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12 Things To Remember Choosing The Best Lens For Digital Camera
Choosing the right lens for your camera is not an easy task. In our article we will talk about the lens characteristics, and those in particular, which require the most of our attention.
1. Focal Length
It depends on focal length how many objects we can place in the shot. The
smaller the focal length is (for example, 18 mm) the more objects you
can display in the image. But perspective distortion also depends on
the focal length. If it is rather small, then the objects could become distorted. It is commonly agreed, that the focal length
which is close to what we see in the surrounding world is about 50 mm.
So, all of the lenses are divided into two classes: wide-angle lenses
(short-focus lenses) and long-focus lenses.
2. Wide-angle Lenses
Wide-angle lens is in fact any lens with the focal length of less than
50 mm. If you shoot with such lens, you can include a lot of objects
into the picture. At the edges and in the foreground the image can
become stretched a bit. As a rule, such lenses are used in the
reportage genre, as well as in the landscape and architecture shooting.
3. Long-focus Lenses
Long-focus lenses are needed when you cannot come closer to the object
of shooting. Nature and sports are usually photographed with the help
of long-focus lenses. But they are also used for portrait shots,
because at the long focus length you will be able to get rid of
perspective distortion, receiving a nice Depth Of Field (DOF).
Also it is important to remember, that in some digital cameras the
focal length will be higher than the value, indicated on
the lens. It is explained by the fact, that the focal length value is indicated for the full-frame cameras only. But some digital
cameras use the cropped matrix, which gave its name to the "crop
factor" term. In other words, crop factor is the value that shows how
much the camera matrix is smaller than the one of the standard filming frame (35 mm).
So,
in order to estimate the exact focal length of the lens, you need to
multiply the value of the focal length by the crop factor of your
camera. For example, the crop factor for Canon 40D is 1.6. So, if you
use a 50 mm lens with that camera, the exact focal length would be 80
mm (50 mm x 1.6).
4. Maximum Diaphragm
It is the maximum possible value of diaphragm for the lens. For the
zoom-lenses a range of the maximum possible diaphragm values is often
indicated. For example, f/3.5-5.6 for the lens with the focal length of 18-105 mm means that the maximum diaphragm for 18 mm will be f/3.5, while for 105 mm it equals f/5.6.
As you know, the smaller the diaphragm is, the less the DOF is, and
the more blur you have in the background. So maximum image quality is shown by all of the lenses at the average values of diaphragm f:8 -
f:16.
5. Focal Ratio or f-number
It is the value of maximum diaphragm of the lens and optics quality.
The lower the f-number is (for example, f/1.4), the more light is transmitted to the film or sensor, so you can shoot in bad light conditions.
Also, high quality glass and special high transparent coating reduces lens over-reflections. That is why large aperture lenses are always considered of best quality, being quite expensive as well.
6. Manual and Autofocus
Now absolute majority of lenses have autofocus function. Therefore,
there are a lot of lenses of the old production series, which are still
of the great interest among the photographers, even despite the lack of
autofocus. The key is in the lens optical characteristics - they all
have their individual effects and bokeh.
7. Minimal Focusing Distance
It is the minimal distance to the object of shooting, needed for the
lens to set the right focus. One more thing is also important - the
distance is measured from the camera matrix, and you won't find this
mark on the body of your camera.
8. Focusing Structure
There are two types of focusing structure - external and internal.
During the external focusing structure some parts of the lens may slide
in and out. Internal focusing means that external parts of the lens do
not move during focusing process. Therefore, you can hold the lens
itself during shooting, and use a polarizing filter, because the front
element of the lens is not rotating.
9. Thread Diameter for Filters
This characteristics is indicated on the lens and shows us the diameter of filters that can be used with that lens.
10. Weight
Please pay special attention to this. The weight of optics is varied
from 400 to 800 grams. Of course, you can find the light 50 mm lenses
of 200 grams, and heavy telephoto lenses of more than 1500 grams.
The weight by itself is not giving you any preference, but it's always
better to choose a light lens for shooting. Most of the photographers
agree, that at the end of the shooting day it feels really hard for a
man to hold a camera (luckily if there's only one camera) with the
heavy lens. But it's probably twice as hard for a girl to carry the
same equipment.
Also, you may find it really handy to hold your camera in one hand, while you work with the external flash in another.
11. System of Image Stabilization
Image stabilization is a very popular and nice function, which will
never be unnecessary. Its main task is to compensate the slightest bits
of lens trembling during shooting (for example, when you take a shot at
the long focal length of 200 mm and more) so as to get a clear picture.
Also,
image stabilization allows you taking pictures at long shutter speed,
what is particularly essential in the conditions of bad illumination.
12. Picture and Bokeh
As we mentioned above, each lens has its own unique picture, which can
be described only by subjective feelings (whether it is sharp or not,
for example). Also lenses differ with their bokeh. It is a special effect, which is created by the lens in the blurring
area. The more the diaphragm is opened, the more visible effect you
have. And remember, that each type of the lens has its own individual
bokeh, but if you want to experiment you can make your own bokeh shape.
Knowledge about the lens characteristics will help you choose the right
optics for your specific photographic needs. But before buying the
lens, pay attention to the possible optical defects, which are
described in our article "What You Should Know About Optical Defects Of
An Image".
Just try to take the most of your lens and its effects to make your shot look artistic and individual and share it in our photo contests!
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