Disclaimer: This is not a scientific article, but rather an attempt to give a basic understanding of how the different focal lengths impact the image.
Let's talk about focal lengths and why they matter. After all, the first thing we refer to, when talking about lenses, is the focal length. Do we need an 18mm, a 35mm, or a 85mm lens? And is one focal length enough, or should we rather get a zoom lens, covering a range of focal lengths? The 18-55mm, maybe?
Does it even really matter? I mean, we can get a 50mm lens, and then move back, when we need more within the frame, and closer when we need to be more focused on the subject, right?
Well, the obvious answer is that, no. it isn't always this simple. We might be in a tight space, and still be needing to include a lot within the image. In that case a lens with a long focal length, such as the XF 90mm f/2, might not be very helpful. Or even the XF 50mm f/2. If we can't move far enough back, to include everything within the frame, then obviously we need a wider focal length. A 23mm maybe, or even 16mm is needed in tight spaces.
Or let's say that we're out in the nature, and want to take some photos of birds, or even some more exciting, such as a wolf, bear, or lion. I know for sure that I wouldn't want to get too close. In those cases, where we would like to keep our distance, a longer focal length, such as the XF 100-400mm zoom lens, is a much better option than, say, any of the 35mm lenses.
Now, this is probably obvious for most. The closer you need to get to people, the more wide the angle needs, if you need to include a lot in the frame. The further you need to be away, the longer the focal length needs to be, if you wish to fill the frame with the subject.
Keeping the distance - the effect of different focal lengths from the same distance
But that is not the only thing to consider, when considering focal lengths. The focal length you chooses also matters, when you are not confined by tight spaces or subjects you wish to keep your distance to. Having a wide angle lens will, as said include a lot in the frame, while having a long focal length will focus in on the subject. Let's take a look at how this works (all photos are shot at f/5.6):
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| John P shot with a 200mm focal length (6.7 degree angle of view) |
In the first set of shots, we are taking the photo at the same distance, but with different focal lengths. In the first shot above, we see our model, John P, being central in the frame, while not seeing a lot from his surroundings. Also, the background is rather blurred out, making it hard to see the details of it. This is caused by the compression of the long focal length, rather than the aperture being opened wide, which is another way of getting a blurry background.
What is this good for? Well, as can be seen, this really separates the subject from the background. Longer focal lengths do this, which makes them preferred by many portrait photographers. However, usually a shorter telephoto length, such as 85mm (56mm on the APS-C sensor) or 135mm (90mm on the APS-C sensor) are preferred over the 200mm, since lenses at this length tend to get long.
Lenses with focal lengths of 200mm or above are generally better used when you need to focus in on a subject, which is not reachable, such as wildlife animal, landscape photos with focus on the details, or sports photography. Within these fields of photography, the photographers are often using tripods to stabilize the lens, so the larger sizes of the lenses is less problematic.
Lenses with focal lengths of 200mm or above are generally better used when you need to focus in on a subject, which is not reachable, such as wildlife animal, landscape photos with focus on the details, or sports photography. Within these fields of photography, the photographers are often using tripods to stabilize the lens, so the larger sizes of the lenses is less problematic.
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| John P shot with a 135mm focal length (9.97 degree angle of view) |
Keep in mind that this image, which was shot with an Olympus Zuiko 135mm f/3.5 adapted to the Fujifilm X-T3 is equal to 202.5mm on a full frame camera. On an APS-C sensor camera, you would need a 90mm lens to get the same effect as a 135mm on a full frame camera. Using a 135mm lens on an APS-C camera will still give you the same areas of usage, as the ones described above. Just be aware that most 135mm lenses, which you can adapt to your Fujifilm camera, or another brand with an APS-C sensor, will be manual focus lenses, so that would prevent you from using them effectively for wildlife or sports photography.
Now we are really getting a sense of where John is. Obviously he doesn't take much space anymore, but if we would have had a person sitting here, we would still be able to get a full body photo of him, as well as getting a sense of the surroundings.
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| John P shot with a 55mm focal length (28.5 degree angle of view) |
Now we take a long jump from the 135mm to the 55mm focal length, and the changes are drastic. First, John P is only a small part of the larger image. Second, look at the background, it has become much more detailed. Remember, we are still taking the photo at the same distance, the focal length has just become that much wider. The effect is not only allowing us to see more of the surroundings, but it also makes the background less blurry. This is because the compression is that much less, when the focal length is less focused in.
At this focal length, which is roughly similar to 85mm on a full frame camera, we are generally dealing with portrait photography. Ironically this can be hard to see here, because our subject is that small compared.
This might make you wonder, because normally we see portraits with blurred out backgrounds, but that is not the case here. There are two reasons for this. 1) the distance between us and the subject, relative to the background, and 2) the closed down aperture. What can be hard to see here, is that the subject is halfway between us and the background. In order to give a more compressed background we either need to be more zoomed in on him - as we saw above, or we need to get closer to him. Another way to make the background blurry is of course to open the aperture more wide, which will make the depth of field in focus much more shallow.
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| John P shot with a 35mm focal length (44.2 degree angle of view) |
With the 35mm focal length, which is similar to 52mm on a full frame camera, we are moving in to more environmental photography. For portraits it's usually used for half- or full body portraits, just as it can be used for general purpose or street photography. You are still able to both isolate the subject, while still getting enough of the surroundings within the frame, to get a feeling of the place.
With the 23mm focal length (35mm on a full frame camera) we have entered the wide angle perspective. While this is only the beginning of the wide angle focal lengths, you still clearly see how these lengths are working. First, the subject disappears a bit in the frame, and much more emphasis is given to the environment. This is great for street photography or environmental portraits, where you want to include the story of the surroundings. It is important to focus on the composition though, since it's easy to loose focus on the subject, having him, her, or it disappearing within the surroundings. Of course, with John P here being so little, he basically is just a small detail of the overall image, but it helps us giving a sense of the importance.
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| John P shot with a 23mm focal length (63. degree angle of view) |
Notice how the background is in focus as well as the subject. This is because the wide angle of the lens makes the depth of field in focus being so wide, that basically everything is in focus. Note that the further we get away from the subject, the larger the depth of field will become, and since there is basically no compression at this focal length, any background out of focus area will have to be created by opening the aperture or getting very close to the subject.
Here we want to show John P with his truck, within the surroundings, so we get a sense of the place. Notice how much we see around him and the truck. The fence, the trees and the sky.
Here we begin to remove the surroundings, but we are not getting close enough that we completely remove any sense of it. We might have something in the back, which we still want to include, but only in order to give a sense of it.
Including or excluding the surroundings
Let's talk about how the focal length of the lens also helps to decide how much of the surroundings will be included. Do we want to show the subject within his/her/its environment, or do we want to show the subject alone without any idea of what is going on around us. Let's look at how we include more of the environment, the more wide we go with the lens, keeping the subject at the same size within the frame:
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| Shot at 18mm |
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| Shot at 23mm |
Here we still get a good sense of what is going on, though we see less of the surroundings, and what we see is more dominating. This is for example good if the trees in the background had been houses, and we only wanted to see John P's house. We zoom in a little, while not too much, so we see the subject and a little about him by allowing certain details of the surroundings within the frame.
Note how the background here is more blurred out than in our previous example with the 23mm focal length. This is because we have moved that much closer to the subject, so the distance between us and the background, relative to the subject, is much larger than before, and the depth of field in focus has become that much narrower.
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| Shot at 35mm |
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| Shot at 55mm |
Considering what you want to include in the photo, might direct your choice of focal length.
In the first photo we see the front of the truck almost overtaking the frame, dominating and seeming very broad.This is caused by the distortion of the wide angle, stretching the front of the truck out. But let's see what happens if we zoom in with a longer focal length.
Making the subject wide or narrow
Finally, wide angle lenses have a habit of distorting things. This can be used creatively, but also something to be aware of, when we are choosing our focal length. It can create drama, but also a comedic element to our photos. Let's look at how that can be done with these two shots:
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| The truck shot with 18mm |
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| Truck shot with 55mm |
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