In photography it’s all about the light. Without light we can take no photos, it’s that simple. It doesn’t matter if you are using studio light, natural light, or inside ambient light. Photography is all about the light. I know, I know, you also need something to be taking photos of. But, and trust me on this, the best subject in the world will not show up in your photo without light.
This of course leads the discussion directly to lenses. Lenses are classified in two main ways. By their focal length, and by their light gathering ability. There are of course other factors such as how many elements they contain, how well the glass is coated to reduce flare and chromatic aberration.Focal length of course relates to the size of the lens, such as 50mm or 300mm.But, the real determination of a lens is it’s speed. The amount of light that a lens can gather. This measured by the maximum aperture, the amount the lens diaphragm opens when the camera shutter is pressed. The wider the aperture, the more light that can enter. In an entirely perverse manner, the smaller the number or f stop, the wider the aperture.
Most folks with DSLR cameras start with the “kit” lenses. These are called kit lenses because they are the lower priced lenses normally sold together with the camera body as a kit. There are of course other lenses sold with cameras, especially the higher end bodies. But most of us probably started off with the older 18-55mm zoom lenses with variable apertures. The lenses whose aperture might start at f3.5 but ends at a f5.6, fairly slow for a 55mm lens. The problem is that lenses made with a constant aperture are of only two flavors. Your choices are either a prime lens, one with only one focal length, or if you prefer a zoom lens, expensive.
Although I own and use prime lenses, I find a zoom lens to be a better choice for me when out in the field or at the beach. As most readers know, I photograph horses. the lens I have found most versatile for that is my 50-200mm zoom. The problem being, my 50-200mm is a variable aperture zoom. The more I thought about it, the more I convinced myself that I wanted a better zoom lens in that focal length range.
To get a zoom range in that focal length I had three choices. Since I use Pentax cameras I could have waited and went with the new Pentax 70-200mm f2.8, except that lens has a $2299.95 price tag. Ouch. And being brand new to the market, not yet available used. Another choice was the Sigma 70-200mm f2.8, but that lens has been discontinued for Pentax K mount. It also has a motor driven focusing mechanism (as opposed to camera driven) which can occasionally malfunction. Since I would need to buy this lens used, my warranty options in case of a failure would be limited. My third option was the Tamron 70-200mm f2.8. Although it is considered to have a slightly slower auto focus speed than the Sigma, and to be slightly nosier when focusing, the Tamron was also considered to be the sharper of the two.
Thus my choice was made. A used Tamron has joined my stable for nature and equine photography. It’s constant f2.8 will allow me to capture the scene in lower light, and of course it can be stopped down to a smaller aperture if I want to. Now I just need to get used to it’s 3.24 lbs weight. Thankfully it came with it’s own tripod collar. Stay tuned for more test shots soon.