The image borders must be black.
The image must not contain people.
The image must be sharp.
The contrast of an image must be sufficient.

Correctly captured image

correct image

Sample images

sample image 41 sample image 42 sample image 43 sample image 44 sample image 46 sample image 47 sample image 48 sample image 49 sample image 50 sample image 58 sample image 97 sample image 98 sample image 99 sample image 100 sample image 101 sample image 102 sample image 135 sample image 136 sample image 154 sample image 344 sample image 345 sample image 346 sample image 350 sample image 351 sample image 352 sample image 353 sample image 354 sample image 355 sample image 356 sample image 357 sample image 358 sample image 359 sample image 360 sample image 361 sample image 362 sample image 363 sample image 364