There are several ways to achieve sharp focus using the technique of focus-peaking: One way is to first focus on the subject using the spotting scope, then attaching the camera and using the lens to obtain critical focusing through focus-peaking. Turning the lens focusing ring gives a magnified view of the subject and allows critical focus to be achieved. Pressing the shutter will revert the image to normal magnification and allow a sharp image to be captured. One some cameras the lens may need to be adjusted toward macro focusing, while on others (including my Sony cameras) the lens needs to be focused at or just beyond infinity. I had mentioned in previous lens reviews that I had gotten sharper images with my Sigma 30/2.8 (APS-C lens) attached to my Sony a6300 (APS-C camera) than when I tried the much more expensive Zeiss 35/2.8 (Full-Frame) lens on the a6300. The reason, I found, was that the Sigma allowed me to focus just beyond infinity to achieve razor-sharp images while the Zeis