PHOTOGRAPHER’S JOURNEY.com

There are several things to consider before buying a new lens for your digital SLR and one in particular may surprise you.

First, the more commonly understood issues:

• It’s generally understood by most digital SLR photographers that a “faster” lens - with a wider aperture such as f1.2, f2.8, etc. - is a good thing. It allows more light to enter through the lens “faster”, thereby making exposures in lower light situations easier. So that’s a basic, and a big thing you need to decide.
• Image quality is critical, obviously. But how do you know how good the lens is? Research on the Internet can get you started. A web site I find particularly effective for reviews of lenses is PhotoZone.
• Usability is important. I own a nice 28-135mm Canon lens with image stabilization. It’s a good lens in a lot of ways and very good for just “walking around.” But I get annoyed every time I point the lens downward because it expands the zoom outward. What’s more, there’s a looseness at the end of the zoom where I can feel some play. It doesn’t affect image quality, but it is a bit annoying. So obviously, these are things that you can only study in a camera store where they are willing to let you play with it for a bit.
• If you are buying a prime lens you should know their limitations (read my article on primes here). But they are an excellent investment for certain shooting situations and although they have fallen out of popularity a bit in recent years as zooms have improved in quality, primes still deliver generally sharper images and “faster” glass.
• Image stabilization is worth it - at least in any lens with a focal length above about 85mm. In my Canon 70-200mm f2.8, the image stabilization buys me the equivalent of about three extra f-stops! In plain English, I can hold a shot steady as if I were opening the aperture and letting three additional f-stops of light in. To me - having way too much caffeine in my system ordinarily - that is simply priceless!
• Speed and sound of the autofocus. Most modern lenses made by Nikon and Canon have fast-focusing, quiet autofocus lenses. Older lenses are not advanced. I recently picked up my old Nikon N70 35mm camera with an attached 70-210mm zoom. I couldn’t believe how slow and clunky - and NOISY - the autofocus felt. So if you’re buying an older lens, be aware that the newer ones are all generally better in this regard.
• Consider manual focus. What??? Did I just write that??? Yep. Sometimes I surprise even myself. The fact is autofocus lenses are awesome for most photography. But some very old Nikkor lenses without autofocus can deliver remarkable quality on a modern digital camera. And obviously, certain situations are not that dependent on autofocus, landscape photography being one of them (although it sometimes helps). Believe it or not, I still use autofocus for some things. Especially macro photography where I find the autofocus just a bit too heavy-handed for my tastes. The point is, it’s certainly nice to have autofocus, and it’s always better to have it as at least an option, but photographers survived very well before it any you may be able to also.

Now for the surprise (helluva dramatic buildup, isn’t it?):

Especially if you are buying yourself a telephoto lens, try to find out the number of aperture blades the lens has.

Huh?

Aperture blades are the little blades that close and open in a circle - thereby allowing light to go through. The wider the aperture the more light gets through. But when you use a wide aperture, the depth-of-field also gets narrower, causing the background and/or foreground to get soft. This softness is called bokeh (which I read somewhere is the Japanese word for blurry).

A lens with more aperture blades creates a more perfect circle, and therefore a much softer bokeh. Make sense? So very good lenses with a beautiful bokeh usually have eight blades. Some lesser lenses have seven or even six blades.

Does this matter on a lens with a wider angle of view? Yes, although not as much. Generally bokeh is not such a critical factor in wide-angle lenses which are typically not used for portraits or other similar shots. Nevertheless, there are situations where even with a wide-angle, you will want a soft background in your shot. So it’s worth considering the number of aperture blades even in a wide-angle lens.

Now, here’s the catch: finding out how many blades a lens has isn’t easy. I found one web site that lists aperture blades for some modern Canon lenses, and I assume it’s accurate but haven’t verified its claims. I didn’t find anything quite so helpful on the Nikon front or for other manufacturers, but the information is out there and some careful Google digging can probably turn it up. If not, and at the very least, ask the representative in the camera store.

Nothing makes me happier than a nice bokeh.

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