I was about to join this debate and then ran the numbers and realized I still don't get this right. I was going to say it's about sensor size and bigger sensors have shallower DOF.
Here's where I go when I need a refresher - Tony Northrup's explanations:
I'm not saying anything about sensor size or depth of field. I'm pointing out the misuse of the term "bokeh". Bokeh is not depth of field. It's the quality of out of focus areas. You want good bokeh when you have a shallow depth of field but bokeh is itself a subjective measure of quality, not quantity.
Calling depth of field "bokeh" is like calling focal length "framing".
He's sorta right in the sense that most people like a "relaxed" character in the out of focus areas which is very hard to achieve with tiny sensors and lenses (while for example basically every modern large format lens is extremely "creamy").
If the statement was that it’s hard to make a tiny lens for a tiny sensor with good bokeh, then I guess that could be correct (I actually don’t know if small lenses can produce pleasing bokeh). I read the comment as the common “bokeh=shallow depth of field”
misunderstanding, though, because the focus was on sensor size rather than the lens.
OK let's talk about depth of field. DOF is both a function of sensor size and lens aperture. That's why small sensors even with 1.8 aperture have no bokeh comparable to 35mm at 1.8.
And anyway with very small sensors you can only get blurriness if you are extremely close to the subject, while 35mm and higher sensor formats allow for MUCH more creativity.
> OK let's talk about depth of field... small sensors even with 1.8 aperture have no bokeh comparable to 35mm at 1.8.
Bokeh is not depth of field. That’s the point.
Yes, small sensors cannot get extremely shallow depth of field. However, shallow depth of field is not bokeh. If you want to say that small sensors cannot achieve narrow depth of the field or massive subject separation or a “destroyed” background or whatever, fine. But don’t call it bokeh because that’s something else.
A lens could yield the same bokeh (blur quality) at f/2 and f/4 even though the depth of field (blur quantity) would be much different.
Here's where I go when I need a refresher - Tony Northrup's explanations:
https://petapixel.com/2014/05/27/tony-northrup-makes-correct...
There's a lot of criticisms of his series, but they're often shallow (they don't seem to watch his whole video) and actually end up agreeing with him.