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Zooming In Don Bradbury offers more thoughts on the zoom factor in digital photography In the mini series on digital photography for computer users, I mentioned a few aspects of the zoom factor in lens design and usage. This feature deserves more comment because it’s possibly the second most important aspect of digital camera design after CCD resolution in the determination of image quality. “Surely not”, I hear you say; the quality of image would benefit more from a good fixed focal length lens performance per se, rather than any advantage the zoom factor might bring? Well, true, but these days the basic quality of virtually all digicam lenses can almost be accepted as a given in any sensible price bracket. That being so, the zoom factor assumes prime responsibility for ‘quality’ in the optical department. I’m not just talking actual zoom range here, although that obviously matters more than a little. It’s the ability to change perspective at all that’s so valuable. Well, that’s related to zoom range, isn’t it? Sure, but provided you go for at least a 3x zoom lens, the change from widest angle of acceptance to narrowest should provide all the perspective angles you need. Perspective
But I digress. We’re talking about perspective, and we’ll take it that all photographers know the advantage of filling the viewfinder with subject, not 50% extraneous matter. That way they don’t have to crop their images beyond reason, thereby losing the advantage of that expensive high resolution CCD they paid for. Acceptance angle, that’s the thing. If you zoom out your lens to reduce the angle of acceptance you can eliminate a lot of distracting stuff in your picture background when you have a portrait in mind, say, or a single feature in any essentially one-plane subject. So move way from such subjects and zoom out the lens; you’ll notice the difference, I promise. Differential focus As I’ve previously mentioned, throwing the background out of focus is not generally feasible to any great extent in digital photography because the CCD is so small in comparison with a film frame. So the lenses are invariably of short focal length, and that means huge depth of field. You can’t have it both ways, so just settle for improved perspective. That will also bring less distortion in full face shots, for example, and less of an ‘in your face’ stance from the photographer, so hated by children, ensuring that they feel less intimidated. Of course, if you are a keen indoor photographer, perhaps of architectural subjects, then the wider angle shots will be your prime requirement. Make sure you get a camera that starts its zoom range at better than 35mm equivalent on a 35mm camera. You might find that quite restrictive of your choice of gear, but it’s so important in cases where you simply cannot step back to include more subject. A lens with a 28mm equivalent acceptance angle is far better then, and there are still some to be had among digicams intended for amateurs, ie the broad mass of offerings without considering high-end stuff which brings interchangeable lenses. In conclusion If you are keen on the subject, don’t even think about a digital camera that doesn’t offer a decent zoom range. That will usually be 3x, perhaps a little more, but 3x should cover 95% of general subjects you’ll want to shoot. Selecting the actual range covered is up to you; make it match your principle subjects. Finally, do make use of the zoom feature. So many amateurs buy a zoomed lens and then never use it. That’s a shame because it’s one certain way to lift you above the ranks of the minions. You paid for it; use it!
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Now,
let me say straight away, we’re not talking simple image
magnification here, primarily. The ability to pull in a distant
object so as to fill the image area can, indeed, be most useful. In
fact, filling the picture with subject matter might even be ranked
in second place, ahead of all other digicam considerations after
resolution; it’s that important. For example, there’s no way I could
have taken the shot of an ancient cross, way above head level,
without using a zoom lens.