Long lens – types and choices

Nikkor  AF-S DX NIKKOR 55-300mm f/4.5-5.6G
at 165 mm, ISO 100, f/10, 1/100 s

My last blog post was about testing a variety of zoom lenses to hopefully end up buying one.

This post is my attempt to explain my decision-making to hopefully help others with their own choices.

As I understand it, there are two types of long lenses, zoom and prime lenses. Zoom lenses will cover a range of focal lengths, whereas prime lenses will have one focal length.

Zoom lenses may vary their widest aperture according to the focal length, or have a constant aperture. The latter allows you to zoom in and out as much as you like without changing exposure - one less thing to worry about. Another factor to consider is the widest possible aperture. The wider the aperture, more light is allowed to come in, making it possible to take good pictures in situation where light is dim and/or the subject is moving. Lens that open up to a wide aperture are sometimes refereed to as “fast”.

For example, my late Nikon 55-200mm f/4-5.6G had an aperture that varies between 4 (at 55 mm) to 5.6 (at 200 mm), and that is pretty standard for this kind of consumer lens that cost below 500 U$. It is good for taking pictures of still subjects when there is a lot of light, or with a tripod when there is a little less light, but it is considered “slow”. The Nikon 70-200 mm 2.8G , on the other hand, not only has constant aperture, but it is also “faster”. This type of lens is better for sports photography, low light situations and moving objects such as flying birds etc. It also costs four times as much.

Months ago, I could not understand why some flickr members could get perfectly in-focus shots of flying birds whereas I could not, at the same focal length. Not only they have faster lenses, but also, very likely, better constructed lenses.

Note that a f/3.5-5.6 can gather more light at the wide end (where you can use f/3.5) then a constant aperture f/4 lens - but if you need to zoom in suddenly you have to change the ISO or shutter speed to compensate for your changing aperture.

I do not know of any disadvantage of having a fast zoom with constant aperture, and I would have gotten one if I could afford one. Among the choices I had, however, price, users' reviews, and whether there is a promotion on the lens or not were the most decisive factors.

And this is the lens I chose: Nikon AF-S DX NIKKOR 55-300mm f/4.5-5.6G . Why? It had good reviews and I found one refurbished for a little less than the regular price. On the downside, it came with 3 month warranty, in stead of the regular 4 years Nikon offers. I may regret this move later, but with a child in college and some recent unexpected expenses, I was not ready to pay much for a lens.

Why did I not chose a Tamrom? Well, first I could not get a good deal on any of the lenses I had tested. Second, the one I was aiming for more strongly, the 70-300 mm, was apparently underexposing the pictures, leading the camera's exposure algorithm to up the ISO more than it would be expected under the light situations. When I looked at the exposure information on my photos from the zoo, I first though that I had done something wrong, but when I went look at consumers' evaluations, I found out that other photographers also came across the same problem.

Nikkor  AF-S DX NIKKOR 55-300mm f/4.5-5.6G
at 98 mm, ISO 800, f/4.5 1/500 s