2. Added tutorial on how the AF system works. 3. Shot down a few myths about how the focus test works. 4. The test chart itself is unchanged from version Print out either this Siemens Star Focus Chart or this Focus Test Chart on regular letter size paper. You can print it on a laser printer or inkjet (doesn't really. Some, like the ISO chart and USAF Resolution Test Chart, will up the test so that the targets fill the frame, while allowing me to focus the lens at.

Focus Test Chart Pdf

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Introduction. Thank you for downloading the Schneider Optics, Inc Century Focus and. Test Chart System. The Focus and Test Chart System is the result of. Glue the distance scale from this page onto a piece of poster board and trim to size. Cut out the notches at the zero point of the scale. If you've used board that's . Focus Test Chart. 1- Print this page on your printer. 2- Place this page on the floor / ground and take an image on a 45 Degree angle. If using a zoom lens zoom.

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. 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. 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.

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.

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:.

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.

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. 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.

Any resizing necessarily incurs fuzziness, which can make interpretation of the results slightly more difficult. 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 possible, print on high-resolution matte photo paper, such as Canon's MP 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. Using the test chart involves taking a picture of it, but it's important that it's done under the right conditions. 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. Fast Shutter — you want a fast enough shutter speed to eliminate the blurring effects of camera shake. 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. 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 on my Nikon D, but I'll go to 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.

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. 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.

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 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. 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 megapixel SLR affords. 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.

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. 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. 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:. 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. 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 Here, the depth of field is almost 10 times larger 7.

In this case , I focus more on the numbers haha, I'm so witty. 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: 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. 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.

This was taken with a mm 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. 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 short answer is, my 60D focuses fine on a good target at three degrees to the lens axis.

Download your “FREE” focusing test chart

CD AF works fine down to about ten degrees. Sure, just manually focus on the center line. I suppose the answer depends on the camera and the nature of the problem. 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? You may have to just try to watch where it focuses, and use only photos where you see it focused on the black. 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.

Because some paintings were missing, I loaded the Minolta pictures and was completely blown away. I am now frantically testing the Nikon because I have commited to the new project the Minolta dies last year. 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.

Any comments would be grealy appreciated. Using the Nikon lens that came standard in the box. Will next try to the the longer focus zoom. However, in this case I think autofocus should not be one of the variables. Instead, use Live View to focus manually, very carefully.

Use enough light for a fast shutter, and use mirror-up delayed release for good measure. I own a Pentax K-5 with the following lenses: Sigma f3,5, a f 2. 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. Shot down a few myths about how the focus test works. The test chart itself is unchanged from version 2.

The test chart has been completely redesigned. It is now much easier to use and it produces more detailed information. The cut-out-and-fold-into-a-box part has been done away with.

See notes further on about how the focus system works for more info. Page 1 of 19 The Internet is wonderful The Internet is a wonderful thing. Among its many benefits is that it provides a platform for anyone with Internet access to publish their thoughts and ideas.

Internet discussion forums, in particular, are very often spoiled by juvenile tit-for-tat jibes and silliness or by people who seem to exist solely to cause problems.

The Internet and this test There has been some discussion in forums on the Internet about this focus test with some folks claiming with a blind, almost religious fervour, that it gives flawed results and trying to dissuade people from using it.

Sadly this is not of much use to people looking for answers. In fact it just adds to their problems.

dumb question: /L about focus

These zealots have justified what they have erroneously presented as fact by occasionally making reference to the works of others that they have either misunderstood or that are not relevant to the context of this test or, in some cases, are simply incorrect.

None of these people has yet presented a single piece of conclusive evidence to support their scurrilous claims; much less provided a mechanism for others to put those claims to the test. This is in stark contrast to what I have done with this test.

In other circumstances their behaviour would be actionable. However, my intent here is not to tussle with these ignoramuses but rather to provide as much useful information as I can on the subject of focus and, in particular, back focus, to anyone who wants it. This is not a business venture. I really like my D70 and have had loads of fun getting to know it and I continue to do so. Page 2 of 19 Although there have been many incidents in Internet forums where the aforementioned individuals have falsely stated that the test described in this document is worthless, there have been many, many more people who have entered into private exchanges with me via email in order to avoid those few forum cretins and who have praised the work, thanked me for my efforts, offered suggestions for improvements and additions, asked me to offer my opinion on their test shots and more.

I have been greatly encouraged by these folks. Thank you all! On the next few pages is a wealth of detailed information on the auto focus system used in the D70 and how it works.

This includes some simple practical exercises you can do to help you better understand the system. Following this is a useful test that will allow you to accurately test your auto focus system and lenses.

I hope this will be of use to you, both in determining whether your D70 needs attention, as well as being both fun and informative. Read on! Page 3 of 19 The auto focus system in the D70 Please note that a number of practical exercises are included in this tutorial and you are encouraged, even urged, to try them all out for yourself as you read through this. Please make sure that your camera is set up correctly first, by following steps 7 through 11 on pages 13 and The auto focus AF system in the D70 is similar to a lot of other AF systems in that it works, essentially, by adjusting the focus to achieve the best contrast between adjacent pixels on the focus sensor.

If you have a subject with little or no contrast, like a clear sky, a white wall or even a just a plain sheet of paper, the AF system cannot function. Try it yourself: First of all, try focusing on the centre of a blank sheet of paper. The reason for this is that there is no contrast - no dark and light objects for the AF system to see in order to set the focus. Now, imagine if you will the simplest possible focus target: A white page with a black line on it. Just such a page is included at the end of this document for you try out.

Go on, try it out! Try aiming at the line on the page square-on as well as from various angles. Notice how you easily get focus lock.

Page 4 of 19 Focus area markers and focus sensors As you may already know, the focus area outlines you see when looking through the viewfinder are not identical to the actual focus sensors. The outlines you see when you look through the view finder look like the black outlines in this picture.

The actual electronic focus sensors are really looking at the areas shown in red. So, the black outlines in the viewfinder are a guide rather than a precise definition.

Also, it can happen that the precise location of the sensors is not in the centre of the viewfinder outline. You could have something like the pic on the right, for example. This is a bit extreme but it illustrates the point. You aim using the black outlines but the camera actually focuses using the sensors shown in red.

Also notice how the focus sensors are not so much rectangles as they are lines. If we use just one horizontal focus sensor for the sake of this explanation, then, when we aim our camera so that a single focus sensor is over the black line, we would have something like the pic on the right. Page 5 of 19 Here we have a section of the black line on our page. No kidding!

Notice the small red selection on each image? This equals highest contrast. Huge contrast! In the picture on the right, however, each pixel has a neighbour that is only very slightly brighter or darker than it is. Not so much contrast.

The AF system sees this and adjusts the lens until it gets to the point where it achieves the greatest possible difference in light levels between adjacent pixels. Clever, huh? Page 6 of 19 Look back at the pictures on page 5 for a moment. Notice how some of the AF sensors are horizontal and some vertical. Each sensor is only able to assess areas of contrast that are not parallel to the sensor. The area of contrast must cross the length of the sensor as in sensor 1 in this pic.

Remember how our black line ran at ninety degrees to the sensor so that the sensor could see the edges of the line. If the sensor is aligned parallel to the line as are sensors 2, 3 and 4 in this pic then it cannot focus because all of the pixels in the sensor would always be at the same light level.

No contrast. In this pic, only sensor 1 would provide useful focus info by virtue of having some pixels in sharp contrast. Remember that the sensor only sees a straight line. It is one-dimensional. Sensor 2 in the pic would see all white. Sensor 3 would see all grey.

The Lens Testing Focus Chart

Sensor 4 would see all black. Try focusing on the line on the paper with the sensor at right angles to the line and then try it with the sensor parallel to the line. Not a lot of folks have a good understanding of that phenomenon.

Rotate your camera to various angles to see how much of an angle the sensor needs to be at relative to the black line before the system will focus reliably. Ok, now switch back to the centre sensor, which has both horizontal and vertical elements. Try the above focusing exercise again. You should find that you can rotate your camera to any angle relative to the line and it will focus. Clever system indeed. Page 7 of 19 And now… The dreaded 45 degree debate As most of you reading this will know, there are folks out there who say that the focus test chart included in this document is, amongst other things:?So the focus isn't "perfect" but it's pretty good and within spec for autofocus.

It's always interesting to see where people are visiting from. I like 's approach because it removes subjective misinterpretations about what should be in focus. Page 4 of 19 Focus area markers and focus sensors As you may already know, the focus area outlines you see when looking through the viewfinder are not identical to the actual focus sensors. I certainly learned a lot when I went through this with my own autofocus problems.

Thanks for posting, yabesh!