A sweet spot is a condition where the camera lens produces its sharpest images. There are three factors that are needed to be understood to obtain sharp images:
1. Aperture that results in sharp images.
2. Focal length (in zoom).
3. Focused areas within the frame.
By photographing with the above factors in their sweet spot zones, the chance of producing sharp images will increase. Maybe you’ve wondered about the different sharpness in results even though the photographs use the same equipment. Perhaps this is the reason.
Aperture sweet spots vary between lenses. Lenses with an f/1.2 aperture may not have the same sweet spot as that of an f/2.8 lens. However, generally speaking, the aperture sweet spot lies two stops between the widest and narrowest aperture. For example, in an f/2.8-f/32 aperture lens, the sweet spot most likely lies at f/5.6 and f/16. You can personally experiment to know the exact sweet spot aperture for your lenses by photographing a scene at different aperture settings and comparing the results.
Before experimenting to discover the lens sweet spots, be sure to prepare various things such as:
- Place camera on a stable tripod.
- Make sure the lighting condition is constant when shooting in these different apertures. This is easier done indoors.
- To facilitate the testing process, use the aperture priority setting, which is the AV mode (Canon) or the A mode (Nikon).
For zoom lenses, the sweet spot is usually located between the mid and the maximum zoom. Zoom lenses usually produce softer photographs at its wide position and the sharpness increase as it is zoomed more. For instance, in a 70-200mm lens, sharper photographs can be obtained at the 200mm zoom than at the 70mm zoom.
As for wide lenses, especially ultra-wide angle (UWA) lenses like the 10-20mm (for APS-c sensors) or the 16-35mm (for a full-frame sensor), the edges of the photography usually appear softer than the center of the photograph. This is most prominent in low-end lenses and in cameras with large sensors. So the sweet spot of a wide lens is the center of the photo frame.
So that’s the basic idea of the sweet spot in photography. Continue to learn and experiment with your camera gears in order to always obtain their maximum performance.