Just wondering if someone can help me understand this.
When using the VRay physical camera - I want to control the intensity of the Dof however, the only parameter that seems to control its intensity is the f-number. The problem here is that this plays havoc with the exposure of the scene.
What I don’t get is that when using our dSLR - its the position of the camera to the subject and the zoom which control the intensity of the Dof and nothing to do with the f-stops.
I am assuming that I am exposing my lack of knowledge here but, if someone could put me straight on this I would appreciate it.
I’m pretty sure DOF does go off the target distance too.
You can work out how much you need to change your shutter speed for however much you’ve changed the f-stop easily enough, but i cant remember how they relate to each other atm. I used to do it all the time.
Now I use standard cams if dof/MB is needed…
DOF is absolutely connected with aperture (f-number) and subject magnification. Wide apertures (small f-numbers) will shrink the DOF. Larger subject magnification (using a more telephoto lens or moving closer to the subject) will also yield shallower DOF. The combination of the two is therefore critical.
I used to have a Canon slr. It had a clever feature where you would target the furthest point you need to be in focus, then the nearest point, and it will calculate an aperture/speed setting to best achieve this.
I use my own scripts to adjust focus and exposure: first i autofocus the camera, then i change the in-focus depth to suit my needs playing with the F number, and lastly i expose with ISOs through the exposimeter. Easy as one, two three
