How many times have you captured an image that looks great as a thumbnail only to lose that sharpness when it is enlarged? If you’re like me, TOO MANY times. It happens to all of us all too often, but it doesn’t have to. You probably know the reasons why and how to avoid the problem, but let’s review them all in one setting to you can get sharp photos every time.
There are several known contributors to soft photos and specific ways to prevent them.
First and foremost – clean the lens
Fingerprints and dust on the lens are the most obvious hinderances to sharp pictures and are one of the most commonly overlooked causes. Carry a small clean microfiber cloth (or packets of lens cleaning wipes) in your camera bag at all times, and keep the lens cap on the lens when it’s not in use.
Become a clean freak with your lenses.
While shooting with the aperture wide open does allow you to use higher shutter speeds, it can also have an adverse effect on image sharpness because of an issue called a spherical aberration.
Simply put, light rays travel in straight lines. When they pass through a lens, the curve of the lens actually bends the light rays and diffuses their focus. The more the rays are curved, the softer the focus. When the entire rounded surface of the lens is utilized (as in when using a wide open aperture), the light-bending is increased and the sharpness on the outer edges of the picture is somewhat softened.
This aberration issue is most evident in less expensive lenses.
It is widely known that an aperture 2-3 stops down from wide open produces the sharpest results. If your shot doesn’t require an extremely shallow depth of field to blur the background, close the lens down a stop or two and compensate the exposure with a slower shutter speed or higher ISO.
But be aware that extremely small aperture openings (f/22 and higher) present their own problem called diffraction. When light is forced through a very small opening, the outer rays bend to get past the small opening, which can soften the image and require a longer exposure time.
Lessons learned: Either aperture extreme will cause a slight softening of the image. Except for special applications, so stay in the middle of the road!
It’s always good advice to buy the best glass you can afford. It is a known factor that THE most critical equipment in your camera bag is not your fancy camera body, but the quality of the glass in front of your camera.
Save your money and invest in quality lenses (f/2.8 or faster). Most of us carry at least one zoom lens, but these lenses, because of the complex grouping of internal glass, are seldom faster than f/2.8, and many are as slow as f/4.5 – f/5.6. The lower the number, the more light that passes through the lens. An f/1.4 prime (fixed length) lens always produces sharper images, though it costs more money.
Believe it or not, the cleanliness or dirtiness of the air can have a significant impact on your photography, especially long-range shots like landscapes. Both heatwaves rising from the hot ground and floating particles of dust and pollutants (what we lovingly call atmosphere) bend the lightwaves, dull the saturation, and blur the focus of your pictures.
Living on the “beach coast” of Florida, steady breezes come in off the ocean that are refreshing on a hot summer day but they contain serious amounts of salt. This air salt can be seen for miles in the distance while driving down the coastline. The saltwater mist hangs in the air and has an adverse effect on both metallic surfaces and photographic subjects.
The most ideal weather for shooting razor-sharp pictures is those delightful hours right after it rains. That happens in Florida like clockwork almost every afternoon and at least once every day, Florida gets a nature-shower that lasts for less than an hour and leaves the air sparkling clear for all kinds of outdoor activities. Thankfully, these daily showers scour the air and rinse the salt from both nature and automobiles.
Depth of Field
Choose an f-stop that will keep your entire subject in sharp focus. If you want to keep your subject in full focus while blurring the background, do the math to figure out the depth of field that will remain in full focus at a particular distance.
Each focal length lens has its own “pocket of precision” or focal zone for each subject-lens distance. Take the time to explore your lens’s capabilities so that you will be prepared.
The depth of field is particularly critical in macro photography. The very nature of the process limits the actual focus on subjects to a very shallow distance. Sometimes this works out well and sometimes it just doesn’t.
Learn the limits of each macro lens’s “pocket” before you make your shot. If your camera allows you to preview the depth of field, use it religiously. Very small changes in the lens-to-subject distance have a very big effect on the focal distance.
Use the One-Third, Two-Thirds Rule
All photographers know that higher number f-stops mean greater depth of field, but maybe some don’t realize that there is an important ratio involved in the field of focus. This ratio must be considered when choosing the f-stop for a particular shot.
While the length of the lens affects how much of the subject will be in total focus, where you set your focus point is also critically important.
This is true whether you are using Automatic, Spot or Manual focusing. Learn to divide the desired focus area into thirds and set the focus one-third into that distance. When you focus on a particular spot, two-thirds of the focal range behind that spot will remain in focus while only one-third of the area in front of that spot will remain sharp.
This is why portrait photographers set their focus on the subject’s eyes. This way the distance from the nose to the ears remain in focus.
Autofocus Versus Manual Focus
Unless your subject has a high level of contrasting edges and is located in the middle of your field of view, you might want to consider using manual focus. Autofocus is a life-saver most of the time, but any higher contrast item in the scene could very well steal the camera’s attention.
Camera autofocus is designed to zero-in on high contrast and those areas in the scene will always set the camera focus. If your subject is located in subdued lighting, try switching to manual focus instead.
Slow shutter speeds in hand-held conditions always present problems. No matter how still you hold, your body is always in motion.
The simple fact that your breathe and have a heartbeat means that slight motion will most likely become an issue with slow shutter speeds. Even the slight motion of pushing the shutter button is a contributing factor in this process. I personally make it a point to not go below 125/th of a second when shooting hand-held. Bracing yourself against a stable surface or using a tripod is always advisable.
Use a tripod and a remote trigger. The ultimate preparation for capturing detailed and sharp photos is to take human motion out of the equation altogether.
Once you mount your camera on a tripod, frame the scene, set the focus, set the appropriate f-stop for the depth of field, switch to the electronic shutter (if available on your camera). Set up a remote trigger using either a cable release or a smartphone app. Then sit back and be ready to pull the trigger when the scene is right.
Compensate ISO for Shutter Speed
If your shot requires a shallow depth of field or lower f-stops, try dialing up more light sensitivity (increased ISO). Most ideal lighting situations accommodate 200-400 ISO, but low lighting scenarios may require you to set the camera to significantly higher ISO.
But keep in mind that ISO determines how sensitive the image sensor is to light and darkness. Very high ISO will yield higher levels of electronic noise in your picture. Noise is the polar opposite of “signal.” Make your choice of ISO carefully if the image is to be enlarged at all.
About Image Sharpening
Nominal sharpening takes place (usually) at the time the photo is taken. However, sometimes additional sharpening may be necessary. Beware, image sharpening should always be the last step in image preparation.
Most photos are intended to be sharp and detailed. But refrain from sharpening your images in the editing process in a ditch effort to bring out more detail. Image sharpening artificially simulates image sharpness and can actually degrade the digital image. Unless you use a sharpen brush, every time you sharpen an image in post-production you also enhance the non-subject elements in the scene.
So make sharpening for detail a last resort.
Make it a habit to capture the highest level of detail in the original shot. Take the time to learn each of these precautions and then consider them briefly before you take your shot. If you discipline yourself to go through this checklist the next half-dozen times you shoot, this will become a mental-muscle memory that you check subconsciously.
Exercise your good habits and you’ll come home with more sharp photos and become a sharpshooter.