The evidence: how much mirrorless cameras need it

These figures come from the camera database at FoCal IQ, built from the results FoCal users upload. As on the camera pages, an adjustment of 1 unit is minimal, 2 or 3 is noticeable, and 4 or more is significant.

DSLRs, for comparison

First, a quick look at Nikon DSLRs, with their old-school separate AF sensor. This is every lens tested on every Nikon DSLR, ignoring which direction the adjustment went:

Only 5% of DSLR results needed no adjustment at all, so 95% could benefit from calibration. Half needed 6 units or more, which is a big, visible improvement. On a DSLR, calibration really is pretty much essential.

This includes every lens, from the cheapest to the most expensive, on every Nikon DSLR from 2007 on, with test errors filtered out. Cheaper lenses and bodies generally (but not always) need more adjustment, but it’s a fair picture of DSLRs as a whole.

Mirrorless

Now Nikon Z cameras, with native Z-mount lenses and with F-mount lenses on the FTZ adapter:

Very different from the DSLRs. Measuring focus on the image sensor clearly works. But there’s still an obvious need for calibration, and it depends on the lens:

• with native Z lenses, 62% could benefit, and 17% needed a noticeable adjustment,
• with adapted F-mount lenses, 80% could benefit, and 46% needed a noticeable adjustment.

An adjustment of 1 won’t make a visible difference on its own, though it does slightly improve your odds of a perfectly focused shot. But look further out. 10% of adapted lenses needed 4 units or more, which makes a clearly visible difference. That might not sound much, but if Nikon sold a thousand of a particular F-mount lens, around 100 of them would be clearly sharper after calibration. What about the one on your shelf?

One camera: the Nikon Z9

Here’s Nikon’s flagship on its own, with both kinds of lens:

With adapted lenses, about 6 in 10 Z9 calibrations needed a noticeable adjustment or more. Even with native lenses it was almost 2 in 10.

Two popular F-mount lenses on Z cameras

The 105mm f/2.8 macro: 76% needed 2 units or more, and over 2 in 10 needed 4 or more. An uncalibrated one would be obviously softer than a calibrated one. The 50mm f/1.8 is similar: 66% needed a noticeable adjustment.

CameraCal, one of the calibration businesses we work closely with, has seen F-mount lenses on Nikon Z cameras needing more than 10 units of adjustment, and even native Z lenses needing 6.

At the very least, it’s worth checking the calibration on your mirrorless camera.

In conclusion

There’s a pretty compelling case for checking the calibration of a Nikon Z camera if you want the very best from it, and doubly so with F-mount lenses on an adapter. If you skipped here, the chapters before this explain the reasons:

• how the AF sensor works,
• the errors that can creep in when the sensor is made,
• how the lens optics, mechanics and correction data add errors,
• how the AF processor’s trade-offs let them through.

FoCal Desktop and FoCal Mobile make checking and calibrating easy, and FoCal Pro tells you much more about your kit, from focus consistency to how well your stabilisation works.

I’ll leave the last word to a freelance sports photographer, posting in a Nikon Z9 group on Facebook:

“Just a heads up… Just because the Z9 is a mirror-less body doesn’t mean you don’t have to AF Fine Tune your lenses, especially your adapted F mount lenses. I shot a dock diving event last weekend and over half my shots were back focused with the 400mm f2.8, and the 70-200mm FL was hit and miss… I just fine tuned three of my most used lenses, and two of the three had to be adjusted. The 400mm was -3, the 70-200mm FL was -2 for tele and +1 on the wide end, and the 24-70mm 2.8 VR was spot on at both ends of its range.”