Photography can be described as the art of capturing light. That means the quality of your lens is very important if not the most important part of your camera.
There are few important things to remember when choosing a lens.
A normal sensor is a camera that has a sensor size that is the same size as a full frame 35 mm film. The 35 mm film has been the standard of what a normal size film should be and that has been carried over to the digital world.
A smaller sensor has the effect of increasing the effective focal length of your lens, all things being equal. All this means is that the field of view on a smaller sensor would be the same as on a 35 mm sensor if the focal length were increased by a factor. The factor can be found in the manufacturers manual. In the case of a Nikon D3300, the crop factor is 1.5, and the sensor is an APS-C. So if you take a 24mm wide angle lens and multiply it by this number, the result is 36mm. This basically means that the 24mm lens on the crop sensor DX camera would behave more like a 36mm lens on a full-frame camera in terms of field of view.
One advantage of smaller sensors over the full frame is the ability to bring the lens closer to the image sensor. You can do this because a smaller sensor means a smaller reflecting mirror on DSLR cameras. When you can bring the lens closer, then you can also make the lens smaller and lighter.
You may be tempted to set your aperture to the smallest setting to capture as much depth of field (DOF) and for the most part, that will work fine. It is important to remember that after a certain aperture setting, the images that you capture will soften and will no longer be very sharp. This is due to diffraction. When choosing a lens, take the time to find out at what point the images soften up. You can use a Lens Diffraction Test Chart to test various aperture setting on your lens to find out.
What focal length do you need? Do you usually take distance or panoramic photographs? For distance, a telephoto lens might be better. For wide panoramic view or closed rooms, a wide angle lens is better. When deciding on the focal length, should you get a prime lens or a zoom lens?
A prime lens is a lens that has a fixed focal length. A telephoto lens is a prime lens with a focal length that can be used for distance. A zoom lens is a lens whose focal length can be adjusted to telephoto and wide angle. Because of the mechanic that goes into a zoom lens, the quality of photographs taken can be less when compared to a prime lens. Photos taken using a prime lens are usually sharper than those taken with a zoom lens. A prime lens can also have a wider range of aperture than a zoom lens.
Sometimes the different colors that move through a lens do not fall on the same place on the sensor. This can cause discoloration of the image, particularly on the edges. This is called chromatic aberration. This can be corrected in post production but you should not rely on this too much. It is better to take a good photograph from the get go.
Contrast and Sharpness
Contrast and sharpness are very subjective. So you should look for lenses with an acceptable level of sharpness and the best way to figure this out is to look at images taken with different lenses or to do your research.
Lens flare is those annoying circle of light that appears when you point your camera to bright objects, like the sun. To test your lens, attach it your camera and slowly pan towards a bright object and observe the image using your viewfinder. Wide angle lenses are more susceptible to lens flare than zoom or telephoto lenses.
Wide lenses are also more susceptible to this than zoom lenses. This can be seen on the edges of an image where straight lights might be distorted. And bent.
If you are not sure if the lens you chose is what you really want, then try to rent the lens first and give it a try.
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