Let’s Focus on Sharp Photos!
Please Note: I intend to keep things as simple as possible here. If there are enough requests to go into more detail about some of the items in the article below that are in Bold Type then another blog may follow this one. (WWW below means What Went Wrong!)
When we look at a photograph that is a bit “blurred” the usual response is to say, ‘Oh, it’s out of focus.’ Then we put it down to experience and probably decide not to get too close to the subject next time. After all modern cameras, digital or camera-phones etc, are so full of automatic features that we expect the pictures we take to be sharp and correctly exposed for most lighting conditions. Subjects much further away than about one metre are usually in focus. In most situations the camera can cope because the focal length of the lens fitted is quite short, say around 8mm to 25mm, and the depth of field in this case will be very wide. Depth of field is the distance between the nearest and farthest camera subjects which can be brought into acceptable focus in the camera, i.e. where there once would have been a film, called the film plane. However, depth of field does not depend only on the focal length of the lens, but also upon the aperture and the distance of the subject. (It also depends upon something called the circle of confusion but I don’t intend discussing that here!).
The aperture of the camera is a little bit like the pupil of your eye, the black hole in the centre of your iris. It opens up and closes down according to whether the light is bright or dim. Automatic cameras can detect the brightness, like your eyes, and adjust the aperture size. A bigger depth of field occurs when the camera aperture is very small and when the subject is at a distance from the camera. So we can more or less guarantee a “nice sharp photo” when the light is bright (camera selects a small aperture) and the subject is say over two metres away - Right? Well, No – not always, because there’s one more thing that produces blurred pictures and it has nothing to do with focussing the lens! It’s the shutter speed.
Please Note: I intend to keep things as simple as possible here. If there are enough requests to go into more detail about some of the items in the article below that are in Bold Type then another blog may follow this one. (WWW below means What Went Wrong!)
When we look at a photograph that is a bit “blurred” the usual response is to say, ‘Oh, it’s out of focus.’ Then we put it down to experience and probably decide not to get too close to the subject next time. After all modern cameras, digital or camera-phones etc, are so full of automatic features that we expect the pictures we take to be sharp and correctly exposed for most lighting conditions. Subjects much further away than about one metre are usually in focus. In most situations the camera can cope because the focal length of the lens fitted is quite short, say around 8mm to 25mm, and the depth of field in this case will be very wide. Depth of field is the distance between the nearest and farthest camera subjects which can be brought into acceptable focus in the camera, i.e. where there once would have been a film, called the film plane. However, depth of field does not depend only on the focal length of the lens, but also upon the aperture and the distance of the subject. (It also depends upon something called the circle of confusion but I don’t intend discussing that here!).
The aperture of the camera is a little bit like the pupil of your eye, the black hole in the centre of your iris. It opens up and closes down according to whether the light is bright or dim. Automatic cameras can detect the brightness, like your eyes, and adjust the aperture size. A bigger depth of field occurs when the camera aperture is very small and when the subject is at a distance from the camera. So we can more or less guarantee a “nice sharp photo” when the light is bright (camera selects a small aperture) and the subject is say over two metres away - Right? Well, No – not always, because there’s one more thing that produces blurred pictures and it has nothing to do with focussing the lens! It’s the shutter speed.
WWW: This magnificent "white" lion picture is spoiled by the cage of course but even more so by the camera focussing on the cage bars and not the lion!
The shutter speed is like a hidden eyelid that will “blink”, i.e. open and close, at different speeds to let different amounts of light in and it works in conjunction with the aperture on most automatic cameras. If you stare for a long time at something without blinking then obviously you let more light in. Meanwhile, if the light changes while you stare, say the Sun goes behind a cloud, your iris will change the size of the pupil to allow in the correct amount of light for you to see something comfortably. In usual daylight conditions your camera selects both shutter speed and aperture to give a correctly exposed picture – automatically! The shutter speed could range from around 1/60 of a second to around 1/500 or even faster, but if the shutter speed is too slow or if you move the camera then you will often get a blurred picture. “Too slow” means below around 1/60 of a second for most people to hold steady, and this is when your camera will automatically selects the built-in flash to provide enough light. If you switch off the flash for some reason, say in a public place where flash is forbidden, then often a red signal is shown on your camera and it might even tell you what shutter speed is needed in the dimmer conditions. Often it says 1/20 or 1/15 or 1/8 of a second, or even slower such as ½ i.e. half a second. In which case it is best to either a) forget it or b) use a tripod to hold the camera steady. If you hold your breath and lean your arm on something like a wall, a chair back, or a convenient person then it may come out reasonably sharp for speeds like 1/15 or 1/8; and well done if it does work!
What Went Wrong ie WWW is followed by a brief explanation in the picture captions. So WWR will be What Went Right!
WWW: The autofocus of the camera concentrated on the cage bars because it was nearer the lens.
| I know it's better that the animals are not kept in cages, but where there is a breeding programme to assist the re-introduction of endangered species, perhaps we can allow it? It can be educational for children as well of course. | 
WWW: Again the automatic focussing system "sees" the bars first and fixes the focus there, the monkeys look blurred.
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WWR: Now the bars are blurred but the monkey is sharper, because the camera was focussed on another nearby object first and then the picture was taken. See text for more details.
WWR: What a contrast! Focussed correctly plus the background is uncluttered and out of focus to add to the drama of the subject! Photo by Sue's News.
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WWW: The camera went too close for the depth of field. Maybe a close-up lens would help or a smaller aperture for a bigger depth of field.
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 WWR: Wow! Beautiful pin-sharp close-up of this impressively imperious eagle! Photo by Sue's News. So what’s left? Well the most obvious thing left of course is the automatic focussing found on most modern cameras and is usually indicated by a sort of click sound, together with a green or yellow rectangle on the camera screen, when you press the shutter button half-way down. This tells you that the camera has now focussed the lens on the subject enclosed by that green rectangle, and it works for the majority of the pictures you take. But, and it’s a Big But, for a lot of close-up type of pictures the object that you want to be crisp and sharp, like a butterfly or a flower, is not always in the place on the screen where the rectangle appears. So you may need to “fool” the camera by making sure that the green rectangle plus “focus-click” operate on the flower etc with the first pressure, then move the camera slightly to re-frame the shot how you require it. Then complete the picture by pressing the shutter button all the way down. Another example of when auto-focus does not work for you is things like animals in a zoo, or pictures through a window and you wind up with a clear and sharp picture of the cage bars or a mark on the window glass! Again you have to fool your camera, but this time by getting the green “focussed” rectangle on another object nearby at roughly the same distance from the camera as the animal etc, and then carefully still holding the button half-way down turn back to the animal and click the button all the way down to take its picture. Glass windows can be a bit difficult, particularly if they are not perfectly clean as the camera wants to focus on the dirty specks. If there is a distant objects i.e landscapes setting on the camera use that to over-ride the auto. If the windows are steamed up as well, e.g. car ferry, train, car you might have to just give up on it! | 
WWR: Cute (I know!) Red squirrel sharp and obviously in its pinewood habitat - background suitably "blurred".
WWR: Fabulous, breathtakingly sharp close-ups of butterflies: a purple emperor above and a painted lady below. Photos by Sue's News.
WWW: The shutter speed is too slow to capture the in-flight action of these tree bumble bees, though some think that this is good because it illustrates the rapid wing action. What do you think?
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There are occasions when the photographer may wish to deliberately include a blurred background for close-ups or for a moving subject, e.g. racing cars, galloping horses, birds in flight. On these occasions you deliberately select a large aperture, fast or slow shutter speed and/or move the camera while taking the picture. But that’s a discussion for another day…
Some links: Sue's News Photos and
G J Griffiths books.
WWR: What can you say? Shutter speed fast enough to capture a sharp portrait of the owls' face, but slow enough to show enough fluttering of its wing feathers and portray the movement! Amazing shot! Photo by Sue's News.
WWR: In-flight action shot of a gull showing the importance of a fast shutter speed to freeze the bird's movement. Photo by Sue's News.
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