The Recent F/stop Controversy

Started 4 months ago | Discussions
mamallama
mamallama Forum Pro • Posts: 56,269
Re: Yep, that's the modern world, all right.
1

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.

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Great Bustard Forum Pro • Posts: 43,167
Re: Yep, that's the modern world, all right.
2

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.

mamallama
mamallama Forum Pro • Posts: 56,269
Re: Yep, that's the modern world, all right.
1

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. Go back and read what I asked for.

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kiwi2
kiwi2 Veteran Member • Posts: 4,751
Re: It's weird, isn't it?

Great Bustard wrote:

Michael Fryd wrote:

kiwi2 wrote:

Why exactly should I be worried about achieving equivalence between the two..??

You shouldn't be concerned about equivalence between these two.

It's weird that so many [intentionally] misrepresent Equivalence saying that they should be shooting Equivalent photos on different formats, even though Equivalence *explicitly* says quite the opposite. It's as if someone said to multiply mi/hr by 1.6 to get km/hr, and they said, "Why should I drive the same speed in Europe as I do in the US?"

So now with a real world example, it suddenly doesn't matter any more...???

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Great Bustard Forum Pro • Posts: 43,167
Disingenuous posting
2

kiwi2 wrote:

Great Bustard wrote:

Michael Fryd wrote:

kiwi2 wrote:

Why exactly should I be worried about achieving equivalence between the two..??

You shouldn't be concerned about equivalence between these two.

It's weird that so many [intentionally] misrepresent Equivalence saying that they should be shooting Equivalent photos on different formats, even though Equivalence *explicitly* says quite the opposite. It's as if someone said to multiply mi/hr by 1.6 to get km/hr, and they said, "Why should I drive the same speed in Europe as I do in the US?"

So now with a real world example, it suddenly doesn't matter any more...???

Remember when Richard Butler said to you:

Disingenuous posting

It's already been made clear in one thread that no one is saying that the f-number of a lens actually changes and that the standard exposure model is based, for better or worse, on f-numbers and light per unit area.

So no, no one is saying that the f-number "becomes" something else. Or "is" something else on a different sensor. You repeatedly reverting to that claim is clearly disingenuous.

You've made apparent that you know this already. You're also seemingly aware that equivalence doesn't claim it, and that there is some value to a whole-image understanding of total light.

If you continue to intentionally misrepresent the idea of equivalence, purely because you want to play games of semantics or because you've decided you don't deem it useful, this thread will be deleted.

Do you remember that? You're doing the *exact same BS* again. Where does Equivalence say, or imply, that one should use one system to get photos Equivalent to photos taken with another system? Where does Equivalence say, or imply, that the differences between System A and System B are *necessarily* going to be so significant that one *must* take Equivalence into account with each and every photo?

Once again, your are *intentionally* misrepresenting what Equivalence says/implies. Your straw man argument is *exactly* like me posting a photo of a scene at f/4 1/400 ISO 100 and f/8 1/100 ISO 400 that look all but identical and then making the specious claim that there's no difference between f/4 and f/8, no difference between 1/400 and 1/100, and no difference between ISO 100 and ISO 400. And you do this kind of ++++ all the freakin' time!

Great Bustard Forum Pro • Posts: 43,167
Re: Yep, that's the modern world, all right.
3

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.

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

threw the lens
threw the lens Senior Member • Posts: 1,410
Re: The Recent F/stop Controversy

I don't find aperture stops difficult.

The lower the aperture number, the faster the shutter speed and smaller the depth of field.

On the rare instance that I want to compare lenses across different systems, I need to take into account the way a change in sensor size affects the depth of field and noise. It is an easy relationship to understand. It only seems to be those with a nagging inferiority complex on four thirds sensors that pop up to try to confuse the issue.

It's not worth creating an alternative to the f-stop, because people would still run into a conceptual brick wall later when they find that a 35mm f1.4 does not have the same depth of field as a 105mm f1.4.

The f-stop is only slightly weird in that a smaller number lets in more light. Apart from that, I'm fine with it.

Great Bustard Forum Pro • Posts: 43,167
Re: The Recent F/stop Controversy
2

threw the lens wrote:

The f-stop is only slightly weird in that a smaller number lets in more light. Apart from that, I'm fine with it.

Consider a 100mm lens at f/2 and at f/4. What f/2 and f/4 literally mean is that the diameter of the aperture is 100mm / 2 = 50mm and 100mm / 4 = 25mm, respectively, since the "f" represents the focal length. The wider aperture (which, by the way, is why we say "f/2 is wider than f/4") lets in more light for a given scene and exposure time.

MediaArchivist
MediaArchivist Veteran Member • Posts: 5,226
refrains and concerns?
1

LoneTree1 wrote:

What is the biggest refrain of people with kit lenses? "Darn, I could do with a few fewer mm's at the wide end."

I'm not sure that is true.

What is the biggest concern of people with tele-zooms? "Why do I need 70mm when I shoot mostly 300mm and why is the long end always the "worst" optically?

300mm primes are pretty expensive, for a reason. How does that affect the common measurements of relative apertures?

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robert1955 Veteran Member • Posts: 4,417
Re: Yep, that's the modern world, all right.

Great Bustard wrote:

[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.

The word relates  is what most antiequivalentists do not get

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Michael Fryd
Michael Fryd Forum Pro • Posts: 11,746
Re: It's weird, isn't it?
2

kiwi2 wrote:

Great Bustard wrote:

Michael Fryd wrote:

kiwi2 wrote:

Why exactly should I be worried about achieving equivalence between the two..??

You shouldn't be concerned about equivalence between these two.

It's weird that so many [intentionally] misrepresent Equivalence saying that they should be shooting Equivalent photos on different formats, even though Equivalence *explicitly* says quite the opposite. It's as if someone said to multiply mi/hr by 1.6 to get km/hr, and they said, "Why should I drive the same speed in Europe as I do in the US?"

So now with a real world example, it suddenly doesn't matter any more...???

With that particular example neither shutter speed, nor aperture are critical, and there is more than enough subject illumination to get sufficient total light for an acceptable level of image noise.  In this situation, the camera settings aren't important at all.

The fact that there are some situations where camera settings are not critical does not mean that this is true for all situations.

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Michael Fryd
Michael Fryd Forum Pro • Posts: 11,746
Re: The Recent F/stop Controversy

threw the lens wrote:

...

It's not worth creating an alternative to the f-stop, because people would still run into a conceptual brick wall later when they find that a 35mm f1.4 does not have the same depth of field as a 105mm f1.4.

...

One is not creating an "alternative to f/stops". The underlying optical property we are talking about is the diameter of the entrance pupil of the lens. "F/stop" is the alternative that we use when we are more concerned about light per unit area than exposure.

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Michael Fryd
Michael Fryd Forum Pro • Posts: 11,746
Re: Really?

Pixel Pooper wrote:

  • Michael Fryd wrote:

Actually, at the same angle of view the "equivalent aperture" is the one with the same diameter. In other words it really is the same aperture; no math needed.

You only need to do the math if you normalize everything to light per unit area (which is a great idea when shooting film).

Whether you are shooting film or digital makes no difference. The reason we use the f/stop is that it gives us the same exposure regardless of focal length or angle of view. If we used aperture diameter it would be more complicated because we would need to change the diameter every time we changed our focal length.

While shooting I am much more likely to change my field of view than my sensor size and if I do change my sensor size it is to take advantage of the differences between the two formats, not to take the same picture on both.

The fact that the same aperture diameter gives the same total light at the same field of view is good to know, but it's not as useful when taking pictures. Whatever format you use, the way to maximize total light is to maximize exposure and your total light is limited by the need to avoid overexposure.

Equivalence is a way of comparing formats, and it is a great framework to understand how things work, but it is not a replacement for f/stops and exposure.

This is the issue. You have built your workflow around "exposure" (light per unit area). While this makes sense for film it isn't necessary for digital.

When taking a photo we need to balance shutter speed (which affects motion blue), aperture (which affects depth of field) and total light (which affects image noise). When you have ample subject illumination, there will be a range of settings that give you the desired results.

The important situation is what happens when there isn't ample subject illumination? How do you balance the three elements?

If we start by picking one, then we have taken it out of consideration for balancing. If we set the camera to a fixed ISO (which selects a target exposure) and put the camera into shutter priority mode, then we are telling the camera to use aperture for balancing. This means that if there is more than ample illumination, we get more depth of field, and when there isn't enough then we don't get as much depth of field as we need.

If we move the camera to aperture priority, we run into the problem that not enough light give us motion blur.

By basing our workflow on exposure we tend to forget about our third choice. Set the aperture to give us the depth of field we need. Set the shutter speed to give us the motion stopping ability we want, and let the exposure fall where it may (Auto-ISO).

This third choice isn't a practical option with film, and our entire workflow and nomenclature is based on the need to hit the sweet spot on the response curve for film.

====

If you have ever shot in aperture priority mode, then you have let the camera pick the shutter speed. If you have ever shot in shutter priority mode, then you have let the camera pick the aperture.   What's so special about exposure?  Why do we have to start by picking an exposure?

====

A typical response is that the photographer needs to pick the exposure as he wants to control the noise in the image.   The fallacy of this is that the photographer should also want to control the depth of field and motion stopping ability.  All three are important.

Building a workflow around exposure (light per unit area) is a holdover from film days.  It was important then, but is an artifically imposed  limitation with digital.

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RUcrAZ
RUcrAZ Veteran Member • Posts: 6,038
A great deal of these postings are null...

….and unimportant, when one considers something called "exposure bracketing."

(Nearly every post (didn't read them all) is "correct," but they are not very critical -within limits, not "outer fringe conditions"- to the fact that you can usually have your cake and eat it by exposure bracketing.)

Pixel Pooper Veteran Member • Posts: 3,175
Re: Really?
2

Michael Fryd wrote:

Pixel Pooper wrote:

  • Michael Fryd wrote:

Actually, at the same angle of view the "equivalent aperture" is the one with the same diameter. In other words it really is the same aperture; no math needed.

You only need to do the math if you normalize everything to light per unit area (which is a great idea when shooting film).

Whether you are shooting film or digital makes no difference. The reason we use the f/stop is that it gives us the same exposure regardless of focal length or angle of view. If we used aperture diameter it would be more complicated because we would need to change the diameter every time we changed our focal length.

While shooting I am much more likely to change my field of view than my sensor size and if I do change my sensor size it is to take advantage of the differences between the two formats, not to take the same picture on both.

The fact that the same aperture diameter gives the same total light at the same field of view is good to know, but it's not as useful when taking pictures. Whatever format you use, the way to maximize total light is to maximize exposure and your total light is limited by the need to avoid overexposure.

Equivalence is a way of comparing formats, and it is a great framework to understand how things work, but it is not a replacement for f/stops and exposure.

This is the issue. You have built your workflow around "exposure" (light per unit area). While this makes sense for film it isn't necessary for digital.

You don't know what my workflow is.

When taking a photo we need to balance shutter speed (which affects motion blue), aperture (which affects depth of field) and total light (which affects image noise). When you have ample subject illumination, there will be a range of settings that give you the desired results.

The important situation is what happens when there isn't ample subject illumination? How do you balance the three elements?

If we start by picking one, then we have taken it out of consideration for balancing. If we set the camera to a fixed ISO (which selects a target exposure) and put the camera into shutter priority mode, then we are telling the camera to use aperture for balancing. This means that if there is more than ample illumination, we get more depth of field, and when there isn't enough then we don't get as much depth of field as we need.

If we move the camera to aperture priority, we run into the problem that not enough light give us motion blur.

By basing our workflow on exposure we tend to forget about our third choice. Set the aperture to give us the depth of field we need. Set the shutter speed to give us the motion stopping ability we want, and let the exposure fall where it may (Auto-ISO).

Auto ISO in M mode does not let the exposure fall where it may, it lets the ISO fall where it may. You chose the exposure when you set the aperture and shutter speed, and if you choose too high or too low an exposure, auto ISO will not be able to bail you out.

This third choice isn't a practical option with film, and our entire workflow and nomenclature is based on the need to hit the sweet spot on the response curve for film.

My workflow has nothing to do with the response curve for film.

====

If you have ever shot in aperture priority mode, then you have let the camera pick the shutter speed. If you have ever shot in shutter priority mode, then you have let the camera pick the aperture. What's so special about exposure? Why do we have to start by picking an exposure?

You seem confused. The workflow you described above using auto ISO in manual started with picking an exposure, then the camera chose the ISO based on that exposure.

====

A typical response is that the photographer needs to pick the exposure as he wants to control the noise in the image. The fallacy of this is that the photographer should also want to control the depth of field and motion stopping ability. All three are important.

That's not a fallacy. Your exposure settings control noise, DOF, and motion blur.

Building a workflow around exposure (light per unit area) is a holdover from film days. It was important then, but is an artifically imposed limitation with digital.

Exposure is not an artificially imposed limitation. If your exposure is to low you get noise, and if it is to high you get blown highlights. This is photography 101. You can't just ignore exposure.

You keep advocating a workflow based on aperture diameter and angle of view, but you haven't explained how that would work in practice. Please explain how you propose we take pictures without using exposure.

Pixel Pooper Veteran Member • Posts: 3,175
Re: A great deal of these postings are null...
2

RUcrAZ wrote:

….and unimportant, when one considers something called "exposure bracketing."

(Nearly every post (didn't read them all) is "correct," but they are not very critical -within limits, not "outer fringe conditions"- to the fact that you can usually have your cake and eat it by exposure bracketing.)

You shouldn't have to rely on exposure bracketing. Choosing an appropriate exposure is the most trivial part of shooting with a digital camera.

RUcrAZ
RUcrAZ Veteran Member • Posts: 6,038
Re: A great deal of these postings are null...

I agree, and that's my point. Exposure bracketing solves a significant number of "exposure" issues, that people seem to spend an awful lot of sound and fury on.

Pixel Pooper Veteran Member • Posts: 3,175
Re: The Recent F/stop Controversy

Michael Fryd wrote:

threw the lens wrote:

...

It's not worth creating an alternative to the f-stop, because people would still run into a conceptual brick wall later when they find that a 35mm f1.4 does not have the same depth of field as a 105mm f1.4.

...

One is not creating an "alternative to f/stops". The underlying optical property we are talking about is the diameter of the entrance pupil of the lens. "F/stop" is the alternative that we use when we are more concerned about light per unit area than exposure.

How can you be more concerned about light per area than exposure, when exposure is light per area by definition?

tcg550 Veteran Member • Posts: 9,085
Re: The Recent F/stop Controversy

I didn't read most of those posts because the idea of changing the term f stop is absurd.

No jargon to get lost in, f stop is the same thing it's been since I learned it and I use it the same way I've always used it to get the results I'm looking for.

Not that complicated.

Bill Ferris
Bill Ferris Veteran Member • Posts: 4,431
Re: The Recent F/stop Controversy
2

Michael Fryd wrote:

it's not so much a technical question as a philosophical one. Is the frame of reference designed for the limitations of film the best frame of reference to use for digital?

Perhaps, I am misreading your comment and question. It appears you consider f-stop to be more relevant to film than to digital. Or at the very least, you see f-stop as a concept or setting that may be more relevant to film than to digital. Is that accurate?

As you and probably everybody participating in this discussion know, the focal ratio of a lens (aka f-stop, f/ratio) describes the ratio of the focal length of the lens to the diameter of the aperture of the lens. Both dimensions are typically measured in millimeters. For example, a 100mm lens with an aperture diameter of 25mm, is described as, f/4. That's the lens's f/ratio. It's the f-stop chosen by the photographer.

The use of f-stop to describe the physical characteristics of a lens applies regardless of the light-sensitive medium used. Whether that medium is a chemical emulsion or a collection of pixels, f-stop has the same meaning. Also regardless of the light-sensitive medium used, f-stop along with scene brightness and shutter speed define exposure: the average brightness of the scene at the image plane. This is another fact of which you and most others in this thread are well-aware.

Within this context, I would say it is more accurate to describe, f-stop, as a concept adopted as a tool of photography than as a concept linked more closely to film or any other mode of containing the light-sensitive medium. The term has no different meaning to a photographer using a chemical emulsion (e.g. glass plate, tin type, film) than to a photographer using pixels (e.g. CCD or CMOS) to capture light. It has no different influence on exposure.

The profound physical and performance differences between chemical emulsions and pixels along with the relative performance characteristics of the modes (glass plates, tin types, film stock, sensor formats) used to precisely positioning these light-sensitive media at the image plane introduce a host of issues relevant to the photographic process. Equivalence, is but one. Frankly, there are too many to adequately address in a collection of books, let alone a single online forum discussion thread.

However, f-stop, is a term having a clear definition. Any lack of clarity on that point in this post, is my failure; not a failure of the long-established and accepted definition of the term. Its meaning and role in determining exposure are the same, regardless of the medium or mode used in the photographic process.

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