We are often faced with a mini challenge of sorts, trying to figure out the right lens to shoot with. It’s not about the right camera, as you may have understood by now, but about the right lens – the optical piece of equipment that sits in front of our camera.
The whole reason that we shoot with a DSLR or mirrorless camera is so that we can choose the right lens for the job. Often making that decision becomes a headache.
Remember, while I do keep saying the right lens, what we are dealing here essentially is a mixture of the right focal length and right aperture. I will come to a detailed explanation shortly.
Let’s just start this discussion by asking a simple question – “What is/are the parameter(s) for selecting the right lens?” As you will realize no doubt, there are more than one.
The right lens is often governed by a number of parameters. Our photographic vision is, certainly one of the most important ones. If you are looking to capture an ultra-wide-angle view of the terrace garden, with the setting sun and the stunning hues of the golden hour as the background then an ultra-wide angle lens is definitely what you need.
If on the other hand, you are looking to capture your 10-year old son taking his first equestrian lessons then you need a wide angle lens with a fast maximum aperture.
Why? Because in the first instance, you need a breathtaking panoramic view. A lens which gives you an up-close tight (crop) view will not suffice. You need to be able to capture the vastness of that scenic view for the viewer. An ultra-wide angle lens allows you to do this.
In the second instance, you need a lens that can give you a feel of the moments when your son gets on the horse, settles into the saddle and starts to get a feel of the animal. His surprise, apprehensions and probably joy mixed with fear when he starts to ride on his own would be best captured if you have a way to zoom in and make a tighter crop.
Filling the Frame
The right focal length allows you to fill the frame. Filling the frame is a cardinal requirement for good photography and one of the 7 composition techniques you should know.
You will always be told how important it is to walk up to your subject, to zoom with your legs and fill the frame. Leaving vast empty spaces around the main subject is never a good approach if you are looking for some eyeballs.
The human eye just keeps searching for something interesting and when it does not find anything in that vast emptiness, it moves on to the next picture.
The right lens also depends on the kind of subject that you are trying to photograph. A fast sporting action would require you to shoot at a faster shutter speed to freeze the moment, such as a striker in soccer taking a shot at the goal.
Again not all sports warrant the same approach and neither does all the action from the same sport. If it were a long distance event and you want to capture the athletes passing you as they lap around the circuit, you will need to be able to pan with them using a slow shutter speed.
I have talked about panning and how to set up your camera to do that elsewhere on this website, so I will not repeat myself here.
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The amount of ambient light available will have a say in the lens that you end up using. As you are aware, quality of light is more important than the quantity.
The adage “more the better” does not apply in photography, at least when it comes to light. That is why you make better images in the shade than under direct sunlight.
That being said, the quantity of light does have a bearing on the photos especially when you put the aperture of the lens you are using in the mix.
The less is the quantity of light, the faster should be the maximum aperture of the lens you use. Let’s say you are shooting about 10 minutes past the golden hour. The sun is below the horizon but there is ample amount of light in the sky.
Unfortunately, however, that’s not enough to make a good portrait image if you are using something like a f/3.5 – 5.6 kit lens. You need something like an f/2 or faster aperture.
A faster lens will give you the liberty to make a good exposure even in low light. You may have to increase the ISO a little bit, but that would be a much smaller number than if you had been shooting at the telephoto end of a kit lens (at around f/5.6 aperture).
A Mix of the Right Focal Length and Aperture
I mentioned earlier that the right lens is often the ‘mixture of the right focal length and the right aperture’. I shall now explain why.
Normally, a lens can be picked for any number of reasons, image stabilization, sharpness, lack of distortion, build quality, brand; but the two primary reasons a lens is picked up is for its maximum aperture and focal length.
Aperture allows a photographer to control the depth of field in his photos. The wider the aperture (smaller f-stop) the shallower the depth of field that he can achieve with the lens. I have already substantiated the importance of right focal length here. So, now to explain the importance of aperture.
The Right Aperture
In the above low light scenario, the fact that you had a f/1.8 lens to shoot with made it possible to get away with a good exposure even without increasing the ISO too much. Every time you increase the aperture (use a smaller f-stop) you double the amount of light that reaches the sensor.
A kit lens will only open to about f/5.6 when used at its telephoto zoom end. That’s three full stops slower than a portrait lens of f/1.8 aperture. That would mean you have to either slow down the shutter speed by three stops and inducing blur or increasing the ISO number inducing noise. A f/1.8 lens is a much better proposition.
Depth of field
I briefly mentioned above this parameter. Faster lenses have a wider maximum aperture. This gives you the critical advantage of being able to shoot with a shallow depth of field.
Shallow depth of field helps you to isolate your subject from the background. Thus in the above f/1.8 example, not only do you get to make a good exposure in low light, but you also get to blur the background.
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Often you may also need to shoot to get a bigger depth of field. Most lenses will give you an overall increase in sharpness when you stop down by one or two stops. If you stop them down further lens diffraction sets in. But there are some lenses which offer crisp sharpness across most of the practical f-stops.