An apparatus for image content replacement, comprising: a camera image receiving unit which is arranged to receive video images observing a scene including a subject such as a billboard; a mask signal generating unit which is arranged to generate a mask signal that defines mask areas of the video images corresponding to the subject to be replaced with an alternate image content, such as for replacing an original advertisement on a billboard with a replacement advertisement; characterised in that the apparatus further comprises: an image selector unit which is adapted to: store at least a first alternate image and a second alternate image, the first and second alternate images (42a, 42b) being different from each other and being appropriate to different conditions within the scene, determine whether a tested value (H, Z, W) derived from a camera telemetry signal or from the video images themselves, is in a first range or a second range, wherein the first range and the second range are divided by a threshold value (T H, T Z, T W), and select the first alternate image as the alternate image content when the tested value (H, Z, W) is in the first range according to the threshold value (T H, T Z, T W) and select the second alternate image as the alternate image content when the tested value (H, Z, W) is in the second range according to the threshold value (T H, T Z, T W). a camera image receiving unit which is arranged to receive video images observing a scene including a subject such as a billboard; a mask signal generating unit which is arranged to generate a mask signal that defines mask areas of the video images corresponding to the subject to be replaced with an alternate image content, such as for replacing an original advertisement on a billboard with a replacement advertisement; characterised in that the apparatus further comprises: an image selector unit which is adapted to: store at least a first alternate image and a second alternate image, the first and second alternate images (42a, 42b) being different from each other and being appropriate to different conditions within the scene, determine whether a tested value (H, Z, W) derived from a camera telemetry signal or from the video images themselves, is in a first range or a second range, wherein the first range and the second range are divided by a threshold value (T H, T Z, T W), and select the first alternate image as the alternate image content when the tested value (H, Z, W) is in the first range according to the threshold value (T H, T Z, T W) and select the second alternate image as the alternate image content when the tested value (H, Z, W) is in the second range according to the threshold value (T H, T Z, T W). store at least a first alternate image and a second alternate image, the first and second alternate images (42a, 42b) being different from each other and being appropriate to different conditions within the scene, determine whether a tested value (H, Z, W) derived from a camera telemetry signal or from the video images themselves, is in a first range or a second range, wherein the first range and the second range are divided by a threshold value (T H, T Z, T W), and select the first alternate image as the alternate image content when the tested value (H, Z, W) is in the first range according to the threshold value (T H, T Z, T W) and select the second alternate image as the alternate image content when the tested value (H, Z, W) is in the second range according to the threshold value (T H, T Z, T W).