Super 35mm Crop Factor and a "Normal" lens.
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cpc
Well-known member
The OP specifically talks about Hitchcock. As it turns out the claim about Hitchcock's love of 50mm is specifically documented in the context of a VistaVision film. It only makes sense to talk about VistaVision then.
Grug said:
And as were To Catch a Thief, The Trouble with Harry, The Man Who Knew Too Much.
MattDavis
Well-known member
A 35mm stills camera pulled the film lefty-righty.
A 35mm movie camera pulled the film uppy-downy.
Therefore, the longest dimension on a movie camera was, in fact, the shortest dimension on the stills camera.
Depending on the area of film or sensor you need to cover, the bigger the area you need, the longer the focal length.
Given a certain spot and a given scene, there's an angle of view that approximates the human point of view. In Stills photography using Full Frame cameras, that's about 50mm.
But if you increase the sensor size, you need to increase the focal length. And vice versa.
So, a little 110 film instamatic with a negative smaller than a fingernail needed a very short focal length - a few milimeters. A whacking great Sinar 5"x4" plate camera needed 120mm. Hasselblad 6x6 cameras favour 80mm. They all gave approximately the same field of view.
Depth of field is not a direct product of angle of view - thus, small sensor/image cameras that use shorter focal lengths, have a wide depth of field even at more telephoto angles of view. A Sinar 5x4 camera using a 120mm lens may be seeing a widish angle of view, but will need to be stopped down to f22 and have the lens raked to bend its plane of focus to achieve the appropriate level of focus on a scene because of the focal length needed to cover its huge image area.
Thusly: a 120mm lens on a 1/3" camera is going to be super telephoto if you were to 'crop' that 1/3" bit out of the same lens covering a 5x4 camera's plate.
Or am I confusing everyone and making things worse?
A 35mm movie camera pulled the film uppy-downy.
Therefore, the longest dimension on a movie camera was, in fact, the shortest dimension on the stills camera.
Depending on the area of film or sensor you need to cover, the bigger the area you need, the longer the focal length.
Given a certain spot and a given scene, there's an angle of view that approximates the human point of view. In Stills photography using Full Frame cameras, that's about 50mm.
But if you increase the sensor size, you need to increase the focal length. And vice versa.
So, a little 110 film instamatic with a negative smaller than a fingernail needed a very short focal length - a few milimeters. A whacking great Sinar 5"x4" plate camera needed 120mm. Hasselblad 6x6 cameras favour 80mm. They all gave approximately the same field of view.
Depth of field is not a direct product of angle of view - thus, small sensor/image cameras that use shorter focal lengths, have a wide depth of field even at more telephoto angles of view. A Sinar 5x4 camera using a 120mm lens may be seeing a widish angle of view, but will need to be stopped down to f22 and have the lens raked to bend its plane of focus to achieve the appropriate level of focus on a scene because of the focal length needed to cover its huge image area.
Thusly: a 120mm lens on a 1/3" camera is going to be super telephoto if you were to 'crop' that 1/3" bit out of the same lens covering a 5x4 camera's plate.
Or am I confusing everyone and making things worse?
Nirv
Carbonite Member
In my naivety I thought it was a long standing photographic term that had passed the test of time! I see that "crop factor" is not only frowned upon but actively used to discriminate people on forums (not just this one).
I am going to swiftly return to my naive state but at least I know now, with the generous assistance of the more learned members, the FOV that Hitchcock thought of as natural and not just the focal length of his favourite lens.
morgan_moore
Major Contributor
Ive not read the whole thread but I take a 50mm to be a normal lens as it does not change scale in an optical view finder offering 100% magnification -a fifty offeres a normal perspective
a fifty does not however provide a normal field of view on small sensors
We have therefore two phrases to consider; normal perspective and normal field of view
ie looking through an OVF is the same as looking through a hole in a piece of card with a fifty
The size of the hole is dependant on the size of the sensor.. this normal perspective may not equate to a normal FOV
To compare when using a tele the image is magnified (and the objects compressed) and a wide the image is shrunk and the perspctive extended)
So a fifty - on any format S35, FF35 or even medium format 645 give a normal perspective - no compression or exageration of the scale of objects seen at different distances
However there is also what could be considered to be a normal field of view rougly equating to the field of view that the eye tends to concentrate on - ie the elements of the scene that are not in the peripheral vision of the viewer
So IMO
A fifty gives a 'normal perspective' irrelevant of the size of imager but a normal field of view is depenent on both the lens and the size of the imager
maybe 28 on a S35 chip or a 35 on a FF35 chip and 50 on a 645 chip..
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a fifty does not however provide a normal field of view on small sensors
We have therefore two phrases to consider; normal perspective and normal field of view
ie looking through an OVF is the same as looking through a hole in a piece of card with a fifty
The size of the hole is dependant on the size of the sensor.. this normal perspective may not equate to a normal FOV
To compare when using a tele the image is magnified (and the objects compressed) and a wide the image is shrunk and the perspctive extended)
So a fifty - on any format S35, FF35 or even medium format 645 give a normal perspective - no compression or exageration of the scale of objects seen at different distances
However there is also what could be considered to be a normal field of view rougly equating to the field of view that the eye tends to concentrate on - ie the elements of the scene that are not in the peripheral vision of the viewer
So IMO
A fifty gives a 'normal perspective' irrelevant of the size of imager but a normal field of view is depenent on both the lens and the size of the imager
maybe 28 on a S35 chip or a 35 on a FF35 chip and 50 on a 645 chip..
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morgan_moore
Major Contributor
Eh? aperture only affects DOF ?
(but DOF is of course affected by lens lenght, aperture and subject to camera distance viewing distance of the audience image resolution etc)
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(but DOF is of course affected by lens lenght, aperture and subject to camera distance viewing distance of the audience image resolution etc)
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David W. Jones
Veteran
There are always two sides to a coin.
In my mind the FS100 having a S35mm size sensor has no crop factor since S35 is my format of reference.
If you want to compare it to a 35mm still frame for your point of reference when making your lens selection then so be it.
In my mind the FS100 having a S35mm size sensor has no crop factor since S35 is my format of reference.
If you want to compare it to a 35mm still frame for your point of reference when making your lens selection then so be it.
morgan_moore
Major Contributor
I would agree that crop factor is a concept introduced with first digital stills cameras and bascially irrelevant today especially in motion aquisition..
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cpc
Well-known member
I just want to clarify that perspective does not depend on focal length. Perpsective is entirely dependent on view point.
What you describe is magnification and geometric distortion from projection.
And because perspective depends on view point, there is a single distance from screen for each screen size and focal length combo from which distance the image appears normal. And this is true no matter how you choose to define "normal", as long as it is a consistent definition. This distance is closer for wide lenses and further back for long lenses.
I also disagree with the disrespect for crop factors around. This is a very useful tool for quick angle of view assessment depending on the size of the capturing frame. Especially with today's abundance of frame sizes. And it is not like the concept wasn't applicable in film days, what with 8mm, 16mm, anamorphics, horizontal film, etc. No matter what frame of reference you choose, you need to be aware of the actual angle of view of the lens+capture frame combo. One may choose not to call it a "crop factor", but it is there nevertheless.
Mitch Gross
Veteran
I miss the days of lenses being marked as one inch, two inch three inch and four inch.
David W. Jones
Veteran
And I miss the days of slapping a Polaroid back on my Hasselblad or Bronica medium format cameras for a client preview... Not! Ha. :beer:
Ryan Patrick O'Hara
Veteran
hahaha, yeah! How did we get sucked into the metric system on that when we've held out on the rest of it for so long!
There actually is an "in-betweeny" position that a lot of people who get all-fired-up about mention of "crop factor" forget:
It's not necessarily about some "wet behind the ears" DSLR shooter demanding to have all comparisons be w.r.t. THEIR new-and-hallowed format; often it's simply because a lot of people shooting with cameras like the FS100, F3, AF100, and even RED.....ARE USING STILL PHOTO LENSES. (Canons, Nikons, Zeiss ZF etc.)
And these aforementioned lenses are talked about, reviewed, marketed, and have their product specs/feature descriptions on major vendors' websites listed as wide, normal, telephoto etc...
So it's not a horrible thing that people NOT using full-frame sensors - but using (and selecting) LENSES spec'ed for 35mm and DSLR cameras - have a rule of thumb to help shift their thinking w.r.t. lens types they see described in photo terms.
That's where "crop factor" (or, a term I like better for the actual value used - "focal length multiplier") came into play for me in a very real way: Because of the LENSES I was considering, and how I saw them described in (their native) photography world; nothing at all to do with the DSLR format, filmmaking history etc.
The people in the "Every-Time-Crop-Factor-Is-Even-Mentioned-I-Burst-A-Vein" camp should consider this.
It's not necessarily about some "wet behind the ears" DSLR shooter demanding to have all comparisons be w.r.t. THEIR new-and-hallowed format; often it's simply because a lot of people shooting with cameras like the FS100, F3, AF100, and even RED.....ARE USING STILL PHOTO LENSES. (Canons, Nikons, Zeiss ZF etc.)
And these aforementioned lenses are talked about, reviewed, marketed, and have their product specs/feature descriptions on major vendors' websites listed as wide, normal, telephoto etc...
So it's not a horrible thing that people NOT using full-frame sensors - but using (and selecting) LENSES spec'ed for 35mm and DSLR cameras - have a rule of thumb to help shift their thinking w.r.t. lens types they see described in photo terms.
That's where "crop factor" (or, a term I like better for the actual value used - "focal length multiplier") came into play for me in a very real way: Because of the LENSES I was considering, and how I saw them described in (their native) photography world; nothing at all to do with the DSLR format, filmmaking history etc.
The people in the "Every-Time-Crop-Factor-Is-Even-Mentioned-I-Burst-A-Vein" camp should consider this.
Crop factor is a really useful for people who shoot on different formats. In this day and age with so many different formats, it's needed more than ever.
I have a Eclair ACL 16mm, a Bealieu Super 8mm, Full Frame still cameras, APS-C and soon to be Super 35mm. All with different crop factors
The crop designation really lets me visualize the focal lengths on the various cameras that's I own. It might not be 100% accurate since some of the older formats are still 4:3, but at least I can get a general idea of what the Field of View is quickly and without much fuss.
Sure it might not be a purist way of viewing things, but it's the way things are now. Everyone I know who is involved in filming uses the term "crop factor" because it's a quick and easy way to communicate, and it's an easy way to make quick calculations to figure out what focal length you need for different types of cameras.
The alternative would be just to berate them and tell them: "WTF?!?! You don't know what the field of view on this Beaulieu Super 8mm is? I refused to use a simple term like Crop Factor to describe it to you. Go down the hall, there's a computer there, go on the internet and figure it out what lens we need. And research quickly, since we need to get the shot off."
I have a Eclair ACL 16mm, a Bealieu Super 8mm, Full Frame still cameras, APS-C and soon to be Super 35mm. All with different crop factors
The crop designation really lets me visualize the focal lengths on the various cameras that's I own. It might not be 100% accurate since some of the older formats are still 4:3, but at least I can get a general idea of what the Field of View is quickly and without much fuss.
Sure it might not be a purist way of viewing things, but it's the way things are now. Everyone I know who is involved in filming uses the term "crop factor" because it's a quick and easy way to communicate, and it's an easy way to make quick calculations to figure out what focal length you need for different types of cameras.
The alternative would be just to berate them and tell them: "WTF?!?! You don't know what the field of view on this Beaulieu Super 8mm is? I refused to use a simple term like Crop Factor to describe it to you. Go down the hall, there's a computer there, go on the internet and figure it out what lens we need. And research quickly, since we need to get the shot off."
Barry_Green
Moderator
Crop Factor is one of those things that is tiresome for some of us because it simply doesn't mean what people think it means. They think they understand it, but in fact they don't. They think one lens "becomes" or "acts like" another lens, and it doesn't. You hear people asking what a "50" is, or "well, I have an APS-C 50, so if I use that on my S35 camera it will look different than your full-frame DSLR 50 will, because your 50 is made for full frame and my 50 is made for APS-C". Which is 100% wrong, they will look identical on that camera.
If people would embrace "crop factor" for what it is -- for what it's actually named for, in fact -- then it would make a million times more sense.
Put simply -- if you're trying to apply the "crop factor" to a lens, then you're doing it wrong. You're thinking about it the wrong way. Crop Factor applies only to sensors, not to lenses. The lens stays the same. The only difference is HOW MUCH of the lens's image gets "cropped off". Everything else stays the same. The f-stop stays the same. The depth of field stays the same. The perspective stays the same. The lens doesn't change. The image the lens projects, doesn't change. Everything is exactly the same. The only difference is -- one sensor "crops off" more of the image than another sensor does.
If people would actually think about it like that, then it would be a valuable thing. But as it is, it just causes confusion.
I read where someone said that the Lumix X 12-35 2.8 lens "becomes" a 24-70 f/5.6 lens when used on an m43 camera. That's ridiculous, and it's that kind of confusion that gets under my skin and why I continually try to point out that people are simply thinking about this the wrong way.
And yes, I know the manufacturers quote "focal length equivalent" in their marketing. Doesn't make it an accurate or educational thing, it just further confuses issues.
If people would embrace "crop factor" for what it is -- for what it's actually named for, in fact -- then it would make a million times more sense.
Put simply -- if you're trying to apply the "crop factor" to a lens, then you're doing it wrong. You're thinking about it the wrong way. Crop Factor applies only to sensors, not to lenses. The lens stays the same. The only difference is HOW MUCH of the lens's image gets "cropped off". Everything else stays the same. The f-stop stays the same. The depth of field stays the same. The perspective stays the same. The lens doesn't change. The image the lens projects, doesn't change. Everything is exactly the same. The only difference is -- one sensor "crops off" more of the image than another sensor does.
If people would actually think about it like that, then it would be a valuable thing. But as it is, it just causes confusion.
I read where someone said that the Lumix X 12-35 2.8 lens "becomes" a 24-70 f/5.6 lens when used on an m43 camera. That's ridiculous, and it's that kind of confusion that gets under my skin and why I continually try to point out that people are simply thinking about this the wrong way.
And yes, I know the manufacturers quote "focal length equivalent" in their marketing. Doesn't make it an accurate or educational thing, it just further confuses issues.
cpc
Well-known member
I have to disagree with Barry. Not with the facts, but with the conclusion.
If someone misunderstands a concept this is not a fault with the concept. It is a problem with that someone. If we discard any misunderstood concept there wouldn't be any concepts in the world at all.
Also, the concept actually can be extended to lenses, although with a slight twist. If you ignore the f-number (because it is dependent on focal length) and instead think of the actual physical aperture, depth of field stays the same between two lenses with equivalent angles of view (but obviously different focal lengths) on differently sized sensors at the same physical aperture (for the same camera-subject distance and enlarged to the same print/display/projection size). Perspective is irrelevant as it is neither lens, nor sensor related.
I guess this is harder to wrap one's head around, but a nice thought experiment nevertheless.
If someone misunderstands a concept this is not a fault with the concept. It is a problem with that someone. If we discard any misunderstood concept there wouldn't be any concepts in the world at all.
Also, the concept actually can be extended to lenses, although with a slight twist. If you ignore the f-number (because it is dependent on focal length) and instead think of the actual physical aperture, depth of field stays the same between two lenses with equivalent angles of view (but obviously different focal lengths) on differently sized sensors at the same physical aperture (for the same camera-subject distance and enlarged to the same print/display/projection size). Perspective is irrelevant as it is neither lens, nor sensor related.
I guess this is harder to wrap one's head around, but a nice thought experiment nevertheless.