It’s only the focal length and f-stop that affect depth of field. Sensor size affects it only indirectly, because you need a different focal length to get the same angle of view.
From an optical point of view, light does not bend differently just because you put a differently-sized rectangle somewhere in its path. Or to put it another way, if you cut the edges off your sensor, that won’t alter the image on the remaining area of the sensor.
Yeah I guess you're right but there are limits on how shallow your DOF can get on smaller sensors. So when it comes to practical irl results you kinda need a larger sensor to get extremely shallow DOF.
> there are limits on how shallow your DOF can get on smaller sensors.
Only in the sense that you generally use a smaller sensor because you want your camera to be small.
If you take a full frame SLR and attach a 100mm f1.8 lens to it, you’ll get a shallow depth of field. Now crop that image down to an area of the sensor corresponding to the size of a phone sensor, and the cropped image will have the exact same depth of field.
> Now, here's the kicker: the bigger the focusing lens is, the larger the cone of light rays is, meaning the the out of focus parts of the image will be more out of focus
From the page [0] it takes the depth of focus image from:
> [Depth of focus] differs from depth of field because it describes the distance over which light is focused at the camera's sensor, as opposed to the subject
The first quote is clearly talking about depth of field, not depth of focus. See also what I quoted in my original comment.
Depth of focus isn’t really relevant to the rendering of an image (except insofar as you want your camera to be built to sufficient tolerances that a sharp image can be obtained when desired).
I assumed you were using “depth of focus” to mean “depth of field”. If you really meant “depth of focus”, then I would say you are mistaken in thinking that the author’s goal is to obtain a narrow depth of focus.
The first quote is definitely talking about depth of focus; the linked image talks about depth of focus and how it compares to depth of field. As I understand it, depth of focus has a similar effect to depth of field. If your rays diverge more quickly on the side of your sensor, you will have a blurrier image for the same distance from the focal plane. Otherwise, how do you think depth of focus presents itself in the final image?
Depth of focus doesn’t present itself in the final image. It’s generally irrelevant to practical photography from the point of vide of the photographer (as opposed to the camera designer or lens manufacturer). The first quote is talking about depth of field (i.e. how quickly focus falls off from the plane of perfect focus).
FWIW, here is what Claude has to say:
>> Is depth of focus, as opposed to depth of field, generally relevant to practical photography?
> Not really, no. Depth of focus and depth of field are related but distinct concepts, and for practical photography, depth of field is what matters almost all the time.
> Depth of field refers to the zone in front of the camera where subjects appear acceptably sharp. This is what photographers think about constantly: choosing apertures to blur backgrounds in portraits, stopping down for landscapes to keep everything sharp, figuring out hyperfocal distance, etc.
> Depth of focus refers to the tolerance zone behind the lens, at the image plane (the sensor or film), within which the image remains acceptably sharp. It tells you how precisely the sensor needs to be positioned relative to the lens for focus to be maintained.
> For the overwhelming majority of photographers, depth of focus is invisible because it's a manufacturing and engineering concern, not a shooting concern. Camera makers deal with it when designing bodies and ensuring sensor flatness, lens mount tolerances, and autofocus calibration. You encounter it indirectly if you ever need to calibrate autofocus micro-adjustments, shim a lens, or diagnose back/front focus issues, but you don't actively manipulate it while composing a shot.
