How to Focus to (or on) Infinity with a Digital SLR Camera

Introduction

When reading manuals, photography magazines or books, you’ll often come across the phrase “focus your camera to infinity”. You may also notice the ∞ (infinity) symbol on one of your camera lenses. Understanding what this means — and how to do it — can help you capture crisp images of distant subjects, especially in landscapes, night-sky shots, or any scene where your subject is far away.

What “Infinity Focus” Really Means

In optics, “infinity focus” means your lens is set such that parallel light rays (from a very distant object) form a sharp image on the camera’s sensor. In practical photography talk: when your lens is focused to infinity, everything in your frame that is far enough away will be in focus. However, a couple of caveats:

• “Infinity” doesn’t mean the farthest object your eye can see; it means “far enough that focusing further doesn’t change the sharpness in a meaningful way.”

• Not all lenses or setups can truly reach infinity focus (e.g., with adapters, macro attachments, etc.)

Why & When to Use Infinity Focus

Here are key scenarios when focusing to infinity is helpful:

• For landscape photography when your main subject is far away and you want everything from mid-distance to the horizon to be sharp.

• For astrophotography / night-sky shots: stars and distant objects benefit from the lens being focused as far as possible.

• For aerial, cityscape, or other scenes where there’s little interesting subject in the very near foreground and you just want “everything out there” sharp.

  
  

How to Set Infinity Focus on Your DSLR Lens

Here is a step-by-step process (with your club’s readers in mind).

1. Check your lens type and its markings

   • Look at your lens barrel; many lenses have a mark showing ∞ (infinity) on the focus distance scale.

   • If your lens has a manual‐focus (“MF”) switch (often labelled AF/MF), switch it to MF.

   • Be aware: some modern autofocus lenses don’t have a hard stop at the ∞ symbol; you may still need to fine-tune by eye.

2. Rotate the focus ring

   • With the lens set to MF, rotate the focus ring until the white (or marked) index aligns with the ∞ symbol on the distance scale. This is the theoretical infinity focus position.

   • Then look through your viewfinder (or live-view) and aim at a distant object (horizon, distant mountain ridge, city skyline, etc.).

   • If the distant object is sharp, you’ve achieved focus at infinity. If not, adjust slightly until it appears sharp.

3. Verify – especially if shooting intentionally distant subjects

   • Magnify the live view (if available) to check sharpness of distant detail.

   • Do a test shot and review at 100 % to ensure sharpness.

   • For night or astrophotography, this step is crucial because many lenses will go “past infinity” (i.e., the ring keeps turning but sharpness degrades) due to manufacturing/thermal tolerances.

4. Compose and shoot

   • Once infinity focus is achieved and verified, compose your shot. If your scene has only distant subjects, you’re good.

   • If you also have important foreground objects, you may want to focus a bit closer than infinity (see the “Hyperfocal distance” section).

Tips & Best Practices

Here are additional tips for success when focusing at or near infinity:

• Use a narrow aperture (higher f-stop number) to increase depth of field. For example: f/11, f/16, f/22. This gives more “forgiveness” if your focus isn’t perfectly precise.

• Use a tripod, especially when using small apertures (which often require slower shutter speeds). This ensures sharp images overall.

• Avoid close foreground objects if you’ve focused at infinity: they may appear blurry because the depth of field starts “far away”. Focusing at the hyperfocal distance (rather than pure infinity) might be better if you want both near and far sharp.

• Be cautious with adapters, teleconverters, extension tubes or macro attachments: these can prevent your lens from truly focusing to infinity.

• Check for “focus shift” or drift due to temperature changes, especially with high-quality lenses that allow rotation past the marked infinity point. Manufacturers sometimes allow this so that even under changing conditions the lens can be fine-tuned.

  
  

Hyperfocal Distance: A Useful Extension (added content)

(This section is an addition to your original article — see below what has been added.)

The concept of hyperfocal distance is closely related to infinity focus and is especially useful in landscape photography.

• The hyperfocal distance is the closest distance at which you can focus so that everything from that distance to infinity appears acceptably sharp.

• If you focus exactly at the hyperfocal distance (and use a sufficiently narrow aperture), your depth of field will extend from about half that distance to infinity.

• In practice: if you want both foreground (rocks, plants) and distant background (mountains, horizon) to be in focus, you might focus at the hyperfocal distance rather than pure infinity.

• Many lenses’ distance scales show DoF (depth-of-field) marks which help identify the hyperfocal setting for a given f-stop.

• Using hyperfocal focusing can give a more balanced sharpness between near and far — something pure infinity focus sometimes cannot.

Common Mistakes and Myths

Here are pitfalls club members often encounter:

• Myth: “If I set the ring exactly on ∞ then everything will always be sharp.” Reality: Some lenses can rotate past the ∞ mark and the true sharp point may be slightly before or after it due to construction tolerances or temperature changes.

• Mistake: Relying solely on autofocus at night or in low contrast. Autofocus may struggle with distant low-contrast subjects (e.g., stars). Instead, you may want to switch to manual focus and verify infinity focus manually.

• Mistake: Having significant near-foreground elements but still focusing purely at infinity. This may leave your foreground blurry. Consider hyperfocal focusing or adjusting composition.

• Mistake: Using very wide aperture (small f-number) with distant subjects and expecting everything to be sharp. A wide aperture reduces depth of field, making focus precision more critical. Narrowing the aperture mitigates this.

  
  

Summary

To recap:

• “Focusing to infinity” means setting your lens so distant objects (and everything beyond a certain distance) are as sharp as possible.

• It’s especially helpful for landscapes, night sky, and scenes where your subject is far away.

• Set your MF switch, rotate to the ∞ mark (or verify by eye), use a narrow aperture, tripod if needed and check your image.

• If your scene includes interesting foreground objects, consider using the hyperfocal distance instead, to keep near and far sharp.

• Be mindful of lens limitations (adapters, extension tubes) and the fact that “∞” on the barrel is a guideline, not a guarantee.