Outdoor Photography. Chiz Dakin
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Название: Outdoor Photography
Автор: Chiz Dakin
Издательство: Ingram
Жанр: Спорт, фитнес
isbn: 9781849658690
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Exposure and contrast
The accuracy of modern autofocus systems means that the camera usually gets the main subject sharp – although this does require you and the camera to agree on what the subject is! Depth of field, however, means that there’s rather more uncertainty about whether other things in the shot are or aren’t sharp.
There’s a very similar relationship between exposure and contrast. Just as the human eye adjusts focus so fast it gives us an impression of immense depth of field, it can adjust almost instantaneously between deep shadow and bright sunlight. Most of the time we don’t see shadows as completely black or bright objects as totally white. We might call them black or white but we can still see detail within them.
However, digital images (like film before them) can’t always stretch this far. If the brightness range (sometimes called tonal or dynamic range) of a scene is too great, the most a camera can do is aim somewhere in the middle.
Again, we’ll go into more detail on this later on. The key point now is that this is another way in which what the eye sees can be different from what the camera records. And understanding that fact is the start of being able to deal with it.
Aperture and shutter speed
Some cameras now have more exposure modes than you can shake a trekking pole at: Landscape mode, Portrait mode, Night portrait mode, Party mode, Alpine bivouac mode (OK, we made that last one up)… And yet the most important task that all of these modes perform is to determine how the camera sets aperture and shutter speed. You might never set these manually but they are still key to every shot.
Aperture just means ‘opening’. There has to be an opening to admit light into the camera, to reach the sensor (or film) which captures the image. Varying the size of that opening is one of two ways in which we control the amount of light admitted.
Graphical display of aperture on screen of a Nikon D3100 (Jon)
However, varying the aperture also affects depth of field. This is a bad thing if it gives us results we didn’t expect, but it becomes a very good thing when we can exploit it to get more control over our results.
Trowbarrow Quarry, Lancashire (Jon) There are deep shadows behind this brightly lit white tree and the dynamic range is very high. However, the shot simply would not work if detail was lost in the tree bark
Raindrop (Jon) Sometimes the camera can freeze movement the eye can’t follow (shutter speed 1/250 sec)
Aperture, as we’ve already indicated, plays a key role in determining depth of field. The combination of these two controls determines the total amount of light that gets through to the digital sensor.
Aperture dictates how wide the lens opening will be: shutter speed determines how long it stays open.
Shutter speed is principally important in determining how movement is captured in the photo. And movement, naturally, is another major way in which what you see can be very different from what you get. This is inevitable in a still picture! The eye sees movement, but the picture is a still.
Sometimes the camera can freeze movement that the eye can’t follow; sometimes movement appears as a blur. Extremely slow movements, like those of the stars, can also be recorded although they appear static to the eye. All of these results depend on shutter speed.
Sensitivity
Well, of course photographers should be sensitive: sensitive to light, to mood, to the fact that your partner’s getting cramp balanced on that pinnacle waiting for a shaft of light… But that’s not what we’re talking about here. We’re talking about what used to be called film speed and is now called ISO sensitivity.
This is a measure of how readily the sensor reacts to light. A low ISO sensitivity rating means relatively bright light is needed to get a decent image. With a higher ISO rating, you can shoot with much less light
In the (good?) old days, we couldn’t change this at will. When you loaded a roll of film you had to keep shooting at the same ISO setting till the film was finished. You might load a slow film which was great for shooting landscapes in bright sunlight, then next day you’d run into all sorts of problems trying to shoot mountain bike action in a shady forest.
Digital cameras have a much wider range of ISO sensitivity settings and you can change the setting shot by shot. This is immensely liberating. In fact it’s one of the best things about digital, and it doesn’t get half the credit it deserves.
Jack Bauer, Tour of Britain 2010 (Jon) High ISO allows action shots even in low light – notice the car headlights (ISO rating 800 and shutter speed 1/1600 sec)
With film, you really only had two controls to play with – aperture and shutter speed. If you wanted to set a small aperture to give good depth of field, you probably had to set a slow shutter speed to maintain the overall exposure level. Now you have the option to increase the ISO level as well, which may allow you to keep the shutter speed the same. This doesn’t just add to the possibilities, it multiplies them.
Most cameras now can vary the ISO automatically to suit the shooting situation. However, if you’re into taking control of the camera (and we repeat, it’s a good idea!), then just remember there are three fundamental controls, not just two.
Final Thoughts
At this point you could certainly be forgiven for feeling discouraged. On the other hand, perhaps you’re beginning to understand why some of your shots don’t turn out the way you expected. And understanding a problem is always a major part of correcting it.
The concept of ‘point and shoot’ is almost irresistible in its attraction, but the reality is always likely to be disappointing, at least until the day that the camera can actually read your mind. Even then, some people will still get better pictures than others, because you will still need to have a clear idea of what it is you want your picture to say and to show.
‘Point and shoot’ also suggests that photography is merely incidental to your outdoor activity, rather than being an integral part of it. Investing just a little more thought and time in your photography will bring much better results, not so much because the shots are better in any narrow technical sense but because you were more involved and had a clearer sense of what each shot was about.
There’s yet another argument. By paying attention to what you’re doing, you’ll get more good shots in the first place. Not only this, if a shot doesn’t quite work, you’ll probably have a much better idea what you need to do differently next time. And when you get a really great shot you’ll have much more idea what you did right. If you never go beyond ‘just’ point and shoot, you’ll never learn anything very much. And since cameras don’t learn either, your photos will never get much better.
Leaving everything up to the camera may give you a shot that ‘comes out’, at least most of the time. It’s less certain, however, that it will give you a shot that matches what you actually saw, let alone what you wanted to say. The key to this is understanding how cameras and lenses СКАЧАТЬ