[Fogel70]

I am assuming the shooter knows their sensor size and decides how bit an image they want

There is no sensor size in equivalent focal length either

EFL is based on 35 mm format. 36 x 24 mm

On most compact cameras I have been using, I have only had a vague idea of the sensor size.
EFL can be quite helpful for fixed lens cameras. Which also was the main point for camera manufactures to introduce EFL, as sensor sizes in digital P&S can vary a lot.

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Last edited by Fogel70; 10-05-2021 at 03:52 AM.

[Lowell Goudge]

You are also assuming the shooter knows the distance to the subject and the subject size.

yes I am assuming that the shooter has at least some concept of size and dimension and is taking an interest in what he is doing. Let’s give the person who picks up a camera some credit for intellegence.

What is equivalent focal length if it doesn't relate to sensor size? That is the whole point.

what’s the whole point? 35 mm equivalent does not actually state anything about the sensor size.

35 mm film is the width of a strip of film, including sprocket holes, equivalence is implied not stated.

A frame on 35mm film is 24 x 36 mm. It is the same as the 1 inch video tube equivalence having a 16 mm diagonal. It also assumes the shooter knows the sensor size

Look up in your manual, it tells you the sensor size (usually) in mm

---------- Post added 10-05-21 at 06:54 AM ----------

EFL is based on 35 mm format. 36 x 24 mm

On most compact cameras I have been using, I have only had a vague idea of the sensor size.
EFL can be quite helpful for fixed lens cameras. Which also was the main point for camera manufactures to introduce EFL, as sensor sizes in digital P&S can vary a lot.

See my other comments above. You need to take at least some initiative and know what you are shooting

[pschlute]

I suppose it may come down to magnification. For example, will a 15-45mm tele lens on his Q camera have about the same magnification as a 83-249mm lens on say a FF camera (or whatever sensor size he is make an equivalence to in the video)....

Michael, this is where the "equivalence" get a bit confusing.

A 16-45mm lens has maximum magnification at 45mm obviously. A 83-249mm lens will have maximum at 249mm. The 249mm lens magnifies the image far, far more than the 45mm lens can, 5 times as much. These are the inherent optical properties of the lenses.

Where the "magnification" equivalence comes from is the fact that the image captured on the smaller sensor on say the Q needs to be enlarged much more than the full frame sensor, and it is this that gives the equivalent image size. Whether it is as good a quality image as a full frame one with a longer lens will depend on the pixel density of the smaller sensor among other things.

As an example I own a K-1 and an older K10D. The FF camera has a pixel count of 36m and the aps-c camera has 10m. If I use a 150mm lens on the former, and a 100mm lens on the latter I will get two images that look the same in terms of magnification and field of view, but one is a 36MP image and one is a 10MP image. Which do you think is going to look better, especially if I want to print the image ?

Put another way....if I use the same 100mm lens on both cameras, but then crop the FF one so it is identical to the aps-c one, I will end up with a cropped FF image of 16MP compared to the aps-c's 10MP.

Equivalence is not about lenses or formats in isolation. It is about lenses; formats;and sensor specification together.

[Fogel70]

See my other comments above. You need to take at least some initiative and know what you are shooting

It is not about what I'm about to shoot, then it is too late. It is about selecting the best camera for my need. Which is where EFL can help a lot.

[Lowell Goudge]

Michael, this is where the "equivalence" get a bit confusing.

A 16-45mm lens has maximum magnification at 45mm obviously. A 83-249mm lens will have maximum at 249mm. The 249mm lens magnifies the image far, far more than the 45mm lens can, 5 times as much. These are the inherent optical properties of the lenses.

this is why I hate the equivalence discussion. It leads to all sorts of mis conceptions. You have assumed that a) you can achieve focus with the longest focal length b) the lens is not an internal focused lens where it reduces focal length to focus at other than infinity

Where the "magnification" equivalence comes from is the fact that the image captured on the smaller sensor on say the Q needs to be enlarged much more than the full frame sensor, and it is this that gives the equivalent image size. Whether it is as good a quality image as a full frame one with a longer lens will depend on the pixel density of the smaller sensor among other things.

hate number 2 you here are correct, you need to consider the size of the enlarged printed image

As an example I own a K-1 and an older K10D. The FF camera has a pixel count of 36m and the aps-c camera has 10m. If I use a 150mm lens on the former, and a 100mm lens on the latter I will get two images that look the same in terms of magnification and field of view, but one is a 36MP image and one is a 10MP image. Which do you think is going to look better, especially if I want to print the image ?

Put another way....if I use the same 100mm lens on both cameras, but then crop the FF one so it is identical to the aps-c one, I will end up with a cropped FF image of 16MP compared to the aps-c's 10MP.

This is the final point, the equivelence is only relevant if the image is not cropped

---------- Post added 10-05-21 at 07:07 AM ----------

It is not about what I'm about to shoot, then it is too late. It is about selecting the best camera for my need. Which is where EFL can help a lot.

If I am about to go and shoot, let’s assume at a baseball game, basket ball game, etc, I go on line and look at the venue, and the playing surface size. I then think about where I will be seated, and do the math, because I have absolutely no idea without doing that what lens is relevant regardless of format.

[Fogel70]

If I am about to go and shoot, let’s assume at a baseball game, basket ball game, etc, I go on line and look at the venue, and the playing surface size. I then think about where I will be seated, and do the math, because I have absolutely no idea without doing that what lens is relevant regardless of format.

My case was about what type of fixed lens camera to buy if you FI want a small pocket camera that you always can bring with you.
Where the EFL was introduced by camera manufacturers to simplify selection the right camera.

[slartibartfast01]

yes I am assuming that the shooter has at least some concept of size and dimension and is taking an interest in what he is doing. Let’s give the person who picks up a camera some credit for intellegence. what’s the whole point? 35 mm equivalent does not actually state anything about the sensor size.

I am not entirely sure what your argument is. Equivalent focal length is completely defined by relative sensor sizes (or film size) as is crop factor.

[UncleVanya]

I’m mildly surprised this hasn’t turned into a religious war.

[normhead]

My rejection of equivalence can be described by my phrase, "just look through the viewfinder." That tells you everything you need to know. Equivalence as a theory can only be justified in this modern day and age, because we can't go to a camera store and try out lenses and camera. It's a secondary approach that leaves too much ground for misunderstanding.

I remember getting my XG-1 and thinking the 1250 is not much different than the 700 stacked converters gets me on my 300. Then I realized, I was thinking 700 APS-C. So, it's actually not that much difference. You find out looking through the viewfinder what erroneous assumptions you made applying a mathematical formula. The viewfinder corrects all mathematic mis-interpretations. It's infallible. As noted above, there are many mistakes you can make with equivalence.

[Papa_Joe]

I would say focal equivalence is a very handy and essential information about a lens if talking about camera systems beside APS-C and 35mm (FF). And it is essential when one is starting to use a new camera system or is going to buy a new compact camera or a new smartphone.

If I tell you that I have been using a 45 mm for a picture. What do you make out of this piece of information? A wrong guess, if I want to.
If I show you the picture and tell you I took it with my Mamiya 645 or with my Nikon S1, you will in the first case see it is a picture taken wit a wide angle and in the second a telephoto picture. In the first case you will see it is quite a wide angle (28 mm equivalent) and in the second you will hardly guess right that it is a 122 mm equivalent.

When I bought my second lens for the Nikon S1 I did not screw it onto the camera first and had a look through it to get it's field of view or took the angel of view from it's data sheet. I just looked into the description an read the euqivalent focal length (80mm - 300mm).

For years I have been using compact cameras on vaction. For this piece of text I had to look onto my Olympus and my Casio for telling you, that the first has a zoom range of 6-24 mm and the second of whooping 4.3 mm - 43 mm. I even didn't know up until now, but I could have told you their FF equivalent, which would have made a lot more sense to you.

Off course I do not put my 26mm - 75mm eqivalent lens onto my K-70. For me it is my f2.8 all the day lens, which goes from quite a wide angle to a short portrait lens and therefore is quite versatile. That is the way I'am thinking of my 17-50 if I grab it out of my bag for a certain use. Nevertheless it is my 17-50 if I adress it and every one using APS-C knows, what I am talking about.

What I wanted to show is, just because you do not need a key figure for your daily work, it does not mean it is useless at all.
It might even be a very handy piece of information under the right circumstances.

[BigMackCam]

I'm always a little surprised at how emotive this subject is, though I do understand why it irks some folks. I've made the mistake of discussing equivalence before now.... Never again

The only aspect that irks me is when camera manufacturers or retailers claim that a smaller sensor camera has (for example) a "28-105mm equivalent f/2.8 lens". Whilst technically correct when stated in that order, it's potentially confusing, as less-experienced photographers (and perhaps a few experienced ones too) might easily expect it to have similar depth-field control to a 28-105mm f/2.8 lens on 35mm FF.

Beyond that, I don't mind if someone talks about equivalent focal lengths. Most of us know it's in relation to full frame. I like the idea of having angle-of-view inscribed on the lens instead of (or as well as) focal length, but as has already been mentioned, the value of that disappears when its used on a different format sensor - so maybe it would be equally confusing.

We don't seem to get so worked up over crop factor, yet that too is anchored to 35mm...

[normhead]

I'd still say the biggest problem with equivalence is the mis-understanding it can foster. It's been along time since anyone spouted the Tony Northrup nonsense, but it's still floating around out there.

Mr. Northrup was the champion of "equivalence is about Depth of Field" which still messes people up. Equivalence is about field of view. Any attempt to extend it beyond that will lead to endless confusion.

[UncleVanya]

And then there are the people who think that an aspc 100mm is less magnifying than a full frame 100 mounted on the same apsc camera.

[Pål Jensen]

The only aspect that irks me is when camera manufacturers or retailers claim that a smaller sensor camera has (for example) a "28-105mm equivalent f/2.8 lens". Whilst technically correct when stated in that order, it's potentially confusing, as less-experienced photographers (and perhaps a few experienced ones too) might easily expect it to have similar depth-field control to a 28-105mm f/2.8 lens on 35mm FF.

It isn't the slightest confusing. Only confusing to those who believes that the number 2.8 refers to DOF. Get your definition straight and all makes perfect sense....

[BigMackCam]

It isn't the slightest confusing. Only confusing to those who believes that the number 2.8 refers to DOF. Get your definition straight and all makes perfect sense....

Years ago, before I understood a lot of the fundamentals, it confused me. Perhaps I'm unique in that respect, but I strongly suspect not...