Steve's Photography Tips: Finding Your Focal Length

Continuing with Steve’s Photography Tips, let’s talk a little about focal length and how it might affect your photos.

Strictly speaking, focal length is the distance between the lens and the image sensor or film for your camera, measured in millimeters. For example, a 50mm lens means that the distance between the lens and the sensor is 50mm. Makes sense, right? Not nearly as tricky as that whole aperture thing. Just don’t go get a metric ruler to measure the length of your lens, because that isn’t quite the same. It has more to do with where the actual lens is inside the whole apparatus that we call the lens. So you can’t just look at a lens and tell the focal length based on the physical length of the lens. Instead, you would have to read the number(s) handily printed on the side of the lens.

The focal length can be changed in a couple of ways. First, you can use a zoom lens, which will be listed by the minimum and maximum focal lengths, such as 18-55mm. There again, when you are zoomed in close, the focal length is 55mm, or when you are zoomed back as far as you can go, the focal length is 18mm. So with a zoom lens, you can change the focal length by zooming in or out. The other way to change the focal length is to use a different lens with a different focal length, having different lenses for different purposes.

Also, the focal length affects the field of view for the photo you are taking. The shorter the focal length, the wider the field of view. The longer the focal length, the narrower the field of view. So a 200mm lens would only see a small part of what a 20mm lens would see. That is another one of those inverse things like the aperture number versus the aperture opening size. But if you know much at all about photography, you probably already know that. A larger focal length will get you much closer to your subject than a smaller focal length, and that’s why all those professional sports photographers have such big lenses on their cameras, so that their photos look like they were right out there on the field with the athletes. So instead of field of view, you are probably more used to thinking about it as “How close does it look like I am to my subject?” Same thing.

Examples

Okay, time for some photo examples, just to clear things up even more. The following photos were taken in the den of our house (which sometimes doubles as a makeshift photo studio, by the way). All of the photos were taken from the same location, since I had the camera on a tripod that never moved. The only thing that changes between the photos is the camera lens. I used the piano in our den as the main subject, just because I thought it would work well. And I used the Canon EOS 60D camera, just in case you were wondering. The camera was about six feet back from the piano, in case you were wondering. Click each photo to see it a little larger and clearer, by the way.

28-105mm Zoom Lens

Let’s start with a zoom lens, zoomed all the way in. As stated above, this one goes from 28mm to 105mm. Not the most powerful zoom there is, but it is a good “general” lens that works for all sorts of situations. As you can see here, it is zoomed in on the music on the piano. This lens has also worked pretty well for some of Jaylin’s sports games, such as football and basketball. If you want to zoom in closer from farther away, you would need a longer focal length, maybe even up to 400mm, depending on what you are going for. It might be important to note here that the longer the focal length, the more sensitive the camera is to the slightest movement. That’s why those pro sports photographers with the big lenses often have a monopod to help steady the camera.

This photo is from the other end of the 28-105mm lens, which is obviously 28mm, if the “28mm” at the lower right of the photo didn’t give it away. The field of view is much wider here than the 105mm photo, so that you can see much more of the piano than just the one piece of sheet music. As stated in the previous paragraph, this makes a pretty good “general” lens if you like to have some average photos and some zoomed in photos. Just don’t expect to get anything really wide. But more on that in a few photos.

50mm Prime

For this photo, I switched to the 50mm prime lens, which as you might expect gives you something in between 28mm and 105mm. Because that just makes sense.  A prime lens is a lens that has a fixed focal length. Or in other words, it doesn’t zoom. If you want to zoom, you do it the old-fashioned way - by using your feet. One advantage to prime lenses is that they usually have a larger maximum aperture, which gives a shallower depth of field. This was discussed a bit in the Understanding Aperture post, by the way. Another advantage is that prime lenses are usually smaller and lighter, since they don’t have as many elements or moving parts as a zoom lens. And they are often sharper focusing lenses, too. The drawback to this particular lens is that 50mm is a pretty narrow field of view for what I would consider general shooting. You have to make sure you have enough distance between you and your subject to get all that you want in the frame. For my Olympus camera, I also have a 25mm prime lens, which I like much better for general shots.

10-20mm Wide Angle

Next up is a 10-20mm wide angle lens. This lens begins to show more of how the field of view can increase with a decrease in focal length. At the 20mm position, the lens gives a nice view of the piano and the wall behind it. And if I had angled the camera down just a bit, all of the piano and all of the bench could have fit into the frame. As you can see, there are some slight differences between this and the 28mm photo above. But let’s zoom out just a bit.

To me, at the 10mm setting, this lens really begins to shine. Look how much you can get into the frame as compared to the 105mm photo above. Or even compared to the 28mm photo. And remember, the camera was only about 6’ away from the piano here. You can even see Laura sitting on the couch over at the left, and the door to the hall over at the right.

There are some slight complications of using a wide lens such as this. As you can see here, the lamp next to the piano creates some blown highlights, or in other words some really bright areas where you can’t see any details. You might be able to reduce that brightness using the Raw file, but I didn’t attempt that here. Another option is to shoot bracketed exposures to create an HDR image. But I didn’t do that here because that isn’t the point of this discussion. Just know that you are much more likely to get a light source, or even the sun, in your frame when you use a wider field of view.

8mm Fisheye

And here to finish off our examples is an 8mm fisheye lens, the widest lens that I have. And here, you can see from floor to ceiling, and from one side wall to another. Laura is still there on the couch, and even one of the blades of the ceiling fan is overhead. The field of view isn’t quite 180 degrees here, but it is getting pretty close. I had to make sure I was behind the camera, so that I didn’t get into the frame as well.

This photo also shows one of the effects of wide angle lenses, and that is the distortion that they can cause. It is somewhat apparent in the 10mm view above, but it is even more obvious here. It can be a little tricky when you are composing your shot, as here is is rather obvious that I wasn’t in the center of the room, since the bending lines aren’t symmetrical. Some people don’t like the bending lines at all, and others like for them to be absolutely symmetrical. I don’t mind either one, as long as the lack of symmetry isn’t too distracting. You can use some programs such as Photoshop to adjust the perspective and straighten some of the lines, but in doing so you lose the edges of your image as well. And I rather like the weird bending lines sometimes, just for something different. Just something to think about if you are considering using a wide angle lens.

Which One Is Best?

All of that brings up the question that I get asked from time to time, “Which type of lens is best?” And to me, the answer is pretty simple: All of them.

Which focal length and which type of lens you should use depends entirely on what type of photo you are wanting to take. For sports, a long focal length is better. For landscapes, you might prefer a short focal length to get as much as you can in the frame. For portraits, you might prefer a prime that will have a shallow depth of field to get you more bokeh. It really is all up to you.

Personally, I find that I go through phases. Sometimes, I like the wide angle shots, even as wide as a fisheye view. Other times, I like a shallow depth of field, to separate my subject from the background. At times I will rely just on one lens exclusively for a while, until I am ready to move on to something different.

Of course the drawback is that lenses cost money. And having more lenses costs more money. The lenses I have are the result of years of buying one at a time when I can. There’s no way I could buy all of those at once. And still afford to eat.

Perhaps the best thing is to get a lens that you can afford, and that you think you will enjoy for a while. Use it, and then start saving for something else you might want to try. Also, there are at least one or two lens rental places out there. I never have used one, but it might be a good way to try something before you buy it, just to see if it is what you really want to do.

So get out there and find the right focal length for you. And don’t be afraid to change your mind from time to time, too.

Be sure to watch for more from Steve’s Photography Tips in the near future!