I have read for many years in marketing literature about how some camera’s viewfinder is “bright”. What does that mean? How would you know if your camera viewfinder is bright or dim? I prefer numbers to hand-waving.
After pondering the issue for a while, it occurred to me that most of us possess an instrument to readily figure out what bright means. Our phones have a built-in camera, and photos from those phones contain EXIF data. EXIF data can be inspected for the “brightness”, which is called “Light Value” (EV). Recall that 1 EV difference equals 1 stop of light.
I use the free program called “exiftool” to inspect the EXIF data. A link where I give more details on this program is here.
Taking a look at the EXIF data from a phone photo, it’s packed with useful information. Note that this Samsung Galaxy S6 phone has a 4.3mm, f/1.9 lens. Because of its teeny sensor, that’s the equivalent of a 28mm lens with a 65.5 degree field of view. Also note that the EXIF data shows a “Light Value” (8.4 shown above).
Why use your phone camera? Because it has a huge depth of focus and the lens fits neatly within your camera viewfinder while blocking external light.
If you use the same lens, aperture, and lighting conditions on each camera, then you can take a picture using your phone through different camera viewfinders and compare them for brightness, via the “Light Value” in the EXIF data.
In the comparisons below, I took a look at the Nikon D610, D7000, and D500 camera viewfinders. I expected the D610 viewfinder to be the biggest and brightest, since it has a full-frame sensor. I was wrong. The D500 is better.
Please forgive the poor exposure in the phone photos below. It's not as smart as Nikon, and the large black expanse fooled the meter. I'm only interested in brightness (EV) and size in the frame, so the exposure technique just needs to be consistent for each camera viewfinder.
Nikon D610 Viewfinder. EV 8.4, 35mm
Nikon D7000 Viewfinder EV 8.1, 35mm
Nikon D500 Viewfinder EV 8.8, 35mm
Cropped view of D610 viewfinder
Cropped view D7000 viewfinder
Cropped view D500 viewfinder
The D610 viewfinder is EV 8.4 and the view width is 1896 pixels in the photo.
The D7000 viewfinder is EV 8.1 and the view width is 1694 pixels in the photo.
The D500 viewfinder is EV 8.8 and the view width is 1930 pixels in the photo.
It struck me that the D500 viewfinder looked bright and large, but I didn't know if it was a psychological effect or real. Now I know it's real. I was surprised to discover that it's even larger and brighter than my full-frame D610 viewfinder.
Try this test yourself; it's an easy way to compare camera viewfinder brightness, magnification, and even focus sensor sizes and focus sensor converage.