Nikon and Canon 50mm f1.8 Prime Lens

For around $100, you can buy a great lens for low light situations. It's a 50mm f1.8 prime lens and is available for both Nikon and Canon.

The 1.8 maximum aperture allows a ton of light to get to your digital sensor and makes it possible to get a good exposure for low light sitations such as dawn, dusk, and indoors. The aperture is essentially the hole in your lens. Think of the number like a fraction, so 1.8 is like 1/1.8. The smaller the number on the bottom of the fraction, the larger it is. For example, if you have a 28-70mm f4-5.6 lens, the biggest your aperture can get is f4 at 28mm and f5.6 at 70mm. F1.8 allows in more than double the amount of light than F4.

There is a side effect of having a large aperture, which is the depth of field. The larger the aperture (the lower the number), the more narrow your depth of field is. Depth of field is how much of the picture is blurry from the point where you've focused it. This is great to bring the focus to your subject and is often used for portraits, images of birds, and macros.

Also, keep in mind that your ISO plays a part in how your picture is exposed. Typically in low light, even with your aperture set at f1.8, you'll need to increase your ISO number. On my camera, the maximum ISO is 1600, so I'll set the camera to that, use aperture priority, and manually set the aperture to f1.8. That way, the camera will figure out the best shutter speed to use. You'll need a shutter speed of at least 1/80th of a second to shoot a sharp image with your 50mm lens (since there's a 1.5x modifier when dealing with DX style DSLR cameras.)

Dealing with aperture, shutter speeds, and ISO to get a good exposure is often confusing at first. Once you figure it out though, it really opens up your possibilities. To recap, for low light, make the f-stop or aperture use the smallest number possible, the highest ISO possible, and your shutter speed as slow as you can without compromising sharpness. For this lens on my Nikon D50, the settings then would be f1.8, 1/80th second or faster, ISO 1600. Modify it from there to your particular situation.

For another example of dealing with these three exposure components, see my review on a 500mm Sigma Telephoto lens.

Tags: camera lens, low light photography, photography, prime lens