Can a used SD card cause "double exposure" ghost images on a trail camera?
Asked 9/29/2023
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My trail camera sometimes shows faint "ghost deer" in night photos, especially on black-and-white infrared images that switch to color after processing. Could a previously used SD card be causing an old image to show through, like a double exposure, or is there another reason trail cams create ghost images at night?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
2y ago
2 Answers
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No. The SD card is just a medium for data storage. It behave completely different than a light sensitive surface, where an effect like this would be possible.
The allocation of images also is not using the exact same locations on the card. For this the SD card controller uses wear leveling and keeps track which storage cells have been used how often. This ensures even aging of the storage cells. So an image would usually not occupy the exactly same space in storage as before, making this effect near impossible.
Additionally if there was data from an old image present in your new image, there is a good chance that parity/error checking on the controller would detect that. Otherwise this would result in a corrupted image. In compressed images like JPG this would lead to large detectable areas of visual glitches.
What is possible, is that the sensor itself was not thoroughly resetted and carried over some residual values form a former image, although I would not know why.
Or, and that would be my guess - the illumination was way shorter than the shutter speed and you had the deer in there, but it was away before the illumination caught it. You can have these effects in a dark environment while using multiple flashes in common photography - either by accident or on purpose. This would result in multiple exposure.
A possible scenario would be that the camera uses something to detect the animals. This is enough to cause a very faint image, the animals was spooked, then the main illumination (IR light?) fired and you got the main image.
Originally by user88965. Source · Licensed CC BY-SA 4.0
user88965
2y ago
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No. A used SD card will not cause true "double exposure" effects in new trail-camera photos. SD cards are only digital storage; they do not retain old images in a way that overlays them onto new ones like film can. Cards also use wear leveling, so new files are not simply written back onto the exact same physical cells.
If card data were corrupted, you would usually see obvious file/image corruption, not a realistic faint animal shape.
A much more likely cause is the camera’s night exposure behavior. Trail cameras often use a relatively long exposure at night, while the flash/IR illumination is only brief. If an animal moves into or out of the frame before or after the flash fires, it can leave a faint blurred or partial "ghost" image from ambient light plus a sharper image from the flash-lit moment. That can look like a double exposure even though it’s just motion during a long nighttime exposure.
So the issue is probably exposure timing and subject movement, not the SD card.
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