The Recent F/stop Controversy

Started 1 month ago | Discussions thread
Great Bustard Forum Pro • Posts: 42,950
Re: Yep, that's the modern world, all right.

mamallama wrote:

Great Bustard wrote:

mamallama wrote:

Great Bustard wrote:

mamallama wrote:

Great Bustard wrote:

mamallama wrote:

Great Bustard wrote:

mamallama wrote:

I love the clarity when just the mention of equivalence results in multiple threads that limit out at 150. A concise one sentence definition of equivalence might help the clarity.

If you can't say it all in a Twitter post, then it isn't worth saying -- that's the world we now live in. Maybe if I ask the POTUS, he can do it just for you.

Now I know why it isn't worth saying.

Well, you were the one asking for the Twitter post version to get some clarity. So the three bullet points I gave:

  • 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.

were too much of a chore for you -- you wanted a "concise one sentence definition of equivalence" in order to have "clarity", but now say that a one sentence definition isn't worth saying because it reflects the same mindset of someone whose politics you don't like. Oh well -- can't please them all, I suppose.

Sorry, that is not a one sentence definition.

No kidding -- I said that my three bullet points "were too much of a chore for you" because you wanted a single sentence. But when I noted that the POTUS is the king of single sentence explanations, you said, "Now I know why it isn't worth saying". But, if you must have a single sentence, here it is:

[Photographic] Equivalence is a paradigm that relates the visual properties of photos of a given scene from different formats based on perspective, framing, and the diameter of the [effective] aperture.

At least we know you are thinking of it as a paradigm.

It wasn't a secret:

A common criticism of Equivalence is that some people say that it does nothing to help them to take better pictures. However, Equivalence is simply a framework by which to compare the IQ of different formats on the basis of six visual properties that are independent of the technology -- the same perspective, framing, DOF / diffraction / total amount of light on the sensor, exposure time (motion blur), lightness, and display dimensions. Equivalence is not an "instruction manual" for how to take a photo, but rather a comparison point for photographs from different systems.

But rather obscure hidden in a ton of words.

It's the first paragraph of the "hidden" section with the title of The Purpose of Equivalence. Hide and Seek was certainly not your favorite game, I guess.

The description of the paradigm is rather vague, however.

Which is exactly what I said below:

Go back and read what I asked for.

There's your single sentence and is no more or less helpful in understanding what Equivalence is about than, say, a single sentence definition of Capitalism:

an economic system characterized by private or corporate ownership of capital goods, by investments that are determined by private decision, and by prices, production, and the distribution of goods that are determined mainly by competition in a free market

Your admission of its vagueness explains why whenever Equivalence is discussed it is like the fable of the three blind men trying to describe an elephant.

My "admission of its vagueness" was me trying (in vain) to explain to you that single sentence explanations are not always useful. Perhaps you recall me giving the example of the tweets by the POTUS to send that point home?

I will just take that for what its worth.

I'm pretty sure you won't. In any case, here it is again:

But, for those for whom the definition as given is too much to handle:

Equivalent photos are photos of a given scene that have the:

As a corollary, Equivalent lenses are lenses that produce Equivalent photos on the format they are used on which means they will have the same AOV (angle of view) and the same aperture diameter. The following rules of thumb, which are a consequence of the above definition, are also helpful to understand:

  • 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.

But, like I said before:

What can you do, right? It's definitely longer than a sentence or two, so I guess that limits its utility to less than 1% of the population, right?

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tex
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