Whether new to photography or a seasoned pro, buying used lens offers a great opportunity to save money. It also allows you to thoroughly inspect the lens before making a purchase.
Scratches on the front and rear glass are to be expected and won’t impact optical quality. Minor scuff marks on the rubberized zoom and focus rings are also normal.
Scratches
In most cases, a scratch in the lens is no big deal. It might reduce sharpness a little and perhaps introduce some flare in high contrast situations, but it should not impact image quality much if at all. Inspect for light scratches and darkening of the coating (some people are loose with their language and might describe these as cleaning marks) by examining the lens with bright reflected light at several angles to make sure that there is no damage.
Also, examine for abrasions or other damage to the glass surfaces on both sides of the lens. Abrasions or thinning of the anti-reflective coating may negatively affect image quality. Examine for internal dust as well. This is typically caused by flaked-off black non-reflective coating on the interior walls of older lenses and can scatter light and etch patterns into the surfaces. If left unattended, fungus can spread from dust to glass and ruin the optical performance of a lens.
Dents
When a lens is dented, it’s an indication that the lens has been physically damaged, possibly by dropping. Unlike coating damage, which is relatively easy to fix, dents are difficult to repair and can have significant effects on optical performance.
Dents to the rear filter threads are especially worrisome because they indicate that the lens was dropped hard enough to knock the glass elements out of alignment. This can impact image quality and resale value.
If you’re buying a used lens from someone you don’t know, it’s especially important to examine the lens thoroughly and ask a lot of questions. This way, you can be sure that the lens matches the seller’s description and isn’t hiding any problems. Also, be aware that you’ll lose the peace of mind that comes with store refunds and manufacturer warranties when buying a used lens from an unknown seller via online classifieds such as Craigslist, Facebook Marketplace or Kijiji.테크노마트카메라
Discoloration
A common problem with older lenses (particularly Takumars) is yellowing due to a combination of materials and coatings that degrade over time. This is a common enough problem that some manufacturers recommend using a UV lamp to cure the lens.중고렌즈
Check for erosion of the lens coatings by shining a flashlight through the lens and examining each element. Significant erosion will reduce the performance of the lens. Check the threads that accept filters for damage – they can become cross-threaded and this is easy to fix, but can compromise the integrity of the lens.
Look for any signs of fungus, which can appear as fuzzy spots and mycelial filaments in some instances. Fungus secretions eat into the multicoatings of the lens elements and can significantly reduce the quality of the image reproduction. Fungus is difficult to completely eradicate without disassembly and is a good reason to avoid any lens that has it. Be especially wary of foreign sellers or those with little or no feedback on their selling history.
Fungus
Fungi are primitive organisms that include mushrooms, mold and mildew. They live in the air, soil, on plants and trees and even inside the body. Some types of fungi cause infections.
Fungal infections occur most often on your skin, nails or mucous membranes (such as the mouth, throat or vagina). Symptoms depend on the type of infection.
Athlete’s foot, ringworm of the scalp and jock itch are common fungal skin infections. Other infections are more serious. These include invasive candidiasis and histoplasmosis. Histoplasma is a genus of fungi that can infect the lungs and other parts of the body. NIAID-supported researchers are investigating ways to prevent and treat fungal infections.
Fungi spread through tiny spores in the air, which you can inhale. People who are more likely to get fungal infections include those with weakened immune systems, such as patients in hospital and people taking medicine that weakens the immune system, such as corticosteroids for asthma.