Focal length 35mm equivalent, but not F-stop?

Started Jul 24, 2014 | Discussions
mostlyboringphotog Veteran Member • Posts: 9,049
Re: A Camera Club Perspective

JBurnett wrote:

Two years ago I moved across country and joined a new camera club with about 50 members. Here are some observations:

  • In a club of 50, about 40 members use APS-C sensored DSLRs
  • I would estimate that 35 of them purchased their APS-C cameras with the kit lens, and had no concept of equivalencies at the time.
  • Even after some educational sessions within the club, probably only 10 could tell you what their APS-C lens is "equivalent to" in terms of FF focal length. The Nikon users are more likely to know than the Canon users, simply because it's easier to multiply by 1.5 instead of 1.6.
  • Maybe 10 understand that there is a difference in depth of field between their camera and cameras with larger or smaller sensors. Only 3 would know where to go to calculate that equivalence (or would ever care to do so).
  • Maybe 25 understand (through personal experience or education within the club) about "noise" and that it is related to ISO and sensor size.
  • Perhaps 2 or 3 would understand any discussion about "light gathering" with regards to sensor size.
  • Most members understand that if a light meter says f/4 at 1/60 at ISO 200 on one camera, they could use the same settings on a different camera. Perhaps 5 still have no idea about the relationships between aperture, shutter speed and ISO. We're working on it, but some may never care and are happier using scene modes.
  • Only one person in the club really cares about equivalencies, because he shoots both full-frame and APS-C bodies at the same time.
  • The majority of time I've been drawn into a discussion about equivalencies, it has been a newer member who wants to move from a P&S to a DSLR or mirrorless. Equivalent focal lengths to what they see with their existing camera makes sense to them. Most of the time, the remainder of "equivalency" talk would cause them to glaze over and shut down. After all, they just want to know what "kit" to buy.

Thanks for your view from the ground up - I do lose what the focus (pun intended) of all this is: is it to help the consumers or the (budding) photographers?

Best advice for the consumers, IMHO, is to show them at least what the scene modes are. As I speak, even this is being superseded by the intelligent auto scene select. And for the budding photographers, my advice is to choose the "sexiest cam" you can afford - at least you will look good even if your photo may not

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Lee Jay Forum Pro • Posts: 55,389
Re: Focal length 35mm equivalent, but not F-stop?
1

I also use equivalence to make purchase decisions, and decisions about what equipment to carry into certain situations. Sometimes I use it for determining what settings I want to use in some situations.
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mostlyboringphotog Veteran Member • Posts: 9,049
Re: because they don't want you to know

tko wrote:

Multiplying focal length isn't a bad thing. A 1000MM equivalent lens can be very useful.

But do you think they want to know that aperture gets multiplied as well? All of the sudden that F2.8 lens you thought was really fast is really only F10 equivalent?

Of course not! Because people might figure out that a true F2.8 FF lens is actually a pretty good deal compared to a smaller format equivalent F10 lens. And the public would know the lenses are smaller because they do less, not because of any magic dust.

What advertise your shortcomings? It's all about marketing.

Neither the focal length nor the aperture is multiplied. A 1000mm with image circle of FF and FL equivalent lens with the image circle of CX format is not an equivalent thing, even if FOV looks the same. BTW, this is MY point of view.

f/2.8 on iphone is still f/2.8 unless the new math is different than the old math. If you are told that iphone can give you the same image quality as FF camera and you believed it, because both can do f/2.8, you need to know more about photography (Of course, this is not true of you).

There are no true f/2.8 FF or false f/2.8 iphone as it's just a ratio.

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Chikoo
OP Chikoo Senior Member • Posts: 1,630
Re: What ordinary people want

Chikoo wrote:

Gerry Winterbourne wrote:

Chikoo wrote:

All camera manufacturer when they publish technical specification of their camera lens publish the focal length and it's equivalent in 35mm. But the same is not done for F-stop. Why?

Ordinary people just want to take photos. Most of them know absolutely nothing about photography and nothing relating to 35mm cameras means anything to them. Quite a few, though, have some former experience with 35mm, or access to people with such experience.

I'll start with APS-C because that was the first widely used sensor size. In use an APS-C DSLR was, and is, very similar to an SLR , with one major difference - the crop factor. I was caught out by this (my fault for insufficient research but caught I was). Focal length has various effects but the one that most obviously affects users who know about 35mm photography is the FOV so stating FLs in 35mm equivalent as well as the actual FL is a simple courtesy to buyers.

The same thing applies to users of other sensor sizes and camera types: either FL means nothing to them or they have some knowledge about 35mm FL/FOV. So that information is useful. But anything beyond is superfluous: you only have to read the Beginners forum here to know how few newcomers understand DOF as a concept, so what earthly use to them is data on equivalency?

On the other hand, anyone who knows - and cares - about such things is able to work them out so the information isn't needed.

Ditto the noise equivalency mentioned elsewhere in the thread: get into that and you should also be asking why camera makers don't publish data on the noise performance of all cameras. Even at the same sensor size, why don't we see noise data to allow us to compare a D700 with a 6D with ...? Because without that it's pointless to look at a P&S noise performance v a specific other camera.

So what makers give is a compromise between completeness and confusion.

A person who has grown up using 35mm camera, and loves the way his f2.8 lens provide a nice bokeh, and sees the new camera in the store which is smaller and lighter, and boasts the same focal length and zoom range + F-stop, will be more than happy to purchase that camera. Only to find out that it is not the same. He is not getting the same quality of picture as his 35mm f2.8 lens gave him for the last 30 years.

That is deceptive to say the least.

This is like stating the hp of a car with a 4 cylinder engine as a ratio of power to weight and sell it saying it is the same or better than the large v8 he currently drives.

This was true even when "I, Roman" ruled the world - that's why they warned "Caveat Emptor".

So if I have a 35mm camera and a m43, will the same exact focal length, fstop give me the same picture given the ISO/DR/SNR is the same on both?

mostlyboringphotog Veteran Member • Posts: 9,049
Re: What ordinary people want

Chikoo wrote:

Chikoo wrote:

Gerry Winterbourne wrote:

Chikoo wrote:

All camera manufacturer when they publish technical specification of their camera lens publish the focal length and it's equivalent in 35mm. But the same is not done for F-stop. Why?

Ordinary people just want to take photos. Most of them know absolutely nothing about photography and nothing relating to 35mm cameras means anything to them. Quite a few, though, have some former experience with 35mm, or access to people with such experience.

I'll start with APS-C because that was the first widely used sensor size. In use an APS-C DSLR was, and is, very similar to an SLR , with one major difference - the crop factor. I was caught out by this (my fault for insufficient research but caught I was). Focal length has various effects but the one that most obviously affects users who know about 35mm photography is the FOV so stating FLs in 35mm equivalent as well as the actual FL is a simple courtesy to buyers.

The same thing applies to users of other sensor sizes and camera types: either FL means nothing to them or they have some knowledge about 35mm FL/FOV. So that information is useful. But anything beyond is superfluous: you only have to read the Beginners forum here to know how few newcomers understand DOF as a concept, so what earthly use to them is data on equivalency?

On the other hand, anyone who knows - and cares - about such things is able to work them out so the information isn't needed.

Ditto the noise equivalency mentioned elsewhere in the thread: get into that and you should also be asking why camera makers don't publish data on the noise performance of all cameras. Even at the same sensor size, why don't we see noise data to allow us to compare a D700 with a 6D with ...? Because without that it's pointless to look at a P&S noise performance v a specific other camera.

So what makers give is a compromise between completeness and confusion.

A person who has grown up using 35mm camera, and loves the way his f2.8 lens provide a nice bokeh, and sees the new camera in the store which is smaller and lighter, and boasts the same focal length and zoom range + F-stop, will be more than happy to purchase that camera. Only to find out that it is not the same. He is not getting the same quality of picture as his 35mm f2.8 lens gave him for the last 30 years.

That is deceptive to say the least.

This is like stating the hp of a car with a 4 cylinder engine as a ratio of power to weight and sell it saying it is the same or better than the large v8 he currently drives.

This was true even when "I, Roman" ruled the world - that's why they warned "Caveat Emptor".

So if I have a 35mm camera and a m43, will the same exact focal length, fstop give me the same picture given the ISO/DR/SNR is the same on both?

Ordinary people want photos in which their spouse look good and their kids don't look blurry because they were running around. If you have 35mm camera and m43, you don't need to ask the question and if you do (no condescension intended as we all need to learn at least once and someone like me, many time but I digress...) there are far better ways to learn than looking for the "equivalent aperture" on a spec sheet. That is my opinion.

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mostlyboringphotog Veteran Member • Posts: 9,049
Re: Focal length 35mm equivalent, but not F-stop?

Lee Jay wrote:

I also use equivalence to make purchase decisions, and decisions about what equipment to carry into certain situations. Sometimes I use it for determining what settings I want to use in some situations.
--
Lee Jay

"I also use equivalence to make purchase decisions,..." I like to challenge this sentiment.

I say that you have not chosen m43 because m43 f/2 is equivalent to f/4 on FF. You know FF can do f/2 as well as f/4.

Also, I will say that you have not chosen FF because f/4 is equivalent to f/2 on m43.

And so without the actual comparison of the real images that you're after, this equivalence is meaningless to make the purchase decision.

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Great Bustard Forum Pro • Posts: 44,107
Re: because they don't want you to know

mostlyboringphotog wrote:

tko wrote:

Multiplying focal length isn't a bad thing. A 1000MM equivalent lens can be very useful.

But do you think they want to know that aperture gets multiplied as well? All of the sudden that F2.8 lens you thought was really fast is really only F10 equivalent?

Of course not! Because people might figure out that a true F2.8 FF lens is actually a pretty good deal compared to a smaller format equivalent F10 lens. And the public would know the lenses are smaller because they do less, not because of any magic dust.

What advertise your shortcomings? It's all about marketing.

Neither the focal length nor the aperture is multiplied. A 1000mm with image circle of FF and FL equivalent lens with the image circle of CX format is not an equivalent thing, even if FOV looks the same. BTW, this is MY point of view.

f/2.8 on iphone is still f/2.8 unless the new math is different than the old math. If you are told that iphone can give you the same image quality as FF camera and you believed it, because both can do f/2.8, you need to know more about photography (Of course, this is not true of you).

There are no true f/2.8 FF or false f/2.8 iphone as it's just a ratio.

http://www.josephjamesphotography.com/equivalence/#onthequick

  • Neither the focal length nor the f-ratio of a lens change as a function of format: 50mm = 50mm and f/2 = f/2 regardless of the format the lens is used on.
  • The effect of the focal length and f-ratio of a lens, however, do change as a function of format.
Gerry Winterbourne Forum Pro • Posts: 16,760
Re: What ordinary people want

Chikoo wrote:

Gerry Winterbourne wrote:

Chikoo wrote:

All camera manufacturer when they publish technical specification of their camera lens publish the focal length and it's equivalent in 35mm. But the same is not done for F-stop. Why?

Ordinary people just want to take photos. Most of them know absolutely nothing about photography and nothing relating to 35mm cameras means anything to them. Quite a few, though, have some former experience with 35mm, or access to people with such experience.

I'll start with APS-C because that was the first widely used sensor size. In use an APS-C DSLR was, and is, very similar to an SLR , with one major difference - the crop factor. I was caught out by this (my fault for insufficient research but caught I was). Focal length has various effects but the one that most obviously affects users who know about 35mm photography is the FOV so stating FLs in 35mm equivalent as well as the actual FL is a simple courtesy to buyers.

The same thing applies to users of other sensor sizes and camera types: either FL means nothing to them or they have some knowledge about 35mm FL/FOV. So that information is useful. But anything beyond is superfluous: you only have to read the Beginners forum here to know how few newcomers understand DOF as a concept, so what earthly use to them is data on equivalency?

On the other hand, anyone who knows - and cares - about such things is able to work them out so the information isn't needed.

Ditto the noise equivalency mentioned elsewhere in the thread: get into that and you should also be asking why camera makers don't publish data on the noise performance of all cameras. Even at the same sensor size, why don't we see noise data to allow us to compare a D700 with a 6D with ...? Because without that it's pointless to look at a P&S noise performance v a specific other camera.

So what makers give is a compromise between completeness and confusion.

A person who has grown up using 35mm camera, and loves the way his f2.8 lens provide a nice bokeh, and sees the new camera in the store which is smaller and lighter, and boasts the same focal length and zoom range + F-stop, will be more than happy to purchase that camera. Only to find out that it is not the same.

See my comment below* about this.

He is not getting the same quality of picture as his 35mm f2.8 lens gave him for the last 30 years. That is deceptive to say the least.

A small camera can give perfectly good bokeh. It might even be smoother than the 35mm lens. What you've just said is deceptive, because bokeh is the character of the out-of-focus blur, not the amount of it. Here's the problem (or part of it) - move away from the briefest description and you need a book to tell the whole story, and even then most readers won't understand it.

I'd also dispute the general assumption that the quality of 35mm film is better than small-sensor digital. Different in several ways, yes, but not overall better or worse.

This is like stating the hp of a car with a 4 cylinder engine as a ratio of power to weight and sell it saying it is the same or better than the large v8 he currently drives.

(* from above). You've introduced a useful analogy. People know there are big cars and small cars and that they have different characteristics. Most people also have a broad view of which characteristics matter to them. Anyone buying a small car knows it's not the same as a big car; anyone buying a small camera knows it's different from a big one. The difference is that the general population knows more about what cars do so there's no need for pointing out similarities; which means there is no meaningful motoring analogy.

For cars things that tend to matter are number of seats, acceleration, fuel consumption. I have no idea of the power-to-weight ratio of any car including all those I've owned.

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Lee Jay Forum Pro • Posts: 55,389
Re: Focal length 35mm equivalent, but not F-stop?

Lee Jay wrote:

I also use equivalence to make purchase decisions, and decisions about what equipment to carry into certain situations. Sometimes I use it for determining what settings I want to use in some situations.
--
Lee Jay

"I also use equivalence to make purchase decisions,..." I like to challenge this sentiment.

I say that you have not chosen m43 because m43 f/2 is equivalent to f/4 on FF. You know FF can do f/2 as well as f/4.

Also, I will say that you have not chosen FF because f/4 is equivalent to f/2 on m43.

And so without the actual comparison of the real images that you're after, this equivalence is meaningless to make the purchase decision.

Nope...wrong. I use equivalence to plot lens (and format) performance envelopes, just like DPReview has started doing in their compact camera reviews (except mine are better). In fact they started doing that because of my repeated suggestions over several years.
--
Lee Jay

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JBurnett Contributing Member • Posts: 835
Re: A Camera Club Perspective

mostlyboringphotog wrote:

Thanks for your view from the ground up - I do lose what the focus (pun intended) of all this is: is it to help the consumers or the (budding) photographers?

Best advice for the consumers, IMHO, is to show them at least what the scene modes are. As I speak, even this is being superseded by the intelligent auto scene select. And for the budding photographers, my advice is to choose the "sexiest cam" you can afford - at least you will look good even if your photo may not

As for choosing a good/sexy-looking cam, our club does have a couple of women who chose white and red DSLRs when they had the choice. "A chacun son gout".

The thing I find interesting in this (and other) discussions is the assertion that camera manufacturers are being deliberately deceptive when stating only focal-length equivalency for a lens on a format less than full frame. I find the focal-length conversion is helpful/convenient, especially when looking at compact cameras. The rest is probably confusing for most beginning photographers. If neophytes thought they had to understand equivalencies before they could purchase or use a camera, a lot would simply forget the whole thing and continue to use their cell phone.

At the camera club, we sometimes have a member who wants to know how he can achieve a certain look with his camera. Occasionally this leads to the discussion of different camera formats (eg. a member with an older, small-sensored bridge cam, looking to take portraits that look the same as the guy using 135mm f/2.0 on FF). Funny, but I don't ever remember hearing anyone say "Hey, no one told me that. I feel cheated by being sold this camera!"

What's very obvious is that, even with excellent explanatory articles such as the one here on DPR, people continue to think about equivalencies in whatever way that makes sense to them, and seems important to them. Perhaps we need a second definition for Circle of Confusion: A prolonged discussion revolving around equivalencies between cameras of different formats. 

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Beachcomber Joe
Beachcomber Joe Senior Member • Posts: 1,256
Re: Focal length 35mm equivalent, but not F-stop?

Chikoo wrote:

Beachcomber Joe wrote:

Why? Large format shooters have managed for years without f/stop equivalents. FF and APS-C don't need them. The only people to whom it seems to matter are MFT users. They are, they tell us, so much smarter and cleverer than the rest of us. That being the case I'm sure they have an app to figure it out themselves and don't need published figures.

Maybe they never needed them because practice told them which lens works best with their camera, and then they stick to it. Another reason why it is difficult for those to change systems because they are do not know how it will work with other cameras/formats.

Now if this was made simpler, it would be simpler for photographers to switch systems without being a first grade mathematician first.

Simpler?

I photograph a subject with my FF digital camera.  The brightness I want in the photograph requires an exposure of 1/125 sec, F/11 at ISO 100.  If I grab my old Crown Graphic, load it with ISO 100 film and shoot at 1/125 sec, f/11 the resulting photograph will have the same brightness level as the FF image.  Taking a MFT camera, exposing at 1/125 sec., f/11 at ISO 100 again the resulting photograph will have the same brightness as the FF digital and medium format film cameras.

No math is required because the same settings produce the same exposure regardless of format or sensor.  How much simpler do you want it to be?

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Beachcomber Joe
Beachcomber Joe Senior Member • Posts: 1,256
Re: Focal length 35mm equivalent, but not F-stop?

Chikoo wrote:

Beachcomber comes along and state "Because it is not necessary". Even an innocent person like me would be ruffled by such forceful statements.

What bothered you most; that it was brief and directly addressed your post, that it was clearly explained without the usual technobabble, or that it was true?

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D Cox Forum Pro • Posts: 25,210
Re: Let's correct it, then.

Great Bustard wrote:

The f-ratio is an *indicator* of light gathering ability, but the same f-ratio on different formats does not gather the same amount of light.

That is, f/2 gathers the same amount of light for a given scene luminance, shutter speed, and lens transmission regardless of focal length *on a given format*, but it does not gather the same amount of light as f/2 does on a different format.

It does.

The number of photons arriving on each square mm is not affected by the size of the sensor. This is the whole point of using f numbers rather than apertures in mm -- a small camera such as 35mm and a large camera such as 10x8 inch, using the same film, need the same exposure time at the same f number.

The intensity of the light is the same.

Likewise for different focal lengths on the same camera (ignoring lens faults such as vignetting).

The difference with digital is that the design of sensors varies greatly, so you are not using "the same film".

Austinian
Austinian Veteran Member • Posts: 9,105
Re: Let's correct it, then.
1

D Cox wrote:

Great Bustard wrote:

The f-ratio is an *indicator* of light gathering ability, but the same f-ratio on different formats does not gather the same amount of light.

That is, f/2 gathers the same amount of light for a given scene luminance, shutter speed, and lens transmission regardless of focal length *on a given format*, but it does not gather the same amount of light as f/2 does on a different format.

It does.

The number of photons arriving on each square mm is not affected by the size of the sensor. This is the whole point of using f numbers rather than apertures in mm -- a small camera such as 35mm and a large camera such as 10x8 inch, using the same film, need the same exposure time at the same f number.

The intensity of the light is the same.

Likewise for different focal lengths on the same camera (ignoring lens faults such as vignetting).

The difference with digital is that the design of sensors varies greatly, so you are not using "the same film".

Think about the area of the sensor(s) or film collecting the light.

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D Cox Forum Pro • Posts: 25,210
Re: Whoops!

Great Bustard wrote:

Wheatfield7 wrote:

Allan Olesen wrote:

Beachcomber Joe wrote:

Because it is not necessary. The f stop of lenses has always been marketed and thought of as an indicator of its light gathering ability, not its depth of field.

The equivalent f-stop also describes the light gathering ability.

You need effective lens area to gather light. A 50 mm f/2 on full frame has much more area than a 12.5 mm f/2 on 4x crop. So the small lens cannot gather as much light.

This is what is known as wrong.

Um, it is absolutely correct.

It is perfectly correct. The illuminance is the same, and therefore the exposure time needed is the same (if the sensors match in sensitivity).

Illuminance determines both exposure time and noise levels, for a given sensor. (Different sensors may have different noise levels at the same exposure. Technology keeps on improving.)

Any lens will gather the same amount of light at any given aperture. A 50mm f2 lens on a 35mm format will gather exactly the same amount of light as a 12.5mm lens on a micro four thirds lens if both are set to the same f/2 aperture.

This is correct, assuming the "amount of light" is measured in lux (i.e. lumens per square meter), which is the appropriate unit.

bobn2
bobn2 Forum Pro • Posts: 64,288
Re: Whoops!
1

D Cox wrote:

Great Bustard wrote:

Wheatfield7 wrote:

Allan Olesen wrote:

Beachcomber Joe wrote:

Because it is not necessary. The f stop of lenses has always been marketed and thought of as an indicator of its light gathering ability, not its depth of field.

The equivalent f-stop also describes the light gathering ability.

You need effective lens area to gather light. A 50 mm f/2 on full frame has much more area than a 12.5 mm f/2 on 4x crop. So the small lens cannot gather as much light.

This is what is known as wrong.

Um, it is absolutely correct.

It is perfectly correct. The illuminance is the same, and therefore the exposure time needed is the same (if the sensors match in sensitivity).

Illuminance determines both exposure time and noise levels, for a given sensor. (Different sensors may have different noise levels at the same exposure. Technology keeps on improving.)

For a given sensor the noise level is determined by the total number of photons that it collects and counts. Of course, for a given sensor, that is in turn determined by the exposure, so long as you always use all of the sensor. However, since Equivalence is about comparison, it doesn't make much sense to talk about 'a given sensor'.  The minimum for a comparison is a given pair of sensors, and then it becomes clear that the important factor is total light (exposure integrated over the whole sensor), not exposure.

Any lens will gather the same amount of light at any given aperture. A 50mm f2 lens on a 35mm format will gather exactly the same amount of light as a 12.5mm lens on a micro four thirds lens if both are set to the same f/2 aperture.

This is correct, assuming the "amount of light" is measured in lux (i.e. lumens per square meter), which is the appropriate unit.

Lux doesn't measure 'amount of light'. It measures light flux. Lumens measures 'power of light'. Lumen seconds measures amount (energy) of light. So, the amount of light collected by a lens depends on the size of the light collector put behind it.

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Bob

bobn2
bobn2 Forum Pro • Posts: 64,288
Re: Let's correct it, then.

D Cox wrote:

Great Bustard wrote:

The f-ratio is an *indicator* of light gathering ability, but the same f-ratio on different formats does not gather the same amount of light.

That is, f/2 gathers the same amount of light for a given scene luminance, shutter speed, and lens transmission regardless of focal length *on a given format*, but it does not gather the same amount of light as f/2 does on a different format.

It does.

The number of photons arriving on each square mm is not affected by the size of the sensor. This is the whole point of using f numbers rather than apertures in mm -- a small camera such as 35mm and a large camera such as 10x8 inch, using the same film, need the same exposure time at the same f number.

The intensity of the light is the same.

Likewise for different focal lengths on the same camera (ignoring lens faults such as vignetting).

The difference with digital is that the design of sensors varies greatly, so you are not using "the same film".

The performance of sensors varies rather less than the performance of film. Of a generation, the efficiency if sensors is within a fraction of a stop. Over 10 years or so, it has only improved by a stop or so. Shadow noise is better, that's improved about two stops.

Film works on almost exactly the same principle as digital, and no-one in film days that using the same exposure on 110 (Four Thirds) and 135 (full frame) would give the same result.

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Bob

Lee Jay Forum Pro • Posts: 55,389
Re: Let's correct it, then.
1

D Cox wrote:

Great Bustard wrote:

The f-ratio is an *indicator* of light gathering ability, but the same f-ratio on different formats does not gather the same amount of light.

That is, f/2 gathers the same amount of light for a given scene luminance, shutter speed, and lens transmission regardless of focal length *on a given format*, but it does not gather the same amount of light as f/2 does on a different format.

It does.

The number of photons arriving on each square mm is not affected by the size of the sensor.

But the total amount of light reaching the sensor is affected by its size, and total light, not light intensity, controls signal to noise ratio.

In other words, exposure is largely irrelevant. Total light is what matters, and total light is controlled by aperture diameter (for a given field of view), not f-stop.

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Lee Jay

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Chikoo
OP Chikoo Senior Member • Posts: 1,630
Re: Focal length 35mm equivalent, but not F-stop?

Beachcomber Joe wrote:

Chikoo wrote:

Beachcomber comes along and state "Because it is not necessary". Even an innocent person like me would be ruffled by such forceful statements.

What bothered you most; that it was brief and directly addressed your post, that it was clearly explained without the usual technobabble, or that it was true?

I was ruffled by

1. It was addressed directly

2. It was addressed as if you were god, and what you state requires no discussion.

Chikoo
OP Chikoo Senior Member • Posts: 1,630
Re: Focal length 35mm equivalent, but not F-stop?

Beachcomber Joe wrote:

Chikoo wrote:

Beachcomber Joe wrote:

Why? Large format shooters have managed for years without f/stop equivalents. FF and APS-C don't need them. The only people to whom it seems to matter are MFT users. They are, they tell us, so much smarter and cleverer than the rest of us. That being the case I'm sure they have an app to figure it out themselves and don't need published figures.

Maybe they never needed them because practice told them which lens works best with their camera, and then they stick to it. Another reason why it is difficult for those to change systems because they are do not know how it will work with other cameras/formats.

Now if this was made simpler, it would be simpler for photographers to switch systems without being a first grade mathematician first.

Simpler?

I photograph a subject with my FF digital camera. The brightness I want in the photograph requires an exposure of 1/125 sec, F/11 at ISO 100. If I grab my old Crown Graphic, load it with ISO 100 film and shoot at 1/125 sec, f/11 the resulting photograph will have the same brightness level as the FF image. Taking a MFT camera, exposing at 1/125 sec., f/11 at ISO 100 again the resulting photograph will have the same brightness as the FF digital and medium format film cameras.

No math is required because the same settings produce the same exposure regardless of format or sensor. How much simpler do you want it to be?

I had my lens set at 35mm on my 35mm camera.

On my APS-C, Should I set it at 35mm? and get the same frame?

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