Is this correct?

[mikegml]

I stumbled upon this 'Reframe' site in which the author makes a statement about the apparent perspective of lenses when shooting medium format compared to the same focal length (not focal equivalent) when shooting in 35mm.

I won't try to explain it as he states it quite well himself and it's possible I misunderstand him (I don't think I do) but I'd be surprised if this is correct, though I wouldn't say it's not, but it doesn't tally with my understanding of how perspective relates to focal length.

http://reframe.gizmodo.com/why-mediu...n-r-1601938278

[PhotomanJohn]

There are some correct statements in what he says but he is a bit confused. There are advantages to medium format over 35 but not what he describes. Perspective is a function of the physical relationship between the camera and the subject (in this case distance) and has nothing to do with format or focal length. If you put the two cameras next to each other and take a picture of the same subject, the perspective will be the same in both images. If you choose lenses for the two cameras that provide the same field of view on each then the images will look the same (ignoring resolution and the like).

Your instincts were correct.

John

[William W]

PERSPECTIVE does NOT relate to FOCAL LENGTH.

Perspective is determined by the CAMERA VIEWPOINT, which is defined by:

> The DISTANCE to the SUBJECT
> The ELEVATION of the CAMERA with respect to the SUBJECT

What the author is doing is using the term ‘perspective’ in a NON TECHNICAL sense and he is also confusing FIELD OF VIEW and transposing that term to a relationship to FOCAL LENGTHS for different CAMERA FORMAT.

“Let's say you're shooting on a 6x7 medium format camera with a 50mm lens. If you compare your images to a 35mm camera, also with a 50mm lens, you will notice the difference in field of view. Your medium format pictures will actually see what a 24mm lens on a 35mm camera would see. Simply put: the larger the film format, the wider angle your lenses become compared to 35mm.
The key point as a result of that difference is that even though the field of view is wider, the geometry, or "look," of the 50mm focal length remains. You don't get the exaggerated perspective that wide angle lenses usually produce on 35mm cameras. In that regard, medium format mimics how your eyes actually see the world, at least more so than the smaller 35mm size. The effect is even more apparent with large format 4x5, 5x8, or 8x10 film.”

I consider this to be wrong and also confusing.

If you place a 24mm lens (that has good IQ, little Barrel Distortion etc) on a 35mm camera and situate the camera at a SD of 12 feet from a Portrait Subject and make a picture (FoV approx 18ft x12ft) and then you also take a 50mm lens on a 6x7 camera (FoV approx 17ft x 14ft), and make a picture with the two Cameras at exactly the same VIEWPOINT - the PERSPECTIVE will be the same.

There might be marginal differences in the OPTICS of the lenses used, but note that a 50mm Focal Length lens which has the IMAGE CIRCLE COVERAGE for a 6x7 format is a big hunk of glass and in it design will have similar conditions (such as Barrel Distortion) to overcome; on the other hand a 50mm lens designed for the IMAGE CIRCLE COVERAGE of a 135 Format camera is much easier to design and much easier to overcome issues such as Barrel distortion ... but a 24mm lens for 135 format has similar design issues to a 50m lens for 6x7 format.


WW

[mikegml]

There are some correct statements in what he says but he is a bit confused. There are advantages to medium format over 35 but not what he describes. Perspective is a function of the physical relationship between the camera and the subject (in this case distance) and has nothing to do with format or focal length. If you put the two cameras next to each other and take a picture of the same subject, the perspective will be the same in both images. If you choose lenses for the two cameras that provide the same field of view on each then the images will look the same (ignoring resolution and the like).

Your instincts were correct.

John

That's what I thought. I await some mathematical/optical genius to say otherwise.

[William W]

There are some correct statements in what he says but he is a bit confused.

What John wrote is a good opening sentence / synopsis.

- he beat me to it.

[mikegml]

PERSPECTIVE does NOT relate to FOCAL LENGTH.

Perspective is determined by the CAMERA VIEWPOINT, which is defined by:

> The DISTANCE to the SUBJECT
> The ELEVATION of the CAMERA with respect to the SUBJECT

WW

That's also what I thought. I'm not sure he's using the term perspective in a non-technical sense either, I suspect he means it literally.

[ajohnw]

Nuts to perspective and format having an effect. The wiki sums it up very nicely in a none confusing manner BUT notice that the red bottle is always nearly the same size. If it isn't then other rules apply.

https://en.wikipedia.org/wiki/Perspe..._(photography)

John
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[William W]

That's also what I thought. I'm not sure he's using the term perspective in a non-technical sense either, I suspect he means it literally.

Maybe he thinks that he is using the word technically correctly, but he isn't.

I think the author uses the word twice -

“But print size aside, it's often easy to detect medium format images even when viewing on the web. It has a certain something, a signature look that is often recognizable but hard to articulate. It comes from the lack of perspective distortion. This makes photos look more natural, closer to what your eye sees in the real world.”

There is not any.

> Of a Lens - there may be: Barrel Distortion; Pincushion Distortion . . . etc.

> Of a picture due to Camera Viewpoint there may be: Keystoning; Foreshortening, Convergence etc (the appearance of which might be exacerbated by the distortions of the lens which is used.)

Note the word ‘distortion’ is NOT usually used in conjunction with these terms like “convergence”, nor (pedantically/technically ) is the word “distortion” to be used with the word “perspective”.

The colloquial joining of the word “distortion” to “perspective is the source of a lot of confusion/misinformation: especially if the words are NOT defined at the outset.

*

“The key point as a result of that difference is that even though the field of view is wider, the geometry, or "look," of the 50mm focal length remains. You don't get the exaggerated perspective that wide angle lenses usually produce on 35mm cameras.”

One cannot “exaggerate” perspective: it simply just is.

Both the above uses of the word "perspective" are colloquial and are outside of the context of the Technical use of the word “Perspective” for Photography and allied Subjects (such as Optics, Technical Drawing etc.).

WW

[loosecanon]

I think the author of the feature has missed what makes so many large format images look different - its due to a number of things.

Firstly large format tend to encourage more considered photography often with a tripod, thinking before pressing the shutter, thinking about composition, thinking about exposure.

Large format images are often laken lower than the standing eye level so many 35mm images are taken at. To me portraits stand out when taken from lower down, as obtained from the traditional waist level finder.

[ajohnw]

It might interest some as to why a large format lens may have much less distortion than the usual 35mm gear. It's down to a tendency to use symmetrical designs such as this one by Schneider. They are in some respects difficult to make but bigger chunks of glass can actually make that aspect easier.



Not that they will definitely look exactly like that in practice.

John
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[Manfred M]

I remember reading a commentary put out by Leica when they decided to branch out into medium format. One thing that they mentioned was that medium format lenses tended to built to less tight specs than 35mm lenses (effectively because images would not be enlarged as much as 35mm for the same output). Their goal was to build medium format lenses to the same optical quality as their 35mm line.

I don't know if this was just marketing rhetoric or if this is something that was really done (and had tangible results).

Medium format lenses tend to be slower than 35mm lenses. It's not uncommon to see primes at f/2.8 (and slower) and zooms at f/4 or slower, so this simplifies some of the optical design issues. Medium format lenses are fairly low volume items, so I suspect that aspherical elements are going to be avoided just because of high manufacturing costs that cannot be ammortized over many thousands of units.

[ajohnw]

Larger formats gain in some ways in the same way as various normal range digital camera gain. Eg for m 4/3 the optical performance needs to be better to match the resolution of a crop camera on it's larger sensor. This is talking max detail level for the same framing. Another similar situation is when people point out that a crop image can be cropped out of a full frame shot when the same lens is used. That one isn't entirely straight forwards the other one is.

The plus for m 4/3 is that the lenses are "smaller" less field to cover so can be made to a better standard as this helps where as it is unlikely to match FF at the same framing just like crop wont. It might never match crop either. This area is the downside of larger formats as they need bigger lenses but as the format is larger they can still achieve higher resolution despite the fact that they are likely to be inferior optically speaking. It's a balancing act and economics have to come into it.

The other factor about lenses of the type that Schneider tend to make is very large image circles so that shift and tilt can be used. That's why they probably make a lot of use of symmetrical designs. The idea is that aberrations going in are more easily cured by something similar going out. It also tends to put the "nodal points" in the best place for that. No idea how well it can work as have never been near one and they seem to have removed data from their site. I get not found messages on the ones I looked at out of curiosity.

I suspect aspheric elements might have problems on lenses that produce very large image circles for tilt shift use. They certainly can when I hook one camera up to a microscope because the area of the optical path used is smaller than should be. Some feel it's down to hot pressing as well.

John
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[AB26]

PERSPECTIVE does NOT relate to FOCAL LENGTH.
WW

William, I beg to differ.

What Photographers refer to when talking about perspective distortion is the fact that lenses of different focal length distorts the distance between objects. With a wide angle lens objects look further apart and with a tele lens objects look more compressed.

The author is correct when he refers to less perspective distortion on a larger format camera than what you will get from a 35mm camera, with the same focal length lens.

Definition of perspective:
"the art of representing three-dimensional objects on a two-dimensional surface so as to give the right impression of their height, width, depth, and position in relation to each other."

[Inkanyezi]

Nononono....

Perspective is not defined in that way, and a lens will not distort it. Look at this image of a toy car in a parking lot. The toy is about 2 cm high, and you may well gauge its size, looking at the oak leaf nearby or at the painted white lines for parking spaces. It is viewed from above, as the camera indeed cannot be brought so close to the ground without digging a hole. Cars further away are the size you'd expect of an ordinary car.

There is no lens distortion of perspective, only that the distance is very close, and that the little toy car is viewed from above, due to its small size. Just as any photograph shows just what the camera saw, from its vantage point, in this image, the camera was very close to the little toy and those other cars were further away. Neither perspective nor distances are distorted. The only thing that influences perspective is distance.

[William W]

William, I beg to differ. . . etc.

Andre, I note that you disagree.

I don't wish to debate this or any related points on similar topics with you any further other than providing the opinion that - if you sat for an exam set by any respectable institution and a question was asked about "Perspective" - I believe that you would be marked incorrect.

WW

[ajohnw]

If people just follow the wiki link they will see what comments like circa 100mm gives eye perspective really mean and that they are factual but only when the framing is kept the same in all respects. No cropping in other words. Like many things this rather simple aspect has been distorted by various instances of information overload usually by people who are just offering an alternative view of the effect that is seldomly of any practical use.

Then if you still don't believe take a 12mm head and shoulders portrait followed by a 300mm one and tell me you can't see any difference. Actually some one who is really into this aspect and has passed some very well regarded examinations is likely to be able to tell the difference in a shift from 100 to 135mm especially if they have seen the models face. Framing needs to be the same. I'm not into shooting where people like that are viewing my shots any more and haven't specifically shot portraits for a very long time - bought a 100mm too. It's a length I just wouldn't be without accounting for crop factor.

100mm? Some have been known to mention down to around 75mm. The 100 tends to be a western thing. wonder why.

It all boils down to producing flattering photographs when needed. I feel it has some bearing on landscape shots too. Depends what you want to do.

Edit - As Bill points out later I am talking about 100mm full frame equivalent. There is a need to account for a cameras crop factor.

John
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[William W]

If people just follow the wiki link they will see what comments like circa 100mm gives eye perspective really mean and that they are factual but only when the framing is kept the same in all respects. . . Then if you still don't believe take a 12mm head and shoulders portrait followed by a 300mm one and tell me you can't see any difference. Actually some one who is really into this aspect and has passed some very well regarded examinations is likely to be able to tell the difference in a shift from 100 to 135mm especially if they have seen the models face. Framing needs to be the same.

If the framing is kept the same and different Focal Length Lenses are used, then the CAMERA VIEPOINT must be changed, thus by definition that will change the Perspective.

In the example as cited above - if a Portrait is Framed the same using a 300mm lens and a 12 mm lens, then the Camera will be MUCH MUCH closer to make the Portrait with the 12mm lens than the 300mm lens.

If, however a Portrait is made using a 300mm lens and then another Portrait is made using a 12mm lens WITHOUT MOVING THE CAMERA OR SUBJECT, then the PERSPECTIVE will be the same - and if the image made with the 12mm Lens is cropped to render the subject the same size as in the image made with the 300mm Lens, and the facial features will be the same in both images.

***

Framing is different to Cropping.

Framing achieved in the viewfinder and is what is done by moving the camera's Viewpoint relative to the Subject.

Cropping is done when the negative or file is made and a portion of he whole is used for viewing.

WW

[ajohnw]

If the framing is kept the same and different Focal Length Lenses are used, then the CAMERA VIEPOINT must be changed, thus by definition that will change the Perspective.

In the example as cited above - if a Portrait is Framed the same using a 300mm lens and a 12 mm lens, then the Camera will be MUCH MUCH closer to make the Portrait with the 12mm lens than the 300mm lens.

If, however a Portrait is made using a 300mm lens and then another Portrait is made using a 12mm lens WITHOUT MOVING THE CAMERA OR SUBJECT, then the PERSPECTIVE will be the same - and if the image made with the 12mm Lens is cropped to render the subject the same size as in the image made with the 300mm Lens, and the facial features will be the same in both images.

***

Framing is different to Cropping.

Framing achieved in the viewfinder and is what is done by moving the camera's Viewpoint relative to the Subject.

Cropping is done when the negative or file is made and a portion of he whole is used for viewing.

WW

Exactly Bill but the problem is that some crop and show this aspect, others talk about it more technically and it all seems to help cause confusion where as the basics are very simple to understand and easy to demonstrate - all people need to remember is that circa 100mm will give something akin to an eye perspective and that departures will not do that as they get further away. The effects in this context are as expected, for shortening etc. This is the useful practical aspect of the effect. Some tutorials start of by saying it's bunkum, that really does help people.

John
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[William W]

. . .- all people need to remember is that circa 100mm will give something akin to an eye perspective and that departures will not do that as they get further away. . .

I think that the context of this OP and this thread: it is most necessary to note that your suggestion as to what people only need to remember is (I assume) referring to a 100mm lens on a 135 Format Camera (aka "Full Frame") ?

WW

[ajohnw]

I think that the context of this OP and this thread: it is most necessary to note that your suggestion as to what people only need to remember is (I assume) referring to a 100mm lens on a 135 Format Camera (aka "Full Frame") ?

WW

Be fair Bill I did mention that later. Perhaps not in the correct place, I usually put put FF after focal lengths in this respect but was in a hurry as going out for what was a very enjoyable meal.

John
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