Basic Photography | When and Why Do You Need Fast Lens?

© 2011 Wazari Wazir | Mother and Son at Kinokuniya Book Store | 50mm | f/1.8 | 1/125 | ISO 1000

Before we talk about when and why do you need a fast lens, lets get to know what is fast lens for those of you who doesn’t know about it. Basically “Fast Lens” refer to the lens that have big aperture at its maximum aperture. Usually any lens that have its maximum aperture which start at f/2.8 and below is consider a fast lens. The reason that a lens with a big maximum aperture is referred to as fast is that it lets more light in and therefore you can use faster shutter speeds even when there might not be much light around. It also make the focusing faster even in a dimly lit room.

Normally lens with big aperture are very-very expensive, for the picture above I use 50mm f/1.4 lens but the price difference between 50mm f1.4 and 50mm f1.2 is very huge, in fact for that price you can get yourself a new semi pro body camera, it’s that expensive. Some people  might be wondering, what’s the benefit of using fast lens? The huge benefit is that, it allowed you to use fast shutter speed especially if you like to shoot under low light condition like inside the building like the picture above where I took the shot in my favorite Kinokuniya bookstore in Suria KLCC shopping mall. The other benefit is that, usually fast lens have better quality glass and produce much richer color and contrast compared to the similar focal length but with smaller aperture.

When do you need fast lens? You need to use fast lens when you shoot in low light area and when flash photography in prohibited, especially indoor sports photography, you can’t use flash there and you need to use fast shutter speed in order to freeze the action. Yes off-course you can increase the ISO so that you can use fast shutter speed but increasing the ISO will make you picture become too noisy, lack contrast and saturation and that’s why indoor sports photographer like to use lens with aperture f/2.8 or larger when shooting indoor sports photography, by using this aperture they don’t have to push the ISO too high in order to use fast shutter speed. No matter how advanced the camera at High ISO, the best ISO is still at its lowest.

Take for an example my picture above, I’ve to use ISO 1000 to allowed me taking that shot at shutter speed of 1/125 with my 50mm f1/4 lens but I use f1/8 for that picture. The reason that I don’t use f/1.4 is that, the depth of field is too shallow, if I was not too careful handholding my camera, I will get a blurry picture, so in order to minimize that effect, I decided to set the aperture at f/1.8. I wish I cam use much faster shutter speed but n order to do so I’ve to increase the ISO and my picture will be too noisy then, so I decided to stick at ISO 1000.

If on the other hand, if  I can shoot this same picture with 50mm f/1.2 lens which is quite heavy and expensive, I can use much Lower ISO like maybe ISO 800 0r lower (ISO 500-400) with the same shutter speed and get better clean shot with minimal grain or digital noise, and usually when there is less grain or noise the contrast will be hight and as a result much more pleasant looking picture to the eyes.

Back to the question above, do you need a fast lens? Well, only you can answer that, if you are landscape photographer where most of the time you like to shoot with a tripod, you really don’t need a fast lens, because most of the times, you will be using small aperture and much longer exposure and you don’t have to worry about camera shake because you are shooting on tripod for most of the times. If you like to shoot portrait inside the studio with lighting all over the place, you really don’t need to have fast lens because you hardly use aperture f/2.8 or below in the studio.

But here the “catch”, if you concern about the quality of your image, whether you like to shoot with large aperture or not, fast lens is the only answer. The built quality of the lens and the quality of the glass is so much better than the cheaper lens at the same focal length and that’s why most landscape, architectural or studio photographers like to use fast lens in their work even though they hardly use that big aperture.

If you like travel photography, investing in a fast lens is a must because most of the times your shooting condition will vary, indoors and outdoors and most place especially inside the monastery, temple or mosque, they don’t allowed flash photography and you can’t use tripod also, so the only way to take good indoor shot is by having a fast lens. Most travel photographers don’t like to use flash in their photography even though some place might allowed it but the reason why they don’t like to use flash is that, they don’t want to attract other people attention, they want to take a picture discreetly especially candid moment like a small kids playing in the dark alley, if they were to use flash, for sure it will attract the attention of the neighborhood. If you like travel photography, investing in a fast lens is a must.

Fast lens is very expensive and it is not for every photographers depending on their needs and interest but it is good to have fast lens in your camera bag because it will be ready for all kind of occasions and will open doors for more photographic opportunity.