Friday, June 3, 2011
EXPLANATION OF LENS AND THEIR FOCAL LENGTHS
I have received some questions about which lens someone should buy. My advice is pretty consistent. There are two factors that should influence your choice of lens. One is what are you going to be photographing with it? The other is what can you afford? If you're someone who wants to shoot mostly landscapes that would mean you could buy a slower lens. The speed of the lens refers to the widest lens opening or F stop (for those people who wanted to know what F6 & F9 discussed in the previous post).
Lenses are always described with their speed, e.g., a 50mm f2.8 lens or a 70-200mm f4 zoom. The 2.8 and 4 are the widest openings for those two lenses. The faster the lens, the more light that can potentially come through it. Faster lenses let you photograph more easily at lower light levels, allows faster shutter speeds and slower ISO settings, makes autofocusing easier and faster for the camera and provides a brighter view finder in a D-SLR. In a zoom lens, the speed of the lens may change with the focal length (called variable aperture) such as a 80-400 with a 4.5 - 5.6 zoom. That means that at 80 the lens speed is 4.5 but it loses a stop speed at 400 at 5.6.
However, faster lens are more expensive, sometimes considerably more. This does not mean that they offer higher quality results. This is a very important thing to consider. In fact, if two high quality lenses are compared the less expensive, slower lens may beat the faster more expensive lens because it is more difficult for designers to maintain quality as the f/stop increases at the wide end. That said, the lowest priced variable apertures zoom lenses will generally not match the quality of the higher priced zooms or single focal length lenses.
Faster lenses are also generally much heavier. Many photographers have welcomed high quality ISO digital settings because they are now able to use slower lenses in the field.
If you are landscape photographer, you can save money by purchasing a slower lens and a tripod. You can shoot in lower light and still get great images. Needing the speed to stop action is obviously not an issue unless you are lucky enough to find a mountain that actually moves. (If you do please email me directions to it). On the other hand, if you are shooting wildlife, sports or your kids playing, you will want every bit of speed you can afford to insure you can "freeze" the action and avoid a blurry subject. You can also, in a "limited" fashion, use flash to help shoot in low light. We will discuss that on another day.
Today, we will be comparing five different lenses. A 50 mm, a wide zoom 12-24, a moderate zoom 17-55, a moderate telephoto 70-200 and a long telephoto 80-400. I've kept the setting on the camera the same for all the images. The post production was minimal; a little straightening of the horizon, (it was early morning before my coffee), sharpening and minimal noise reduction. I had to adjust exposure on some slightly due to their wider focal lengths including more of the bright sky.
The images are all of the view of the golf course from my backyard. You're getting bored of seeing this golf course, aren't you lol? But it's close and at 7AM, that is a good thing. All lenses are the Nikon brand, the only brand I own. When you find a brand that you trust, you tend not to stray (although there are some very good lenses made by Tamron and Sigma and you might save a few dollars). Please do not comment or email me thinking I am dissing your brand, whatever it may be. I am just telling you about the brand I know and trust. If you are getting images that satisfy you with a lens made by Hasbro, then by all means keep using it.
The first image was taken with the 50mm. This is sometimes referred to as a normal view. They are great lenses for portraiture and some close up work although they cannot replace a good macro lens.
Next is the12-24 lens set at 12. You can see how much more is included in the image. This can be good or a bad thing. You do need to watch out for distortion on each side of the image almost a bending in effect. I use this lens for some landscapes and during wedding receptions. Images taken during the reception can be fun and include lots of the guests dancing from a different perspective. You can also see that there is something on the grass but it is a little small to know what it is for sure.
Next is the 70-200 2.8 lens. It's one of my favorite lenses and it's also a versatile lens. I use it for portraiture, wildlife, intimate landscapes and during the wedding ceremony in low light; especially in low light when a flash is not allowed.
Now we come to the 80-400 lens. It's a little slower but if you're shooting at a high ISO in bright sunlight, it will perform really well for you. It's a really good inexpensive (I use the term loosely) 400 length zoom and a great lens for wildlife. You should always use your legs to get as close as you can then use the zoom to be selective. The one caveat to getting closer with your feet is safety, not only yours but also the animals. If you're in a national park and you decide you want your wife to take a picture of you feeding Yogi the bear, then all bets are off. That is when Darwin's theory of survival comes into play. So remember, I am not saying to shake Yogi or Smokey's hand. In this image it is quite easy to see that we have been seeing the golf courses maintenance staff at work.
The last lens is one I use a lot, it's my 17-55 2.8 zoom. I use this for environmental portraiture, some nature, some wildlife (when I am close enough to the subject) and it's really good for candid street photography, especially when you master shooting from your hip. This was shot at 17mm.
So we have a real simple comparison of five different focal lengths lenses. If anyone would like me to explore any particular lens in a little more in depth, please just comment on which lens it might be.
If people would like to submit their own images for a critique, I would be willing to have a day where I critique a few images. Let me know!!