What Are Digital Camera Focus Scales, and How Accurate are They?

I recently had a question with regard to my article about the zone-focusing technique: “How accurate is the focus scale…” used for zone-focusing? That’s a great question, I guess I’ve been wondering myself!

If you’re not familiar, a digital camera focus scale is those numbers on the lens display or camera screen that tell us how far our focus distance is. It’s a digital representation of the scales inscribed on manual lenses.

But are they accurate enough to use as a focus aid? Are they exact, close enough, or way off? What are they good for? I thought it’d be time to put these questions to bed with some controlled tests.

Are Digital Focus Scales Worth Anything?

Watch this video on YouTube.

Testing method

I wanted to test both Fujifilm and Nikon cameras since those are the ones that I use on a regular basis. You can use this same technique with other brands.

I set up a fake plant that has several layers, or “planes,” which would help determine if the camera is focusing near or far. A little piece of gaffer’s tape indicates where I’m measuring from. Then, the camera was set on a tripod, with the focal plane both 7 feet and 30 feet away from this piece of tape. These distances represent a kind of “portrait distance” and a typical “street photography zone-focusing” distance.

I used three different techniques to focus at the “plane” containing the piece of tape as best I could, at 70mm with the Nikon Z6III, and 55mm with the Fujifilm X-T50, and an aperture of f/2.8 for a shallow depth of field. This would help me better see where it’s sharp.

1. Command autofocus on that plane, note the displayed distance, and assess sharpness in the photos.
2. Set the focus distance display in the camera to both 7 and 30 feet, take a photo, and assess sharpness.
3. Use focus peak highlights until the plane is in focus, note the displayed distance, and assess sharpness in the photos.

There are, of course, many other variables here, such as different lenses, different focal lengths, the positioning of the numbers on the scales, and more. This is intended to give us a basic idea of how accurate these are.

Results

This is what I noted for the six different scenarios.

And before we look at the results, it’s worth noting that the Fujifilm scale is interpreted by moving the marker on a fixed scale. The Nikon distance is set with a number that’s displayed in different increments. Interpolation is required for both.

Noting the displayed distance using autofocus

All photos were sharpest using autofocus.

7 FEET

• The Fujifilm camera showed just inside of 7 feet, maybe around 6.8.
• The Nikon scale showed exactly 7 feet.

30 FEET

• The Fujifilm camera was directly under the center of the “3” in 30 – where exactly is 30 feet on that scale?
• The Nikon scale goes from 7 to infinity (with this lens); this mark was just on the inside of infinity, which is about where it should be for a 70mm lens.

Setting the camera’s focus distance to the measured distance

7 FEET

• The Fujifilm camera isn’t as sharp as when using autofocus, which displayed 6.8 feet. It’s a bit sharper behind the 7-foot mark, meaning it’d be sharpest if I had set around 6.8. But as we saw before – where is 7 feet? The middle of the “7” or the beginning?
• The Nikon distance on the screen had to be interpolated between 6.6 and 7.3, but is quite blurry at the 7-foot distance. It’s the sharpest in front of that despite 7.3 being displayed.

30 FEET

• The Fujifilm photo is just slightly soft when setting a distance of 30 (setting the scale right in the middle of “30”) and appears sharpest about five feet behind that distance. That’s consistent with what the scale showed in autofocus.
• The Nikon photo is quite soft at a set distance of 30 feet. I had to interpolate between 25 and 35 on the screen; the scale on the lens is useless for setting 30 feet. Even though 35 was displayed on the screen, the photo is sharper at actual distances closer to 30.

Noting the displayed distance using focus peaking

7 FEET

• The Fujifilm camera scale showed just inside of 7 feet, maybe around 6.8, and fairly sharp (go back to my discussion on where “7” really is).
• The Nikon camera showed 7.9 feet on the screen scale and was sharpest at a distance behind 7 feet. However, reviewing the video, this was an error on my part. The peaking was best at 7.3 feet, which would have made it sharper.

30 FEET

• The Fujifilm camera was just at the beginning of the “30,” again confirming to me at least that 30 feet is the beginning of the number.
• The Nikon camera was actually boldest between 35-40 feet on the scale, which matches what I found when setting a distance of 30 feet.
• Both photos were sharp using focus peaking at 30 feet.

Conclusion

This was more of just a “fun” test to see how accurate these displayed focus distances are, and they’re pretty close!

In Fujifilm cameras, the scale appears pretty accurate so long as you measure from the beginning of the number and not the middle of it.

Nikon cameras are a bit more difficult to work with; the camera screen scale (which is new as of late 2024) seems “chunky,” offering little refinement, and was front-focused. However, for lenses that have them, the LCD screen is easier to read.

Does it matter?

In practice, however, is any of this really important? Looking at the big picture, so to speak, what do you use these focus scales for?

One of the primary purposes of using these focus distances is to “zone focus.” Fujifilm cameras display your depth of field in the camera display; with Nikon, you’ll only see the depth of field in lenses that have an LCD display. You can look depth-of-field tables to have some numbers to hang your hat on.

Regardless, when you’re zone focusing, you’re estimating your subject distance with an aperture of around f/8 or smaller and a focal length of 50mm or less, knowing that’ll give you enough margin of error for sharp photos. This is a great technique for street photography, shooting from the hip.

No one is looking at a bird far off in the distance, using a 400mm lens at f/4 and saying, “That bird is 127 feet away, let’s set that on the focus scale.” And no one is doing like a product shoot, measuring the distance from the product to the focal plane of the camera, and setting that distance.

No matter how good you think your eyes are, you’re not going to guestimate distances more accurately than your camera. The limiting factor is the photographer’s abilities, not the camera. And what you have in the camera works just fine.

I was doing these tests on the telephoto end with a wide-open aperture to see where it was sharpest. When using the zone focus technique, you’re going to have acceptable sharpness.

I hope you found this a fun and informative little test, and maybe it answered some questions for you.

If you have any other comments to add about the camera’s focus distance scale, please let me know in the comments.