Tuesday, October 21, 2008

How to Take Sharp Digital Images

Getting your digital images perfectly sharp is something that most photographers want - however clean, crisp, sharp images can be difficult to achieve.

Perhaps before we start exploring how to improve sharpness it would be good to talk about the main causes for lack of sharpness:

  • Poor Focus - the most obvious way to get images that are ‘un-sharp’ is through having them out of focus. This might be a result of focussing upon the wrong part of the image, being too close to your subject for the camera to focus, selecting an aperture that generates a very narrow depth of field or taking an image too quickly without checking it is in focus.
  • Subject Movement - another type of ‘blur’ in shots is the result of your subject moving - this is generally related to shutter speed being too slow.
  • Camera Shake - similarly you can get blur if you as the photographer generate movement while taking the image - this often relates to either shutter speed and/or the stillness of your camera.
  • Noise - ‘noisy’ shots are ones that are pixelated and look like they have lots of little dots over them (get up close to your TV and you’ll get the same impact).

Here’s a list of 10 basic things to think about when shooting to get sharp images (note - there’s also a lot you can do in photoshop after taking you images).

1. Hold Your Camera Well

A lot of blur in the photos that I see is a direct result of camera shake (the movement of your camera for that split second when your shutter is open). While the best way to tackle camera shake is to use a Tripod (see below) there are many times when using one is impractical and you’ll need to shoot while holding your camera. I’ve written a tutorial previously on how to hold a digital camera but in brief - use both hands, keep the camera close to your body, support yourself with a wall, tree or some other solid object etc.

2. Tripods

Regular readers of this site will have seen my recent series on tripods and know that I’m a big fan of them as a way to reduce (and even eliminate) camera shake. While not always practical, the result you’ll get when you do go to the effort of hauling one around can be well worth it.

3. Shutter Speed

Perhaps one of the first things to think about in your quest for sharp images is the shutter speed that you select. Obviously - the faster your shutter speed the less impact camera shake will have and the more you’ll freeze any movement in your shots. As a result you reduce the likelihood of two of the main types of blur in one go (subject movement and camera movement). Remember the ‘rule’ for handheld shutter speeds:

Choose a shutter speed with a denominator that is larger than the focal length of the lens.


  • if you have a lens that is 50mm in length don’t shoot any slower than 1/60th of a second
  • if you have a lens with a 100mm focal length shoot at 1/125th of a second or faster
  • if you are shooting with a lens of 200mm shoot at 1/250th of a second or faster

Keep in mind that the faster your shutter speed is the larger you’ll need to make your Aperture to compensate - this will mean you have a smaller depth of field which makes focussing more of a challenge (read more on Shutter Speed).

4. Aperture

Aperture impacts the depth of field (the zone that is in focus) in your images. Decreasing your aperture (increasing the number - say up to f/20) will increase the depth of field meaning that the zone that is in focus will include both close and distant objects. Do the opposite (for example moving to f/4) and the foreground and background of your images will be more out of focus and you’ll need to be more exact with what you focus your camera upon. Keep in mind that the smaller your aperture the longer your shutter speed will need to be - which of course makes moving subjects more difficult to keep sharp (read more on Aperture).

5. ISO

The third element of the exposure triangle is ISO which has a direct impact upon the noisiness of your shots. Choose a larger ISO and you’ll be able to use faster shutter speed and smaller aperture (which as we’ve seen help with sharpness) but you’ll suffer by increasing the noise of your shots. Depending upon your camera (and how large you want to enlarge your images) you can probably get away with using ISO of up to 400 (or even 800 on some cameras) without too much noise but for pin sharp images keep it as low as possible). Read more on ISO.

6. Image Stabilisation

Many cameras and lenses are now being released with different forms of image stabilisation (IS) which won’t eliminate camera shake - but can definitely help reduce its impact. I find that using IS lenses that it will give me an extra two or three stops (ie I can use slower shutter speeds but 2-3 stops) when hand holding my camera. Keep in mind that IS helps with camera movement but not subject movement as it allows you to use slower shutter speeds (not good for moving subjects).

7. Focus

Perhaps the most obvious technique to work on when aiming for sharp lenses is focussing. Most of us use ‘Auto Focussing’ with our cameras but don’t assume that the camera will always get it right. Always visually check what part of the image is in focus before hitting the shutter and if it’s not right try again or switch to manual focus mode. This is particularly important if you’re shooting with a large aperture (small depth of field) where even being slightly out can result in your subject being noticeably out of focus.

8. Good lenses

This one is for DSLR owners - if you have the budget for it invest in good quality lenses as they can have a major impact upon the sharpness of your images. For example shortly after buying my DSLR I was in the market for a everyday zoom lens that would give me the ability to have both wide (ish) and telephoto zoom capabilities. I bought a Canon EF 28-135mm lens. It was a good lens (and reasonably priced) but it wasn’t as sharp as some of my other lenses. A few months later I borrowed a Canon EF 24-105mm ‘L series’ (the professional series of lenses from Canon) lens from a friend and was amazed by the difference in sharpness between the lenses. While the first lens was good for what I paid for it I ended up going for an upgrade and the new lens is now almost permanently attached to my camera.

9. Get your Eyes Checked

Since I was young I’ve worn glasses but in recent years I’ve been a little slack in getting my eyes checked. Recently I got them tested for the first time in a number of years and was surprised to find that they’d deteriorated significantly. Getting new glasses improved a number of areas of my life, one of which was my photography. Also connected with this is checking the ‘diopter’ on your camera (if it has one. The diopter is a little adjustment that you can make to how your viewfinder works - it’s particularly useful for people with poor eye sight - it’s usually a little wheel next to your viewfinder.

10. Clean equipment

Recently my wife and I went on a window cleaning frenzy at our place. Over the previous months the grime on our windows had gradually built up without us really noticing it. When we did clean them though we were amazed at how much more light got through and how much better the view outside was. The same can be true for your camera’s lens. Keep it clean and you’ll eliminate the smudges, dust and grime that can impact your shots. Similarly - a clean image sensor is a wonderful thing if you have a DSLR as getting dust on it can produce noticeable blotches in your end images.

11. Lens Sweet Spot

Lenses have spots in their aperture ranges that are sharper than others. In many cases this ’sweet spot’ is one or two stops from the maximum aperture. So instead of shooting with your lens wide open (ie where the numbers are smallest) pull it back a stop or two and you might find you get a little more clarity in your shots.

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