The 50 mm as standard - how it came to be

"I have never asked a camera shop for a "normal" lens, nor do I know anyone who has done so."

 

Good for you and really so what, doesn't mean anything. I"ve done it, I've seen it done at school. I have had photo teachers refer to 50 mm lenses as normal. Not sure what the big deal with the term is for you. Use the term with most experienced photographers and they will know you are talking about a 50 or even a 55 or 40 for that matter. Are you saying your not cognizant with the term as meaning a 50mm Ed?

 

Also it could be a language issue as well. I don't know what your native tongue is or where you live.

I tend to think of "normal" as a line drawn from a point, perpendicular to a plane ;) In statistics, to "normalize" is to group data into non-overlapping categories, expressed as a ratio relative to the modal value. In digital audio, "normal" is the loudest level without distortion, except when recording, where "normal" is about 20 dB below maximum. In education, "normal" is a curriculum intended to produce teachers. By definition, "normal" is conventional, something expected, or average. That usage allows for considerable flexibility.

My experience with "what is a 'normal' lens" for a format is more like what Uhooru says, except that I am not familiar with what photo teachers say (despite spending my entire adult work life in photography, I have yet to have my first formal "class" in it). Within the industry, though, I don't recall ever coming across a "knowledgeable" person who would not understand what I was talking about if I were to ask, "what would be a 'normal' focal length for such-and-such sensor/film format." (It would be around 50mm fl, more or less, for a standard 35 mm film camera.)

 

I have no idea where the term "normal" came from, though. Likewise, I have no idea how/when the term "prime lens" came to represent a fixed focal length, nor when the term "medium format" took over (I still stick with terms like "120 roll film", or "two and a quarter square," or "6 by 7," and that sort of thing). I even have a hard time considering 4 x 5 (inch) to be "large format;" I always reserved that term for 5 x 7" or larger. I suspect that the popular photo magazines were responsible for much of the popular terminology, but I dunno; that's not where my photo "education" came from.

 

But these terms do tend to come into popular use, and it's something of an uphill battle to fight against them.

Edited July 7, 2018 by Bill C

I tend to think of "normal" as a line drawn from a point, perpendicular to a plane ;) In statistics, to "normalize" is to group data into non-overlapping categories, expressed as a ratio relative to the modal value. In digital audio, "normal" is the loudest level without distortion, except when recording, where "normal" is about 20 dB below maximum. In education, "normal" is a curriculum intended to produce teachers. By definition, "normal" is conventional, something expected, or average. That usage allows for considerable flexibility.

 

I use the term normal to denote a lens that gives a familiar/expected perspective that we are used to from our naked eye vision. This also agrees with the definition you stated in your comment above.

 

I have always treated normal as in normal perspective, not as in what focal length I would normally use in photography.

I use the term normal to denote a lens that gives a familiar/expected perspective that we are used to from our naked eye vision.

 

That can be a good approximation, but as your thinking gets more advanced you eventually come to the realization that the camera lens/format doesn't stand alone. At some point you end up viewing the image, and this is the other part of seeing a normal perspective.

 

If you ascribe to the idea that we typically view images from a distance roughly equal to the diagonal of the print, or screen, or whatever, then the "normal" lenses should have a focal length equal to the diagonal of the film/sensor. (The concept is pretty well explained in Rudolph Kingslake's book, "Optics in Photography," I think; I've previously linked to it where the pertinent section could be read online in "preview" mode.)

That can be a good approximation, but as your thinking gets more advanced you eventually come to the realization that the camera lens/format doesn't stand alone. At some point you end up viewing the image, and this is the other part of seeing a normal perspective.

 

If you ascribe to the idea that we typically view images from a distance roughly equal to the diagonal of the print, or screen, or whatever, then the "normal" lenses should have a focal length equal to the diagonal of the film/sensor. (The concept is pretty well explained in Rudolph Kingslake's book, "Optics in Photography," I think; I've previously linked to it where the pertinent section could be read online in "preview" mode.)

 

I do understand that a ‘normal’ perspective focal length would vary depending on the sensor/film size, if that’s what you are referring to.

I do understand that a ‘normal’ perspective focal length would vary depending on the sensor/film size, if that’s what you are referring to.

 

No, what I'm trying to say is that there is another part to this - the part where you actually view the images that you have actually captured with your sensor, or whatever.

 

Here is an example of how this is pertinent. Consider if you were to photograph, for example, a family group using what we normally consider a wide lens (say a 28 mm lens on a standard 35mm camera), and some of the heads are near the corners of the frame. And then if you make some moderately small prints, say 4x6 inch or 5x7 inch prints, then you will almost certainly notice that heads near the edges have become curiously elongated - oval shaped - in a direction away from the center of the frame. I think you would have to say that this is not a normal perspective - these people did not have elongated heads as far as you could see when you photographed them, did they?

 

In my example, are you now to pronounce the lens used, the one that produced the elongated heads, as the problem?

 

Now here's a curious thing about the print(s). IF... you make prints that are large enough that you can view them from up close enough to duplicate the original angular view that the camera had, then THE ELONGATED HEADS WILL REGAIN THEIR NORMAL PERSPECTIVE - they will no longer appear elongated. (I originally referred to smaller prints because most people cannot focus their eye close enough; however if someone is very near-sighted and views with only one eye, then they can probably undo the elongated heads on the small print.)

 

Again, my point is that the camera lens, alone, does not stand alone - a major part of how we see "normal perspective" in an image depends on how we view it. So there have to be some assumptions about how we're gonna view the image.

Returning to 50mm lenses on 35mm cameras, among my own cameras, you get a 50mm lens on an SLR as standard almost all the time, but cheaper popular cameras with a fixed lens are more likely to have a 45, close to the frame diagonal; for example my Retinettes, Canonet, and Yamato Pax-series RF cameras; the Olympus Trip has a 40 mm.

Fwiw, the reference to Kingslake can be found here: Optics in Photography

 

The pertinent parts start around page 7 or 8, with the concept of a "center of perspective." If one doesn't already understand these things, it can be eye-opening, to say the least.

My preference is a 35mm lens, it pulls you in close to the subject matter; a feeling of being a part of...

 

However, a 50mm has a lot going for it. Being somewhat lazy.....

 

4 Reasons Why Everyone Should Have a 50mm Lens

Quality and cheap.

 

Not everyone has bags of gold coins:))

Returning to 50mm lenses on 35mm cameras, among my own cameras, you get a 50mm lens on an SLR as standard almost all the time, but cheaper popular cameras with a fixed lens are more likely to have a 45, close to the frame diagonal; for example my Retinettes, Canonet, and Yamato Pax-series RF cameras; the Olympus Trip has a 40 mm.

Also though not a fixed lens camera, a standard lens on a Leica C or CL is a 40mm and the fixed lens on the popular GRD versions is an equivalent 28mm and the cult classic Rollei 35 models, despite their name, uses different variations of a 40mm lens. Except for the 28 Ricoh, I would consider anything from 40mm to 55mm to be "normal" lenses.

My preference is a 35mm lens, it pulls you in close to the subject matter; a feeling of being a part of...

 

However, a 50mm has a lot going for it. Being somewhat lazy.....

 

4 Reasons Why Everyone Should Have a 50mm Lens

 

Makes sense Allen. To me, the science is good to know if it assists in making photographs, but its also easy to get bogged down in the physics and actually over-think it all. At the point it doesn't help me take pictures I just lose interest.

Fwiw, the reference to Kingslake can be found here: Optics in Photography

 

The pertinent parts start around page 7 or 8, with the concept of a "center of perspective." If one doesn't already understand these things, it can be eye-opening, to say the least.

It is interesting about the viewer's view point, but I wonder if given enlarged prints and proper viewing distance in order to see the camera's perspective doesn't basically naturally occur. I would think the viewer would, where possible walk into the proper viewing distance naturally there the photo feels "right", but then a lot of people will view a a highly enlarged print and just about put their noses in it and wonder why it seems distorted.

A choice to allow the user the broadest photographic possibilities in a single lens......

people will view a a highly enlarged print and just about put their noses in it and wonder why it seems distorted

Just the opposite is true. Very wide angle lenses cause heads to elongate toward the edges and corners, appearing egg-shaped. This is a special kind of distortion caused when you render 3 dimensional objects to a flat plane. If you view a print close enough, the distortion goes away. The "correct" distance is equal to the focal length times the degree of enlargement. For example, the correct viewing distance for an 8x10" print taken with a 16 mm lens would be just 5". Lenses longer than 35 mm have very little distortion of this type, and in its absence, the viewing distance is not critical. If people look closely at most enlargements, it is to see details.

 

Ancient Greeks designed their buildings to offset perspective. Columns of the Parthenon are several inches larger in diameter at the top. Renaissance painters often rendered bodies larger at the head than at the feet in large portraits, viewed presumably from floor level.

 

For the fun of it, I took a few pictures at Chicago Botanic Garden, using only a manual 50 mm lens. It seems a bit long for the environment, but generally there's enough room to back up. I think I rather like the mild compression of the background. I definitely like the ability to focus when and where I want.

 

Sony A7Riii + Loxia 50/2

Edited July 8, 2018 by Ed_Ingold

I believe I said pretty much the same. "I would think the viewer would, where possible walk into the proper viewing distance naturally there the photo feels "right", but then a lot of people will view a a highly enlarged print and just about put their noses in it and wonder why it seems distorted." Too close will be distorted too, not the same way but your peripheral vision will blur out at the edges etc. Here is a photo taken with a Hassleblad MF 40mm lens.. I do like how the wide angle captures the sense of space and geometry that doesn't show in normal and telephoto lenses but is just another trade off.

I have to get that Hassleblad out of mothballs, its such a great camera. I just own an 80 and its still cool.

There's an optical or should I say perceptual distortion of some sort (maybe you guys can explain it) where one of my stereo speakers (one on the left) appears to be larger than the one on the right. I was thinking this might be caused by the left one being surrounded by the steal shelving where the one on the right is surrounded only by white wall.

 

I decided to see if my camera can record this by shooting the two separately at 50mm since that does make it look as my eyes see the two in my living room with regards to vertical/horizontal positioning with the least amount of wide angle effect distortion. I shot two sets one about 8 feet away and the other about 12 feet away. See the Bridge screengrab below.

 

It appears to me that the camera recorded the perceptual size difference( illusion?) which does indicate 50mm even on an APS-C sensor can at least record a reasonable flat field appearance and rule out the lens is amplifying or attributing to this illusion or optical trick. I gave up fixing horizontal/vertical lens correction because it would require too much cropping and force me to move my furniture to shoot at a lower (centered) position. I shot it standing up just as my eyes would see without viewing through a camera viewfinder. Vertical slant is evident but I did align the top of the shelving to be horizontally correct as best as possible.

 

I still see the speakers as being differently sized with the one the right looking thinner. Do you all see the same?

Edited July 8, 2018 by Tim_Lookingbill

Back in the day when I "managed" the photo department in an Photo / Electronic Store (That because I was the employee, ex. possibly the store manager who knew something about photography) 35mm Nikon, Pentax, Canon, Hanimex, etc., etc. came with a 50mm lens. Anything else was a special order. Even the medium format was pretty much the same, came with the standard lens for the format. This was a pretty decent store with a reasonable inventory. No Leicas or Hassies, except special order. I only worked there for a few years, but can't recall a single order for just a camera body, and we wouldn't have sold one that way, because we'd have been stuck with the lens.

Tim, it looks like the pic on the lower left is distorted where the metal frame shows as a trapezoid instead of rectangle. With your 50, I imagine maybe the camera was slightly tilted up from level which I don't see nearly as much in the pic above it. Also is the lamp straight up and down in that room? You see some of the same distortion in the photo on the upper right, ie the edges tilting away from each other. You will get distortion not only if the the horizontal is level but also if the camera is tilted up or down. Looks like the camera was slightly tilted up. Also the speakers look like they are at different angles facing the camera on the left compared to the right, and that could factor into your size perception. Plus on the upper 2 photos there appears to be more distortion on the left right than the left just looking at the lamp pole.

Tim, it looks like the pic on the lower left is distorted where the metal frame shows as a trapezoid instead of rectangle. With your 50, I imagine maybe the camera was slightly tilted up from level which I don't see nearly as much in the pic above it. Also is the lamp straight up and down in that room? You see some of the same distortion in the photo on the upper right, ie the edges tilting away from each other. You will get distortion not only if the the horizontal is level but also if the camera is tilted up or down. Looks like the camera was slightly tilted up. Also the speakers look like they are at different angles facing the camera on the left compared to the right, and that could factor into your size perception. Plus on the upper 2 photos there appears to be more distortion on the left right than the left just looking at the lamp pole.

So, Uhooru, you do see the two speakers as differently sized or the left one slightly wider and the right one taller/thinner?

 

From my explanation none of this has anything to do with the lens distortion or whether the lamp is leaning (It is actually leaning due to a warped base).

 

Aside from that I did point out in my previous post that I am seeing the differences viewing with just my eyes. IOW this is a real optical effect that I was able to capture on camera with a 50mm lens even with minimal vertical distortion. I believe it has something to do with the framing of the metal shelving around the left speaker making it appear bigger.

 

I first saw this when I was trying to balance the left/right speakers on my stereo amp toward center and stepping back far enough to hear the difference when I noticed the left speaker appeared fatter or bigger than the right speaker which appears taller/thinner.

 

In fact on second look with just my eyes the differences are a bit more pronounced than the posted image shows.

Hard to say Tim, but the one, on the right top, does look a little taller and thinner than the one on the top left and difficult to compare the bottom two. Also especially, on the bottom left, the tilt distortion would add to it looking wider. But also, the left side speakers are facing at a slightly different angle to the lens and that could effect the view. but maybe you're right that the frame is effecting the perception of size. Ed?

I went back to set the speakers perfectly spaced apart, facing forward (not at an angle) using a metal measuring tape measuring from the wall to speaker front and across left and right to establish center. Stood perfectly in the middle far enough to see both speakers in focus and within view-able peripheral. I turned both eyes left to right back and forth without turning my head or body and the left one is now only slightly larger than the right. So 3/4 view angling of perfectly mitered four sided rectangular boxes enhances this optical effect.

 

I was beginning to think my left eye was warped or inducing some sort of barrel distortion.

You see more of the side of the speaker on the left, and the right speaker is in shadow. Acoustically, the right speaker would be louder, especially in the base. The corner walls act as an extension of the speaker horn. Placement has less effect on studio monitor speakers, which are highly directional, and usually of infinite baffle design (no passive bass port).

 

Another factor is eye dominance. You tend to see with one eye, which guides the other eye. However when you concentrate, that dominance may shift temporarily, and you see from a different position and angle through the other eye. That said, the camera was not exactly in the center between the speakers and normal to the wall.

 

The photo of the young lady sitting looks expansive because with a wide angle (e.g., CF40) lens, she is relatively closer and larger than the background than if taken with a longer lens from further away for the same background coverage.

Yep, that's what wide angle does.