Pre-meet proof

Evidence to request before you spend time travelling.

01Request the full lens name, mount and serialAsk for photos of the name ring, mount and serial. Confirm generation, mount and whether it is a full-frame or crop-format design.
02Request backlit front and rear element photosCurrent angled photos can reveal coating damage, haze, fungus threads and element separation better than a straight-on listing image.
03Arrange a test on a known compatible bodyUse a body you trust or verify the seller's body with another lens. Bring a high-contrast flat subject for corner testing.

Physical inspection

What to inspect under bright light before powering on.

01Inspect glass with angled lightLook across—not directly through—the elements for coating scratches, haze, fungus, balsam separation and cleaning marks. A few internal dust specks are common.
02Check mount, filter thread and barrel alignmentThe mount should sit flat with intact contacts and screws. Test a known filter gently; never force a dented thread.
03Move zoom, focus and switches through full travelFeel for grinding, abrupt tight spots, excessive wobble or zoom creep beyond the model's normal behaviour.

Function test

A short, repeatable test of the device's expensive functions.

01Test autofocus near, far and repeatedlyDefocus between attempts and listen for squeal, chatter or stalls. Check that manual-focus override and focus-distance reporting work if supported.
02Shoot through the aperture rangeTake frames wide open and stopped down while watching for exposure inconsistency, error messages or aperture blades that respond slowly.
03Run a flat-subject corner comparisonPhotograph a detailed flat subject square-on, refocus and compare all four corners. One persistently soft side can indicate decentering or impact damage.
04Test stabilisation and controlsAt a suitable slow shutter speed, compare stabilisation off and on. Verify custom buttons, limiters and control rings recognised by the body.

Account & lock check

Confirm the next owner can activate and use the device normally.

01Match serial to receipt and service recordsCompare the physical serial with any original receipt or repair document. Do not rely on box labels alone because boxes can be swapped.
02Check a reputable stolen-gear registryUse a relevant regional registry if available and keep the sale record. A clean search is supporting evidence, not a guarantee of title.
03Confirm normal firmware communicationThe camera should identify the lens correctly without communication errors. Reset any custom lens button or dock configuration you do not need.

Price proof

Comparable facts to record before negotiating or paying.

01Compare the exact version and mountCompleted sales must match generation, mount and included collar or hood. Adapted and native versions often have different value.
02Separate cosmetic wear from optical faultsBarrel scuffs may be modest; haze, fungus, decentering and damaged coatings require a repair-risk discount based on real service quotes.
03Verify high-value accessoriesConfirm tripod collar, hood, caps, case and drop-in filters are correct for the model. Generic filters should not inflate the price.

STOP

Walk-away signals

Pause the transaction when one of these cannot be resolved with direct evidence.

Branching fungus, milky haze or rainbow-edged element separation is visible.
The mount is bent, loose or shows impact around its screws.
One side remains soft after careful refocus and alignment.
Autofocus stalls or aperture errors appear on a known-good body.

Safe-use boundary

Evidence helps. It does not certify the device.

DeviceProof is a general private-sale inspection aid, not an appraisal, authenticity certificate, electrical-repair guide or guarantee. Meet in a public place, keep personal passwords private, use only known-safe cables and accessories, and never bypass an owner, activation or organisation lock. Do not open mains-powered equipment or damaged batteries. Stop immediately for swelling, smoke, burning smell, exposed conductors, abnormal heat or threatening behaviour.