Today’s Question: Back in the “old days”, a lot of the various 35mm camera lenses had a marking on the lens containing distance measurements for feet/meters where you could easily tell the distance at which you were focusing. What is an accurate way to obtain the distance measurements with a lens that does not contain any measurement indicators?
Tim’s Quick Answer: A laser measurement tool can provide accurate distance information, although they are limited in terms of the maximum distance they can measure accurately.
More Detail: Knowing the distance at which you’re focusing be helpful for a variety of purposes, such as to calculate depth of field for a photo. However, as noted in today’s question, it isn’t as common as it used to be for lenses to have markings indicating the current focus distance.
If you want to be able to measure distance to a subject in the field, I recommend a laser measurement tool. In my view these fall into two basic categories: more accurate and longer distance.
Some laser measurement tools provide accuracy within a fraction of an inch. However, devices that are this accurate are also limited in terms of range. For example, many such devices can only measure accurately out to around 100 feet. One such tool with accurate measurements up to 165 feet can be found here:
https://www.amazon.com/GLM165-22-Ergonomic-Cordless-Digital-Measure/dp/B0943T93KB/
There are also devices with greater range, but with lower accuracy. These are often marketed to golfers or hunters, typically offering a range on the order of hundreds of yards. The accuracy is generally within about a couple feet, but for most calculations in photography that is generally accurate enough. For example, this device has a range of 1200 yards (3,600 feet, or about two-thirds of a mile):
https://www.amazon.com/Acer-Rangefinder-Slope-Switch-Vibration-dp-B0GHYDVJ36/dp/B0GHYDVJ36/
