Sunday, May 14, 2006

Improving sharpness - photo tips #2

Recently I was asked how to improve the sharpness of images. As with most things there are a few easy answers and there's the complicated way of explaining it all too. Defining and improving sharpness is a science. For this article I'm going to try to keep to the straightforward stuff.

The first thing you should appreciate is that sharpness in a photograph is not easy to define - it's a perception dependent on numerous factors. These include; contrast, colour balance, definition, level of detail, grain or noise, level of blur across the image and difference in the levels of blur between adjacent areas etc.

There are five main things that affect sharpness: the quality of the lens, the qualities of the sensor or film, the nature of the subject being photographed, focus and movement of the camera in relation to the subject.

The single greatest cause of unsharp photographs is camera shake. Camera shake may be virtually imperceptible when you take a picture but it can really make your images look softer than they should - which is the reason camera manufacturers put so much effort into building cameras that are smooth and don't vibrate when you take a shot - using devices such as mirror bounce suppression mechanisms. Many professional cameras allow you to lock the mirror up before taking the shot. Minimising camera shake is also the reason why tripods are so popular with professional photographers and the proliferation of anti-shake systems in cameras and lenses. Yes, an awful amount has been and continues to be invested in finding ways to keep the camera 'still' in relation to the subject.

When hand holding your camera to take a picture, support the camera properly from underneath using the heel of your hand, gently squeeze the shutter button while breathing smoothly out, don't jerk the camera abruptly away after taking the shot and choose as high a shutter speed as you can (watch for camera shake warning symbols in your camera display - generally as a rule of thumb you need to use a shutter speed matching or higher than the focal length of your lens eg 1/100 for 100mm lens, 1/250 for a 200mm lens etc)

An image will also look sharper if texture on the subject is clearly defined by the lighting - in fact the quality of the light plays a huge role in the how sharp we perceive an image to be. Strong colours that contrast with each other will also give an image a sharper look than subdued pastel colours.

Contrast is absolutely key to our perception of sharpness. In fact image manipulation software uses increased contrast between pixels on the edges between light and dark areas as the main means of sharpening pictures.

When it comes to sharpening images using software you do have to watch out for oversharpening. As a photographer working for printed publications I do not sharpen my images before submitting them. Each printer will have their own optimal sharpening settings, dependent on another vast set of factors ranging from the printing process to the type of paper, inks etc. This brings me to a bit more advice. If you're hoping to sell your images commercially, save your original image file without applying any sharpening and if you shoot JPEGS in camera, turn off the sharpening feature. Remember you can always sharpen an image but you cannot undo sharpening once applied without seriously damaging the quality of the original image.

I hope you find these tips useful. Please let me know. By the way when I save an image for the web in Photoshop, with the longest side having a pixel size of between 500-800, I usually set the radius to 0.3 and sharpen between 120 and 150 percent.

All the best,


PS If you fancy reading more here's a link to an index of my most popular articles
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