Close-up ring (extension ring, extension tube)

When taking close-up shots with a short shooting distance to obtain an image with a large optical magnification, a close-up ring with a thickness and length equivalent to the "extension amount" when the lens is out of the focus range or the focus cannot be adjusted. You can focus by using. If you use a "close-up ring", the optical performance of the lens may not be fully exhibited.

Extender, rear converter lens

An extender or rear converter lens is a lens that can be attached to the mount side of a shooting lens to extend the focal length.
If you use an "extender" or "rear converter lens", the optical performance of the lens may not be fully exhibited.

Reverse ring

The reverse ring is a ring for attaching the shooting lens in the opposite direction (reverse) during magnified shooting.
A general shooting lens has a reduced optical system with an optical magnification smaller than the same magnification. A "close-up ring" is often used for magnified photography, but since the taking lens is designed as a reduction optical system, the higher the magnification, the lower the optical performance.

Therefore, when shooting at an optical magnification of 1x or higher, you can use it in an optically advantageous way by attaching the shooting lens in the opposite direction and exchanging the object and image to form a magnifying optical system. For example, a 0.5x reduction optical system lens becomes a 2x (= 1 / 0.5) magnifying optical system, which is the reciprocal of 0.5 when used in reverse.

Mount adapter

If the mount is different between the camera and the shooting lens, it cannot be used normally, but it may be possible to use it with the "mount conversion adapter". Machine vision lens includes converting F mount to TFL-II mount or C mount.

ND filter

A filter that adjusts the amount of light without changing the color balance (color temperature) is called an "ND filter".
Use this when the image is too bright even after adjusting the aperture of the shooting lens and the exposure time (shutter speed).
Glass and film materials are commercially available, and the general attenuation amount is "ND2", which darkens the amount of light by one diaphragm, "ND4", which darkens the amount of light by two diaphragms, and "ND8", which darkens the amount of light by three diaphragms. It is a target. For applications that require fine adjustment, the ND filter indicated by the "OD value", which indicates the "optical density", is also used.

So is there no need to study CCNA? Of course not.

It is very necessary to learn CCNA, it is the foundation of CCNP Enterprise and CCIE Lab, only if the foundation is firm, ten thousand feet tall building can be built steadily, learning CCNA is a process of foundation, only if you learn CCNA well, you can lay a good foundation for the next CCNP and CCIE learning.

Therefore, we should consider its foundation and necessity. It belongs to the Cisco certification entry-level certification, suitable for obtaining practical network technology door of zero-based people and weak foundation people, for people who want to engage in network management, the first step of career should start from passing CCNA 200-301. After obtaining this certification, you will have more skills to work with and be able to manage and optimise network systems. The Cisco Network Engineer level certification is the official recognition for engineer level professionals working in networking.

After reading so much, we should all have our own understanding of what a CCNA network engineer is like, but of course, we must not stop there after learning CCNA, because as we mentioned earlier, it is only the foundation and does not have much value for career development, in the follow-up we still have to study hard to pass the CCNP and CCIE certification as soon as possible!