Mirrorless Cameras and Lens Calibration
Anthony Sinfield from CameraCal here. We have seen a lot of information, some correct and some incorrect about mirrorless cameras and lens calibration. The other day we were incredibly excited to have the opportunity to calibrate one of the new flagship Nikon Z7 mirrorless cameras for a regular customer.
You might be thinking, “hang on a minute, I thought you didn’t need to calibrate a mirrorless camera!” and yes, it is true that with the majority of them don’t. This is because most mirrorless cameras use a different method in which focus calculations are done on the imaging sensor chip and not on a separate focusing sensor, unlike DSLRs, which do.
The fact that most mirrorless systems don’t have an ‘exclusive’ autofocus sensor does eliminate the need for AF micro adjustments for the body to be done, but some mirrorless cameras such as the Sony A7 series and some Olympus models allow for micro adjustments . This is in order to combat element displacement errors or when using lens adapters such as the Sigma MC-11 or the Metabones adapters .
The Nikon Z7, however, is different, it uses the same autofocus system that is found in the Nikon DSLRs, which is Phase Detect AF Pixels. This can unfortunately lead to front and back focusing issues because the phase-detect system must be properly installed and (very importantly) precisely aligned during the manufacturing process. If there is even a slight deviation, which does happen quite a bit in manufacturing due to quality control tolerances, autofocus would be off. A heavy knock to the camera can also lead to the de-alignment of the sensors and give need for a mirrorless camera and lens calibration.
The way that the phase-detect system works is that it works out when an object is front or back focused, it then sends exact instructions to the camera lens on which way to turn its focus and by how much. Here are the steps of how Phase Detection works:
1. The light that passes through the edges of the lens is evaluated by the image sensors.
2. How the light reaches the sensors then determines how far an object is front or back focused and by how much. The AF system then instructs the lens to adjust its focus accordingly.
3. Step two is repeated until focus is achieved. If focus cannot be achieved, the lens restarts the whole process, resulting in what is known as ‘hunting’ where the focus goes in and out.
Although the Nikon Z7 is not yet supported by Reikan’s FoCal , our preferred software calibration solution, we were able to calibrate the customers Nikon’s 300mm F4 PF and Z7 with an AF Micro adjustment result of +3. Even though the calculated AF fine tune value was not very high, at 300mm on full frame sensor it will make a considerable difference, especially wide open.
As we have previously mentioned this lens is one of Nikon’s most consistent and from our experience rarely needs any calibration, and if it does then this is to compensate for any front/back displacement of the sensor in the camera body.
Mirrorless cameras and lens calibration will continue to be a hot topic until more cameras like the Nikon Z7 are in use and problems with lenses need to be addressed.
If anybody has bought into the new Nikon Z7 system we strongly suggest that you get your lenses calibrated.
About the author: Anthony Sinfield is the founder and managing director of CameraCal, a business that offers professional camera and lens calibration. The opinions expressed in this article are solely those of the author. This article was also published here .