sk66
Suspended / Banned
- Messages
- 9,557
- Name
- Steven
- Edit My Images
- Yes
There's been something in the back of my mind regarding DOF and focal length and I figured why not throw it out there...
Lets say I choose to use a longer lens from further away for a different perspective. Theoretically, if I keep the FOV at the subject the same the DOF remains the same (FL and Distance cancel each other out)... so far, so good; everything is tracking.
But here's the part that's getting me... lets say I have a subject at 50ft with the BG 50ft behind them and I then double the focal length and back up to 100ft. I have not doubled the distance to the BG so the increase in subject distance does not entirely negate the increase in FL magnification for the BG. Therefore the BG details are recorded larger.
This is where my problem is...because DOF/sharpness is a perceptual thing having to do with both how OOF something is (detail/contrast) AND how large it is (perception); isn't the BG *actually* more OOF even though the math/theory says it isn't?
Lets say I choose to use a longer lens from further away for a different perspective. Theoretically, if I keep the FOV at the subject the same the DOF remains the same (FL and Distance cancel each other out)... so far, so good; everything is tracking.
But here's the part that's getting me... lets say I have a subject at 50ft with the BG 50ft behind them and I then double the focal length and back up to 100ft. I have not doubled the distance to the BG so the increase in subject distance does not entirely negate the increase in FL magnification for the BG. Therefore the BG details are recorded larger.
This is where my problem is...because DOF/sharpness is a perceptual thing having to do with both how OOF something is (detail/contrast) AND how large it is (perception); isn't the BG *actually* more OOF even though the math/theory says it isn't?