The Recent F/stop Controversy

Started 1 month ago | Discussions thread
Great Bustard Forum Pro • Posts: 42,954

riveredger wrote:

Great Bustard wrote:

Indeed. However, an important lesson that Equivalence explains is that, for a given DOF and exposure time, the same total amount of light is projected on the sensor for *all* systems. So, for a larger format to have a light gathering advantage over a smaller format, the larger format *must* use a more narrow DOF or a longer exposure time. That's worth knowing, methinks, even if one is otherwise uninterested in other Equivalence related topics.

While correct, I do not think it adds clarity to the discussion. The short version is that a larger sensor will always capture more total light than a smaller sensor, given the same exposure. The other consequences of exposure decisions remain the same, irrespective of format.

Well, I guess we disagree. I think the following three statements below add significant clarity:

  • For a given exposure, more light is projected on a larger sensor.
  • For a given scene, DOF, and exposure time, the same amount of light is projected on all sensors, regardless of size.
  • Thus, the only way for a larger sensor to collect more light is to use a more shallow DOF or longer exposure time.

To me, that's all good-to-know stuff, and only one bullet point outside what I once saw written here on DPR: "If it takes more than a sentence or two to explain, it's probably not worth knowing." 

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