used for first focusing
To understand what "used for first focusing" means, we need some context. However, based on the phrase alone, it seems like it might be referring to something related to photography or optics.
If we assume it is about photography, "first focusing" could imply the initial adjustment of the focus on a camera lens. In photography, the focus is an important aspect that determines how sharp or blurry the subject appears in the image. To achieve accurate focus, there are a few techniques that can be used:
1. Manual Focus: On some cameras, there is a focus ring on the lens which can be rotated to adjust the focus manually. By turning the ring, you can bring the subject into sharp focus.
2. Autofocus: Most modern cameras, particularly digital ones, come with autofocus capability. Autofocus uses sensors to detect contrast and automatically adjusts the lens focus accordingly. Different autofocus modes, such as single-point or continuous autofocus, can be selected based on the subject and shooting conditions.
To perform "first focusing," you typically start with a rough estimate of the focus distance and then fine-tune it using manual focus or allowing the autofocus system to adjust until the desired focus is achieved.
Please provide more information if you have a specific context for "used for first focusing" to give a more accurate response.