Thursday, March 27, 2008

Why Use An SLR?

photographySecond in a series that gently explains digital photography and makes helpful recommendations.

In the last article I established at length that there is no good reason, other than making large prints, to get a digital camera with more than 6 megapixels. In fact I recommended this same figure for both point'n'shoot compact cameras and their larger more "pro" cousins, digital SLRs. So why consider an SLR at all? That's what I'll elaborate on in this article.

Actually, I've already begun. In the previous instalment I revealed that the SLR sensor is ten times as large as that in compact digital cameras, and that this means ten times more information is captured from the light that hits it. Since photography is all about the light, this is a good thing. A very good thing.

So too I mentioned that compacts are limited in that they have a single fixed lens. This is inevitably a zoom, allowing the user to choose a focal length in order to frame a shot creatively. For example the highly-regarded Fujifilm Finepix F30 has the equivalent of a 36-108mm lens, presenting a slightly wide to moderate telephoto aspect. The ability to capture light is also very reasonable for a zoom, from f/2.8 at the wide end to f/5.0 at the telephoto.

But what an SLR allows you to do is change the lens to suit your style of shooting, or the requirements of a given session. Need a fish-eye for funky effects? A rectilinear 15mm for very wide vistas? A 500mm extreme telephoto? All of these are available.

Furthermore, SLR lenses may be had in much faster builds, depending on the focal length. In the "normal" range f/1.4 is not unheard of -- that's two whole stops faster than f/2.8. The lens lets in four times the light and this makes it reasonable to shoot indoors in restricted lighting, without a flash or tripod.

One of the most important advantages of an SLR with a fast lens is control over depth of field. A wide open lens at f/1.4 has a very thin depth of field. That is, only a thin slice through the focal plane is in focus. Exactly how thin depends on focal length and subject distance, but it is quite possible to have a person's eyes in focus but their nose blurred! While this is not always desired it is sometimes flattering, and results (if properly used) in those sorts of model shots point'n'shoot users are always striving for. But they can't achieve the look they want, because at portrait focal lengths their lenses are several stops too slow.

Control of depth of field is critical for image composition for one simple reason: photography is three-dimensional! I'll write more on that later.

Though compact digitals may these days have dozens of menu options, an SLR is unbeatable for tweakability and ease of use. There are far more buttons dedicated to specific tasks, cutting down time spent in annoying menus. This is due to the fact that there is simply more physical room on an SLR. The ergonomics are far more suited to serious photography, by which I mean photography where the photographer is in control. So too the range of possible uses are extended through add-on accessories -- flash, remote release, bellows, macro adapters, etc., etc. The range of applications is extensive, from dentistry to astronomy.

Compacts are made very cheaply and can break after a short fall... believe me, I know! Though much heavier, an SLR can generally survive all sorts of physical abuse, and might still be in operation decades hence. The overall build quality of SLRs is very good in this world of disposable electronic gadgets.

To be fair we should consider the negatives associated with SLRs. First, they are bigger and heavier. Second they are more expensive -- not necessarily too much more so to start, but once you get the bug for lenses it's game over! Third, they are more complicated and require a deeper appreciation of how to use them as photographic tools. (One might consider this a good thing.) And lastly, they are not nearly as stealthy as compacts. They tend to make more noise, require more space, and get more attention, which is not necessarily what you want on a police line, in a war zone, or even when taking candid shots in the street.

In the last couple of years DSLRs have become irresistible thanks to decreasing prices and technology that has caught up with film quality. In my next article I'll make a purchase recommendation.


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