The fallacy of 35mm "equivalent focal lengths"

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SirPeepsalot Contributing Member • Posts: 550
Re: The fallacy of 35mm "equivalent focal lengths"
1

Nothing and everything is a fallacy when underspecified, when people talk about format equivalence in photography it implies equivalence of composition and perspective, sometimes also DoF but no other imaging aspects. The above are provably equivalent from their commonly-accepted definitions by multiplying the focal length by the ratio of the diagonals of the formats being compared.

BAK Forum Pro • Posts: 24,645
Re: The fallacy of 35mm "equivalent focal lengths"

I may have reached three or four lines deeper than you.

I don't think he'll find anything useful for the precis.

Anyway, I just finished spending an hour with one of my David Bailey books, imaging that I'm visiting England.

Did you ever do any work with him?

April in England is only a couple of weeks away.

BAK

OP Tony Beach Forum Pro • Posts: 11,967
Re: Okay. What now?

sybersitizen wrote:

Tony Beach wrote:

When I want an idea of what a camera can do (i.e., what it is equivalent to) I look at its actual focal lengths and apertures, and then the size and pixel density of its sensor. The only limitation actually described by "equivalent focal length" is how wide a FOV you can capture in the file. Many consumers (and even some participants in the forums here at DPR) falsely think that when the camera is sold to them with some extraordinary "equivalent focal length" that they would need an enormous lens to replicate that, and that's misleading and fallacious.

I don't think anyone here would choose to argue with those three sentences ... at least I wouldn't. Maybe this thread would be much shorter if you said exactly that in the first post.

Ideally that's what a discussion accomplishes. I would certainly incorporate what I'm reading in the replies into a rewrite of the OP, but it's what it is now, so that's something to consider for the future.

Some (myself included) might feel that there is no guilty party at work intentionally trying to deceive or mislead the population of camera buyers; but rather it's just that many things are more complicated than can be easily presented and digested by the population of buyers of any complex product category, and this qualifies as one of them.

If one wants to invoke the equivalent AOV then should also invoke the equivalent DOF. Indeed, the terminology could be made more sensible than it is now.

A question now is: Are you in favor of camera manufacturers describing and labeling products differently (replacing equivalent focal length with equivalent FOV) and including the many associated caveats in those descriptions and/or labels? And the same thing regarding camera reviews and forum discussions of equivalence?

Yes.

Mark Scott Abeln
Mark Scott Abeln Forum Pro • Posts: 13,636
A fourth

tony field wrote:

Of course there is the third angle of view which is based upon the diagonal of the format. This is the standard by which "Equivalence" works.

I find that using the square root of the area of the sensor is the most useful of all, because it removes the influence of the aspect ratio, and it ends up being an unbiased "average" angle of view over the entire sensor. Clearly, it makes no difference if comparing sensors with the same aspect ratio, and only a slight difference between 3:2 and 4:3 sensors.

Actually, this method works best for equivalence, especially considering the total light on the sensor during exposure, because the results will be exact instead of approximate. This may be important when comparing widescreen formats with square formats.

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OP Tony Beach Forum Pro • Posts: 11,967
Re: The fallacy of 35mm "equivalent focal lengths"

mamallama wrote:

Tony Beach wrote:

mamallama wrote:

Tony Beach wrote:

Describing a lens as having an equivalent focal length is simply wrong. I can't make it any more concise than that.

Provide a concise precise technical definition of equivalent as you are using the term. That will save a lot of the round robin discussions that have taken place.

I just did.

Where?

Sorry, I should have been more clear.

If you have already stated it then copy and paste the precise definition of equivalent here.

My point is there is no such thing as an "equivalent focal length" because all focal lengths have their own unique characteristics.  By invoking one limited aspect of a focal length as its used on a given sensor the other equally important aspects of that focal length are explicitly being disregarded.

It's more accurate to say a focal length when used on a particular format has a particular FOV.

Our learned folks here at DPR use the term equivalent focal length in discussions and in their lens specifications. They are very definite in the definition of how they are using the term equivalent. It is not a fallacy. It is how the whole industry uses the term.

Now you are coming along claiming it is a fallacy. That is why I want to know your definition of the term.

AOV.

Neil-O Regular Member • Posts: 134
Re: Okay. What now?
1

sybersitizen wrote:

Tony Beach wrote:

When I want an idea of what a camera can do (i.e., what it is equivalent to) I look at its actual focal lengths and apertures, and then the size and pixel density of its sensor. The only limitation actually described by "equivalent focal length" is how wide a FOV you can capture in the file. Many consumers (and even some participants in the forums here at DPR) falsely think that when the camera is sold to them with some extraordinary "equivalent focal length" that they would need an enormous lens to replicate that, and that's misleading and fallacious.

I don't think anyone here would choose to argue with those three sentences ... at least I wouldn't. Maybe this thread would be much shorter if you said exactly that in the first post.

Some (myself included) might feel that there is no guilty party at work intentionally trying to deceive or mislead the population of camera buyers; but rather it's just that many things are more complicated than can be easily presented and digested by the population of buyers of any complex product category, and this qualifies as one of them.

A question now is: Are you in favor of camera manufacturers describing and labeling products differently (replacing equivalent focal length with equivalent FOV) and including the many associated caveats in those descriptions and/or labels? And the same thing regarding camera reviews and forum discussions of equivalence?

I agree.  This is far from the first time someone has raised this issue, but there's a good reason we still use equivalent focal length - no-one has yet come along with an acceptable alternative that doesn't cause further confusion.

I doubt anyone ever will.  There are other walks of life where a rule of thumb exists harking back to days of yore, and I suspect we will still be referencing the 35mm film camera for a very long time after such cameras cease to have any real relevance in the modern world.

OP Tony Beach Forum Pro • Posts: 11,967
Re: So two lenses of same focal length on same camera aren't equivalent

FingerPainter wrote:

The logical extension of what you are saying is that the 28-70mm 28.D @ 70mm on your D800 isn't equivalent to the 24-70mm 2.8E @ 70mm on the same camera because the latter out-resolves the former.

I have to wonder how useful a definition of focal length equivalence that is.

That is not to say that it isn't useful to know that one lens / sensor combination will out-resolve another,

But let's go further. You also take into account the effects of the sensor in your assessment of "equivalence". So by your approach, the 24-70mm 2.8E @ 70mm on a D5 at 1/125 f/4 ISO 100 isn't equivalent to the same lens on a D850 at the same settings.

When a lens isn't equivalent to itself when used at the same settings, I think we've gone too far off into the weeds.

Focal length equivalence of a lens is a property of the lens, not of a lens/body combination. The very real effect you are describing does not negate the concept of focal length equivalence. Rather it points out that one shouldn't expect same quality outputs from equivalent focal length, even at identical pixel counts.

What I'm actually saying is that there is no such thing as equivalent focal length. It should instead be referred to equivalent AOV. The very fact that effective equivalence can be changed by changing cameras or lenses even when using the same format demonstrates the fallacy of the term.

SirPeepsalot Contributing Member • Posts: 550
Re: So two lenses of same focal length on same camera aren't equivalent
3

Tony Beach wrote:

FingerPainter wrote:

The logical extension of what you are saying is that the 28-70mm 28.D @ 70mm on your D800 isn't equivalent to the 24-70mm 2.8E @ 70mm on the same camera because the latter out-resolves the former.

I have to wonder how useful a definition of focal length equivalence that is.

That is not to say that it isn't useful to know that one lens / sensor combination will out-resolve another,

But let's go further. You also take into account the effects of the sensor in your assessment of "equivalence". So by your approach, the 24-70mm 2.8E @ 70mm on a D5 at 1/125 f/4 ISO 100 isn't equivalent to the same lens on a D850 at the same settings.

When a lens isn't equivalent to itself when used at the same settings, I think we've gone too far off into the weeds.

Focal length equivalence of a lens is a property of the lens, not of a lens/body combination. The very real effect you are describing does not negate the concept of focal length equivalence. Rather it points out that one shouldn't expect same quality outputs from equivalent focal length, even at identical pixel counts.

What I'm actually saying is that there is no such thing as equivalent focal length. It should instead be referred to equivalent AOV. The very fact that effective equivalence can be changed by changing cameras or lenses even when using the same format demonstrates the fallacy of the term.

AOV is a pure function of focal length and format diagonal length, so if there can be an equivalent AOV there can be an equivalent FL.

OP Tony Beach Forum Pro • Posts: 11,967
Re: Even though you're right, you're actually wrong

Lee Jay wrote:

When I crop, my 35mm-equivalent FOV

Even a lens used on 35mm format can have its equivalent FOV changed. The issue then becomes how much latitude you have in doing that. Compared to my S95, my 50mm f/1.8D lens just became a 50mm-150mm equivalent lens.

Gerry Winterbourne Forum Pro • Posts: 15,903
Re: The fallacy of 35mm "equivalent focal lengths"

Tony Beach wrote:

Gerry Winterbourne wrote:

hesbehindyou wrote:

thinkinginimages wrote:

I think "equivalence" created more confusion than it was worth.

I've often wondered why we don't just go with field of view? I'm assuming that it's because it's not a property that's inherent to the lens but will also involve the sensor...

It's not just that although it is, of course, a factor. What do we mean by field of view? If we mean width there's the problem that it gets wider the further away the scene; so the FOV for portraits at a few metres away would be tiny compared to the FOV with the same lens used for a landscape. So we'd really have to mean angle of view.

But I've never come across anyone who thinks of scenes in terms of how many degrees (or radians) they cover. And angle of view isn't linear with focal length - especially at wide angles - so there's another complication to have to deal with.

It's not a complication at all, but rather an opportunity:

An opportunity to complicate things by changing something linear and easy to understand with something that isn't.

Many wrongly assume that if you double or halve the focal length the AOV (or FOV for a given distance) changes accordingly. It's easy to imagine the photographer saying she wants to zoom twice as "close" to the subject and having the lens designating degrees instead of putative millimeters facilitates rather than hinders that.

Which is precisely why using focal length in millimetres is the best method.

There have always been different formats, going up to full plate. While it's silly to contemplate putting a full plate lens on a 35mm SLR there has always been some ability to swap lenses between formats. Now, it's easy to print the focal length of a lens on a body and it is a single number regardless of the body used. But printing the angle of view is tricky because you'd have to do it for every format the lens might be used on, as you say ...

For ILC lenses, and even on the front of compact cameras, the lens has its actual focal lengths printed on it. Now when I turn on my S95 the camera will display the "equivalent focal length" which I find marginally useful inasmuch as I know I'm fully or partially zoomed -- but seeing a number followed by a degree symbol rather than a misleading "mm" symbol would be more useful for me, and I am arguing here that others would find that more useful too.

Really? Which angle of view do you want? The horizontal or the diagonal? Do you want it to distinguish between different aspect ratios (which many cameras now offer)?

Do you really believe that giving a lens's AOV as 8.25 degrees (or 8 degrees 15 seconds) will mean anything to anyone? Compared, say, to 46.8 degrees (46 degrees 48 seconds)?

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Gerry Winterbourne Forum Pro • Posts: 15,903
Re: The fallacy of 35mm "equivalent focal lengths"

Tony Beach wrote:

thinkinginimages wrote:

Tony Beach wrote:

Preface

Ironically, even here at DPR equivalent focal lengths are often divorced from a complete understanding of what is or isn't equivalent. There is this idea that if a lens covers a certain FOV on a given format then it is somehow equivalent to whatever focal length that would cover that FOV on a 35mm format camera.

[This is a good place to suggest to anyone that doesn't want to read a long post (I usually don't like reading long posts) that you might want to skip to the picture below and take a long look at it and draw your own conclusions. Just be prepared for me alluding back to the "Getting into the weeds" portion of this post if you have any questions or concerns about what I'm presenting.]

The reason for this post is that I got to thinking about "reach" the other day as I was researching a compact camera to give my girlfriend for her upcoming birthday. “Reach” is one of the factors I was considering, and I’ve settled on a Panasonic Lumix DC-ZS70 with (among other features I think will be valuable to have) its 20 MP sensor and a 30x zoom. However, I don’t for a minute buy into the “24-720 mm equivalent focal length” which is how the camera is marketed (for instance, here and here). Will this new camera get more reach than the Canon PowerShot S95 it will be replacing? Undoubtedly, but I will have more to say about that later this week when I have the new camera in hand. Will it get more reach than I have with my D800, NIKKOR 70-200/2.8 VR and TC-14eII? I'm thinking it should, but that too remains to be seen.

Getting into the weeds

There are three things that add up to reach:

1.) Optics -- which includes the actual focal length (and not the equivalent focal length), and just how good the optics are (I looked at a 70-300mm lens for my D800 and it was sent back because it didn't have any more resolution at 300mm than the 200mm lens focal length I already had).

2.) Pixel density -- which is essentially how many linear pixels in a mm of the image circle covered.

3.) Aperture diameter -- which is what true equivalence is all about. As it relates to reach small apertures have more diffraction, and because smaller apertures restrict light coming to the sensor the exposure ends up being noisier which in turn negatively effects resolution.

Given all of that, what is the actual “equivalent” focal length of the Canon PowerShot S95 compared to what I routinely get with my D800? After some testing with various lenses I concluded that at 35mm my NIKKOR 28-70/2.8D matches the longest focal length of my S95, so it's a third of the published 105mm "equivalent" focal length of that compact camera. I expect the DC-ZS70 to do better than the S95 with its 129mm lens rather than the 22.5mm lens on the S95, and with its 840 pixels per linear millimeter rather than the 490 pixels per linear millimeter on the S95.

Will the DC-ZS70 do better than what I get from my D800 with my longest current focal length? Well here's the math so far for the D800 compared to the S95:

At 35mm my D800 with its 204 pixels per linear millimeter beats my S95 at 22.5mm with its 490 pixels per linear millimeter. That's not true of all the lenses I tested, and some could possibly do even better, but I did test my old NIKKOR 18-70 DX kit lens and at 50mm it barely matched the S95. One might have expected the S95 having 2.4x as much linear resolution as my D800 at the sensor level would translate to its 22.5mm lens being equivalent to a 54mm lens, and while reasonably close to that it's only 65% of the way there (35mm rather than 54mm). Some of this is about optics, for sure; but as I will show in the visual examples below diffraction is also a factor.

Maybe I should break out my D300 and crop its final output to 4:3 aspect ratio, which would work out to 10.8 MP and be a bit closer to the 9.98 MP for the S95, but at 181 pixels per linear millimeter that's only a difference in linear resolution per millimeter of 12.5% more for the D800 (i.e., it's barely noticeable). The thing is when it comes to focal length equivalence (if you define that as reach rather than FOV coverage area) is that it's not about the sensor's format or aspect ratio, it's about the relative pixel densities -- so if I put one of my 105mm focal length lenses on my D300 you're going to have a hard time at the pixel level telling the difference between its output on that camera and its output on my D800 (the one thing that will be obviously different will be the FOV, but that's not reach).

Given all of that, I'm expecting the reach of the ZS70 at about 105mm to beat my current longest lens on my D800. I'll try to test that hypothesis next week. In the meantime...

A picture is worth a 1000 words (if not more)

Okay, so now comes the visual evidence to back up what I'm writing about here:

As always, it's important to view this at its "original size" or "100% zoom."

My final thoughts (for this post)

For me that upper right crop at f/22 says a lot. Why? Because the aperture diameter at f/22 for a 90mm lens is 4.09mm, and that's (essentially) the same aperture diameter as f/5.6 for the 22.5mm lens used on the S95 (4.02mm). The middle crops are basically "web size," which in this context is the full frame of the S95 file and the equivalent FOV of the D800 file both sized to 1080 vertical pixels in height -- and for all practical purposes that's enough for a lot of people, and if that's the case I could probably have taken a good 20mm lens and gotten "good enough" results on my D800 under these conditions.

Well written. In a big overview I think "equivalence" created more confusion than it was worth. Taking the sensor and "mechanics" out of the equation, it's more about magnifications, and angles of view, the optics. What does 20X mean in common terms? Why equivalence in 35mm terms? It's such an old point of reference. (Been there.)

I use MFT. I don't think "2X (or 1/2) equals 35mm, so...". 14mm is wider, 150mm is narrower, 20mm is close to the human eye, etc. I'd lose my train of thought if I had to calculate every sensor size.

Thank you for that. My proposal would be to simply say in degrees the AOV of the lens.

Which AOV?

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OP Tony Beach Forum Pro • Posts: 11,967
Re: So two lenses of same focal length on same camera aren't equivalent

SirPeepsalot wrote:

Tony Beach wrote:

FingerPainter wrote:

The logical extension of what you are saying is that the 28-70mm 28.D @ 70mm on your D800 isn't equivalent to the 24-70mm 2.8E @ 70mm on the same camera because the latter out-resolves the former.

I have to wonder how useful a definition of focal length equivalence that is.

That is not to say that it isn't useful to know that one lens / sensor combination will out-resolve another,

But let's go further. You also take into account the effects of the sensor in your assessment of "equivalence". So by your approach, the 24-70mm 2.8E @ 70mm on a D5 at 1/125 f/4 ISO 100 isn't equivalent to the same lens on a D850 at the same settings.

When a lens isn't equivalent to itself when used at the same settings, I think we've gone too far off into the weeds.

Focal length equivalence of a lens is a property of the lens, not of a lens/body combination. The very real effect you are describing does not negate the concept of focal length equivalence. Rather it points out that one shouldn't expect same quality outputs from equivalent focal length, even at identical pixel counts.

What I'm actually saying is that there is no such thing as equivalent focal length. It should instead be referred to equivalent AOV. The very fact that effective equivalence can be changed by changing cameras or lenses even when using the same format demonstrates the fallacy of the term.

AOV is a pure function of focal length and format diagonal length, so if there can be an equivalent AOV there can be an equivalent FL.

No, my point has been you can't conflate those things without ultimately suffering the consequences of such misinformation. For the focal length to be equivalent the aperture also needs to be the same. While diffraction is the same relative to the f-number as it relates to the format, if you want to print larger or crop for more reach then you will discover that the visible diffraction of the shorter "equivalent" focal length is just as visible as it would be on the longer focal length if it also used the equivalent  aperture.

When a camera is marketed as having an equivalent focal length to a larger format and it's marketed as having an f/2.8 lens many assume they are getting something that is equivalent when they are in fact getting less light and more diffraction. In the example I showed in the OP, using f/22 on a 90mm lens resulted in the same end result as using f/5.6 on a 22.5mm lens, which when you consider the role of diffraction shouldn't be surprising because both were using the same aperture size.

tony field Forum Pro • Posts: 10,223
Re: A fourth

I prefer using "standard definitions" as provided by Joe's Equivalence or DPR's "focal-length multiplier". At least these are a common reference. If someone has a deviation from the common reference, for conversation it should be carefully defined as you did. For example I could state that silver lenses are not equivalent to black lenses and leave it up to the reader to figure out what I mean.

Personally I have no use for equivalence other than approximate comparison of different cameras systems, realizing that all of the technically defined parameters of equivalence are accurate and demonstrable. These tenants are easily proved even using a single camera to perform all of the tests.

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Gerry Winterbourne Forum Pro • Posts: 15,903
Re: So two lenses of same focal length on same camera aren't equivalent
4

Tony Beach wrote:

What I'm actually saying is that there is no such thing as equivalent focal length. It should instead be referred to equivalent AOV.

Wrong. The AOV isn't equivalent, it's equal.

The difference is very simple - equal means being the same while equivalent means having the same effect ...

The very fact that effective equivalence can be changed by changing cameras or lenses even when using the same format demonstrates the fallacy of the term.

… which therefore demonstrates not the fallacy of the term but its correctness.

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SirPeepsalot Contributing Member • Posts: 550
Re: So two lenses of same focal length on same camera aren't equivalent
2

Tony Beach wrote:

SirPeepsalot wrote:

Tony Beach wrote:

FingerPainter wrote:

The logical extension of what you are saying is that the 28-70mm 28.D @ 70mm on your D800 isn't equivalent to the 24-70mm 2.8E @ 70mm on the same camera because the latter out-resolves the former.

I have to wonder how useful a definition of focal length equivalence that is.

That is not to say that it isn't useful to know that one lens / sensor combination will out-resolve another,

But let's go further. You also take into account the effects of the sensor in your assessment of "equivalence". So by your approach, the 24-70mm 2.8E @ 70mm on a D5 at 1/125 f/4 ISO 100 isn't equivalent to the same lens on a D850 at the same settings.

When a lens isn't equivalent to itself when used at the same settings, I think we've gone too far off into the weeds.

Focal length equivalence of a lens is a property of the lens, not of a lens/body combination. The very real effect you are describing does not negate the concept of focal length equivalence. Rather it points out that one shouldn't expect same quality outputs from equivalent focal length, even at identical pixel counts.

What I'm actually saying is that there is no such thing as equivalent focal length. It should instead be referred to equivalent AOV. The very fact that effective equivalence can be changed by changing cameras or lenses even when using the same format demonstrates the fallacy of the term.

AOV is a pure function of focal length and format diagonal length, so if there can be an equivalent AOV there can be an equivalent FL.

No, my point has been you can't conflate those things without ultimately suffering the consequences of such misinformation. For the focal length to be equivalent the aperture also needs to be the same.

No, a focal length is a property of a given lens design and remains the same at all apertures.

While diffraction is the same relative to the f-number as it relates to the format, if you want to print larger or crop for more reach then you will discover that the visible diffraction of the shorter "equivalent" focal length is just as visible as it would be on the longer focal length if it also used the equivalent aperture.

Diffraction is an optical phenomena which does not even enter into standard DoF calculations, much less composition and perspective.

When a camera is marketed as having an equivalent focal length to a larger format and it's marketed as having an f/2.8 lens many assume they are getting something that is equivalent when they are in fact getting less light and more diffraction. In the example I showed in the OP, using f/22 on a 90mm lens resulted in the same end result as using f/5.6 on a 22.5mm lens, which when you consider the role of diffraction shouldn't be surprising because both were using the same aperture size.

Any assumption about fitness for purpose based on marketing statements is on the asummer, and again diffraction plays no role in format equivalence.

OP Tony Beach Forum Pro • Posts: 11,967
Re: The fallacy of 35mm "equivalent focal lengths"

Gerry Winterbourne wrote:

Tony Beach wrote:

Many wrongly assume that if you double or halve the focal length the AOV (or FOV for a given distance) changes accordingly. It's easy to imagine the photographer saying she wants to zoom twice as "close" to the subject and having the lens designating degrees instead of putative millimeters facilitates rather than hinders that.

Which is precisely why using focal length in millimetres is the best method.

If I halve or double the degrees I will change the AOV (FOV of the subject at a given distance) by that much, which won't happen when just changing the millimeters by that much.

Which angle of view do you want?

In terms of percentages it doesn't matter.

The horizontal or the diagonal?

Personally I'm partial go horizontal.

Do you want it to distinguish between different aspect ratios (which many cameras now offer)?

Sure, that can be done.

Do you really believe that giving a lens's AOV as 8.25 degrees (or 8 degrees 15 seconds) will mean anything to anyone? Compared, say, to 46.8 degrees (46 degrees 48 seconds)?

Same as describing lenses by their millimeters (which I am in favor of doing), the numbers are rounded off (by as much as 5% for millimeters, but I would argue for the nearest whole percentile for degrees). Truthfully, when I'm using a zoom lens I look into it and decide if it's covering the area I want to have covered and only notice the focal length (or "equivalent focal length" on my S95) after the fact.

Gerry Winterbourne Forum Pro • Posts: 15,903
Re: The fallacy of 35mm "equivalent focal lengths"

Tony Beach wrote:

Gerry Winterbourne wrote:

Tony Beach wrote:

Many wrongly assume that if you double or halve the focal length the AOV (or FOV for a given distance) changes accordingly. It's easy to imagine the photographer saying she wants to zoom twice as "close" to the subject and having the lens designating degrees instead of putative millimeters facilitates rather than hinders that.

Which is precisely why using focal length in millimetres is the best method.

If I halve or double the degrees I will change the AOV (FOV of the subject at a given distance) by that much,

Read the numbers of your graph - what you say is clearly untrue. 12mm to 24mm (your factor of two) gives angles of 122 and 84 - a ration of about 1.5.

which won't happen when just changing the millimeters by that much.

No, I'm afraid it does exactly that.

Which angle of view do you want?

In terms of percentages it doesn't matter.

The horizontal or the diagonal?

Personally I'm partial go horizontal.

Do you want it to distinguish between different aspect ratios (which many cameras now offer)?

Sure, that can be done.

Do you really believe that giving a lens's AOV as 8.25 degrees (or 8 degrees 15 seconds) will mean anything to anyone? Compared, say, to 46.8 degrees (46 degrees 48 seconds)?

Same as describing lenses by their millimeters (which I am in favor of doing), the numbers are rounded off (by as much as 5% for millimeters, but I would argue for the nearest whole percentile for degrees). Truthfully, when I'm using a zoom lens I look into it and decide if it's covering the area I want to have covered and only notice the focal length (or "equivalent focal length" on my S95) after the fact.

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tony field Forum Pro • Posts: 10,223
Re: The fallacy of 35mm "equivalent focal lengths"

With aov and you have a Zeiss lens that can be mounted on full frame, aps-c, and m34, does that become more complicated?

What happens to aov if you change your zoom lens from 50 mm 100mm

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pforsell
pforsell Senior Member • Posts: 2,261
A monstrous disaster
15

The faster this thread disappears from the face of the Earth, the better. It would be best if nobody would ever remember even having seen this nonsense.

Don't worry about it, just look here.

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tcg550 Veteran Member • Posts: 8,837
Re: The fallacy of 35mm "equivalent focal lengths"

Is this the topic that finally puts it all to rest?

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