Why does the GoPro Hero HD have a wider field of view at lower video resolutions?
Asked 2/25/2011
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The GoPro Hero HD specs list a 170° field of view in WVGA, 720p, and 960p modes, but only 127° in 1080p mode. Since the camera has no optical zoom, why does the field of view get narrower at the higher resolution? I would have expected a wider field of view when more of the sensor is used. What is happening technically?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
15y ago
2 Answers
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The only thing I can think of is that the cam doesn't have the processing power to encode all the pixels in the sensor, so you can either crop the frame (which reduces the field of view) or you can use the whole sensor and subsample (skip pixels/rows like video DSLRs do), which reduces the resolution but maintains the full field of view.
edit: looking more closely at the specs, the HD hero takes 5MP stills so it must be a case of variable subsampling rates. Given this I can't see why they couldn't produce a 1080p signal by subsampling the whole sensor. I wonder if it's something to do with the lens, i.e. it's too soft in the corners for full HD.
Originally by user1375. Source · Licensed CC BY-SA 4.0
user1375
15y ago
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This is usually due to how the camera reads the sensor for each video mode, not because the lens changes.
At lower resolutions, the camera can use most or all of the sensor and reduce resolution by subsampling or pixel binning/skipping. That preserves the wider area of the sensor, so the field of view stays very wide.
At 1080p, the camera may not be able to read and process the full sensor fast enough, or it may need a cleaner 1920×1080 output. A common solution is to crop the sensor to a smaller central area and record that. Cropping narrows the angle of view, which is why 1080p can show only 127° instead of 170°.
So the difference is likely:
- lower-res modes: full-sensor readout with skipping/binning/subsampling
- 1080p mode: cropped sensor readout
In short, field of view depends on how much of the sensor is used for that mode. Higher output resolution does not always mean a wider view if the camera switches to a crop.
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