How to Test a Camera Body Before You Sell It: 8 Checks
Updated: 16 Sep 2026 · Camera Sell Online
When you sell a camera on Camera Sell Online, the price you see after the OTP is confirmed at on-site verification, where the camera is checked against the model, accessories, age and condition grade you selected. Most surprises at that point are not about scratches; they are about things nobody checked: a sensor full of dust, a stuck dial, a card slot that does not read. These eight checks take about 15 minutes with a charged battery, a memory card and a lens, and they need no special tools.
1. Sensor dust test
Dust on the sensor shows up as soft dark spots in the same place on every photo, most visibly at small apertures. To test: fit any lens, set the camera to aperture priority (A or Av), choose the smallest aperture such as f/16 or f/22, set the lowest ISO, point at an evenly lit plain surface (a white wall, a clear patch of sky or a blank laptop screen), defocus slightly so no texture shows, and take a photo. On the rear screen, zoom in and scroll across the whole frame. A few faint spots are normal on a used mirrorless body, because the sensor is exposed every time the lens comes off; a frame peppered with dark specks or streaks is what a buyer notices first.
What you can safely do: use a hand blower (never compressed air from a can, never your breath) with the camera facing down, then repeat the test. Do not touch the sensor with a swab or cloth unless you have done it before; a wet-cleaning mistake costs more than the dust.
2. Hot and dead pixel test
Put the lens cap on (or the body cap), set ISO to 1600 or higher, set a shutter speed of 2 to 5 seconds, and take a photo of pure black. Zoom in on the rear screen or a computer. Bright red, green, blue or white dots that stay in the same place are hot pixels; small numbers are common on older sensors and many cameras map them out with a "pixel mapping" or "pixel refresh" menu option (Olympus, Panasonic, Fujifilm and some Sony bodies have one). Then photograph a bright plain surface and look for black dots: those are dead pixels. Note what you find; at on-site verification the camera is checked as it is, and a known issue told in advance is different from a hidden one.
3. Shutter and mirror
Take ten photos in a row at 1/250 s and ten at 1/4000 s (or the fastest speed the camera has). The sound should be identical each time. Listen for a scrape, a double clack or a delay, and check that none of the frames has a dark band across the top or bottom edge; a band at fast speeds means the shutter curtains are not travelling evenly. On a DSLR also check the mirror does not stay up after a shot. If the camera shows an error code when you press the shutter, write the code down exactly; it is the first thing a technician will ask for.
4. Buttons, dials and the mode dial
Press every button once and turn every dial through its full range: the mode dial should click into each position, the command dials should change the value on the screen one step per click, and the four-way pad or joystick should move in all directions. A dial that skips values or a button that needs pressing twice is a repair item. On bodies with a lock on the mode dial, make sure the lock releases.
5. Ports and doors
Open every rubber port cover and check it closes flush. Plug in the USB cable that came with the camera and confirm the camera is recognised by a computer or charges (on bodies that support USB charging); test the HDMI port if you have a cable, and the microphone and headphone sockets with any 3.5 mm plug. Open and close the battery door and the card door several times; both should latch firmly. A cracked port cover or a battery door that pops open is exactly the "high wear and tear" line in the Below Average grade.
6. Rear screen and viewfinder
With the camera on, look at the rear screen against a plain grey menu page: lines, dark patches or a corner that stays dim are panel faults, not dirt. If the screen tilts or flips, move it through its full travel and check that the image never flickers or cuts out, which points to a worn ribbon cable. Then look through the viewfinder: on an EVF, look for dead pixels and lag; on a DSLR optical finder, small dust specks on the focusing screen are harmless and common. Test the eye sensor by covering it with your hand: the display should switch between screen and viewfinder.
7. Memory card slots and formatting
Insert a card in each slot, format it in the camera's menu, take a few photos, and play them back. A slot that reports "card error" with a card that works elsewhere, or that needs the card wiggled to be read, is a faulty slot. Also test the card door detection: the camera should refuse to shoot (or warn) when the door is open on bodies that check it.
8. Wi-Fi, Bluetooth and the last things to remove
Open the wireless menu and confirm the camera can create a Wi-Fi network or pair with the brand's phone app; if it pairs, un-pair it and delete the camera from the app afterwards. Then, before the pickup, back up your photos, remove the memory card, remove any copyright or author name you typed into the camera's menu, and do a factory reset ("Reset all settings" or "Initialize"). Charge the battery so the camera can be tested at the door.
What to do with what you found
Nothing on this list changes the grade wording: the four grades on the site describe use and wear, which you can read about in camera condition grades explained. What the tests give you is knowledge. If everything passes, pick the grade the wear points to and book with confidence. If something fails, the site's FAQ points to WhatsApp or a call for anything the form does not cover; mention the fault there before you book the pickup, so the price you agree on is the price you receive.
