Note 77: The newly bought lens is dusty. What should I do?

Everyone wants the newly bought lens to be spotless, but the reality is that there is still some dust in the lens after the new lens is unpacked. What should I do at this time? Return or accept? Such a thing happened to me recently. I went to the physical store and bought a Panasonic 20mm f/ 1.7 lens. I picked one that looked clean and had no traces of use, so I put it on the fuselage and took a few trial shots. Make sure the focal length and aperture are all right. Get ready. But suddenly I found dust on the front lens. It's not very big, but it's obvious. I thought it was outside, so I went back and blew it. The lens has been screwed to the fuselage, so I'm sorry to find someone to change it. When I got home, I found that I was in trouble. Dust can't be blown off, and the brush can't be brushed off. Looking closely with a flashlight, I found that there was dust in the front lens. Although it is normal to say that there is dust in the lens, which generally will not affect the imaging, it is still disturbing: how can there be dust in a brand-new lens? I checked it online, and everyone has different opinions. Some people say that the new lens should be brand-new and the dust should be returned. Some people say it's normal to go into the dust, so don't take it to heart. I specially consulted an expert I trusted, and his answer was: "This is related to personal psychological endurance. If it were me, I would definitely change it because I have obsessive-compulsive disorder. " At first, many people (including some professional photographers) said that the new lens was a little gray and there was no problem, but they were a little relieved when the expert said it. What should we do? After thinking about it, we decided to take two steps: (1) take more shots to confirm whether the dust has an impact on imaging; (2) Try to contact the seller to see if we can exchange the goods. I took a few more pictures at home, and tried different focusing distances with large aperture and small aperture. Then I put the photos on the computer and found no traces of dust. It is also found that this lens has excellent imaging, very sharp and strong resolution, and the color and contrast are very satisfactory. Do you want to change it? I tried to contact the merchant by phone. The service attitude of the merchant is very good. If you confirm that I haven't photographed the exterior (it will make the lens stick a lot of dust and it is difficult to clean), let me take it to the store to have a look. When I got to the store, the seller asked me to choose another one. I started to choose again. I told the seller not to put this now. Maybe I still want it. I picked three more and found them all more or less perfect. There is dust in the back lens of one, and there is also dust in it. This is definitely not allowed, because the dust behind will have an impact on imaging. I picked a cleaner one, but there is a small scratch on the bayonet. I wanted this (a clean lens is more important), but I found that the lens was a little stained. Chatting with the boss, the boss's behavior is very scary: pick up a lens cloth and wipe it. I said, ha, wipe it all at once. So he did, rubbed it for a while and wiped off the stain. At this time, I thought: it seems that it has been rubbed for so long. I wonder if the camera is hurt. Well, since none of them are perfect, I'll choose the original one. In this way, I tossed and turned and took the original. After coming back, I took some photos outside and sent them home for computer inspection. I am very satisfied with the performance of the camera. Since the imaging is good, I won't miss the dust any more. To sum up, my feeling is: if you find the newly bought lens a little dusty, don't worry (of course, try to choose a clean lens when you buy it). At this time, it is necessary to do more shooting to check whether the imaging effect of the lens and dust affect the imaging. If you find that the imaging is satisfactory and focused. There is no problem with the aperture. It is best not to exchange goods at this time. There is always a risk in exchanging goods: a clean lens is selected, but the image is not as good as before. This is not worth the loss. After all, imaging is the most important thing. Besides, the camera will go up in smoke sooner or later. If you think of the possibility of returning, try not to shoot outside, so as not to get too much dust on the lens. The following points should be known about the dust in the lens: the dust behind the lens has far greater influence on imaging than the dust in the middle and front. Generally speaking, the dust in the front lens group has no visible influence on imaging (of course, too much dust will not make imaging soft), while the dust in the rear lens group may have an influence on imaging. Therefore, the cleanliness and integrity of the rear lens are very important. In fact, there is a lot of dust in the new lens, but it is generally invisible. It is said that if you shine bright light (such as a flashlight) into the lens from behind (the aperture should be fully open), and then look into the lens from a certain angle in front, you will be shocked for the first time: a lot of dust! This is normal. Don't try to open the lens and clean up the dust yourself unless you are confident in your skills. Lens is a precision instrument, and the difference of 0. 1mm (even smaller) during installation will have a great impact on imaging.