Jeffrey’s Autofocus Test Chart
Jeffrey's Autofocus Test Chart, on a clipboard, in the light by a
window
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 Michael Tapes Design, 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 199; see all), most recent last...

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 years, 4 months 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 years, 3 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 (2 years, 3 months 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 (2 years, 3 months 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 years, 2 months ago) comment permalink

H Jeffery,

Amazing! I always suspected my D7000 was a little “out” and your info and great chart confimed this, with a -8 adjustment needed on my 50mm F1.8D prime to bring it back into full sharpness. Just need to “do” the other lenses now. Thanks once again… Brilliant!

KR… Rob

— comment by Rob on December 10th, 2015 at 12:00am JST (1 year, 11 months ago) comment permalink

In a recent blog, Ming Thien points out that some cameras focus differently in different kinds of light. His Nikon D5500 was correct in daylight but back-focused in incandescent light. This might be a warning to those of us who check our cameras at home with Jeffrey’s chart but then take pictures outdoors. Worth reading, http://blog.mingthein.com/2015/12/21/review-the-nikon-d5500/

— comment by Graham Phillips on December 24th, 2015 at 7:14am JST (1 year, 11 months ago) comment permalink

Responding from Western Australia to the post by “C. Lalnunkima (Mamz Chhangte)” (August 11th, 2014):

You can see the effect of varying the angle between the chart and the lens axis in “You Can’t Test Autofocus with a Slanted Target” at http://www.dpreview.com/articles/2978485979/busted-digital-photography-myths

The short answer is, my 60D focuses fine on a good target at three degrees to the lens axis. CD AF works fine down to about ten degrees.

— comment by Wilba on January 3rd, 2016 at 4:34pm JST (1 year, 11 months ago) comment permalink

Is this chart available for manual focusing?

Sure, just manually focus on the center line. If the center line is not in focus in the result, I’d guess your mirror (or eyes 😉 ) need an adjustment. —Jeffrey

— comment by Peter Chung on January 19th, 2016 at 4:15am JST (1 year, 10 months ago) comment permalink

Is there a way to fix the focusing issue apart from sending the unit to service center??

I suppose the answer depends on the camera and the nature of the problem. Many advanced cameras (and some lenses) now include the ability to calibrate focus, but you’d have to check for your specific issue. —Jeffrey

— comment by Ajay on January 29th, 2016 at 9:06pm JST (1 year, 10 months ago) comment permalink

Hi Jeffrey,

I appreciate your effort in putting this together. My camera, an Olympus Em-1, seems to lock focus on even the lightest gray sample. I filled the viewfinder so none of the black is visible, and still get the focus confirming beep at shutter half-press. If I then slide to one side while holding the shutter button halfway down, the black print appears perfectly sharp. Any Suggestions?

Thank you,
Chris

That’s some pretty sensitive autofocus (which seems like a good thing in any other situation). You may have to just try to watch where it focuses, and use only photos where you see it focused on the black. —Jeffrey

— comment by Chris Pope on February 7th, 2016 at 10:24am JST (1 year, 10 months ago) comment permalink

6 years ago, I did a photoshoot for a friend in Japan of her fathers paintings using Minolta A200 (8Mpix, fixed lens, bought in 2005, used mainly for hiking). Filed the images away. Last year I was asked to help put on an exhibition and decided some high quality archive photos should really be made (of same pictures). Thinking its time to get a “real” camera I splurged some “real” monry on a new Nikon 7100. Because some paintings were missing, I loaded the Minolta pictures and was completely blown away. They are MUCH sharper than my Nikon images, which certainly looked Ok at the time. I am now frantically testing the Nikon because I have commited to the new project (the Minolta dies last year). Tried your test charts; the Nikon autofocus seems to lock even on the 5% prints (no lock when pointing at a blank wall). So the tests so far are inconclusive (yes, tripods, delayed release etc were all used to minimize vibration both when taking the paintings and for these tests). As the auto focus actaully workign seems to be a problem, I think I’ll just try manually changing the autofocus tweak to see what happens. Any comments would be grealy appreciated. Using the Nikon 24-55 lens that came standard in the box. Will next try to the the longer focus zoom.

It’s difficult to guess what the problem might be, since so many variables go into the final result. However, in this case I think autofocus should not be one of the variables. Instead, use Live View to focus manually, very carefully. Make sure the camera is perfectly perpendicular to the painting, and stop the lens down to about f/11, which for many lenses is about the sharpest you’ll get it. Use enough light for a fast shutter, and use mirror-up delayed release for good measure. —Jeffrey

— comment by Stan on April 12th, 2016 at 6:14am JST (1 year, 7 months ago) comment permalink

Hi Jeffrey

many thanks for putting in the hard work designing your extremely useful chart and writing your extensive blog, it has saved me a great deal of time and money. I own a Pentax K-5 with the following lenses: Sigma 10-20 f3,5, a 17-70 f 2.8-4, and a 70-300 f4-5.6 – and they all required caibration, but not until I discovered the Pentax body was back focusing also! Thanks to you, I was able to dial out the body using PK-Tether and your chart, then seat about fine tuning the lenses themselves. They all required different amounts of compenstion to get them bang on. Nice one, Jeffrey.
Regards

Glen
Norfolk, UK

— comment by Glen Withers on April 24th, 2016 at 5:44am JST (1 year, 7 months ago) comment permalink

hi i have a D5100 nikon camera that has autofocus problem with some lenses. the question is how i can dial down or up the focus with this camera. I think that it is not possible with my camera. is it true?
dese- iran

I don’t know anything about that camera, sorry. Google Search seems to. —Jeffrey

— comment by dese on April 26th, 2016 at 8:14pm JST (1 year, 7 months ago) comment permalink

Update on my comment Apr 12th. I believe I have an understanding of what is going on. Much careful manual adjusting of the focus did not change the situation that apparently my 8MP Minolta was autperforming the new Nikon D7100. HOWEVER – I realized the problem might be simple perception; I was comparing the pictures as they were being scaled on my monitors which are also pixelated. Picking a feature that looked sharp on the Minolta and blurry on the D7100 and then adjusting the size of each image ot get the same size pixels on the monitor, I saw that the D710 at 24MP was about 1.7x better than the 8MP Minolta, about what I would expect. So an embarassing lesson. As I said before, the initial impression was quite startling. One has to be very careful making these comparisons. On the plus side, I learned a lot about the D7100. It is much harder to use than the Minolta. Next issue is getting the white balance right; grey cards and the D7100 manual’s hints completely failed – ended up doing some 200 pictures by hand. Am experimenting with white balance “lens caps”. Thanks for the blog – Stan from California.

— comment by Stan on April 26th, 2016 at 11:52pm JST (1 year, 7 months ago) comment permalink

South Africa

Hi Jeffrey,

Would it nit be better to replace the low contrast center section on the chart with 18% grey plain card to ensure that the autofocus has absolutely no target to focus on?

Better in the way you cite, but worse in that then there’s no way at all to see where the focus falls in that part of the frame. —Jeffrey

— comment by Nigel on May 22nd, 2016 at 9:19pm JST (1 year, 6 months ago) comment permalink

From London, England.

Hi, this set of focus charts has probably saved me some money. Identified the front focus problem on my Pentax and has given me some clear and consistent results between lenses so I can adjust it when I get access to a PC running PK-Tether software (sometime next week). Putting the camera into DEBUG_MODE with PK-Tether will allow me to recalibrate the autofocus system. I’ve seen a brief demo on another Pentax camera and with the help of these charts it should take me just a few minutes. No sending off my camera to a service company for me then, which is a relief. Later in the year I’ll have more money but for now it’s tight so any saving is extremely welcome.

Thank you!

— comment by Fire Angel on June 15th, 2016 at 6:06am JST (1 year, 5 months ago) comment permalink

Hi Jeffrey,
Thanks for putting together an excellent chart and explaining everything in detail. I just purchased a second hand Nikkor 200mm F/4 micro and wasn’t totally happy with my first outing, in terms of focus. So I used your chart the way you stated and found the lens and camera (Nikon D750) were performing just fine (with maybe a hint of front focus). Thus now I know it’s me that needs to improve. I really appreciate the effort you’ve gone to.

Thanks,
David – CA, USA.

— comment by David on June 30th, 2016 at 2:32pm JST (1 year, 5 months ago) comment permalink

Depth of field always includes 1/3 foreground, 2/3 background from the point of focus, up to and including infinity (and beyond). The total depth of field varies with the aperture setting but the ratio is always 1/3:2/3. This fact is aptly demonstrated by the depth of field scale on the lens of every fine film camera – an idea that seems to have sadly been lost with digital SLRs.

(See http://www.kenrockwell.com/leica/images/40mm-f2/D3S_6584-focus.jpg for an example)

Great lesson & great chart, but keep in mind the 1/3:2/3 rule. If you calibrate it for equal fore & aft distances, you’re actually setting it for front focus.

The “⅓ : ⅔” idea is just a rule of thumb that often is “close enough” in many common shooting scenarios, but it is by no means always true. Sometimes the ratio approaches 50/50; sometimes it’s much more skewed. The details are in the specific shooting situation (optics, aperture, focus distance). —Jeffrey

— comment by Shaun Lovell on July 18th, 2016 at 5:14am JST (1 year, 4 months ago) comment permalink

I recently buy a Canon 6D and sigma art 24:105 lens, as far as i know that suppose to be a sharp and acurate lens but my percentage of missed shots was extreamly high, this site helped me a lot to confirm my suspect for backfocusing issue.
I tested lens on this chart with all focall lenghts and in 5 diferent lenghts, 0.45m, 0.7m, 1.00m, 2.5m, not infinity and summary of test is when i increase distance from target there is more and more backfocusing, at 2.5 m is eaven hard to find focus spot.
One god point is that sigma has a usb dock to fine tune every focall lenght in 5 points and i hope so that can me managed and resolve by Sigma corp.
Thanks for this site, it is extreamly helpfull.

Cheers

— comment by Mark on September 12th, 2016 at 12:08am JST (1 year, 2 months ago) comment permalink

I am going to test my Nikon D610 camera with you exciting chart and different lenses.
As far as concern the intelligent observation about the difference in background vs foreground depth of field,
I suppose this should be at least partially compensated by the smaller size of the characters in background.
My 2 cents. 🙂
I’m in Rome Italy.

— comment by Simone Cabasino on October 22nd, 2016 at 7:13am JST (1 year, 1 month ago) comment permalink

Thank very much for a detailed explanation and the chart. I learned a lot.
I am going to put my D7100 and lenses through this test.

I also suggest to poke a tooth pick through the middle of the focus reference bar to increase sensor detection sureness.

— comment by EdC on January 3rd, 2017 at 8:45am JST (10 months, 22 days ago) comment permalink

Thank you for providing the testsheet. I have using an NX500 with kitlens 16-50 for about one year now and I have trouble with sharpness and autofokus with moving things like fast mountainbikers. I tried the 5% version (printet with laserprinter) of the testsheet, but the AF locks still on the grey, I have to print it on another printer to check, if it works.

— comment by Johannes on January 19th, 2017 at 8:31am JST (10 months, 6 days ago) comment permalink

I am interested in the comment above regarding zoom lenses and aperture. Specifically because I use manual focus on my prime lenses, but I need auto focus on my zoom, which I use to shoot equestrian competitions in Florida. Doing so means I need a fixed shutter speed, so my aperture is automatically adjusted and I also use every focal length available to me in my lens. If this technique is not ideal for my situation, I am concerned I will make bad matters worse if I try to make any adjustments to my camera.

So long as you can reset any adjustments you make to the settings, and can test them during a non-critical time, I’d suggest just giving it a try. I’m not an expert in this by any means, but I’d think that the adjustment for one situation should work for all situations for the given lens. To make things most precise, test with the biggest aperture (smallest f number). —Jeffrey

— comment by Perry on March 3rd, 2017 at 10:09pm JST (8 months, 21 days ago) comment permalink

Estava com um grave problema nas minhas fotos, e ficava frustrada a cada trabalho, porem teve uma dica sua que foi fundamental para eu ajustar a configuração da minha máquina.
trabalhar com o Obturador Rápido. Agora consegui a nitidez que eu queria. Muito obrigada!!!

— comment by Silvia Mortais on April 24th, 2017 at 1:21am JST (7 months ago) comment permalink

Hi Jeffrey,

I have done the test and have determined that my D7100 has a bit of front focus going on …for example the #3 in the foreground is sharper than the #3 in the background. Now that I have determined this I am unsure how much to adjust the AF fine tune …I know where to go to do this, I just don’t understand how many increments I should move the focus backwards?

Thank you
Tracy
Ontario Canada

— comment by Tracy on May 24th, 2017 at 3:57am JST (6 months ago) comment permalink

USA Thanks for the great site and information

— comment by Gary on July 22nd, 2017 at 11:43pm JST (4 months, 2 days ago) comment permalink

Hi, Egill here from Iceland. I have been very frustrated by my D7000 focus issues. Thank you so much for all the work you put into these instructions. They have helped me a lot.

Best regards,
Egill

— comment by Egill Másson on September 24th, 2017 at 7:10pm JST (2 months ago) comment permalink

Just an FYI note, the LensAlign link above does not work anymore. in fact http://www.rawworkflow.com/ as a domain does not appear valid anymore.

Thanks for the heads up… it looks like Michael renamed the company.. the host is now michaeltapesdesign.com. —Jeffrey

— comment by Wesley on October 6th, 2017 at 11:14pm JST (1 month, 18 days ago) comment permalink

Thank you for this resource. I own a Pentax K-50 and am seeking to get my lenses tuned (Sigma 28mm f1.8, Sigma 17-50 F2.8, Tamron 10-24 3.5-4.5) and this should be a massive help. Combing through the comments section is also very informative. Someone mentioned using “PK Tether” as a means of extending their Pentax’s fine tuning capabilities. The lens adjustment in camera lists a +10 to -10 feature and the poster stated using PK tether made it possible to exceed this by “fine tuning the camera body”. Do you know, or have you encountered anyone who can explain how PK Tether allows this procedure? As “Tether” allows you to enter the camera’s Debug mode. I have downloaded the zip file but I am more than a little bit jittery about poking around in the Camera’s Software/Firmware to modify the lens adjustment parameters. The 28mm f1.8 seems to be nearly spot on at -10 but I can go no further.
I have a subtle neurological issue that prevents me from being absolutely steady, forcing me to rely on higher shutter speeds and ISO’s to get decent shots. So my interest in making sure my lenses are as dead on as possible is quite keen.
I appreciate your time and again, appreciate this resource…………………Karl

— comment by Karl Waller on November 22nd, 2017 at 11:13pm JST (1 day, 23 hours ago) comment permalink
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