Complete Guide to Inspecting Second-Hand Cameras and Lenses: Checking for Shutter Curtain Wear, CMOS Dead Pixels and Scratches, Lens Mold and Delamination, and Hidden Issues

1. Inspection of second-hand lens physical and optical core defects (fatal injuries can be vetoed by one vote)

When inspecting a lens, don’t just look at the appearance and quality. The underlying defects are all hidden deep in the lens group:

1. High light pen transmission method (complete exposure of mold and atomization):

• Shine the mobile phone flash or professional LED highlight pen from the rear group of the lens directly to the front group, and look directly into the front group of the lens;
• Mold (Fungus): Spreads out in the shape of spider webs or snowflakes. The acid secreted by the fungi has corroded the coating, leaving irreversible etching marks even if it is cleaned!
• Balsam Separation/Hazing: Old lenses use natural Canadian gum or glue to glue the two lenses together; aging of the glue will decompose into a milky white cloud or edge rainbow oil film. This kind of "cataract" will cause a serious loss of contrast, and the cost of heavy glue will be extremely high. Resolutely veto it with one vote!

2. Aperture contraction lever and motor damping:

• Manually pull the aperture linkage lever, and when you let go, the aperture blades must rebound crisply and instantaneously; if there is any lag, it means sticky aperture inside the blades, which will cause serious exposure loss during high-speed continuous shooting;

3. Bayoin Screws and Kuangliang:

• Check whether the bayonet screws have any signs of disassembly and wear. Install the fuselage and shake it. It is strictly forbidden to have any looseness or excessive shaking.

2. Second-hand camera body core function detection process

The most expensive parts of the body are the sensor (CMOS) and mechanical shutter group:

1. CMOS scratches and wipes (physical scrap risk):

• Remove the body cover, turn on the sensor cleaning mode, raise the reflector/open the curtain, and use a highlight pen to scan the surface of the low-pass filter sideways at 45 degrees;
• If there are minor scratches (many caused by violent wiping by the previous owner with rough cotton swabs), black lines will always be left in the sky when shooting landscapes at a small aperture!

2. CMOS Dead & Hot Pixels Test:

• Put on the lens cap, set to M mode, ISO 100, shutter 1/1000s to take a pure black photo;
• Set to ISO 3200, shutter for 1 second and take a pure black photo;
• Import into the computer and magnify to 100% for observation: If there are isolated pixels that are always white and shiny at 1/1000s, it is a "physical dead center";

3. Shutter times and mechanical shutter curtain form:

• Check whether the mechanical curtain is deformed, scratched or oily; use a card reader to upload the latest photo to CameraShutterCount to read the real EXIF shutter firing times.

3. Electronic interface and motherboard stability limit test

1. Dual card slots are fully loaded for reading and writing: Insert dual cards and continuously shoot at high speed to clear the cache and test whether the motherboard storage controller will report a memory error;
2. Body anti-shake and sensor center reset: Listen for a slight reset sound from the sensor when shutting down, and after turning on the camera, half-press the shutter button to see if the viewfinder image is stable without high-frequency abnormal noise.

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