Manual focus is particularly helpful when autofocus is distracted by glass, branches or a very small detail. The best focus can be difficult to judge on the full camera display, however. Focus magnification enlarges a selected area before capture. It does not automatically change the recorded focal length or final framing.
Magnify the right detail
Set the complete composition first. Then move the magnified area onto the detail that actually needs to be sharp, such as small lettering or the nearer eye. Turn the focus ring slowly through the sharpest position and slightly back again. Comparing both sides helps distinguish an apparently clear setting from the best position.
A tripod allows finer work because the enlarged view does not keep drifting. Handheld, every small movement is magnified too. Support yourself and avoid swaying forwards or backwards after focusing. At close distances, a tiny distance change can shift focus again.
Use peaking as an indication
Focus peaking marks contrast edges with colour. It can quickly indicate the approximate focus plane, but it is not an exact guarantee for every detail. High sensitivity can highlight many edges and suggest more sharpness than the file actually contains. Magnified inspection remains useful for critical areas.
Choose a marking colour that stands apart from the subject and briefly disable it when necessary. You can then see whether the overlay hides subtle softness. Also check whether the camera previews at the working aperture or with the lens open. This can affect how clearly depth of field appears in the preview.
Return to the composition before release
Exit magnification and check the frame edges before release. The composition may have shifted unnoticed while you worked on detail. Check whether the shutter button reactivates autofocus and changes your manual setting. With electronically coupled focus rings, switching off or changing lenses may also reset position. A test frame inspected afterwards confirms the result better than the distance scale alone.
