What focal length do I need on a Canon 70D to frame a 1.9m x 1.2m blackboard from 1.8m away?
Asked 9/5/2015
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I’m setting up a home studio to record math classes. The blackboard is about 1.9m wide and 1.2m tall, and the camera will be roughly 1.8m from the board on a tripod. I’m considering a Canon 70D. How do I work out what focal length lens I need to capture the full board in frame, especially for video recording?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
11y ago
2 Answers
1
Record with 3:2 still pictures, or 16:9 movies? It matters, a little. Assuming the later, see a field of view calculator at http://www.scantips.com/lights/fieldofview.html
Canon 70D is a 3:2 1.6x 22.5x15mm DSLR, but offers 16:9 movies, which is a complication (HD format is only 12.65 tall usable).
Instructions:
Enter 1.8 m distance at top,
Enter 1.6x crop and 16:9 in a 3:2 DSLR in option 3,
Select option 5, and specify there to use option 3 sensor and to find focal length for 1.2m Vertical,
then it computes field of view H 2.13 and V 1.20 meters
with a 19mm lens
Or recording 3:2 still pictures computes 22.5mm focal lens is 1.8 x 1.2 m field of view.
Originally by user38978. Source · Licensed CC BY-SA 4.0
user38978
11y ago
0
Generated from our catalog & community — verify before relying on it.
On a Canon 70D, the needed focal length depends on whether you’re shooting stills or video, because video uses a 16:9 frame rather than the camera’s full 3:2 sensor area.
From the measurements given:
- For 16:9 video, about a 19mm lens gives roughly a 2.13m horizontal field of view and 1.20m vertical field of view at 1.8m distance.
- For 3:2 stills, about a 22.5mm lens gives about a 1.8m × 1.2m field of view.
Since your board is 1.9m wide, video framing is the better fit here: a lens around 19mm on the 70D should capture the full height and enough width. In practice, choosing something a little wider can give you extra framing room and make setup easier.
A field-of-view calculator is the simplest way to check this: enter camera distance, sensor/crop format, aspect ratio, and the width/height you need to fit.
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