Understanding Your Lens (Part 1)

As promised, I will start this series of tutorials on understanding how lenses work.

This first tutorial is a direct follow up to my previous post on why zoom lenses are better than prime lenses in real life photography. Here I will discuss how to creatively use a zoom lens to change perspective. I decided to tackle this technique first because most beginners do not understand this. I bet even those who claim to shoot with only prime lenses are ignorant about the concept and that is why they quickly dismiss the importance of cheap zoom lenses while boasting the superiority of their f1.2 prime.

In this lesson I will be using my Pentax K5 and my only lens, a Sigma 17-70, which you can get brand new for about $300. For the price, it’s totally worth it. My subject is Thomas the Tank Engine because the rain here in Brisbane is not allowing me to capture proper landscape shots. At any rate, the examples should give you an idea of how we might apply the concepts in real world shooting.

Without further ado, allow me to demonstrate the effects of varying focal lengths and how they affect composition.

Let’s have a look at how a nifty-fifty (50mm) lens might render a scene. Since I am using a camera with APS-C (crop) sensor, I will have to use a focal length of 35mm. This focal length is how your eyes would normally perceive the scenery. It’s what tells you that a particular spot and angle have the potential of creating a nice photograph. This is the perspective that your eyes send to your brain. Here’s the shot:


Apologies for the crappy shot but that is not the point. We could translate this to a real landscape scenario though. A typical theme goes something like this: Assume that Thomas is a huge rock that you have chosen as your foreground and the toy house is a mountain. With a 50mm lens, all you can do now is step foreward, back, left and right to properly position the foreground against the background. The problem here is that given the distance between the rock and the mountain there is not much you can do to change their relative sizes. In the example above, Thomas and the house look like they are of the same size. This makes the shot confusing because the viewer can’t concentrate on one subject. The relative significance of the background house is equivalent to the foreground Thomas. Boring and downright bad. If you only brought your nifty-fifty in this location, you are better off going home than waste your time and disk space.

Cheap zoom lens to the rescue. Supposing that the mountain isn’t really that good. It’s summer so it looks pale and generally uninteresting. However, the foreground rock has got some vibrant green mosses growing and some flowers. Naturally, you would want the foreground to dominate the frame while making sure that the background isn’t distracting. What does a photographer with a zoom lens got to do? Shoot WIDE. Here’s the same scene shot at 17mm:


Not quite a huge rock with flowers but you get the point. Let’s analyze this for a bit. For starters, I did NOT move the subjects at all but just changed the focal length and distance to foreground. Notice that in this shot, the size of Thomas relative to the FRAME, is almost the same as the first shot. But look at what happened to the background. The toy house now seems a lot farther and smaller. The exaggerated perspective created by the wide angle lens makes the foreground appear so much larger than it really is thus shifting the compositional balance to the front. This is the technique used by majority of landscape photographers where they prefer to use ultrawide lenses (12mm or wider) to create this wild perspective that hits you right in the face.

Before I continue, I would like to point out that the use of ultrawide lenses is easily abused by beginners. N00bs think that ultrawides allow them to include everything in the frame. BAD! Had I done that in my example, the frame would now have included pillows, TV, PS3 and cabinets…stuff that distract from the main subject. The main purpose of ultrawides is to allow you to approach your subject.

Back on topic. Now supposing that the situation is the opposite. The mountain is very beautiful. It’s showing wonderful autumn colors. The rock on the foreground however, is just ordinary but significant enough to be used to anchor the composition. The problem is that the mountain is far and a lake is in between your chosen foreground. There’s no way you can approach the mountain without walking several miles. You need to take the shot before the mist fades away. What can you do?

Lens compression to the rescue! Here’s the same setup shot at 70mm:


Again without rearranging the subjects I have managed to bring the background house “closer” and relatively bigger than my foreground. The size of Thomas relative to the FRAME has remained approximately the same and yet the house has now occupied the entire background. The roof has even disappeared from the frame. This is the effect of lens compression. It brings the background closer to the front and larger in the frame. The composition now has made the background significant.

This is the reason why I’m stuck with a general purpose lens. Since I shoot mostly landscape, I don’t really give a damn about wide apertures. Bokeh addiction is for n00bs who just got rid of their point-and-shoot. Take a look at that last shot because that was taken at f11. I could have used f5.6 to make the background disappear in a creamy blur. Ultrawides, on the other hand, have no lens compression at all. And 50mm prime? Limited and boring unless you have an endless supply of subjects to shoot with.

So let’s summarize what was covered:

1. Use a wide angle to emphasize the foreground and increase foreground to background distance.

2. Use longer focal lengths for lens compression to bring the background closer while maintaining the size of your foreground relative to the frame.

As I have said time and again, your cheap zoom lens is good enough for just about anything. I hope you find this post helpful.

Until next time.

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6 thoughts on “Understanding Your Lens (Part 1)”

  1. I don’t get all the ‘pros’ going on about how primes make you think about your composition. Like a zoom lens takes the responsibility of composing an interesting frame away from you…

  2. Being ultra pedantic, but it’s your positional change that changes the perspective and the spatial relationship between the objects, the lens changes the angle of view that allows you to see all of the objects. If you shoot from one position they all stay in the same place relative to each other regardless of the length of the lens.

    1. I can see what you mean now. And yes I did move a bit to make the foreground object size be the same with respect to the frame. You are correct.

  3. I don’t suppose you happen to have an easy way to understand using tilt and the schflumpugugmugmugm principle (with apologies to the esteemed Austrlan gentlemen who’s name I can’t spell) to move the plane of focus?

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