In photography, the term "tack sharp" describes an image which shows the main subject in sharp focus, with clean lines, crisp details, and no blurring. Achieving this level of sharpness is one of the keys to a truly eye-catching picture.
Taking tack sharp photos is all about reducing camera shake to an absolute minimum. There are many different ways you can do this. Some apply to all situations, while others can only be used in certain circumstances, but each one helps reduce the amount of camera shake by a small fraction. The more methods you can use, the sharper your shots will be.
General Tips for Maximum Sharpness
These tips can be applied in all situations, and you should bear them in mind at all times, as they can make a big difference to any photograph.
1. Use the Sharpest Aperture
Camera lenses can only achieve their sharpest photos at one particular aperture. This is typically 2 to 3 stops down from the widest aperture, putting it around f/8 on most lenses.
Your choice of aperture should be based on other considerations first (such achieving an acceptable shutter speed and depth of field), but try to stay close to this optimum aperture wherever possible.
2. Switch to Single Point Autofocus
When focusing, most cameras will try to keep as much of the scene acceptably sharp as possible. This is fine when you want to see detail everywhere, but it does mean that no one object will be super sharp.
Switch your camera into single point focus mode. This tells your camera to focus sharply on just one point (typically in the centre of the frame). Before composing your shot, focus by aiming this point at your subject and half pressing the shutter. This will keep the subject as sharp as possible.
3. Lower Your ISO
The higher your ISO speed, the more digital noise you'll get in your photo. This causes sharp details to appear fuzzy, affecting the overall sharpness of the image.
Wherever possible, use your camera's lowest ISO setting (typically around ISO 100 or 200), as long as it doesn't negatively affect other settings such as your shutter speed.
4. Use a Better Lens
Good quality lenses make a big difference to the sharpness of your photos, and more expensive lenses are generally sharper than cheap ones. Obviously, changing a lens can be very costly, but think of it as an investment in better photos.
5. Remove Lens Filters
Filters reduce the sharpness of your lens, affecting the final image quality. When they're not needed, take them off to improve clarity.
6. Check Sharpness on Your LCD Screen
One of the great advantages of digital over film is that you can examine your photos immediately. After taking a shot, use your camera's playback feature and zoom in to 100% to check how sharp it is. If you see any blurring, you can reshoot it there and then.
Improving Sharpness with a Tripod
For the ultimate in sharpness (which is, after all, what we're aiming for) you need to use a tripod, even if you're shooting in daylight. As with lenses, good tripods are not cheap, but they'll transform your photos.
7. Make Your Tripod Sturdy
The purpose of a tripod is to hold your camera as still as possible, so you need to make sure yours is nice and sturdy.
Avoid extending the center column and legs of your tripod more than is necessary. The taller you make your tripod, the more it will wobble, and the harder it'll be to get pin sharp images.
If your tripod has a hook underneath, hang something off it to provide extra stability. Many professionals carry an empty "rock bag" that they can fill with stones to give a good, heavy weight which will hold the tripod still even in strong winds.
8. Use a Remote Cable Release
Pressing the shutter button on your camera can cause minute shaking. You'd think this would be too small to make a difference, but it can be noticeable in the final photo. A cable release or remote control is an inexpensive way of avoiding this problem.
Alternatively, use your camera's self-timer - 2 seconds is plenty of time for any vibrations caused by touching the shutter button to die down.
9. Turn Vibration Reduction Off
Many cameras and lenses come with a built in vibration reduction system, which works to stabilise the image when hand-holding your camera. Unfortunately, when your camera is mounted on a tripod, this system can be confused by the lack of movement, and actually cause slight tremors as it moves around trying to find some.
This is particularly true of older image stabilisation systems, so it's best to disable them completely to improve image sharpness when shooting using a tripod.
10. Use Mirror Lock-up
Another source of vibration in cameras is the mirror in front of the sensor. When you press the shutter button, this mirror flicks up out of the way, and this can cause the camera to move slightly.
Mirror lock-up (MLU) holds the mirror in its retracted position, so that when you take the shot it doesn't need to move. Most digital SLRs have this feature, and it can make a big difference to how sharp your photos turn out.
Taking Sharper Photos when Hand-holding
Sometimes it's not possible to use a tripod. For example, you might be in a church where it's not allowed, or you might be photographing an event where you have to move around quickly and don't have time to carry and set up a tripod. In these situations you'll have to hand-hold your camera, but there are still ways to maximise the sharpness of your shots.
11. Find a Makeshift Tripod
We're surrounded by objects and surfaces that make perfect natural tripods. Resting your camera on a wall, or wedging your lens between the wires of a fence can help provide a bit more stability, holding your camera still and reducing blurring in your photos.
12. Increase Your Shutter Speed
A faster shutter speed is less susceptible to movement, so increase it as far as you can. As a bare minimum you should stick to the rule of thumb that says to use a shutter speed of at least "1/focal length". So for a 100mm lens you'd want to use a speed of 1/100 of a second or faster.
13. Shoot in Burst Mode
Rather than taking photos one at a time, switch your camera to its continuous shooting (burst) mode and snap several shots at a time. You'll usually find that if you fire off 10 shots at a time, 1 or 2 will be sharp. Be sure to bring a big memory card as this technique uses a lot of space.
14. Turn Image Stabilisation On
Although vibration reduction systems can cause problems when your camera is mounted on a tripod, they work wonders when you're holding it. In optimum conditions they can give you as much as 3 extra stops of exposure, which can make the difference between a photo which is blurry and one which is sharp as a tack.
15. Steady Yourself
When hand-holding your camera, the biggest source of vibration and movement is your body, so try to hold it as still as possible. Tuck your arms into your sides or lean up against a wall or tree for some extra support.
When shooting, even your breathing can cause tiny movements in the camera, so try to breathe slowly and gently, and press the shutter button in between breaths when you're relatively still.
16. Squeeze the Shutter Button
When pressing the shutter button, do so as gently as you can. Make sure your finger is in contact with the button to begin with (rather than hovering over it) and gradually squeeze down on it rather than pushing it quickly. Once the button is down, hold your finger there until the camera has finished taking the shot.
Sharpening Photos in Editing Software
No matter how careful you are to keep vibrations to a minimum while shooting, most photos can still benefit from a bit of sharpening in a graphics program such as Photoshop.
17. Apply an Unsharp Mask
The unsharp mask is the photographer's favourite tool for improving sharpness. It works by increasing the contrast along the edges in your image, producing better separation between objects and giving the impression of a sharper picture.
To apply an unsharp mask in Photoshop, load your image and go to Filter > Sharpen > Unsharp Mask. Adjust the settings to suit your scene; try starting with values of Amount 100%, Radius 1.5, Threshold 4 and tweaking from there.
Achieving tack sharp images isn't impossible, but it does involve doing as many "small things" as you can. Each might only make a tiny difference, but the cumulative effect will result in vastly sharper photographs.