such as these.

Set your lens to the largest aperture (F/2.8 if your lens is an F/2.8 lens, F/4 if it's an F/4 lens, etc.). Set the camera to single shot, single point AF and use the center focus point. When initially setting up the lens align system in Live View, also use the center focus point (use your camera grid display to help you find the center point if needed). For every fine tune adjustment shot, make sure you defocus the lens manually and let the camera achieve auto focus each time by pressing the shutter button on the remote release. As we are on the subject of shutter, I have found that even pressing the camera shutter manually will induce vibration in some shots and spoil the results. You can set your camera to a 5 sec. self timer to reduce vibration but better yet, use a wired or wireless remote release. Combine this with the exposure delay option in your camera and set exposure delay to at least 2 seconds. Using a remote release and exposure delay has had a tremendous impact on getting consistent image sharpness for me.  In an alignment test like this, this is crucial.

Another crucial aspect of lens calibration is lighting. Ideally you want to do this test in the same light that you would use the lens in real life situations. I usually shoot in outdoor natural light. Unfortunately performing calibration tests outdoors is not easily manageable for me so I use a 24 x 36 daylight fluorescent soft box on a light stand to light the focus target and ruler. It uses a five socket head and each socket has a 85W daylight balanced bulb. I have also tried a single 250W tungsten bulb (in a ceramic socket) with a white umbrella to diffuse the light and it seems to work fine. You can use any lighting as long as it is diffused, slightly higher than the target, pointing downward on it and as close to it as possible without being intrusive. Since your lens aperture has to be wide open to perform the tests, getting sufficient lighting should not be too difficult. I thrive to get a shutter speed of at least 1/250 for most of my testing. On f/1.4 to f/2.8 lenses this is usually quite easy to achieve even at 100 or 200 ISO. Too little light might result in the camera hunting for focus or missing focus altogether. When lighting the focus target and ruler, make sure to turn off other sources of lighting in the room (don't mix tungsten, fluorescent, daylight or LED lighting). There is information on the net that the type of lighting can influence AF calibration but more on that in another blog entry perhaps.

Regarding lighting again, the focus target has to be properly lit without too much highlight blowout so turn on the highlight "blinkies" function on your camera and check to see that they are minimally present in your test pictures. So that the shot to shot exposure during testing remains constant, I switch my camera to manual exposure mode and try a few shots at different shutter speeds to make sure the lighting is sufficient. I turn off any in camera settings that might influence final exposure such as D-Lighting in Nikon cameras.

Michael Tapes recommends using a black background behind the focus target. This is wise. I find that using a light background makes it more difficult to perform the initial alignment in Live View. It doesn't have to be black but darker is better.

Set your camera to any color picture style to initially align the focus target with the lens. Zoom all the way to maximum in live view using the zoom in "+" button on Nikon cameras. This will help you see the alignment target much better. To help you align the LensAlign to the camera lens, use a flashlight to shine light on your lens frontal glass from the back of the alignment sighting ports. After alignment has been achieved, turn Live View off and do your test shots using the monochrome picture style on your camera. In this way you will not need to lock your white balance to a certain preset to take your test shots.  You will not have to be worried about color consistency at all. The monochrome mode might need some tweaking. On Nikon cameras, that picture style is quite soft by default. I increase the contrast to +2, the sharpness to +5 and the clarity to +1 to make it easier to notice focus shift differences between each shot when evaluating final images.

I strongly suggest comparing your final test images in a software image viewer that will allow you to view your images or portion of your images side by side at their original size 100%. When evaluating text crispness, you might want to try viewing two images one on top of the other instead of side by side. Try both.  The angled scale is used to quickly evaluate front or back focus (the number zero should be sharp and in the focus "zone"). Absolute sharpness is measured with the focus target card to the left of the ruler. I use the focus target itself plus the lettering underneath (see photos below).

I usually test my Nikon lenses with the AF fine tune using even numbers only (-10, -8, -6,-4, -2, 0, +2, +4, +6, +8 and +10). I do this because I have found that I can't optically see a noticeable difference between a fine tune shot with a difference of only one. For example, I can't see a difference between a shot at 0 and +1 or 0 and -1. Since I can't see a difference by pixel peeping at actual image size between images with an adjustment of only 1, I adjust fine tune by even numbers only. I start seeing subtle differences in the zone of focus on the ruler and crispness of the focusing target card at increments of at least two. Your mileage may vary (see footnote below). I perform the test at least twice. This ensures that if one of my test shots is not in focus, I can use the other shot with the same fine tune number when comparing images. Don't forget that every time you dial a negative fine tune adjustment number, you bring the focus point forward. Every time you dial a positive number, you send the focus point rearward.

Here are a few sample photos of one of my own lens calibration test showing an example of the results you can achieve with LensAlign.

First an image of the complete LensAlign system and what to expect after a shot has been taken with a dialed in adjustment value of -4 in this case. Notice the smaller half black, half white vertical rectangle above the letter "A". This is precisely where the focus point has to lock on when taking test shots. I only include a very scaled down version here but the details will be very clear when viewed at full size on a desktop monitor. Some LensAlign reviewers suggest looking at the images in the back of the camera and using the camera zoom button to check for proper focus. I don't advise on using this method. Comparing the images on a desktop or laptop monitor side by side is the only way to get reliable results.

The next two photos show the LensAlign ruler zoomed in. Here you can see the general zone of focus first with no fine tune dialed (or zero fine tune) and then with -4 dialed in bringing the focus point forward and closer to the middle of the ruler. After carefully examining all my test images for this particular lens and camera, -4 was the AF fine tune value in which the focus target was the sharpest. It is clear by these examples that with the lens as is (no fine tune dialed), the auto focus is slightly back focusing (the zone behind the number zero is more in focus). In the photo on the right, the zone of focus front and back of zero is just about perfect. Once initial back or front focusing is determined using the ruler, the actual target test card has to be examined for sharpness to determine final fine tune adjustment value.

The next image shows the difference in sharpness (in this instance crispness of text) between a setting of zero or no fine tune adjustment and a fine tune adjustment of -4. Here the images are slightly scaled down and probably reduced in resolution by the image host but there is still a subtle but definite difference in contrast/crispness of the text in the -4 version of the image. I can conclude that this particular lens is back focusing slightly when it is not adjusted. If I was to use the lens stopped down, I would probably never notice a difference in real world usage. but with this lens wide open at F/2.8 and the resulting reduced depth of field, I would notice that on some of my shots the point of focus is not quite where I want it to be if I would leave the lens as is.

I hope some of the tips in this post will help you use the LensAlign system more efficiently. Many details have to be taken care of for test reliability and initial alignment can be a core but the more I use the system the easier it has become to setup and analyze the results.

If your lens is considerably back or front focusing on any camera you mount it on, consider getting it professionally calibrated by the lens manufacturer. By the word "considerably", I mean that in camera adjustment limits are either insufficient to get the lens to focus on where you need it to focus or you need to dial in an auto focus adjustment value close to the limits of the available settings (-20 or +20). If every lens that you mount on the same camera exhibits constant back or front focusing by the same amount, this means that your camera needs adjustment, not your lenses. This happened to me with a brand new Nikon D5100 many years ago. It was severely back focusing with every lens that I had. I brought it to my local Nikon headquarters and they quickly fixed the issue.

I have found out recently that fine tuning fast lenses of f/1.4 to f/2.8 is easier than fine tuning relatively slow lenses of f/4 to f/5.6 This is logical since depth of field is reduced on fast lenses and fine tuning implies shooting a lens wide open. The difference in focus area sharpness is easier to assess with a fast lens because the area of sharpness is so small. Everything in front and in the back of the area of sharpness quickly becomes blurred. The opposite is true with slower lenses. I can easily see a difference between what is sharp and what isn't between a test shot taken at camera focus tune value of -4 and zero or zero to +4 on an f/1.4 or f/2.8 lens but I can hardly see any difference at all with the same values on an f/5.6 lens. Put a 1.4 TC on the same f/5.6 lens and at f/8, the difference between a value of zero and -4 or +4 becomes virtually impossible to perceive.  When I tested my 500mm f/5.6 PF lens with TC-14 III attached, the increased depth of field made my fine tune test images much harder to analyze. With no fine tuning I could see that the lens was back focusing but I had to load up a test image with a value of -6 before I could see a better result that I could readily perceive. The results with values between -6 and -12 were very similar and at -14 it became clear that the lens was now front focusing slightly.