An Introduction To Focal Lengths for Photographers
When I bought the Sony a7R III, one of the first lenses that I bought was the 24-70mm f/2.8 G-Master zoom lens. One of the benefits of having a zoom lens (compared to a prime lens) is that you get to experiment with different focal lengths without having to change lenses.
Beyond convenience, I first only understood changing focal lengths as a way to adjust the composition in a photo. I would zoom in to focus on the details in a certain scene or (and more commonly) zoom out to photograph high-rise buildings in Downtown Los Angeles.
In this blog post, I’m going to be sharing information about focal lengths that I have learned in my experience with travel, street, and lifestyle photography.
Minimum Focusing Distance and Focal Lengths
Camera lenses will have different minimum focusing distances (the minimum distance between the lens and the subject necessary to get the subject in focus) based on their focal lengths. For example, the Sigma 35mm f/1.4 DG DN ART lens has a minimum focusing distance of 30cm (or 11.8 in.). The longer Sigma 85mm f/1.4 DG DN ART lens has a minimum focusing distance of 85cm (33.5 in.) As the focal lengths get longer, so will the minimum focusing distance. As a result, you’ll have to stand further away from your subject if you want to get it in focus.
When you’re working with a model and you want to get a full body shot with a longer focal length, you need to make sure that you have plenty of space to fulfill that minimum focusing distance and still be able to give creative direction.
In this beach lifestyle photoshoot with fashion model Erla Garcia, I had plenty of space to back up and capture full body photos with the Sigma 85mm ART lens.
Focal Lengths and Image Compression
Going a bit further with minimum focusing distance, you’ll notice a difference in image compression between different focal lengths because of where you’re standing in relation to your subject - not necessarily because of the focal length itself. The longer the focal length, the further away you will likely be standing from your subject in order to achieve focus, and as a result, the more compressed the background will be. When the background is more compressed, it will look a lot bigger and closer up in the photo.
When I’m doing lifestyle photography with a model and I want to show more of the environment, I’m going to opt for a wider lens like the Sigma 35mm lens where there is a more even balance between the model and the background, compared to an 85mm lens.
The photos on the left were taken with the Sigma 35mm lens and the photos on the right were taken with the 85mm lens. The models were standing in the same spot for these photos, but you can see the difference in the background between these two lenses and how much bigger they appear in the photos.
Cropping Photos vs. Getting A Longer Focal Length
If you have a wide angle lens and you want the final photo to focus on a particular subject in the frame, you might feel inclined to simply crop the photo. For example, you photograph a model wearing a watch and you want a close-up photo of the watch, but you just crop that photo to only include the watch.
While there isn’t anything inherently wrong with cropping a photo a little bit, it’s important to know that doing so will decrease the quality of the photo because you’re losing megapixels compared to using a longer focal length, which would capture the desired subject in full resolution to begin with. Alternatively, you can use a teleconverter, but this will also result in a potential decrease in image quality.
The photos below were taken with two different lenses - the Sony 24-70mm f/2.8 G-Master lens and the Sigma 85mm f/1.4 DG DN ART lens respectively. If I had taken the wide angle photo and cropped it in to fit the composition of the 85mm lens, the image would have decreased in image quality had I exported in full resolution.
How Do Focal Lengths Affect Shutter Speed Settings
When first starting street photography at night, I paid attention to the exposure triangle (shutter speed, aperture, and ISO), but I didn’t think much about how the focal length of the lens I was using would affect that - specifically shutter speed. The longer the focal length, the more you might want to increase the shutter speed in order to compensate.
One thing that I used to hear a lot was your shutter speed should be double the focal length. For example, if you are using a 35mm lens, then your shutter speed should be 1/70 sec. or faster. This is a good starting point, but there are a lot of other factors to consider (Does your lens have image stabilization? Are you able to brace yourself on a solid surface that will keep your hands steady? Are you trying to get a long exposure shot?)
There isn’t one right answer to decide what your shutter speed should be in comparison to your focal length because the results you are trying to get in a photo might differ from what another photographer wants to achieve. But I think it’s important to understand this correlation between focal lengths and shutter speed just as base knowledge.
The photo below was taken with the Sony 24-70mm f/2.8 G-Master lens at 24mm, but with a shutter speed of 1.6 seconds. By using a tripod, I’m able to eliminate shake and capture a sharp image without having to worry about the shutter speed rule.
Focal Lengths and Portrait Photography
If you do portrait photography, you’ll notice how shorter focal lengths will distort a person’s features compared to longer focal lengths. The wider focal lengths create more of a fisheye lens effect compared to wider focal lengths that will also compress the background.
Just as I previously mentioned, there’s not a right or wrong answer when it comes to which focal length you should use for portrait photography. My best advice is to experiment with different focal lengths and see if there is a certain style that you gravitate towards. I personally prefer to use my 85mm lens for most portraits - especially if I’m going to be photographing models close up. However, if I’m trying to get a full body shot, I might opt for the 35mm lens since I’ll have a shorter minimum focusing distance and can give direction to the model while shooting more easily. It’s good to try and get a variety of different focal lengths with the same photoshoot if you have the option.
In the examples below, I photographed DeAnza and Austin with a 35mm lens (on the left) and an 85mm lens (on the right). The 85mm photos cause less distortion in their faces compared to the 85mm lens.
What Is My Favorite Focal Length?
As of the time of writing this, it might come as no surprise that my favorite focal length for all of my photography is 85mm. I have experimented with focal lengths ranging from 10mm to 200mm.
As someone who does a mix of travel, street, and lifestyle photography, I find myself reaching for the Sigma 85mm prime lens more often than anything else. Part of the reason has to do with the lens being fairly small and that I try to shoot with prime lenses more than zoom lenses. But the focal length of the 85mm lens has a lot of attributes that help achieve the kind of photos I prefer to take.
When working with models, the 85mm offers less distortion compared to wider focal lengths, but I also don’t have to back up so far away from the model where I would struggle to give direction. Keep in mind that I mainly shoot outdoors, so I will usually have plenty of space to back up. If you photograph in a cramped space, you might find the 85mm lens to be doable, but a bit more difficult to work with.
As a street photographer, the 85mm lens is a great length to capture close-up candid moments without disturbing others. It’s also great for capturing specific details in the city.
Final Words
I hope this blog post provided a helpful introduction into how focal lengths can affect your photography and possibly help you determine what focal length you might want to try when starting your photography journey.
While zoom lenses can be very expensive compared to prime lenses, experimenting with lenses of different focal lengths can help you figure out which focal lengths you’re most comfortable with and which fit your style the best.
