GaryPolter
TPF Noob!
- Joined
- Sep 2, 2010
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I think something finally clicked in my brain. So as Helen said, the thin lens equation assumes a fixed focal length.
So let's say I tell my lens to have some fixed focal length of 50mm. This means for "infinitely" far objects I need to have the lens 50mm away from the image sensor. If an object is 1000mm away, then to focus it, the lens will move, but the focal length stays the same. Put another way, the focal ring will only move the lens closer/further from the image sensor. When I use the focal ring to move the lens 52.6mm away from the sensor then this image will be in focus.
To ask if other objects will be in focus is not a good question because for that I'll need to calculate the depth of field which requires other values such as aperture.
So let's say I tell my lens to have some fixed focal length of 50mm. This means for "infinitely" far objects I need to have the lens 50mm away from the image sensor. If an object is 1000mm away, then to focus it, the lens will move, but the focal length stays the same. Put another way, the focal ring will only move the lens closer/further from the image sensor. When I use the focal ring to move the lens 52.6mm away from the sensor then this image will be in focus.
To ask if other objects will be in focus is not a good question because for that I'll need to calculate the depth of field which requires other values such as aperture.