How to distinguish the original lens and OEM lens of Sony SLR camera?

The premise of choosing a lens: whether it is new or second-hand, you must choose a lens that has not been repaired. Modern lens manufacturing technology is extremely complicated. Besides optical design and material selection, the most important factor that determines the quality of lens is probably the assembly quality. Top-class lenses usually adopt the design of metal lens barrel and pressure ring to ensure the accuracy of lens installation, and after manufacturing, they will undergo precise inspection and adjustment to ensure the optical quality, while middle and low-grade lenses often adopt the method of relaxing the tolerance limit to improve the fault tolerance, which is beneficial to mass production and reduce the cost. Since we all condescend to choose second-hand lenses, let's not consider middle and low-grade lenses and rely on them directly. Major lens manufacturers have their own quality control and inspection systems, such as Lycra. Each lens is assembled by hand. After completion, dozens of items such as optical axis coaxiality and lens spacing will be inspected, and the lens will be fine-tuned according to the inspection results to make its optical performance reach the best state. This meticulous work attitude and slightly complicated workflow make Lycra an optical legend. Although he has no structural innovation, his lens is the best in both workmanship and optical performance. The quality control methods of top lenses in other factories are basically similar, but the strength is different. Once this kind of lens is disassembled, it is difficult for the maintenance master to restore it to the best state when leaving the factory, and the imaging quality will be greatly reduced. Some manufacturers will adopt some special techniques in their production. For example, the well-known Ricoh film machine GR 1 has become a classic with the excellent image quality of 28mm GRlens. Although it is rumored that this lens was actually designed by Schneider, Ricoh's new technology introduced in production also contributed. This new technology is called lens matching system. Generally, there will be some small errors after lens polishing. Ricoh's system will measure the optical axis error of each lens, and then match the lens with the closest performance to form the lens. Imagine if this lens can be removed and put back, can it still have its original performance? Therefore, the premise of choosing a lens should be a lens that does not need to be disassembled and repaired. Generally, such lenses have very attractive prices. However, even if the other party swears that the repair operation was completed by a company's special maintenance center, you must never buy it cheaply, otherwise it is very likely that you will only get a top-level avatar that is superficial. Two years ago, a third-generation XGP of the author was sent to the maintenance point for oil removal because of oil leakage in the aperture, and it was only taken back a week later. After shooting, it is found that the resolution of the disassembled XGP in the center is reduced by about 8%, which is a depressing figure. Once the lens is disassembled and washed, it is hard to say that it can still maintain the original quality, and the more high-grade the lens, the more obvious this "disassembly and washing effect" is. Disassembly So, how do you judge whether a shot has been disassembled? The most obvious thing is, of course, to see if there are passive marks on the front and rear screws, and then to see if there are scratches on the lens barrel inside through the front lens group. If there is, it must have been dismantled and repaired. A screwdriver can't scratch the inner lens barrel through the glass, can it? But then again, some careful maintenance technicians can't find the traces of the lens being dismantled, so they have to touch the lens themselves. In addition, friends who are a little lucky and really uneasy have to choose expensive new lenses. /Ji Xiang/157.htm Go here and have a look!