What are the shift lens and paraxial lens in SLR lens, and what are their advantages?

Generally, buildings are standing on the ground. In order to take a complete picture, the camera should be tilted slightly upward. Because the lower part of the building is close to the upper part and far from the upper part, the convergence effect of "the lower part is big and the upper part is small" will be adopted. The lens itself is not deformed, and the reason for this phenomenon is the perspective relationship. The axis-shifting lens can be adjusted to make the vertical line vertical and parallel.

The structure of axis-shifting lens is different from that of ordinary lens, and the middle can be bent and staggered.

So as to realize the simulation of Shaughnessy's law of large format camera (I know some words may not be understood, but you can search Baidu. If you talk about it all here, you can write a book, if you are interested in the principle.

Let's talk about the effect first

In addition to adjusting the perspective of the building (this is only a primary function, and most people who know about shifting lenses will stop there), moving the lens can also control the depth of field. In principle, according to Chaath's theorem, it can make the grass under your feet clear all the way to the farthest tower head, which is really clear and within the focus range.

You can also let the person in front of you, the left half is clearly focused, and the right half is empty outside the depth of field.

Now some single camera and small DC have this simulation function, and some are called toy mode or model mode.

That's just a simulation.

In fact, the axis-shifting lens used in 135 camera is affected by the bayonet, flange, image field and other factors, and the axis-shifting effect is much worse than that of large-format camera.

Paraxial, to be precise, there is no such name as paraxial lens.

Only paraxial cameras.

Paraxial camera is a kind of camera, which is different from the popular SLR, and is called parallel name with SLR, double reflex and newly invented single electricity.

The characteristic of paraxial camera is that the light path of framing is different from that of shooting lens, and it is next to the lens.

So it's called a paraxial camera.

Unlike the double reflex, this camera has no reflector, and the viewfinder is not called a lens, but is composed of some optical lenses. The early Seagull 205 and the Leica M series mentioned upstairs are representatives of this kind of camera.

Paraxial camera is characterized by small shutter vibration.

But there is parallax when shooting, especially at close range.