Definition of “Standard-„ or „Normal-„ lens wrong?!

[Aussibum]

Hello everyone,

I am of the opinion that the term “normal lens” or “standard lens” should be linked to the magnification factor rather than the angle of view.

I would like to suggest a simple experiment to everyone from my own experience: If a lens with a 50mm focal length is used on a camera (regardless of the sensor size) you experience the following: The enlargement of the image corresponds exactly to the enlargement of the eye. To do this, simply leave the other eye open without the lens-camera system and walk around. If you do this with a different focal length, deviating from 50mm, this experience quickly becomes uncomfortable or leads to dizziness / headaches.

How much the viewing angle is restricted by the crop of the camera sensor is irrelevant here. The only important thing here is the magnification factor, which is determined exclusively by the focal length!

This is also understandable for everyone who connects his 50mm “normal lens” to a crop sensor instead of 35mm format. The experience of being able to take pictures with both eyes open will continue to be pleasant throughout the day.

Unfortunately, I have not yet identified any sources of proof for this, but I am afraid that the original references have neglected the connection of the magnification factor via the angle should only be related to the small image format 24x36 (viewing angle). In addition, the crop sensors and, more recently, the "equivalent focal lengths" were added, which have obscured the true relationship between the "normal lens" or "standard lens".

In any case, you can't walk around with a 33mm lens on an APS sensor or a 18,5mm lens on a 1’ sensor with both eyes open without irritation!
I ask everyone to try this out for themselves if possible and to form their own opinion.

I would be grateful for any original sources stating the connection between “normal lens” or “standard lens” to the magnification factor and thus to the 50mm focal length.



Sincerely

 

[embie]

Maybe better in "open talk" ?

--
"Travel is fatal...for prejudice, bigotry and narrow-mindedness" (Mark Twain) - "The world...is our home" (eMBie)
You can edit and repost my pictures until you drop but they will still be mine Please respect my copyright

 

[Aussibum]

Maybe better in "open talk" ?

Can you move it?

 

[embie]

Maybe better in "open talk" ?

Can you move it?

Sorry Aussibum...that's a job for the moderator, or...

You can copy/paste your text in the "other" forum.

Regards,

eMBie

 

[Smaug01]

Hi. Was this discussion in relation to a Challenge with a requirement to use a normal lens? If so, maybe it should be left here.

If it's more general, I can move the thread to Open Talk. Let me know.

***********

My position, for what it's worth, is that if the Challenge Host doesn't define 'normal lens', then a standard definition of that would be used. (I seem to recall that it is 40-50 mm, on a 35 mm frame.) It's 40-60 mm, according to several sources cited here: https://www.dpreview.com/forums/post/65217678

If s/he has a different idea than the standard definition of what a 'normal' lens is, s/he should define it.

In the end though, it is the host's definition that counts, as s/he moderates her/his own Challenge.

 

[tony field]

You also have to factor in the magnification Factor associated with the optical viewing system. My old Canon systems and Nikon systems had different image viewing size using the same focal length lens. Even adjusting the diopter control to match your eyesight results in apparent difference when viewing with both eyes open

 

[Barry Twycross]

My position, for what it's worth, is that if the Challenge Host doesn't define 'normal lens', then a standard definition of that would be used. (I seem to recall that it is 40-50 mm, on a 35 mm frame.)

I'm the only host I'm aware of to run a normal lens challenge recently, I used 1-2x the long side of the sensor for a focal length. That was more to conveniently slot it into a series of focal length challenges than any fundamental factors.

Though a good definition of normal is around the diagonal of the sensor (which is 43mm for FF).

However, the OP makes no sense.

I am of the opinion that the term “normal lens” or “standard lens” should be linked to the magnification factor rather than the angle of view.

You're going to have to define what you mean by magnification, as it doesn't correspond to any normal definition.

I would like to suggest a simple experiment to everyone from my own experience: If a lens with a 50mm focal length is used on a camera (regardless of the sensor size)

That makes no sense, the sensor always makes a difference to what you see, and 50mm is not special except it's near to the diagonal of full frame. On an 8x10 it's an extreme wide angle, on a phone sensor, it's an extreme long lens. There's no commonality in any magnification between these.

And the angle of view does make a difference.

 

[Tim Reidy Productions]

I have no idea what a standard lens is,

but a normal lens is a lens that is between a wide and telephoto length.

It is closer to what a eye would see.

I will let the others argue over numbers.

 

[jrtrent]

I have no idea what a standard lens is,

but a normal lens is a lens that is between a wide and telephoto length.

It is closer to what a eye would see.

I believe that "standard lens" and "normal lens" are synonymous terms:

Photography, Sixth Edition , by Barbara London and John Upton, "a normal focal length lens, also called a standard focal-length lens, approximates the impression human vision gives . . . the relative size of near and far objects seems normal"

I will let the others argue over numbers.

Tamron has said that the 40-60mm equivalent range is, "Generally speaking, a focal length range that provides a similar perspective to the human eye . . ." Sigma agrees, saying in their literature on the DP2s, "A lens with a focal length of 40mm to 60mm on a 35mm film camera is known as a 'standard lens' because it delivers natural perspective, close to what the human eye perceives."

 

[CptAmerica]

I'm the only host I'm aware of to run a normal lens challenge recently

A little off topic.. but I think a fun challenge would be to have specific FL only challenge, regardless of sensor size. 20mm only! 200mm only! ... etc.

Anyway, back to your regularly scheduled foruming.

 

[CptAmerica]

I have no idea what a standard lens is,

but a normal lens is a lens that is between a wide and telephoto length.

It is closer to what a eye would see.

I will let the others argue over numbers.

The problem with that, is there is no lens that sees ANYTHING like what the eye sees. My eye, when looking straight ahead at an object in the slight distance directly in front of me, sees my target subject at right around 90 or so mm on full frame. However, if I focus my mind on the totality of what fits into my vision as a whole (peripheral included), it's gotta be somewhere around 10mm or even lower.

So, do you compare "close to what eye sees" using your total vision arc? or how far away or how relatively large something appears out in front of you? Or do you split the difference? Personally, i choose how far away something looks out in front of me, which on a FF camera, is a bit telephoto.

Anytime I see somebody say "50mm is about what the eye sees", I cringe.

 

[Tim Reidy Productions]

I have no idea what a standard lens is,

but a normal lens is a lens that is between a wide and telephoto length.

It is closer to what a eye would see.

I will let the others argue over numbers.

The problem with that, is there is no lens that sees ANYTHING like what the eye sees. My eye, when looking straight ahead at an object in the slight distance directly in front of me, sees my target subject at right around 90 or so mm on full frame. However, if I focus my mind on the totality of what fits into my vision as a whole (peripheral included), it's gotta be somewhere around 10mm or even lower.

So, do you compare "close to what eye sees" using your total vision arc? or how far away or how relatively large something appears out in front of you? Or do you split the difference? Personally, i choose how far away something looks out in front of me, which on a FF camera, is a bit telephoto.

Anytime I see somebody say "50mm is about what the eye sees", I cringe.

cannot comment due to previous comment of arguing of numbers.

eyes are not a lens and a camera, and work differently. but we know our own fov.

 

[Barry Twycross]

I'm the only host I'm aware of to run a normal lens challenge recently

A little off topic.. but I think a fun challenge would be to have specific FL only challenge, regardless of sensor size. 20mm only! 200mm only! ... etc.

Anyway, back to your regularly scheduled foruming.

I decided I liked that idea enough I'm reviving my series with that as the first challenge (the 20mm one).

 

[CptAmerica]

I'm the only host I'm aware of to run a normal lens challenge recently

A little off topic.. but I think a fun challenge would be to have specific FL only challenge, regardless of sensor size. 20mm only! 200mm only! ... etc.

Anyway, back to your regularly scheduled foruming.

I decided I liked that idea enough I'm reviving my series with that as the first challenge (the 20mm one).

Awesome! I think it makes for an interesting challenge. Might also be cool to give a "no cropping" rule... so we really get to see the full FOV with that focal length and sensor combo.

 

[Barry Twycross]

I would like to suggest a simple experiment to everyone from my own experience: If a lens with a 50mm focal length is used on a camera (regardless of the sensor size)

simply leave the other eye open without the lens-camera system and walk around.

Quite easily disproven.

Apart from the fact that the image zooms when I change the diopter adjustment, so immediately it's proven false.

Here's a picture with 2 different cameras, with 2 different sensor sizes, both with 50mm lenses, looking at the same target.





The bottom left is the other eye open. The top image is one camera's viewfinder, the right image is another (it is focused if you put your eye to the viewfinder, just difficult to get in one frame.)

 

[Aussibum]

Hi. Was this discussion in relation to a Challenge with a requirement to use a normal lens? If so, maybe it should be left here.

If it's more general, I can move the thread to Open Talk. Let me know.

***********

IMHO not necessarily . I picked this forum for a reason.

My position, for what it's worth, is that if the Challenge Host doesn't define 'normal lens', then a standard definition of that would be used. (I seem to recall that it is 40-50 mm, on a 35 mm frame.) It's 40-60 mm, according to several sources cited here: https://www.dpreview.com/forums/post/65217678

If s/he has a different idea than the standard definition of what a 'normal' lens is, s/he should define it.

In the end though, it is the host's definition that counts, as s/he moderates her/his own Challenge.

I do not attempt I new definition (according to Wiki). Rather to add/merge to the existing definition the element of the magnification factor of a 50mm lens which is very close to the magnification factor (of any 50mm lens/camera system) of to the human eye. Meanwhile I am looking for sources to approve/backup my (in itself logic) practical experience who anybody can experience for themselves.

Thank you for your offer and kind regards.

 

[Aussibum]

I would like to suggest a simple experiment to everyone from my own experience: If a lens with a 50mm focal length is used on a camera (regardless of the sensor size)

simply leave the other eye open without the lens-camera system and walk around.

Quite easily disproven.

Apart from the fact that the image zooms when I change the diopter adjustment, so immediately it's proven false.

Here's a picture with 2 different cameras, with 2 different sensor sizes, both with 50mm lenses, looking at the same target.



The bottom left is the other eye open. The top image is one camera's viewfinder, the right image is another (it is focused if you put your eye to the viewfinder, just difficult to get in one frame.)

Thank you for this input.

So far I see that the round Logos nearly have the same size = same magnification factor! That is exactly my point!
This would not be possible with e.g. a 35mm lens.

 

[Barry Twycross]

I would like to suggest a simple experiment to everyone from my own experience: If a lens with a 50mm focal length is used on a camera (regardless of the sensor size)

simply leave the other eye open without the lens-camera system and walk around.

Quite easily disproven.

Apart from the fact that the image zooms when I change the diopter adjustment, so immediately it's proven false.

Here's a picture with 2 different cameras, with 2 different sensor sizes, both with 50mm lenses, looking at the same target.



The bottom left is the other eye open. The top image is one camera's viewfinder, the right image is another (it is focused if you put your eye to the viewfinder, just difficult to get in one frame.)

Thank you for this input.

So far I see that the round Logos nearly have the same size = same magnification factor! That is exactly my point!
This would not be possible with e.g. a 35mm lens.

You seem to be ignoring the other logo from the other format, which clearly is not the same size. This depends on format, and on viewfinder optics. As I said, this changes as I change the dioptre adjustment.

In no way is this an intrinsic quality of 50mm. It is a coincidence if it happens at all, for any focal lengths, for any format, for any viewfinder.

To make it clearer, below is just the logos extracted from the above image, the sizes are 308, 297, and 180 pixels. Even the ones you claim are the same size, are not.

 

[jrtrent]

Hello everyone,

I am of the opinion that the term “normal lens” or “standard lens” should be linked to the magnification factor rather than the angle of view.

I would like to suggest a simple experiment to everyone from my own experience: If a lens with a 50mm focal length is used on a camera (regardless of the sensor size) you experience the following: The enlargement of the image corresponds exactly to the enlargement of the eye.

Cameras have a specification called viewfinder magnification. These are done with a 50mm lens. My Pentax SP1000 film SLR (same format as full-frame digital) had a viewfinder magnification of .88x, meaning that with a 50mm lens, items were smaller in the viewfinder, .88 times the size, of what they were when viewed with my eyes. Pentax suggested their 55mm lens to better approximate life-size viewing. My friend's Topcon viewfinder had .86x magnification, and Topcon had a 58mm lens that gave life-size viewing.

Many of today's full-frame DSLR's have a viewfinder magnification of .7x, and would need about a 70mm lens to get close to life-size viewing. The same is true of my FZ300 bridge camera, whose viewfinder is listed as "Magnification: Approx. 3.88x / 0.7x (35mm equiv.)"

To do this, simply leave the other eye open without the lens-camera system and walk around. If you do this with a different focal length, deviating from 50mm, this experience quickly becomes uncomfortable or leads to dizziness / headaches.

How much the viewing angle is restricted by the crop of the camera sensor is irrelevant here.

The only important thing here is the magnification factor, which is determined exclusively by the focal length!

The magnification of the viewfinder system also plays a part. Neocamera has an interesting chart where they also take coverage into account to determine the effective size of what you see in various DSLR viewfinders.

https://www.neocamera.com/article/viewfinder_sizes?sort=size

This is also understandable for everyone who connects his 50mm “normal lens” to a crop sensor instead of 35mm format. The experience of being able to take pictures with both eyes open will continue to be pleasant throughout the day.

My 1.5x crop sensor Samsung DSLR's viewfinder has .95x magnification, so with a 50mm lens it would be pretty close to life-size viewing. My 2X crop sensor Olympus E-300 DSLR was even closer, having 1.0x viewfinder magnification.

However, I like using about a 50mm equivalent normal focal length lens because that's what helps my pictures look more like what my eyes saw at the scene:

Photography, Sixth Edition , by Barbara London and John Upton, "a normal focal length lens, also called a standard focal-length lens, approximates the impression human vision gives . . . the relative size of near and far objects seems normal."

So I use 35mm, not 50mm, on my Samsung, and I used 25mm, not 50mm, on my Olympus, even though that meant the viewfinder image made objects appear smaller than life size (using Neocamera's method, that would be about .60x for the Samsung and .47x for the E-300).

Unfortunately, I have not yet identified any sources of proof for this

Since viewfinder magnification is a specification that is determined by using a 50mm focal length, any camera whose viewfinder has close to 1.0x magnification should make objects appear close to life-size in the viewfinder when using a 50mm lens.

 

[Aussibum]

Hello everyone,

I am of the opinion that the term “normal lens” or “standard lens” should be linked to the magnification factor rather than the angle of view.

I would like to suggest a simple experiment to everyone from my own experience: If a lens with a 50mm focal length is used on a camera (regardless of the sensor size) you experience the following: The enlargement of the image corresponds exactly to the enlargement of the eye.

Cameras have a specification called viewfinder magnification. These are done with a 50mm lens. My Pentax SP1000 film SLR (same format as full-frame digital) had a viewfinder magnification of .88x, meaning that with a 50mm lens, items were smaller in the viewfinder, .88 times the size, of what they were when viewed with my eyes. Pentax suggested their 55mm lens to better approximate life-size viewing. My friend's Topcon viewfinder had .86x magnification, and Topcon had a 58mm lens that gave life-size viewing.

Many of today's full-frame DSLR's have a viewfinder magnification of .7x, and would need about a 70mm lens to get close to life-size viewing. The same is true of my FZ300 bridge camera, whose viewfinder is listed as "Magnification: Approx. 3.88x / 0.7x (35mm equiv.)"

To do this, simply leave the other eye open without the lens-camera system and walk around. If you do this with a different focal length, deviating from 50mm, this experience quickly becomes uncomfortable or leads to dizziness / headaches.

How much the viewing angle is restricted by the crop of the camera sensor is irrelevant here.

The only important thing here is the magnification factor, which is determined exclusively by the focal length!

The magnification of the viewfinder system also plays a part. Neocamera has an interesting chart where they also take coverage into account to determine the effective size of what you see in various DSLR viewfinders.

https://www.neocamera.com/article/viewfinder_sizes?sort=size

This is also understandable for everyone who connects his 50mm “normal lens” to a crop sensor instead of 35mm format. The experience of being able to take pictures with both eyes open will continue to be pleasant throughout the day.

My 1.5x crop sensor Samsung DSLR's viewfinder has .95x magnification, so with a 50mm lens it would be pretty close to life-size viewing. My 2X crop sensor Olympus E-300 DSLR was even closer, having 1.0x viewfinder magnification.

However, I like using about a 50mm equivalent normal focal length lens because that's what helps my pictures look more like what my eyes saw at the scene:

Photography, Sixth Edition , by Barbara London and John Upton, "a normal focal length lens, also called a standard focal-length lens, approximates the impression human vision gives . . . the relative size of near and far objects seems normal."

So I use 35mm, not 50mm, on my Samsung, and I used 25mm, not 50mm, on my Olympus, even though that meant the viewfinder image made objects appear smaller than life size (using Neocamera's method, that would be about .60x for the Samsung and .47x for the E-300).

Unfortunately, I have not yet identified any sources of proof for this

Since viewfinder magnification is a specification that is determined by using a 50mm focal length, any camera whose viewfinder has close to 1.0x magnification should make objects appear close to life-size in the viewfinder when using a 50mm lens.

Thank you for your feedback. So far your experiences are closest to what I am trying to communicate.
The link shows me how much the different magnification factors of the OVF/EVF jeopardizes any attempt to calculate the magnification of camera systems even if you would always use the exact same lens every time. With the simplified calculation for a Kepler system the magnification is M=(f lens) / ( f ocular). Sadly the f ocular is never given and from the magnification factor given from the camera manufacturer for their OVF/EVF cannot be calculated.

Also the experiment from Barry made me realize that this must be repeated with focus at infinity because at close focus the focal length differs.

However it seems I am the only lucky (or unlucky) person who can adapt and use my very same 50mm on three different sensor sizes (FF, APS-C and 1“) and even though the field of view changes the magnification factor makes my experience viewing pleasant over all these sensor sizes using that very same 50mm lens. On the other hand, if I use the dedicated, so called normal (equivalencized) lens, of 18,5mm focal length on my 1“ sensor the viewing is very unpleasant when having both eves open with one eye at the viewfinder.

I then ask all you extremely smart people in a constructive way here who attempt to debunk my suggestion for an explanation:

What is then the correct explanation for this experience?