Techniques

Focal Length Affects Perspective by Todd Henson

Different focal lengths alter the perspective within the frame.

If you’re like me one of your first lenses was a zoom lens. These can be very useful and very convenient, giving you a lot of options in framing your shot. But you may have also fallen into one of the traps I did, lazily using a zoom lens to change the framing of the shot without thinking about how the different focal lengths affect the perspective within the frame.

Take a look at the photographs in this post. What they are intended to show is how different focal lengths alter the perspective within the frame. If we can learn this lesson zoom lenses become even more powerful tools, letting us more intentionally choose a focal length to alter how the image looks, how one element in the frame relates to another, instead of just choosing what to include and exclude from the frame.

Example: Wide Angle Focal Length

A wide angle focal length (22 mm) stretches out the perspective, pushing the foreground and background further apart.

Wide angle focal lengths, such as 22 mm, are often used to include more of the scene. But they also have a way of making an object that is close to the camera look very far away from an object in the distance. They stretch out the perspective.

Notice in the 22 mm image how small the distant waterfall is compared to the nearby waterfall.

Example: Normal Focal Length

A “normal” focal length (50 mm) more closely resembles the perspective our eyes see.

The 50 mm focal length has an effect very similar to what we see with our eyes. The perspective is very natural. That’s why focal lengths in this range are very popular for street photography.

Compare the 50 mm image to that of the 22 mm image. Notice how the waterfalls appear closer together in the 50 mm image. Also notice how the distant waterfall is larger than it was in the 22 mm image. The perspective is compressing.

Example: Telephoto Focal Length

A telephoto focal length (80 mm) compresses the scene, bringing the foreground and background closer together.

The 80 mm focal length is at the small end of the telephoto range. Telephoto focal lengths are often used to pick out details in a scene, allowing you to exclude non-essential elements and “zoom” in on the real subject. But they also allow us to compress the perspective.

Look closely at the 80 mm image. Notice how much closer together the waterfalls are when compared to the other images. Also notice the relative sizes of the waterfalls. They look close together and similar in size. This is the compression effect caused by a longer focal length.

Conclusion

Zoom lenses are great tools not only because they let us zoom in and out, quickly framing a shot, but because they include so many different focal lengths allowing us to alter the perspective within the image to suit our vision. Start thinking intentionally about how you want the scene to look.

Use focal lengths intentionally to create the perspective you envision.

Do you want your subject to look very large compared to the background? Then use a wide angle focal length and get close to your subject. This will make the subject look large in the frame and push the background further into the distance.

Do you want to make your subject look very close to the background, maybe a mountain or monument? Then use a telephoto focal length to compress the scene and make the background look much close to the subject.

Sometimes it’s very useful to zoom with your feet instead of with the zoom lens. Pick a focal length on the zoom lens to give you the desired perspective, then move with your feet to position yourself in the correct place to line up the subject with the background.

Now it’s your turn. Head out with a zoom lens, or with multiple prime lenses, and use the different focal lengths intentionally to alter the perspective within the image. Experiment, see what you can come up with, and have fun!


Choice of Aperture for a Clematis in the Garden by Todd Henson

One day while visiting my folks I was taken by the sight of this beautiful purple clematis flowering in their garden, hanging from a black metal trellis. Thankfully I had my camera with me that day, though only a single lens, the 16-35mm f/4. I don’t often use this lens for photographing flowers, but it seemed like a good time to start.

The photos in this post show 3 different angles I tried when photographing these lovely flowers. They weren’t all that high off the ground so I used the 35mm end of the zoom to focus in on the flower without too much distracting background. Then I experimented with framing and with aperture.

I most often use the 16-35mm when I’d like a lot of depth of field. Wide angle lenses are usually good at providing this. But when photographing these clematis I was more interested in a shallow depth of field. The widest aperture of this lens is f/4 and that ended up being the aperture I used for my favorite shots of this series. I did, however, create 2 images at f/8 to show you the difference this makes.

I held the lens physically close to the subject, probably very close to the minimum focusing distance of the lens. Even with an aperture of f/8 the background is nicely blurred, but it does still have some detail. Notice the difference when I opened the aperture one more stop to f/4, its widest setting. It throws the background even more out of focus, but it also throws some of the main flower out of focus.

There’s no right or wrong in these situations. It all depends on what look you are going for. For myself, I tend to prefer the images with a shallower depth of field. Which do you prefer?


Tips For Blurring Moving Water by Todd Henson

I’ve been asked in the past how to blur moving water from rivers and waterfalls in a photograph. It all comes down to shutter speed. The slower the shutter speed the more blur in the water. Below are a number of tips to help you do this. You don’t have to follow all of these tips to blur water. Pick whichever ones you’re able to use. Just realize some of them may not get the shutter speed as slow as you’d like. That’s when you may need to try the other tips.

Stabilize Your Camera

If you want a sharp image of everything but the water you’ll first need to stabilize your camera. The best way to do this is to put it on a good tripod. If you don’t have a tripod you can try resting the camera on something stable such as a stone wall or a large rock or tree. Just be careful not to let the camera drop.

Use a Remote Shutter Release or Self-Timer

To reduce the chance of introducing shake into the camera during the exposure it’s best not to press the shutter button with your finger to start the exposure. Two options for avoiding this are a remote shutter release, or setting the camera’s self-timer such that your exposure begins some number of seconds after you press the shutter button.

Using the self-timer is the least expensive option if your camera supports it, though you will lose a little flexibility in choosing exactly when to start the exposure.

There are two options for remote shutter releases: cable releases that attach to a special connector on your camera and wireless releases. At present I use a simple cable release that just presses and optionally locks the shutter. Some higher-end cable (and wireless) releases include intervalometer features which let you take a photo every so many seconds for some period of time.

Shoot Early, Late, or on an Overcast Day

It’s best if it’s not a bright sunny day as the sunlight can blow out the white highlights in the water. Try to photograph very early or very late, before the sun is up or after it has gone down. Or pick an overcast day when clouds will hide the sun. This reduces the quantity of light in the scene, reducing the chances of blowing out highlights, and requiring a longer exposure in your camera, increasing your chances of blurring the water.

This was shot on an overcast morning. Less light meant a longer exposure. ISO 200, aperture f/36, shutter speed 15 seconds.

Adjust Your ISO

Set your ISO to the lowest setting your camera allows. The ISO controls how sensitive your camera’s sensor is to light. The lowest setting, for example, 100 or 200, will require more light to make an exposure. Your camera will need more time to collect more light which will help you achieve the slow shutter speed you’re after.

Stop Down Your Aperture

Stop down your aperture as far as your can. To do this use a larger f-stop number, such as f/16, f/32, etc. This closes down the aperture, making a smaller opening that light will need to travel through, requiring more time for the camera to gather enough light to make the exposure. This lets you shoot using slower shutter speeds. Be aware, though, that the very smallest apertures can cause diffraction, which may reduce the sharpness of your photo. If this happens you’ll need to open up the aperture just a bit.

A wider aperture results in a faster shutter speed allowing you to see more detail in the water. ISO 200, aperture f/4, shutter speed 1/50 second.

A narrower aperture results in a slower shutter speed allowing you to blur the water. ISO 200, aperture f/11, shutter speed 1/8 second.

A wide aperture results in a faster shutter speed, freezing action and showing more detail in the water. ISO 320, aperture f/6.3, shutter speed 1/1250 second.

A small aperture results in a slower shutter speed, helping convey action by blurring the water. ISO 320, aperture f/25, shutter speed 1/60 second.

Use a Polarizing Filter

If everything above still isn’t enough to slow the shutter speed down enough to create the blur you’re after then you may need to resort to filters that fit over your lens. The first to try is a polarizing filter if you already have one.

A polarizing filter is often used to reduce reflections and glare on surfaces such as water and leaves, to create richer colors, and to darken skies. A side effect of these filters is reducing the amount of light that reaches the sensor, usually by about 1 to 2 stops. This isn’t a lot but it might be enough to get the shutter speed slow enough to blur the water.

Using a polarizing filter and a small aperture helped slow down the shutter speed, blurring the water from the fountains. ISO 200, aperture f/25, shutter speed 1.6 seconds.

Use a Neutral Density (ND) Filter

If nothing else will get the shutter speed slow enough you’ll want to invest in a neutral density filter. Think of this as sunglasses for your camera lens. It’s a dark filter that reduces the amount of light entering the lens. Neutral density filters are available in a range of levels, some reducing 1 stop of light, some 3 stops, some 5, 10 or even 15 stops of light. You can even find variable neutral density filters that let you turn the filter like a polarizer to change the density of the filter. With neutral density filters you’ll be able to slow the shutter speed down as much as you’d like.

You can also stack filters, using multiple neutral density filters to slow things down even more. And you can stack a polarizing filter and neutral density filters. Just be aware that if you stack too many filters you may begin to see the filters at the corners of the image. If this happens you either need to remove some of the filters or crop the image when you’re finished.

A polarizing filter in the middle of the day allowed a slow exposure, but not slow enough to really blur (or still) the moving water. ISO 200, aperture f/22, shutter speed 1/8 second.

A polarizing filter and a 5-stop neutral density filter in the middle of the day allowed a slow enough exposure to blur (or mostly still) the moving water. ISO 200, aperture f/22, shutter speed 4 seconds.

It's reasonably early in the morning without a filter. ISO 200, aperture f/11, shutter speed 1/80 second.

Adding a Singh-Ray Gold-N-Blue Polarizer and a 10-stop neutral density filter shifted the colors and slowed the shutter speed way down, introducing a lot of blur into the water. ISO 200, aperture f/11, shutter speed 67 seconds.

In this triptych I used a Singh-Ray Vari-N-Duo filter, which combines a polarizing filter with a variable neutral density filter, to gradually slow the shutter speed down by increasing the amount of neutral density. All images are ISO 200 with an aperture of f/25. The left image has a shutter speed of 1/8 second. The center image has a shutter speed of 4/5 second. The right image has a shutter speed of 8 seconds.

I hope these tips for blurring moving water have been useful to you. It can be a lot of fun and it can really add a nice dynamic to a photograph. So head out there and try a few of them out, see what kinds of interesting photographs you can create.


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