Wednesday, 6 January 2010

Tips for Sharper Shotz (1)

What’s apparent from pictures submitted for publication is that many photographers can’t get shots sharp. A surprisingly large percentage are just not up to the task. With technology getting better by the day, why aren’t pictures razor sharp? Here I look at the root causes of unsharp shots and suggest some basic remedies to make your photos as sharp as a tack. Most pictures exist either as a monument to the skills of the photographer or they appear as something less than special. Aside from poor composition, what usually lets the shot down is a lack of image sharpness. The reasons for not getting photos pin-sharp are both technical and creative. Many photographers add a blur or subject motion to a shot for creative reasons - and this is most effective, but it's not hard to spot pictures that are just plain unsharp through lack of technical skill or ignorance.

Not focused, or just blurred?
If the shot has a slight double image, then it’s blurred. This means that the subject has moved between the shot starting and finishing, which is why it shows double. If you are not a steady person, you’ll often see multiple fuzzy images where clearly there should only be one. More than likely a photo like this is actually focused, it’s just that your movement has weakened the apparent sharpness of the focused image.

If the photo is fuzzy all over (like the padlock in this example, click to enlarge) it’s plain out of focus. This is usually caused by the camera’s auto focus mechanism not latching on to the subject correctly. Either because the subject is moving too fast, there’s insufficient light (like the human eye, cameras need light so they can 'see' to focus) or because the technology is not up to the job.
This happens frequently despite the amazing technology at our fingertips. Now I’ve said this before, but I’ll repeat myself again, ‘just because technology is improving, it doesn’t mean we can stop thinking...’.
Marketing departments still apply the Kodak credo from decades ago: “...You take the pictures and we’ll do the rest...”. Providing that the shooting conditions are good, you should get acceptable results. But if the subject is moving too fast, is too far away, is insufficiently lit, or is masked by things like telephone lines, wires, vertical blinds, glass or even heat haze, things may not be as sharp as the brochures promised.

Minimum shutter speeds for sharp shots
Super wide-angle lenses (interiors): 1/25s
Wide-angle lenses (interiors, landscapes, people): 1/60s
35-75mm (standard portrait focal length settings): 1/125s
Medium telephoto lens: 1/250s+
Long telephoto lens setting (200mm+): 1/500s+
Minimum speeds for image stabilised lenses
Super wide-angle lenses (interiors): 1/4s
Wide-angle lenses (interiors, landscapes, people): 1/8s
35-75mm (standard portrait focal length settings): 1/15s
Medium telephoto lens: 1/30s
Long telephoto lens setting: 1/60s

Sharpness is controlled by shutter speed

The photographic bit that makes a shot sharp is the shutter. This is like a door. It opens to start the picture-making exposure bit and closes once sufficient light has got into the camera to make a nice, bright shot. Unfortunately what tends to ruin the result is that, in-between the start and the finish of this process, the subject, you, the lens, or all three might move, so you get a blurred result.
OK, the easy answer is to make the shutter go quicker so no blurring occurs, right? Good idea, but remember that you need light to make a shot. If the shutter fires too quickly (most D-SLR cameras can go as fast as 1/4000s), not enough light gets onto the sensor to make the shot and the photo comes out dark.

Subject clarity is also controlled by depth of field
So, the speed of the shutter regulates light passing into the camera, and it also influences sharpness. What else helps make the photo ‘come out’? It’s the aperture or f-number.
The aperture is that bit in the lens that opens and closes just like the iris in your eye. Like the shutter, this aperture action controls the amount of light that reaches the digital sensor, thus it a significant impact on whether the resulting photo is light enough, or too dark. Aside from letting more or less light travel into the camera, different apertures create different depths of field. In layman’s English this means that the larger your aperture number (a smaller physical hole in the iris), the more 'stuff' you get sharp around the bit that the lens has focused on. It’s hard to put into words.

Much better to see it illustrated (cont'd).

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