Basic Photography Article - #4 Achieving Sharpness
In this article I'll be talking about sharpness and how to achieve it. First, you have to be looking for sharpness (or lack of) to know if what you're doing is working. As you shoot and look at the LCD on your camera, zoom in and/or use a loupe like the Hoodman loupe to see your image magnified. It is impossible to evaluate sharpness on that tiny LCD at normal magnification. If it's a picture of a person or animal, make sure the eyes are sharp. When you edit your pictures, zoom in on the computer monitor to evaluate sharpness. Of course if the image isn't sharp on your computer, it may be too late to do much about it. It's better to be checking while you're shooting and still have a chance to correct your problems.
I NEVER shoot a picture that is blurred, out of focus or unsharp for any reason. All examples of such pictures were painstakingly produced purely for illustrative purposes.
A loupe that magnifies the LCD image to evaluate sharpness. It also blocks ambient light and improves the contrast as you evaluate your shot. Be sure to focus the loupe.
Unintentional Camera movement
Unintentional Camera movement is a major cause of soft images. There are several techniques you can use to minimize camera movement. In the last article we talked about subject movement which can also affect sharpness.
Make sure your grip provides a solid platform for your camera, and that your body is as stable as possible. The right hand holds the camera, and pulls it into the face. The left hand supports the lens from underneath and the elbows are tight into the body. Take a deep breath, let part of it out, and gently press the shutter release. When possible brace yourself or the camera on a solid support. As a general rule, most photographers cannot dependably hand hold a camera at a shutter speed slower than 1/focal length. For example with a 200mm lens, that means 1/200 sec or faster. Also with a cropped sensor don't forget the effect of the crop factor. So for example a 100mm lens on a Canon crop body behaves like a 160mm lens (1.6 crop factor), so again you would want a shutter speed faster than 1/160 sec. If necessary, increase the ISO to get a faster shutter speed. Sharp and noisy beats soft without noise. This is a general rule, and some photographers are sturdier, some may be more shaky, so test with the exercises below.
Shooting a burst at your camera's fastest frame rate may help get a sharp shot. Usually one of the shots will be somewhat sharper than the others. Some lenses have stabilization that helps counteract movement when you shoot handheld. Canon calls it IS (Image Stabilization), Nikon calls it VR (Vibration Reduction) and Sigma calls it OS (optical stabilization). Depending on the lens, this may allow you to hand hold two to four shutter speeds slower than the rule above, but you should test as in the exercises below.
A shutter speed of 1/30th sec with a 200mm lens was too slow and caused motion blur. At first glance it seems almost sharp, but zoomed in, everything appears soft.
Hand held shutter speed test at 200mm. At 1/500 sec each dot still looks like a sharp dot. This is a safe hand held speed.
Hand held shutter speed test at 200mm. At 1/30 sec, the dots are blurred into streaks due to camera movement. Definitely not a safe hand held speed.
If you have never used one, you won't believe how a good tripod can improve the sharpness of your images. A good tripod should be light enough that you will carry it, yet sturdy enough to support your heaviest camera and lens. A good tripod is not cheap, but it can be a lifetime investment. Better to spend the money for a good tripod the first time, rather than waste time and money on cheap tripods that are too heavy or too unstable. Here is an article on buying a tripod.
There are a couple of tips to improve sharpness on a tripod. Pressing the shutter button can induce shake and vibration, so either use a cable release, or if you don't have one, use the camera's self timer. Extend the largest, heaviest legs first, then the smaller legs. Use the lowest practical height, and only extend the center column when the legs are fully extended and you still need more height. Many tripods have a hook on the bottom of the center column for hanging a weight such as your camera bag for added stability. If you do hang a weight, don't let it swing. Make sure all of your legs are locked securely, and the tripod head is locked down tightly. Watch where you stand, and don't kick the tripod during an exposure.
Also, some lenses with image stabilization can induce vibration when used on a tripod. The motor within the lens actually creates movement as it searches for movement. Then it moves more to correct its own movement. Some lenses don't do this while others do. Read the manual for your lens and see if the manufacturer recommends turning IS off, or just turn it off to be sure it's not a problem. If your lens doesn't have image stabilization you don't have to worry about this.
When you aren't able to use a tripod, (situations like sports, or in crowded areas) a monopod offers a level of support that is better than hand held, but not as sturdy as a tripod. A monopod also takes the weight off of your arms, and prevents muscle fatigue that causes loss of steadiness. Here is an article on how to use a monopod.
This image was shot on a tripod, but image stabilization was on and caused the diagonal blurring you see in the close-up.
Lack of proper Focus
Improper focus point selection can cause your image to be soft in the wrong places and sharp where you don't need it to be.
There are several focusing techniques that can help.
Choose a focusing mode in which you select the focusing point, and can place it over the part of the subject that you want to be sharp. When you use the focusing mode where all points are active, the camera will usually select the closest object it sees, whether that is your intended subject or not. One common technique is to aim your camera so that a focus point is over your main subject and lock the focus and recompose. Different cameras use various methods to lock focus, so read your camera's manual. Also many photographers (almost all sports or wildlife shooters) use what's called back button focus. Most cameras focus when you press the shutter halfway, but back button focus removes the focus function from the shutter button, and allows you to reassign it to another button on the back of your camera. You then focus by pressing that button with your thumb. Release, and the focus is locked, or hold it down to track movement. It does take some practice to remember to focus before shooting since it's not linked to the shutter button. Read your camera manual to learn how to reassign the focus button.
You can find some articles on back button focus here. If you are shooting a stationary subject, one technique for achieving critical focus is to use live view (using the cameras LCD to view and compose), then zoom in to 5X or even 10X, and fine tune your focusing manually. This only works on a tripod. Also be sure to match your focus mode to the shooting situation. For a stationary subject you can use a focus mode that doesn't change once you focus (Canon calls it one shot, Nikon calls it AF-S). For moving subjects you want a mode that keeps the subject in focus as it moves (Canon calls it AI Servo, and Nikon calls it AF-C). Once you focus be sure you don't move. With a close subject and shallow depth of field, even breathing can cause your focus to shift. Think tripod! Make sure your camera has actually focused. Some viewfinders will light up the focus point, or light an indicator, or beep (most cameras allow you to turn the beep on or off). By whatever means be sure the camera has actually focused. This is often a problem at close range where the subject may be closer than the minimum focusing distance of the lens.
In this focusing mode all points are active and generally the camera will select the point over the closest object it sees.
This is an extreme example where the camera chose to focus on the flower, the closest object and not the girl and horse which were the intended subject.
this focus mode the photographer can choose which point to make active and place it on the subject.
Every lens has an aperture range where it is sharpest, Usually it is two or three stops smaller than the widest aperture. For many types of photography this is not that big a concern, especially if stopping down forces you to use a shutter speed that is too slow to hold steady. Also, generally the more expensive the lens, the sharper you can expect it to be. Again for many photographers, even the less expensive lens will perform adequately. Use a lens hood to shield your lens from light that might cause flare and decrease contrast and sharpness. Also while many photographers use a UV or clear filter to protect their lens, many feel it decreases sharpness, particularly when shooting into the light.
Sharpening during Processing
If you shoot JPEGs, then your camera makes some image adjustments, including adding sharpness. If you shoot RAW files, there is no sharpening until you add it in Lightroom or Photoshop. Lightroom has a sharpening section in the develop mode as well as some presets. You can use unsharp mask or smart sharpen in Photoshop. Also Photoshop CC has a filter to correct camera shake. It's rarely perfect but it may make a slightly blurred image at least usable if not sharp.
Things that increase apparent sharpness
Shooting at or near wide open creates a shallow depth of field that blurs the background and makes the subject in focus seem even sharper. Notice that the wide open aperture may not be the very sharpest for the lens, but our eyes see it as sharper.
High contrast lighting makes subjects appear sharper, and low contrast lighting makes things seem less sharp. You may not be able to change the lighting contrast of natural light, but you can change the contrast of your image in processing.
A shallow depth of field makes the subject appear sharper. Additionally the wide open aperture allows a faster shutter speed. Also note that eyes are perfectly sharp.
Low contrast lighting on a cloudy day makes this shot look softer, even though it is sharp and in focus.
Contrasty light on a sunny day makes this plane look even sharper.
Your Practice Assignments:
1: Either download and print a focus target or use a sheet of text taped to a flat surface. Keeping a constant aperture (to minimize the effect of aperture on sharpness), shoot a series of hand held exposures at increasingly slower shutter speeds. You may have to change ISO to keep the aperture constant. Turn off IS, VR or OS. Shoot 5 exposures at each shutter speed. If you are using a zoom lens do the test at the shortest focal length, middle focal length and longest focal length. If you have several lenses, repeat for each lens. When you load the images on your computer zoom in to 100% and evaluate sharpness. For each focal length, the slowest shutter speed where 4 out of five images are sharp is the slowest shutter speed you can reliably hand hold. That also means that 20% of your shots will be soft, so in actual shooting situations, shoot more than one!
2) Repeat the test above, but turn on image stabilization and evaluate to see how much it realistically improves your ability to hand hold.
3) Do the tests above with the camera on a tripod (I hope you're impressed by the difference) and with IS on for one series and off for the other. If IS causes blur in your images, remember to turn it off when you use a tripod.
4) Read your camera manual to learn how to setup back button focus. Practice using it for a couple of days until it becomes second nature.
5) Read your camera manual and learn how to change focusing patterns and how to select the active focus point.