So, you have a camera or lens that you think is not as sharp as it should be. If you are already expert at these things, what follows is not for you – you already know how to analyze the problem, you can anticipate possible causes, and you know some of the pitfalls of looking at the issue in unrealistic ways. But if you aren’t certain about how to deal with the issue, perhaps the following might help… so feel free to read on.

Perhaps you just got a new lens or a new camera and you don’t think it is performing as you expected. Or perhaps you have long suspected a problem with your equipment. On the other hand, maybe some gear that you have used with confidence for a while seems to not work as well as you recall it working in the past. It can be tempting to blame the equipment – and in some cases you may be correct – but it is a very good idea to first try to analyze and understand the problem and look for other possible causes… and solutions.

It is critical that you try to control the variables that might give rise to the issue, and then to try to a) determine if the problem is real, and b) figure out specifically what might be the cause. The range of possible causes is larger than you might imagine: problems with the camera’s autofocus (AF) system, an out of adjustment or “weak” lens, less than optimal choice of lens settings, issues with camera stability, insufficient care with the use of AF, using the wrong AF settings, aperture choices, shutter speed choices, subject motion, and more. While a real equipment problem is a possibility, it is probably at least as likely that the problem lies elsewhere. Fortunately there are ways to wade through this minefield and develop some rational understanding of what is going on.

What follows is a sort of ad hoc description of how I might approach this. It is not meant to be the only way to deal with such issues, it leaves out some possibilities, and the sequence could be changed around in some ways.

1. Eliminate technique errors first. If you rely on AF, are you careful to place the AF points on the primary subject? A common cause of “bad focus” is that the camera accurately autofocuses… on something other than the subject you had in mind. In order to minimize this you could choose to use only the center AF point for your test and be careful to place it over the main subject. If you use multiple AF points, watch the indicators that tell you which points are activated when you shoot. Use an appropriate shutter speed if you shoot handheld. A “rule of thumb” suggests that you might tend to be OK with a shutter speed that is 1/focal length. On a full frame camera this suggests that 1/50 second might be a decent shutter speed when using a 50mm lens. (Multiply by the crop factor if using a cropped sensor camera – e.g. 1/80 second might be right for a 50mm lens on a 1.6x cropped sensor body.) But this varies from shooter to shooter and is far from 100% reliable. Unless it is impossible to do so, try higher shutter speeds to minimize the possibility that the camera is moving at the time of exposure. Be careful to avoid “punching” the shutter release button, which can create camera motion at the instant of exposure. Be aware that shooting at very large apertures makes autofocus much more challenging. The DOF may be only a few inches deep, and a slight misalignment of the AF point could more easily create missed focus.

2. Avoid misconceptions about “sharpness.” Some imagine that every exposure should be razor-sharp, even when viewed at 100% magnification on their monitors. In the real world, it just doesn’t work this way. A photograph that seems slightly less than perfectly sharp at this resolution can make a wonderful and very large print. And speaking of prints, two more things. First, if you haven’t done so, get to a gallery and look at actual photographs that are regarded as great work. You’ll perhaps be surprised that many of them are not as large as you imagined, and if you look closely at the very large ones you’ll find that quite a few are not as “sharp” as you imagined either. Second, keep in mind that a print can often be a better way to judge the quality of a photograph than a screen. You will probably never make a print that is five or six feet wide, but when you look at images from modern DSLR cameras at 100% magnification it is equivalent to inspecting such print sizes at nose length. Watch out when comparing sharpness from different cameras and different formats. A common complaint is that “my old 12 megapixel camera is sharper than my new 21 megapixel camera when I inspect 100% magnification crops on my computer.” Well, yes, it should look that way even if the sharpness is the same. You are looking at a smaller portion of the overall (large pixel dimension) image when you inspect the 21 megapixel sample – it is the same as looking at it under higher magnification. There are other issues to be concerned about, but you get the idea.

3. Deal with camera stability issues first. No “sharpness” or “focus” test is going to tell you much about your lens or camera if other factors could contribute to softness or even be the primary cause. Ideally, a focus test should be done with the camera on a tripod, you should use mirror lockup (MLU) or live view (LV) to control the variable of mirror vibration, and you should use a remote release. If you don’t have a solid tripod you can try other methods of stabilizing the camera – perhaps place it on a solid surface. If you don’t have a remote release, you may be able to use the self timer instead – though some cameras may not allow you to combine mirror lockup and the self-timer.

4. Use a good focus target. The best sort of target is a flat subject whose plane is parallel to your sensor/film – in other words it should not tilt in any direction. It should probably contain a reasonable amount of detail with good contrast – some obvious pattern is generally going to be fine. Some people use things like newspaper attached to a wall, a bookshelf with books that extend about the same distance, a brick wall (among photography nuts there are probably more photographs of brick walls than of grandchildren… ;-), or even a real focus chart if you happen to have one lying around. There are other target possibilities, such as rows of carefully placed objects, but the flat surface presents the fewest variables in most cases. Take some care when you mount the camera on the tripod to make sure that its position is centered in all dimensions relative to your target – not too high/low or off-center to the right/left.

5. Use an aperture that would usually produce optimal sharpness. Some neutral aperture like perhaps f/8 is generally a good choice. Larger apertures introduce some additional variables, though you might end up shooting at a larger aperture if narrow depth of field (DOF) turns out to help you quantify a focus problem rather than a sharpness problem. Smaller apertures (like f/11, f/16, f/22, and so forth) are generally not a good choice for these tests for several reasons: Very large DOF masks focus issues if AF is the source of the problem, and these apertures will introduce diffraction blur into the test image, even with the best of lenses.

6. Turn off image stabilization on lens and camera. First, you won’t need it when doing your test with the camera on a tripod. Second, it can introduce an additional variable that could affect sharpness.

7. Make an exposure. I recommend using raw mode. Allow the camera/lens to autofocus on the subject and make an exposure. Better yet, make perhaps three exposures in this way so you have more than one data point. While you have everything set up, it can be useful to run the test at each of the apertures that you might use in your photography. Perhaps shoot from the largest to about f/11 on a cropped sensor body and from the largest to about f/22 on full frame. If you have a zoom lens, you might try the process at a few representative focal lengths as well. You’ll learn a lot about the personality of your lens from this process, and you’ll learn it more quickly than if you just picked it up over time through general photography.

8. Bring your raw images through your usual post-process work flow. RAW files must be sharpened in post in order to achieve optimal resolution, and you would never forego this step with a “real” photograph – so why would you forego it here? In the end, the sharpness you achieve from a sharpened raw file defines what your camera/lens system is capable of. (If you are a bit more of a casual shooter and you usually shoot jpg, you could do the test in jpg mode and make sure to use in-camera sharpening of a fairly neutral character.)

9. Inspect the images for sharpness – but be careful! I am convinced that if you know what you are doing the best way to evaluate the image quality is by producing a print at the size you typically create. If you get very sharp prints, then it really doesn’t matter whether there is some incremental difference in sharpness at 100% magnification on the screen. If you usually share electronic jpg files online or in email, you might make a point of viewing the files at your typical resolution. (Be aware that setting the magnification to 25% or some other smaller size in your image editing program may not produce as good of a screen-based image as actually going through the steps to downside the photo to your target dimensions.) Be somewhat critical in your inspection, but avoid obsessive pixel-peeping. Even a really wonderful photograph will look less sharp at 100%, so don’t imagine you have a problem if you can find a tiny bit of “softness” that will never be visible in your real output size.

In most cases, if you understand what sharp screen images do and do not look like and if you eliminate other variables that could be causing problems, you may now find that you have pretty good image quality. If so, you may want to look back at the variables that we eliminated in this test and and see if they might point to the cause of your sharpness issues. If the camera is sharp on the tripod but not when hand holding the camera, it seems pretty likely that the problem might be due to less than careful camera handling, a shutter speed that is too low, or similar. Of if your focus is inconsistent in normal shooting but consistent in this test, you might just have to be more careful about things including careful placement of the AF points on your subject or avoiding camera movement when you press the shutter button.

Let’s say that you observe that your f/8 test shots look pretty good but your wide open shots are not quite as good. Several possibilities are worth considering. First, lenses almost universally are at least a bit softer wide open than they are when stopped down a bit. Don’t mistake this normal effect for a problem with your lens. Some lenses are more affected by this than others, and a bit of reading – especially in reliable lens tests and reviews – may alert you to what to expect. In the end, a lens that is a bit softer wide open is probably not exhibiting a problem at all. However if you do have a AF problem, it will more likely reveal itself in the narrow DOF images produced at the largest apertures, so you may want to see if you can rule in or rule out an AF inaccuracy. Your lens/camera (it could be either or both) might be front- or back-focusing a bit – in other words, placing the optimum focus on a plane just in front of or behind your subject. Short of using front/back-focus test targets, you can try a couple of simple techniques to test for this, testing the camera at the largest aperture. One is to use a target that places an object in the center of the frame along with a few other objects slightly to the sides that are a bit closer to and further from the camera. Use center-point-only focusing and place the center point directly on the central object and make a few exposures. Alternatively, you could AF your original flat-plane target to make the first exposure, then switch AF off and manually refocus a bit closer and a bit further away for your follow-up exposures. If you consistently notice that instead of the main subject being in focus that one of the objects in front of or behind it is in better focus, you may need to micro-adjust your lens (if this is possible on your camera) of have it adjusted at a service center. (Be aware that DOF is a bit deeper behind the subject than in front of it – and don’t mistake this for a back-focusing lens.)

Finally, let’s say you have arrived at this point and even after eliminating all the variables mentioned above you are still not getting the image sharpness you think you should get. Now what? If possible, I would share the test images with a few people who know how to interpret these things and ask for their feedback. They might catch something you overlooked. They might point out that your expectations are simply not realistic and that the performance that you think is substandard is actually fine. Or they may confirm that you do have an equipment problem. At this point, unless you are prepared to live with it and work around it, your best bet is probably to send the equipment to your manufacturer’s service center. Hopefully you discovered the problem while the gear was still under warranty, in which case the repair will likely be free or inexpensive. If you discover the problem after the camera is out of warranty, just consider the cost of repair to be the normal a maintenance cost of using a high quality camera. In the same way that things get out of adjustment and need repair on your car, you should expect that camera gear will go out of adjustment and need repair, too.

I’ll end by looping back to where I started. Many perceived “sharpness” problems are not equipment problems at all. First work to eliminate those sources of softness. Then run some basic tests that isolate possible problems and, depending upon the outcome, make changes to how your shoot or use the knowledge from the test to carefully describe the issue when you send your equipment in for repair. Finally, I want to repeat my earlier disclaimer: this is not a definitive coverage of all possible issues related to sharpness nor does it cover all of the possibilities for testing and analysis.

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