Jeffrey’s Autofocus Test Chart
Jeffrey's Autofocus Test Chart, on a clipboard, in the light by a
Nikon D200 + 70-200mm f/2.8 @ 70mm — 1/320 sec, f/2.8, ISO 400 — full exif
Testing SLR Autofocus

This post describes an autofocus test chart I've developed, why I think it's better than others I've seen, and how to use it to test the autofocus of your camera and lens:

  1. Introduction
  2. What Makes a Good Test Chart
  3. How to Print It (downloading offered here)
  4. Preparing to Use It
  5. Taking the Shot
  6. Interpreting the Results

1. Introduction

If you suspect that your modern SLR or SLR lens has autofocus problems, you can use a chart like the one offered on this page to perform some tests.

The basic premise of a chart like this is that when photographed at an angle, the paper slices through the plane of focus. Depending on the situation, that plane can be very thick, encompassing the whole chart (leaving the whole chart in focus), or, more usefully, it can be very thin, leaving only the areas of the chart that intersect with that thin region in focus.

The illustration below shows proper autofocus and the result one might expect from it, where the region of what is actually in focus is more or less centered on the focus target. It also has views for the problems of back focus and front focus, where for some reason, the lens actually focuses on a region either behind or in front of the focus point (resulting in the in-focus area on the chart to be above or below the focus target). Mouseover the buttons under the chart to see those views.

Illustration of properly working autofocus
Back Focus   -   Proper Focus   -   Front Focus

mouseover a button to see that view

  (Camera side view from Digital Photography Review)
Example of properly working autofocus

It has to be said....

It must be said on a page like this that while there is certainly broken or miscalibrated equipment out there, it's probably safe to say that the majority of “is my autofocus broken?” concerns are rooted not in miscalibrated equipment, but in the user's misunderstanding of the equipment, or of proper technique.

If you suspect you have equipment with autofocus problems and mention it on a photography forum, such as those at Phil Askey's most excellent Digital Photography Review, be prepared for three types of responses: “me too”, “are you sure?”, and “it's all your fault.”

About that last group, sadly, some people seem to enjoy being combative and ignore all evidence that the user actually does understand the issues at hand, and persistently, incessantly post “it's all your fault – you don't understand anything” type responses. Just ignore them.

However, the “are you sure, did you consider...” responses tend to be from respectable forum members trying to help. Even if it does turn out that your equipment is at fault, you can always pick up good hints and tips from these people, so embrace and appreciate them. I certainly learned a lot when I went through this with my own autofocus problems. It turns out that the major cause of my problems was broken equipment, but in trying to understand where the problem lay, I learned a lot and improved my technique.

Oh, and I came up with an excellent autofocus test chart....

Jeffrey's Autofocus Test Chart (mini thumbnail version)
What You See      What the Autofocus Sees
mouseover a button to see that image

2. What Makes a Good Test Chart?

Many factors make an autofocus test chart good or bad, but the two most overwhelmingly important are:

  1. the ability to ensure that the autofocus locks on to the exact location you intend, and
  2. that it allows you to clearly interpret relative crispness of focus across the scene.

Without the first, the test has absolutely no meaning, and without the second, you can't grasp the meaning it holds.

Two popular autofocus test charts I've seen and used (and learned much from), by Tim Jackson (no longer online) and Leon Goodman, don't address either of these concerns as well as they could, which is why I developed the chart presented here.

Update (December 2008) — If you'd like to do serious focus-related lens calibration, also consider the LensAlign Focus Calibration System from the, the makers of the WhiBal.

I consulted with them on the product during its design (“consulted” in the “had discussions and lent my expertise and opinions” sense, not the “got paid for my time” sense, though they did kindly give me one), and believe it's a fantastic tool for lens testing and calibration.

It's better than my chart in every metric... except price. :-)

I'll go ahead and add a third important characteristic of a good test chart – perhaps the most important – proper instructions, because it's easy to draw the wrong conclusions from an improperly used chart. The two charts I link to in the previous paragraph excel in this area, and reading through them is highly recommended.

Ensuring Autofocus Lock

Toward the first goal, the middle my test chart has a high-contrast black bar – the autofocus target – surrounded on all sides by liberal expanses of low-contrast gray that the camera autofocus can not lock on to. For an illustration of this, see the “What the Autofocus Sees” button in the super-shrunk view of the chart, at right.

(Testing to ensure that your camera's autofocus system can indeed not lock onto the low-contrast gray is an important step in Preparing to Use the chart.)

Below is a small section of the chart at full resolution, from slightly left of center, showing part of the black bar that is the focus target (with the red line added here just to indicate the vertical centerline of the chart).

Full-resolution section from Jeffrey's Autofocus Test Chart

However, here's what the autofocus sees:

Full-resolution section illustrating how an autofocus system sees Jeffrey's Autofocus Test Chart

This provides a clear target for the autofocus. The low-contrast gray extends quite a bit from side to side, but more importantly, it extends the full height of the page. This means that even when the chart is viewed at a steep angle like that shown in the photo at the top of this page, a large area of low-contrast gray still presents itself around the target, buffering it from anything else that the autofocus might lock on. Thus, with the precautions discussed later, you're sure that the autofocus locks onto the target bar if it locks onto anything at all.

Ease of Interpretation

Toward the second important feature – allowing you to interpret relative focus – I've filled the area around the target with lines and boxes that, when viewed at an angle, make it quite clear how focus progresses as you inspect up and down the page:

An example of perfect autofocus, as seen with
Jeffrey's Autofocus Test Chart
Nikon D200 + Nikkor 17-55 f/2.8 @ 55mm — 1/1250 sec, f/2.8, ISO 400 — full exif

It should be readily apparent how useful the lines and blocks are when viewed this way, but it's perhaps useful to contrast this with a different method I've seen.

I've seen autofocus test charts that use lines of random Lorem Ipsum text, because, as the author correctly notes, we are hypersensitive to the crispness of text, so it makes for good test fodder. The problem with this approach is that we don't really care about absolute crispness, but want to scan up and down to gauge relative crispness. For this, random lines of spaced text are not as good because there's no continuity as you scan vertically.

On the other hand, this chart's vertical lines make for something that would be smooth and consistent throughout a vertical scan if focus were perfect throughout, but since focus is not perfect throughout, the smooth and consistent nature of the lines highlight clearly what is and isn't in focus.

Additionally, when some of the lines are dashed, the individual blocks making up the line become convenient visual markers of distance from the focus target, allowing you to quickly compare a block above the target with its counterpart the same distance below the target.

3. How to Print The Test Chart

The test charts are provided as 2,449 × 3,299 pixel grayscale GIFs, which, when printed at 300 ppi, fit nicely on US Letter or A4-sized paper.

The key to properly printing the test chart is to get a result in which the gray areas are faint enough that your camera's autofocus system can't lock onto them, but are distinct enough that you can use them to gauge the results. With my printer on my paper in the light I use for tests with my camera, “25% gray” seems to be the sweet spot.

Your situation may be different from mine, so I've built seven different versions of the test chart, each with differing levels of gray for the low-contrast areas. The 5% version is the most faint, while the 35% is the darkest:

Download Jeffrey's Autofocus Test Chart (version 1.0)
5%   ·   10%   ·   15%   ·   20%   ·   25%   ·   30%   ·   35%
On Windows, right-click the desired link, and on a Mac, ctrl-click the link,
then select the “Save Target As” or “Download Linked File” item to download the chart image.

I'll suggest that you start with the 25% version that worked for me, printing and testing as instructed below, returning to try a lower-contrast version if need be.

Photoshop's 'Image Size' dialog

Be sure to print at “100%” without any “fit to paper” option so that the resulting print is as crisp as your printer can produce. Any resizing necessarily incurs fuzziness, which can make interpretation of the results slightly more difficult.

It makes sense to select the “center image on page” option, if your print dialog offers it. Depending on the printer, you may have to select borderless printing in order to fit the full image onto the page, or just as well, let a tad be cropped off. Either are better than resizing to fit the page.

If printing from within Photoshop, be sure to tell Photoshop that it's to be printed at 300 ppi by selecting “Image > Image Size...” and unchecking the “Resample Image” box, then change the Resolution to 300, as shown at right.

If possible, print on high-resolution matte photo paper, such as Canon's MP-101. Besides giving a crisper print, the paper is more sturdy, which makes it resistant to curling and warping (both of which are detrimental to its successful use in testing focus).

After printing, test the appropriateness of the low-contrast gray by lighting the chart well, filling the viewfinder with the gray area, and checking to see whether the autofocus can lock on to it. If it can, you need to move to a lower-percent gray.

The version you've printed holds promise if the autofocus system can't lock onto the gray, but the quick test you've just done is only preliminary. Be sure to check again under actual conditions after setting up for the real shot, as described below.

4. Preparing to Use It

Using the test chart involves taking a picture of it, but it's important that it's done under the right conditions.

The Setup

  • Bright — you want enough light for the autofocus system to do its job, and to allow for a fast enough shutter speed, to reduce overall shake-induced blur.

  • Wide open aperture — the wider the aperture (that is, the lower the f-stop number), the more shallow the depth of field becomes, thereby accentuating any focus-related problems. Using aperture-priority exposure mode makes this easy to ensure.

  • Autofocus On — lest you forget :-)

  • Fast Shutter — you want a fast enough shutter speed to eliminate the blurring effects of camera shake. As one suggestion, you should have enough light to get at least a 1/1,000th second exposure at ISO 400 or lower. (That should cover most bases, but if you're skilled enough to think this page might be useful, you're probably skilled enough to know what shutter speed you need to eliminate shake-induced blur.)

    You might also consider using a tripod, and a remote shutter release.

  • IS? / VR? — I've never heard of an image-stabilization or vibration-reduction feature causing changes in focus accuracy, but just in case, if you have equipment with these features, it might make sense to test both with and without them.

  • Low ISO — the ISO sensitivity is not particularly important in its own right, but it's important to realize that while increasing it allows you to get more sensitivity from the sensor, but it does nothing for the autofocus system. If you know you have plenty of light for the autofocus system and merely want to push the shutter speed really high, increasing ISO is fine. Just realize that pushing it too high adds some level of noise-induced blur to the overall picture.

    Personally, I like to keep the ISO under 400 on my Nikon D200, but I'll go to 800 if needed when doing a quick focus test that I'll not put too much stock in.

  • Square to the Chart — it makes interpretation easier if you're exactly square to the bottom of the chart (that is, you're aiming straight to the chart on the horizontal plane, without any side-to-side angle). The top-center and bottom-center of the chart has small black “sightlines” that can be of help.

  • Chart is Flat — if the chart is not perfectly flat, its slight rumples can have a large impact on the focus. It's okay if just the corners of the chart float a bit off the table. The focus is on the main part of the chart, so to speak, and that's the section that must be perfectly flat.) Using a heavy-stock paper helps a lot.

  • Exposure Compensation — especially in really bright light (e.g. direct sun), automatic exposure tends to underexpose the fairly uniform brightness of the chart, so you may need to dial in some compensation. A few sample shots should make it clear whether this is necessarily.

  • Enough Distance — nothing will work if you're closer than the minimum focus distance of the lens, so be sure that you're far enough away that you're not bumping up against that limit. Note that some lenses have a different minimum-focus-distance between manual focus and autofocus. Zoom lenses can have a different minimum depending upon the focal length in use.

Deciding how far away you should be from the chart is influenced by what kind of test you want (some lenses display autofocus accuracy that varies with subject distance), the focal length of the lens, and the nature of your autofocus sensors.

Understanding Your Autofocus Sensors

It's possible that the active area of the camera's autofocus sensor exactly matches the indicator you see in the viewfinder, but it's not likely. More likely is that the active area of detection is a bit larger, perhaps asymmetrically so.

The photo sequences below illustrate the pitfalls of not understanding your camera's autofocus sensors. The right-hand image is just a closeup of the central part of the full-frame left-hand image. Mouseover the four descriptions below the pictures to see the story unfold...

  Improperly Performed Test
Improperly performed autofocus test, step 1 of 4
Full Frame
Improperly performed autofocus test, step 1 of 4 (close-up view)
Closeup View
  1.  Scene with my camera's autofocus target indicator, over the focus target.
  2.  Focus point I intended to be chosen (marked with purple star) and intended in-focus region (green band)
  3.  Orange region shows actual active area of my camera's autofocus sensor
  4.  Possible focus point chosen by camera (purple star) and resulting in-focus region (green band). Unexpected!

The final result above appears as if the camera/lens has back focus, but in reality, it's just picking an unexpected spot to focus on. It would be nice if the indicator in the viewfinder exactly matched the active area, but since that's not the case, it behooves you to understand your sensors.

I should be clear that the illustration above is just to make a point, and it's unlikely that any camera actually has an autofocus sensor shaped like that shown in steps 3 and 4.

I'll leave the detailed description of mapping your autofocus sensors to the link in the previous paragraph, but in short, one way to measure the active area is to get close enough to the chart so that the low-contrast gray area fills the width of the viewfinder, and place the sensor indicator right in the middle of it. Having nothing high-contrast anywhere nearby, it shouldn't be able to lock onto a focus, but instead, should hunt around until it gives up. (If it can lock onto the low-contrast gray areas, you'll need to use one of the lower-percent gray versions offered in the How to Print It section.)

Then, as you move the aim toward the high-contrast black running up and down the sides of the chart, keep trying the autofocus, and once it's able to lock on, note where the black begins relative to that edge of the sensor indicator. You can do the same moving the other way, and up and down, and so “map” the true active area of your sensor.

If you have multiple sensors, they may well each have their own characteristics, so you may wish to map them all, but for the purposes of testing your autofocus system, it's sufficient to use only the middle sensor.

Of course, the more you can fill the viewfinder with the chart, the better. Even if the scenario above results in a valid test, chart is too small to really make out much detail from it, even with the resolution my 10-megapixel SLR affords.

5. Taking the Shot

After taking into account everything in the previous section, it's a simple matter to take some shots. Take multiple shots at different angles of attack. A lower angle shows the depth of the in-focus field the most clearly (and with it, the accuracy of the autofocus system), but requires the most care to ensure that the autofocus sensor does not see the top of the chart instead of the intended target.

(There's an example of a valid test with very low angle of attack in the next section.)

While shooting, keep the following in mind:

  • Keep double-checking that you're square to the chart

  • Be very careful not to allow yourself to move the camera between achieving focus lock and actually taking the picture. Some people, for example, have an unconscious habit to move forward a half an inch in the process of taking the shot, and such movement would absolutely destroy any meaning to this test.

  • If you're near the minimum-focus distance of the lens, keep that in mind as well.

  • Pause occasionally to double-check that the autofocus can't lock on the low-contrast gray (by pointing at the wide expanse of it in the upper half of the chart and confirming that focus can't be found.)

Once I've set up for a particular shot, I take it, then point the camera at something far and autofocus there, then return to autofocus on the chart, taking a second shot. I then do the same with something near (if I'm not already near the minimum-focus distance of the lens) and return for a third shot. This way, I feel sure that the autofocus is starting from scratch each time.

I got used to taking multiple shots set up the same way because my lens was giving somewhat random results. I guess that's one symptom of being broken, because after it was fixed, the results were consistently spot on.

6. Interpreting the Results

After taking the shots, I load them into Adobe Lightroom and make a couple of quick adjustments to make the results a bit easier to see (I convert them to grayscale, and adjust the contrast a bit to accentuate the low-contrast region). Lightroom is excellent for this because it lets me quickly zoom and pan on an image (more quickly even than Photoshop), and to quickly flip back and forth among multiple images.

In interpreting the results, I look at both the vertical progression of the lines, and the numbers that run up and down the sides. Consider this example:

Perfect autofocus results, as seen with Jeffrey's Autofocus Test Chart
Nikon D200 + Nikkor 17-55 f/2.8 @ 55mm — 1/3000 sec, f/2.8, ISO 100 — full exif
The Clear Area is Clearly Clear

The depth of field here is only about 8 millimeters (a third of an inch), so it's fairly easy to see the effects on the chart as it slices through the in-focus region. The more clearly focused parts of the vertical lines seem to be properly centered on the target stripe, and comparable numbers (e.g. the left-side “2” above the midline and the left-side “2” below the midline) seem to be about equally fuzzy.

Actually, in this case, there might be the slightest bit more sharpness to the numbers above the midline, but it's so slight that it could well be because the autofocus picked the top edge of the target stripe rather than the bottom edge. That's how good the autofocus was with this shot.

(Frankly, it could be that the bottom sets of numbers have the slight edge in sharpness.... the more I stare, the fuzzier everything becomes!)

Let's look at another example...

Perfect autofocus
results with a low angle-of-attack view of Jeffrey's Autofocus Test Chart
Nikon D200 + Nikkor 17-55 f/2.8 @ 17mm — 1/6000 sec, f/2.8, ISO 100 — full exif
A Low Angle of Attack

Here, the depth of field is almost 10 times larger (7.6 centimeters; 3 inches), which makes it more difficult to draw conclusions from the vertical lines. In this case, I focus more on the numbers (haha, I'm so witty). Clicking through to the larger version and comparing the two “5” above with the two “5” below, they feel fairly close in their fuzziness, although the upper pair are a bit sharper. In this case, that's to be expected because we're close enough to the chart that the depth of field is not evenly distributed in front of and behind the focus point: about 3.5 centimeters are in front, and 4.1 behind.

Depth of Field Measurements

Pedantically speaking, “Depth of Field” doesn't really refer to the region that's “in focus”, but rather, “of acceptable focus.” The difference reflects the fact that as you move in front or behind the focus point, the focus starts tapering off immediately, and continues to do so indefinitely. What's considered “acceptable focus” changes depending on the intended use and the resolution of the medium capturing the image (that means, among other things, that the depth-of-field calculations are camera dependent). The current Wikipedia page on Depth of Field has a good presentation of the concepts.

My Online Exif Viewer reports on the depth of field if the image data contains all the requisite data required to compute it. Some of this data is in the Maker Notes section of metadata, which Photoshop strips, so for best results, check with an original straight-out-of-the-camera image.

A Few More Samples

Here are a few more samples to inspect. As with most images on this post (and on my blog, for that matter), clicking through on the image brings you to a larger version.

An example of autofocus back focus, as seen with Jeffrey's Autofocus Test Chart

At first glance this one might appear to be okay because the target is clearly focused, but comparing, for example, the lower-left “4” with the upper-left “4”, shows that there's a bit of back focus here.

This was taken with a 200mm lens from a medium-close distance (about three yards), which results in a depth of field evenly split on either side of the focus point. Had it been taken with a short focal length at a close distance, it's possible that the depth of field would start to skew more toward the rear, and as such, a result like this might be expected. That's not the case here, so this shows back focus.

An example of severe autofocus front focus, as seen with Jeffrey's Autofocus Test Chart

Some pretty severe front focus

An example of autofocus front focus, as seen with Jeffrey's Autofocus Test Chart

Front focus

An example of severe autofocus back focus, as seen with Jeffrey's Autofocus Test Chart

Severe back focus

7. Conclusion

I would expect that the only people who actually read this far are those suffering from really bad autofocus problems, and are desperate to understand them. You have my sympathy, and I hope that my test chart and what I've so verbosely presented here are helpful.

The 30 most-recent comments (out of 174; see all), most recent last...

Jeffrey – Many thanks for the awesome tool! Just tested my “new” Nikkor 80-200mm AF 2.8. Old lens, I know. Based on my testing, there is quite a bit of back focus with my D7000 body (focused strip is around the top 8,9,10,11 area on your test chart). HOWEVER, when I use the AF Fine Tuning available on my D7000, I see absolutely no effect. Results are identical with or without the AF Tuning (set at -10 for back focus). Is this an indication of a lens issue, or is there a setting on the D7000 I am overlooking? AF Fine Tune is set to ON, and the value of -10 is saved, and in effect only when my 800-200mm is attached. Does your numbering scale correlate to the AF Tune settings in any way? Any help is greatly appreciated!

— comment by Greg Clayton on May 11th, 2014 at 1:34am JST (1 year, 5 months ago) comment permalink

Follow-up – cranking the AF Tune setting to the maximum back focus correction value of -20 did bring the focused strip into the 6,7,8 range. Can’t go any lower with the setting on the D7000, so I guess that’s the best it will ever be…. unless lens maintenance could improve the situation. Any advice?
Thanks again!

— comment by Greg Clayton on May 11th, 2014 at 1:51am JST (1 year, 5 months ago) comment permalink

Thanks for publishing this info and the very good chart. I just got D7100 and my 35/1.8G was already decent but it had to be stopped to f/5. Now with +10 fine tune it’s sharp wide open even at Made a nice difference. Mark in New Mexico

— comment by Mark on May 19th, 2014 at 10:38am JST (1 year, 5 months ago) comment permalink

Hi Jeffrey,
Can’t wait to try your wonderful chart. Just thought that I would mention that I use Nikon’s ViewNX software for post processing (I almost exclusively shoot in RAW). One “quick fix” to focus problems is to use the sharpen slider in ViewNX. By default the slider is set all the way to the left (softest). Using this of course has no affect on depth of field, but will sharpen the focused area considerably. Of course, like everything else, too much sharpening, especially in portraits, is not always a good thing. Thanks for a great site!

— comment by Ron on July 21st, 2014 at 11:32pm JST (1 year, 3 months ago) comment permalink

Hello Mr. Jefrey,
If you can mention how much should be the camera angle from the zero degree focus chart sheet placed flat on the ground or table? Because, i was just wandering, the angle of the camera, (how much angle it slant from towards the chart would have impact on the result too. By the way, i’m using/testing Nikkor 18-105mm (Kit lens) on D7000. And if you can specify and notify me, it would be a great help from such possiple error in the process. Anyway, i do really appreciate your experiment and kind information. Thanking once again for your great contribution for the Photographic society. God Bless You.
-Mamz Chhangte.

45° is probably fine. You want a high enough angle so that you have “enough” clear white above and below the focus target. —Jeffrey

— comment by C. Lalnunkima (Mamz Chhangte) on August 11th, 2014 at 2:43am JST (1 year, 2 months ago) comment permalink

I too started testing my camera with the Tim Jackson test sheet and after messing about for a while deciced that it was a joke, blurrrrrred text and lines with nothing sharp! I was just about to create my own and i found this post!

— comment by JP on August 22nd, 2014 at 10:49pm JST (1 year, 2 months ago) comment permalink

Thanks for your chart! It’s really useful. I’ve tested my lenses and my zooms all have some bit of front or back focus without much practical consequences. Anyway, I have a somewhat old camera body (Pentax ist DL) that doesn’t allow focus correction, so I cannot do much about it.

A funny thing is that my prime lens is spot on. Is it something that you have noticed in your tests ? Are the focusing problems worst with zooms than with primes ? This would not be surprising since the design of zoom lenses is much more complex than that of primes.

Another usage I’ve found to your chart is to check if my manual focusing skill is better than the autofocus. And I must say that the AF system of my Ist gives much better and predictable results than my manual focus. Same thing if I try to manually correct the AF, I usually overcorrect and the final result is much worse.

So, in my case, I will let the AF do its job alone. It’s already good enough like that.

— comment by Carl on August 30th, 2014 at 10:19am JST (1 year, 1 month ago) comment permalink

Thanks for you chart. I knew there was something wrong with a camera lens combination did not know what, until I stumbled upon your chart.

— comment by Jos on September 1st, 2014 at 3:11pm JST (1 year, 1 month ago) comment permalink

Thank you so much Jeffrey! I was considering buying a purpose made chart at a cost of £40-£50 but someone suggested your blog. I found it very easy to follow your instructions and when I had finished I discovered that there is nothing wrong with my equipment! What a waste of money if I had bought one! Thanks mate.

From Yorkshire in England. :-)

— comment by Michael on October 19th, 2014 at 7:33pm JST (11 months, 22 days ago) comment permalink

Just spent some time with the chart and my Nikkor 18-200mm on my D7000. Was getting very frustrated with the lens to a point where I wanted to sell it. Using the chart was able to determine that ti had a real issue with severe back focusing. Dialed own the focusing down and was able to get much better results. Thanks!

— comment by TMG on November 24th, 2014 at 3:44am JST (10 months, 17 days ago) comment permalink

Hi, firstly thanks very much for the target and the wealth of information. I tried it, I think successfully, by displaying it on a standalone LCD monitor. I used the 5% version and had to lower the brightness of the display to make sure that my D7100 didn’t autofocus on the grey area. It was easy to level the LCD vertically using a spirit level, and similarly used the level on my tripod. It worked like a charm. Thanks again.

— comment by Kazi on November 28th, 2014 at 11:40pm JST (10 months, 12 days ago) comment permalink

Might the problem that some commentators report with backfocus to one side and frontfocus to the other be caused by a misalignment of the sensor (i.e., not precisely parallel to the plane along which the lens is projecting the image)?

A misalignment of the sensor could certainly cause that, but I’d be surprise if it were possible for a sensor to get misaligned. Along the same lines, but more likely, is that the mount can get out of whack a bit, so that any lens is not exactly perpendicular. This happened to one of my cameras once. —Jeffrey

— comment by Mark Traugott on November 29th, 2014 at 6:52pm JST (10 months, 11 days ago) comment permalink

Greetings from Hong Kong,
Thank you so much for sharing .It is much appreciated.

In one evening , I was able to check and adjust the auto focus of my Sony A33 & A55 bodies with out doing any collateral damage.
While doing so, I discovered that not all lenses auto focus well: the older lenses with longer focus travel(for given focus range, you have to turn the focus ring through a wider arc) seem to be more consistent in achieving correct auto focus.

The following list are lenses I have tried with your chart starting with the ones that auto focused well.

1) Minolta 50mm 1.7 (large aperture helps)
2) Minolta 35 ~105 (Beer can)(always dependably sharp, even before the bodies were fine tuned)
3) Minolta 35~ 200 XI
4) Minolta 70~ 210 Beercan
5) Minolta 24~105 (this lens produces softer portrait images which I like, but would not produce sharp images with auto focus until I adjusted the A33 body), even now sometimes it misses the sweet spot.

6) Minolta 50mm 2.8 macro. I found it impossible to achieve ‘pin sharp ‘auto focus with this lens at 5 feet from the target with either bodies, the A55 is a bit better. A delicate hand is needed to to focus manually because rotation is such a tiny amount.

7) Sigma 28mm 2.8, my copy of this lens will always front focus to a point that the photos look slightly blurred on my computer screen (not pixel peeping). In fact it was this fault that led me to find your blog. I have decided to use manual focus with this lens (not so easy with the A850 body though.)

I also found that your chart gives some idea of the bokeh behaviour of a particular lens, this is an added bonus.
Many thanks

— comment by Tony Lo on December 12th, 2014 at 7:37am JST (9 months, 30 days ago) comment permalink


Thank you, sir! This site has been such a blessing. I recently purchased a refurbished Sigma 30mm 1.4 Art for my Pentax K-7 and had been getting rather frustrated with how many shots had missed focus — really apparent when wide open. I have other fast primes in my kit and had never had a problem with focusing those wide open, so was pretty sure it was the lens and not my technique. Running tests with your chart confirmed it had a back focus problem and will be heading out to test it in the field today. I’m so glad you have kept this domain up and running for so long — love the throw back html feel! Wish more websites nowadays would cut the fluff and stick to the nitty gritty like yours. Clear, concise, and thorough explanation/walk through of how to fine tune your lenses.

Thanks again, God bless, and Merry Christmas!
Evan from San Antonio

— comment by Evan Wharton on December 13th, 2014 at 2:43am JST (9 months, 29 days ago) comment permalink

Hello Jeffrey, I am just preparing to use your focus chart to help with focus issues I have with my 18-35mm f1.8 Sigma. I shall be using the Sigma USB dock to apply any changes I deduce from shooting your chart.

I know this may seem like a dumb question but should I set my 7D to shoot with just one AF point selected centred on the horizontal black line on your chart or should I leave all AF points selected?

Many thanks, John

I’m not familiar with the camera specifically, but I’d guess just use the one focus point so that there’s no confusion about where the camera is trying to focus. —Jeffrey

— comment by John Dabney on December 17th, 2014 at 4:55pm JST (9 months, 24 days ago) comment permalink

Thanks for the chart! I was using a tripod and found it tough to get the picture framed exactly right, but I think I got there in the end. I’ve adjusted two lenses so far: -3 did the trick for my macro and was able to leave my 50mm prime alone. On my way to take my adjusted macro for a spin :-)
Chris (currently in Sabah, Malaysia)

— comment by Chris Smolder on January 31st, 2015 at 11:38am JST (8 months, 10 days ago) comment permalink

Wow!!… The chart was good, the fact that you offered it with different grey scales was great but, the whole process explanation was simply amazing. This is one of the cases where saying Thanks can not cover enough the feeling of gratitude.

Since there is not another word for it… Thanks you so much!!

— comment by DS on January 31st, 2015 at 10:30pm JST (8 months, 10 days ago) comment permalink

Thanks for the chart 😀

I have Nikon d3s and D800 with 14-24, 24-70, 70-200, 50 1.4 and 85 1.4 and just like many others have been dealing with AF issues. I have taken the camera/lenes number of times to Nikon for adjustments but each time it did not fully fix the issue.

Here is something to keep in mind, first the body itself can have an issue – futher, each of the individual points could also be not accurate. What I did is had boht of my camera’s tested and each of the indiviual points re-calibrated. Once that is done the back/front focus you’ll find should be caused by the lens and not the body.

The issue I am running into is that it seems that the fine tune adjustment changes based on the aperture, so once i dial in my lens at 1.4 once I go to 2.8 there is a focus shift. Further the focus shift also seems to happen based on the target distance, what works at 1m is off at 5 meters. On zoom lenses things are even worse as the fine tune adjustment also varies on the focal length making things even harder to control. I wonder if the quality of the lenses that I have is just low or if that is a standard behavior – those that are testing can you also see if you run into the same problem?

All the best,

— comment by JarekN on February 9th, 2015 at 8:27pm JST (8 months, 1 day ago) comment permalink

Two questions came to maine as I read through all this:
1) I was taught that the range of acceptable focus is 1/3 in front the focal plane and 2/3 behind. Maybe I missed it but I didn’t read anything about compensating for this. I note your comments in one example shot in section 6 about the lower #4 being less sharp than the upper #4 and I thought the 1/3-2/3 “rule” would explain that observation. Or is the angle of the chart meant to provide this compensation?

2) Some focal points are either | or — and the the center focal pint is + . How much of a difference can focal point selection in the viewfinder affect results? I am assuming that the center focal point should always be used in these tests as distortion is more likely as the chosen focal point is moved away from the center point and toward the frame edge.

How the area of acceptable focus extends frontward and rearward depends on the subject distance, focal length, and aperture. It’s never longer in the front, and often much further to the rear (such as infinity). But the best focus is what you want to aim for at the point of focus, without regard to how physics happens to treat the areas in front and behind. As for which focus points to use, in theory it doesn’t matter, but I suppose in practice it may matter slightly for low-quality lenses. You should probably test/calibrate with whatever focus point you tend to use most, I guess. —Jeffrey

— comment by Len on March 19th, 2015 at 12:13am JST (6 months, 23 days ago) comment permalink

Absolutely fabulous and simple system! I love it. I used this to calibrate all of my Canon bodies with about ten lenses and now I have much more reliable autofocus (something that I was never happy with). All lenses were equally back-focused for one body and on a 7d, the lenses were all over centre — some bang-on, some front, some rear… I was able to go through and register them all and accurately set the micro-adjustments by lens.

Just a wonderful tool.

PS, I used the 10% scale.

— comment by ChrisE on April 2nd, 2015 at 5:27am JST (6 months, 9 days ago) comment permalink

This answered my question…back focus indeed! I just bought a used Nikon 24-70mm f2.8 and took some practice portraits and noticed the eyes where not in focus even though I had my AFS spot point right on the eye. After printing the test sheet and running a few test shots I managed to fine tune the auto focus within my D7000 and now it’s bang on! Thanks for this super helpful blog, saved me $225 to send the lens to Nikon to fix.

Dave – Kelowna, British Columbia, Canada

— comment by Dave on April 4th, 2015 at 9:37am JST (6 months, 6 days ago) comment permalink

I’m only leaving a comment because I noticed that this was published over seven years ago, and it is STILL helping an incredible amount of people. So thank you.

I printed out my chart today, but I don’t have my camera with me, so I will be doing the test tomorrow – but I am incredibly excited. I have been ultra frustrated with my camera’s seeming soft-focus.

Anyways. Thank you. :)

— comment by Mandy on April 19th, 2015 at 10:53pm JST (5 months, 21 days ago) comment permalink

I’ve printed the chart (25%) with à black and white laser beam printer.
All the uniform grey patches are then printed with small black dots on the white paper (simulation of grey).
It’s now much more easier to use this new chart than the original chart with the grey patches.
Thanks to the non uniform grey patches.

Best regards.
Gerard Teissedre from France.

— comment by Gerard on May 5th, 2015 at 9:05pm JST (5 months, 5 days ago) comment permalink

Hi Jeffrey

I would like to really thank you for sharing the chart & tips. You can’t imagine how frustrated I’ve been with my D7000. I don’t know if it’s just me but I had to enter significant values to correct for back focussing for the 50mm 1.8 D and the Sigma 17-50mm 2.8 HSM. Tomorrow will calibrate rest of the lenses. Thanks again mate!

— comment by Marcus on July 10th, 2015 at 10:06am JST (3 months ago) comment permalink

How do you animate these charts? I use diagramming software to design charts. but animating part , how did you do it?

It’s just using javascript to choose among different images to display. —Jeffrey

— comment by Evan Raymonds on August 5th, 2015 at 8:38pm JST (2 months, 5 days ago) comment permalink

I am having AF problems with a lot of lens at the moment. I hope to correct the focus error via camera AF fine tune function. It is really helpful after reading your comprehensive introduction on AF calibration. Many many thanks for sharing!

— comment by Timo Tao on August 7th, 2015 at 5:58am JST (2 months, 4 days ago) comment permalink

Simple, but excellent and very useful tools. Thanks for making them available. Of the half dozen lenses I use on the D7100, only the 50mm f1.8 D was spot on. All the zooms were a pain, because the focus point shifts from front focus to back focus as I zoom in. Had to compromise on some and chose full zoom in on the longest zoom I had (I suppose that’s why you have long lenses).

— comment by Vic Natoli on August 10th, 2015 at 9:02pm JST (2 months ago) comment permalink

Jeffrey. Finally a complete, yet simple explanation. You’ve removed my doubts and right now I have no more questions. Good job!
Sigma offers the possiblity of calibrating some of its lenses via a USB dock. This requires taking 16 shots at different apertures and focal lengths. In order to do this properly I was searching around and found your precise instructions. I have extended your chart to be three pages high because I will be testing at 30 meters distance with an expected DOF of up to 60 cms (three pages taped together gives me about 90 cms so I should be ok).
Thank you very much!

— comment by Jacques on August 12th, 2015 at 9:28pm JST (1 month, 29 days ago) comment permalink

Thanks for the info and the charts. I just adjusted my 35mm f/1.8G to -13 to correct it on my D7100. One note to those that may not see a difference on Nikon cameras, the adjustment only corrects the Viewfinder focus sensor on the D7100. It does not correct in the Live View focus mode which is using the image sensor. It is documented in the manual as such, and I verified it. Also, before I made any corrections, I shot once in Viewfinder and once in Live View, and compared results. I had a small discrepancy and Live View was less back focused than the lens. A big thanks from Cincinnati, OH.

— comment by Al Hannan on August 30th, 2015 at 10:15am JST (1 month, 11 days ago) comment permalink

Hello from Rochester, NY. I’ve had my new Canon 7DMII and 400 f/5.6 prime for a little over a month (was shooting the Nikon D7100 with 300 f/4 for a year). I’ve love the Canon gear and have been nailing things left and right. My bird keep rate has gone up to 75% or better. Then, for unknown reasons, for about a week now, I can’t hit anything. Maybe 10% keep rate…at a loss for a reason. I treat my gear gently. Thought maybe fine-tune was the answer and I have posted the results on my FLICKR page. As you can see, the words in the bar are blurry. This was at 10M and 8 M. I had good focus lock. Any ideas as to what the problem might be? Thanks in advance…Zaph

The image at Flickr is too small and/or low quality to determine much of anything, but if this had happened to me, I’d be pouring over the manual to recheck all the various settings for focus tracking. I can never keep them straight anyway, and if Canon is anything like Nikon, they’re spread out all over the place. )-: The fact that you used a tripod implies it’s not a tracking issue, though, so maybe it just needs to be fine tuned. Odd that this would happen suddenly like this, but this is not an area where I have much experience. (I made the chart before fine-tuning was common.) —Jeffrey

— comment by Zaphir Shamma on September 24th, 2015 at 6:53am JST (2 weeks, 3 days ago) comment permalink
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