Nikon's manual fisheye head is installed on d4 camera, and the focus of the photos taken is clear, what is the reason for the blur around?

Example: AF-S 70-200mm F2.8G IF ED VR lens refers to Nikon G lens with internal focal length of 70-200mm, constant maximum aperture F2.8, ED ultra-low dispersion lens, VR anti-shake system and AF-S ultrasonic motor.

Ai: Automatic indexing and automatic maximum aperture transfer technology. Nikon manual lens, released by 1977, with green number as the minimum aperture number.

Ai-s: automatic index shutter automatic shutter index transfer technology. Nikon manual lens, 198 1 released, and the minimum aperture number on the aperture ring is orange.

AF-I: lens with built-in motor and CPU contacts. Nikon called it "I" design, which was introduced in 1992. Mainly used for professional telephoto lenses. After the introduction of AF-S, AF-I withdrew from the historical stage.

AF-S: S: S stands for Silent Wave Motor, which is equivalent to Canon's USM ultrasonic motor. It can focus quickly, with high precision and quiet.

ASP: aspheric lens. Nikon's "ASP" and Canon's "AL" have the same meaning.

CRC: Close-range correction close-range correction system, which adopts floating lens design to ensure that the optical quality will not decrease when shooting close-range.

D: Distance focusing distance data transmission technology. The biggest difference between D lens and non-D lens is that D lens supports 3D matrix photometry.

DC: defocus-image control Defocused image control is the original lens of Nikon, which can provide unique defocused image control function. Its biggest feature is that it allows fuzzy control of the background or foreground of a specific object to obtain the best out-of-focus imaging.

DX: DX series lenses are specially designed by Nikon for digital SLR cameras with APS-C format, and cannot be used on Quan Huafu models.

ED: ultra-low dispersion ultra-low dispersion lens. Nikon lens with this logo adopts compound dispersion design and special low dispersion glass lens to reduce chromatic aberration, thus improving the image quality, contrast and definition of telephoto lens.

Fisheye lens: Fisheye lens, with the viewing angle of 180 on FX camera, can capture the whole scene in the picture. For example, AF fisheye 16mm f/2.8D autofocus fisheye lens.

G: The biggest difference between G-type lens and D-type lens is that G-type lens has no aperture ring design, and the aperture adjustment must be completed by the fuselage, which supports 3D matrix photometry. This design reduces the weight and production cost of the lens.

Two: the second-generation product Logo after the lens upgrade

IF: internal focusing technology, the conventional lens focuses by moving the whole lens system or the front lens group, while the front lens group will not shift when the IF lens focuses.

M/a: Manual/autofocus, manual/autofocus switching.

Macro: Macro lens, the general magnification is 1: 2 or 1: 1.

N: nanocrystalline coating. This is an anti-reflective coating, which originated from the development of NSR series (Nikon step and repeat) semiconductor manufacturing equipment. Nikon ultra-low refractive index coating is adopted, which has excellent multiple properties. The main feature of this ultra-low refractive index coating is its ultra-fine nano-sized crystal particles (1 nm is equivalent to one millionth of a millimeter), which can almost completely eliminate the reflection of different wavelengths in the internal lens, and is particularly effective in suppressing ghosts and glare unique to ultra-wide-angle lenses.

NIC: Nikon integrated coating Nikon integrated coating.

P: P lens, manual focusing lens with CPU, electronic contact of AF lens. At present, Nikon has only three P-type lenses: 500mm F4P IF-ED,1200-1700mm F5.6-8pif-ED and 45mm F2.8P

PC: The perspective controls the shifting lens, which can move the optical axis of the lens to adjust the perspective. It is often used in architectural photography.

RF: Back focusing and back group focusing technology. Unlike if, the RF lens is focused by the rear lens group. Because the rear lens group is smaller than the front lens group, it is easy to drive, ensuring faster focusing speed and the same lens length.

S: Slim is a sign of some thin lenses of Nikon, such as AIS 50/1.8s.

SIC: super integrated coating super composite coating. This is an improved NIC coating technology.

Tc: remote converter rangefinder.

VR: Vibration damping electronic vibration damping system, similar to Canon's IS lens anti-shake system, has been developed to the second generation, which can reduce the shutter speed of 3-4 gears.