0

THe resolution of the Sony Cyber-shot DSC-RX100 is 5472 x 3648 pixels.Sensor width = 13.20 mm, Sensor height = 8.80 mm, aspect ratio=1.5. However, when taking videos the resolution changes to 1,920 x 1,080 (16:9 aspect ratio). SO that suggests that the camera crops part of the sensors when taking videos. Is it possible to know/compute the size of the part of the sensor that is involved in taking videos?

  • The video is is surely near full sensor width or height, and is then resampled smaller to 1920x1080. There is a discussion of this at scantips.com/lights/fieldofview.html#hd – WayneF Jan 19 '18 at 14:37
  • Thanks Wayne, good link. There is some cropping also in width as your link shows. I just needed a precise measurements of the sensor size in video mode and it seems that it is not easy. – Filippo Bandini Jan 20 '18 at 13:15
2

Make a setup with a couple of rulers arranged horizontally and vertically, and the camera on a tripod, spaced so that the rulers fill the entire frame. Take a still picture, then a short video, without moving the camera. The change in field of view will be proportional to the amount of the sensor being used.

  • Thanks a lot Mark. I also tried to do so. The exact size of the sensor can be computed via this calibration procedure only if the focal length and focus parameter do not change in switching from camera to video mode. That is not certain, also because in video mode there are not metadata information about focal length. My impression is that focal length and focus parameter (i.e. which modify this distance between image plane and the lens) slightly change in video mode compared to camera mode. – Filippo Bandini Jan 20 '18 at 13:07
  • @FilippoBandini good point. I'm used to a DSLR where the lens focal lenght can't change unless you do it yourself. But I find it unlikely that the lens is changing, rather the camera is using a different magnification for the preview. – Mark Ransom Jan 20 '18 at 13:27
0

The sensor size is 8.8mm height by 13.2mm length. This is a 1.5 ratio i.e. 8.8 X 1.5 = 13.2.

When shooting video, the ratio changes to 16:9. This is a fraction 16 ÷ 9 = 1.7778 (in decimal format). If we know the dimensions of one of the two sizes of a rectangle, we can compute the other using this decimal fraction. Likely in video mode, full length of the sensor is being utilized. Thus the revised height is 13.2 ÷ 1.7778 = 7.4249. That’s the height in millimeters. The video format becomes 7.4mm height by 13.2mm length.

  • 2
    When I use my Pentax K-01 for video I get cropping on both axes. I assume it's to make the resizing math work out better for the camera. You can't assume the full width will be utilized until you measure. – Mark Ransom Jan 18 '18 at 22:52
  • Actually the vast majority of cameras that do not shoot 4K are do a downscale or pixel-skip from full-width. With 4K, the majority take a crop so Full-Width 4K has become a desirable feature. There are a handful of cameras with oversized sensor that get more than full-width in video compared to 3:2 or 4:3 stills. – Itai Jan 19 '18 at 4:44
  • The Sony Cyber-shot DSC-RX100 significantly crops in both dimension, with the larger cropping on the vertical direction. – Filippo Bandini Jan 20 '18 at 13:13

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.