The other week I got a question about how to focus on infinity with a kit-lens. These lenses usually do not have an infinity mark. In this post I will answer this question in more detail. What is focusing on infinity, and when to do this?
What is focusing on infinity?
Most older (and the more expensive) lenses have a distance scale, that includes a little infinity symbol (∞). This distance scale shows at what distance the lens is focused when the focus ring is turned to a liked position. Usually, this distance scale starts at infinity and ends at the closest possible focal distance for the particular lens. The image below is a Nikon 10-24 lens. As you can see it starts at infinity. The next stop is 0.5 meters, or 2 feet. The distance scale ends at 0,24 meters, as this is the closest distance this lens can focus on. This means, that this lens is capable of focusing on objects that are 24 CM’s away, but not any closer.
If you set the lens to be focused at the infinity symbol, it means that the lens is focused at a distance far away, like the sky, or a landscape in the far distance. At this setting, light is entering the lens almost parallel and not converging (read this page to understand converging light), this is why, starting at a certain point, all subjects in the distance appear to be sharp.
As manufacturers have to calibrate the lens to work at this distance, it is a little more expensive to have this option on your lens. That is why most modern lenses (autofocus lenses) do not have this option anymore.
When to focus on infinity?
I personally barely focus on infinity. Only when the conditions are not optimal for manual or automatic focus, like when I shoot a night sky, as in the picture above, or during fireworks. If you know your lens, this is also useful in situations where you need to be quick. If you know at what point the sharpness of your lens starts when aiming at infinity, this is a good option if you need everything from that distance to be sharp but do not have the time to focus precisely (which is really never since autofocus has become so good). For more detailed information on your lens, I refer to the manual of your lens.
How to focus on infinity?
You can set your lens to focus on infinity by turning the camera or lens to manual mode. On most lenses you will find a M/A or M/MA switch. Setting this switch to “M” will turn off the autofocus. You could also turn off autofocus in your camera’s body, check your manual/instruction book on how to do this.
Like mentioned, not all lenses have a distance scale and an infinity mark. Like any Nikon or Canon kit-lens (18-55 and 70-300). Is it still possible to focus on infinity with these lenses? Well, not manually, but there is a trick. Set your camera to autofocus and focus on a subject far away. During night time this could be the moon, a bright star, or a lid building in the far distance. During day time this could be done by focusing on a cloud in the sky or mountain in the far distance. Now lock your focus by pressing the AE-L / AF-L button, reframe your photo and take the picture.
If you do not know how to lock focus with your camera, check your manual, or ask in the comments below!
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Thank you for reading and kind regards,