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quixoticcassandra
14-Dec-2014, 08:02
I just purchased an Arca Swiss 6x9 monorail, so I'm wondering what my options are for architecture. I'd like to get something with at least a 70 degree field of view that will still perform with 20mm or 30mm of front rise. I've been looking at the comparison charts for 6x9, and in particular the following columns: angle of coverage, weight, possible rise, cost (of course) and max aperture (for ease of looking at the ground glass). Is there anything else I should be looking for? What about sheer bulk? Will I run into problem with the back of lens either hitting the bellows or hitting the glass? Related to that, should I also be trying to get something with a small focal length?

I used to have a 6x9 Nagaoka, and the lenses on it were tiny (eg a Schneider Angulon 65mm weighing only 80 gms). But I think they were also fairly ancient (there was also a Graphlex Optar 101mm and a Tominon 75mm). On the chart, I don't see anything nearly that small. Has modern glass gotten both better and heavier? Or is any modern glass even specifically made for 6x9?

Thanks in advance.

Dan Fromm
14-Dec-2014, 09:00
Ignored and delusional seeress, which focal lengths do you want to use? Why do you think you need 30 mm rise? Re movements, as you've found out with your Nagaoka the corners are lost before the edges, how badly do you need good image in the corners?

I shoot 2x3 Graphics (no movements to speak of) and a 2x3 Cambo SC (more movements than I need). Lenses made specifically for 2x3 (6x9 in metric) typically don't have huge coverage. But lenses down to 65 mm for 4x5 should fit your camera -- they fit mine - and will give you the coverage you need.

A few suggestions: 65/8 or /5.6 Super Angulon or the much harder to find Ilex or Fuji 65/8. 90 mm ditto. And from there up, lenses for 4x5. FWIW, I have the Ilex, also a recently acquired 65/8 Fuji that I haven't tried out yet.

You might also look into ancient lenses. For example, Berthiot's 90/14 Perigraphe has immense coverage, is a short normal lens on 2x3, and isn't very expensive. The lens is in barrel, can be stuffed into the front of an Ilex #3.

If you need a lens significantly shorter than 65 mm that covers 4x5, such lenses are quite expensive.

My shortest is a 35/4.5 Apo Grandagon. It and the 45/4.5 cover up to 6x12, might do for you. If a 125 or so mm circle is really enough, think about 47/8 and /5.6 SA and the very uncommon f/8 Ilex equivalent. I have an f/5.6 SA, like it very much. But it may not allow the movements you think you need.

quixoticcassandra
14-Dec-2014, 10:12
Good catch on the literature stuff, Dan.

I'd like the 30mm, because on my previous unit (a Mamiya 645 with a shift lens that had a maximum shift of 16mm), there was too much foreground in the architecture shots. And I'm assuming that coverage for the corners will somewhat correlate with the amount of available rise shown on the chart.

Thanks for the recommendations. I'll certainly look into those. The /5.6 Super Angulon did catch my eye (one of the only lenses on the chart which had a view angle above 75 degrees), but the cost will mean that it will be a potential purchase much further down the road.

Do I need to worry about weight on such a relatively small monorail?

Bernice Loui
14-Dec-2014, 10:52
Wide angle lenses will distort front to back perspective. Any wider than normal focal length lens will make the foreground larger than back ground and the wider the angle of coverage, the greater this distortion.

The standard Arca bellows will not allow 30mm of camera movement with a 47mm lens. Lenses shorter than 65mm requires a recessed lens board and bag bellows to function properly on the 6x9 Arca.

View cameras are a bit different than roll film or mass brand cameras as the angle of view required, images to be made evaluated then specific lenses chosen before the camera. The camera is to support the choice of lens, not what lens fits a specific camera. Basically opposite from the photo main stream norm.

In the end results, the Arca 6x9 many not be much of an improvement over the Mamiya 645shift lens.

Example, the Schneider 72mm Super Angulon XL has an image circle of 229mm, image circle required to cover 4x5 = 153mm, allowing the 72mm SAXL to have 76mm of camera movement on 4x5 sheet film, or greater than one film edge of 6x9 film format. Beyond that, there will be more image detail and information recorded on 4x5 over 6x9 for a similar wide angle lens perspective.

As for stability, the heavier the camera, the more stable it will tend to be. Generally, stability with a 6x9 camera is not an issues as long as the camera support is good.


Bernice




Good catch on the literature stuff, Dan.

I'd like the 30mm, because on my previous unit (a Mamiya 645 with a shift lens that had a maximum shift of 16mm), there was too much foreground in the architecture shots. And I'm assuming that coverage for the corners will somewhat correlate with the amount of available rise shown on the chart.


Do I need to worry about weight on such a relatively small monorail?

Dan Fromm
14-Dec-2014, 11:16
Um, 645 is half frame 6x9. I think your shift lens is a 50 mm. If so the 6x9 equivalent will be 100 mm. Not wide angle at all, normal for the format. 90/8 SAs are relatively inexpensive, will substitute. The 125/5.6 Fuji has been widely praised, has ample coverage and, again, isn't that expensive.

Go read lens catalogs. Here's a collection of links to many: http://1drv.ms/1w0vbMD Shop at www.keh.com, www.igorcamera.com and of course sold items on ebay.com to get an idea of what's around at what sort of prices.

quixoticcassandra
14-Dec-2014, 13:27
Um, 645 is half frame 6x9. I think your shift lens is a 50 mm. If so the 6x9 equivalent will be 100 mm. Not wide angle at all, normal for the format.
So if I get a 75mm or a 90mm, I'll have a bit better coverage than I have on the Mamiya...which is all I'm asking.





Go read lens catalogs. Here's a collection of links to many: http://1drv.ms/1w0vbMD Shop at www.keh.com, www.igorcamera.com and of course sold items on ebay.com to get an idea of what's around at what sort of prices.

Wow! That will keep me busy for a while. Thanks!

quixoticcassandra
14-Dec-2014, 14:39
The standard Arca bellows will not allow 30mm of camera movement with a 47mm lens. Lenses shorter than 65mm requires a recessed lens board and bag bellows to function properly on the 6x9 Arca.



Thanks Bernice. I'll certainly stick to 65mm and longer. In fact, when I tally up the lenses which are 300 gms and lighter -- and those within my budget -- it looks like they're mainly in the 100mm and longer focal length range.

Bernice Loui
14-Dec-2014, 23:01
Suggest something like a Schneider 105mm f4.5 Xenar in a Copal shutter as a start. These were also available in 135mm, 150mm and on up to 300mm in shutter. The 105mm Xenar should be about $100 USD in good condition.

Beyond that there are a number of modern Plasmats from 135mm on up for $100 USD and up.


Others, Kodak 101mm Ektar 105mm Ektar, 203mm Ektar (optically nice, often shutter issues).

APO Ronar and APO Artars in shutter and many, many others. There are lots to choose from for not a lot of $.

It really depends on the specific imagine making needs.

Keep in mind larger image circle or coverage is not always an advantage as the extra light inside the bellows will cause flare lowering image contrast or other less than desirable side effects of all that extra un-needed light bouncing around inside the camera bellows.


Bernice




Thanks Bernice. I'll certainly stick to 65mm and longer. In fact, when I tally up the lenses which are 300 gms and lighter -- and those within my budget -- it looks like they're mainly in the 100mm and longer focal length range.

Dan Fromm
15-Dec-2014, 04:58
Bernice, the shorter lenses you mention have image circles not much longer than their focal lengths, won't allow the rise the OP wants on 2x3. I have two 101/4.5 Ektars (good lens) and a 105/3.7 Ektar and had and sold another (overrated according to my tests, the 101 is better, and barely covers 2x3). Tessar type lenses faster than f/5.6 usually cover no more than around 1.1 times their focal lengths.

Oh, and by the way, I was mistaken when I said in post #5 above that a 50 mm lens on 645 sees the same view as a 100 mm lens on 2x3. The 2x3 equivalent of 50 mm on 645 is roughly 65 mm. More evidence of cognitive decline, I fear.

ic-racer
15-Dec-2014, 05:10
I just purchased an Arca Swiss 6x9 monorail, so I'm wondering what my options are for architecture. I'd like to get something with at least a 70 degree field of view that will still perform with 20mm or 30mm of front rise. I've been looking at the comparison charts for 6x9, and in particular the following columns: angle of coverage, weight, possible rise, cost (of course) and max aperture (for ease of looking at the ground glass). Is there anything else I should be looking for? What about sheer bulk? Will I run into problem with the back of lens either hitting the bellows or hitting the glass? Related to that, should I also be trying to get something with a small focal length?

I used to have a 6x9 Nagaoka, and the lenses on it were tiny (eg a Schneider Angulon 65mm weighing only 80 gms). But I think they were also fairly ancient (there was also a Graphlex Optar 101mm and a Tominon 75mm). On the chart, I don't see anything nearly that small. Has modern glass gotten both better and heavier? Or is any modern glass even specifically made for 6x9?

Thanks in advance.

I'd look for a Super Angulon 75mm which is a common lens and likely to be found used at a reasonable price. I don't see that it has been mentioned yet.
https://www.schneideroptics.com/info/vintage_lens_data/large_format_lenses/super-angulon/data/8-75mm.html

Emmanuel BIGLER
15-Dec-2014, 05:55
I just purchased an Arca Swiss 6x9 monorail, so I'm wondering what my options are for architecture.

Congratulations for your purchase. I have been using the Arca Swiss 6x9 monorail for 14 years now so if you have any question regarding this camera, please feel free to ask everything you would have in mind. My use is mostly on rollfilm and a few shots on instant 3x4" Fuji film pack. Too bad that Polaroid P/N 665 is discontinued, but this is another story.

The standard leather bellows for the Arca Swiss 6x9, ref. #071000 is recommended for focal lengths above 75 mm and up to 150 mm. For focal lenghs shorter than 75 mm, you can use either the short pleated leather bellows ref. #071010 which is essentially the same as #071000 but with less pleats, or the ultra-short leather bag bellows #071011 which is made of two large square pieces of leather stitched together by the edges. With those short bellows you may, or not, need a recessed board according to what you are doing. My 55 mm (see below) is mounted on a flat lens board.

The standard lens for 6x9 [56 mm x 82 mm in many rollfilm backs] is has a focal lenth of 100 mm or 105 mm and I have a Zeiss Planar 2.8-100 and an Apo Sironar S 100. The planar is nice, a f-number of 2.8 is a blessing for focusing and framing, but its image circle is limited by some baffles to 120 mm only, not more than a good old 100mm Tessar.
The Apo Sironar S covers 75 like all Apo Sironar S , i.e. 150 mm in diameter for a focal length of 100 mm.

One of the lenses I use most in 6x9 is the Rodenstock Grandagon-N 6.8 75 mm covering 102, i.e. about 180 mm in image circle. This is a moderate wide-angle in 6x9, a general-purpose lens in 6x9 like the 35 mm in 35 mm photography.
The 6.8 version is lighter and cheaper than the 4.5 Grandagon-N version but with 180 mm of image circle will cover more than you'll ever need in 6x9.

And I have the Apo Grandagon 55 on a flat lenboard ; 110 covering about 150 mm in diameter (it covers the 4x5" format). This lens delivers outstanding results.
In the kind of pictures I make, I have no need for a recessed board for the 55 combined with the short pleated bellows #071010.
I know a French professional architecture photographer who has worked for years with the Arca Swiss 6x9 and he also had the Apo Grandagon 35 mm - covering 120. He used it only for frontal shots in order to avoid unaesthetic projection effects as mentioned above by Berenice Loui.

An regarding the stability of the camera, suffice to say that Arca Swiss function carriers in use in the 6x9 model are designed to support a 8x10" format frame.

quixoticcassandra
15-Dec-2014, 20:03
I'd look for a Super Angulon 75mm which is a common lens and likely to be found used at a reasonable price. I don't see that it has been mentioned yet.
]

Thanks ic. Would it matter whether it's f8 or f5.6? I guess I'd prefer the latter, since it'd be easier to focus with.

quixoticcassandra
15-Dec-2014, 20:22
I just purchased an Arca Swiss 6x9 monorail, so I'm wondering what my options are for architecture.

Congratulations for your purchase. I have been using the Arca Swiss 6x9 monorail for 14 years now so if you have any question regarding this camera, please feel free to ask everything you would have in mind. My use is mostly on rollfilm and a few shots on instant 3x4" Fuji film pack. Too bad that Polaroid P/N 665 is discontinued, but this is another story.

The standard leather bellows for the Arca Swiss 6x9, ref. #071000 is recommended for focal lengths above 75 mm and up to 150 mm. For focal lenghs shorter than 75 mm, you can use either the short pleated leather bellows ref. #071010 which is essentially the same as #071000 but with less pleats, or the ultra-short leather bag bellows #071011 which is made of two large square pieces of leather stitched together by the edges. With those short bellows you may, or not, need a recessed board according to what you are doing. My 55 mm (see below) is mounted on a flat lens board.

The standard lens for 6x9 [56 mm x 82 mm in many rollfilm backs] is has a focal lenth of 100 mm or 105 mm and I have a Zeiss Planar 2.8-100 and an Apo Sironar S 100. The planar is nice, a f-number of 2.8 is a blessing for focusing and framing, but its image circle is limited by some baffles to 120 mm only, not more than a good old 100mm Tessar.
The Apo Sironar S covers 75 like all Apo Sironar S , i.e. 150 mm in diameter for a focal length of 100 mm.

One of the lenses I use most in 6x9 is the Rodenstock Grandagon-N 6.8 75 mm covering 102, i.e. about 180 mm in image circle. This is a moderate wide-angle in 6x9, a general-purpose lens in 6x9 like the 35 mm in 35 mm photography.
The 6.8 version is lighter and cheaper than the 4.5 Grandagon-N version but with 180 mm of image circle will cover more than you'll ever need in 6x9.

And I have the Apo Grandagon 55 on a flat lenboard ; 110 covering about 150 mm in diameter (it covers the 4x5" format). This lens delivers outstanding results.
In the kind of pictures I make, I have no need for a recessed board for the 55 combined with the short pleated bellows #071010.
I know a French professional architecture photographer who has worked for years with the Arca Swiss 6x9 and he also had the Apo Grandagon 35 mm - covering 120. He used it only for frontal shots in order to avoid unaesthetic projection effects as mentioned above by Berenice Loui.

An regarding the stability of the camera, suffice to say that Arca Swiss function carriers in use in the 6x9 model are designed to support a 8x10" format frame.

Thanks Emmanuel. I suspect that I'll start out with a 75mm something-or-other. The angle of coverage is just what I'm looking for, and it's good to know that it will do its stuff with a wide angle bellow.

On the really wide angle stuff that Bernice was talking about, I've seen non-architectural examples of the phenomenon (such as in section 6.14 in Leslie Stroebel's book on LF). But I can't wrap my head around what an architectural example would look like. Would the parallel lines start to become non-parallel at some point?

Lightbender
16-Dec-2014, 00:41
"On the really wide angle stuff that Bernice was talking about, I've seen non-architectural examples of the phenomenon (such as in section 6.14 in Leslie Stroebel's book on LF). But I can't wrap my head around what an architectural example would look like. Would the parallel lines start to become non-parallel at some point? "

No, pretty much all LF lenses are rectilinear.. straight lines stay straight lines. Some may have slight distortion, but i doubt anyone would notice it unless they put a ruler on the print.

Regarding a lens for you, it really depends on your price point and your patience. The best price /performance/availability will be a f8 Super Angulon or Fujinon, which you can easily find for $150. If you are patient, you may be able to find a f5.6 at that price or even a 4.5 (rodenstock) at around $200. 90mm is your best bet, but just slightly wider than normal. 65mm and 75mm are not hard to find either.

The brighter lenses are easier to focus, and have slightly more coverage, but I doubt you will need more coverage.

Dan knows about probably every 6x9 lens there is, so if you have questions, post here.
i have more 6x9 lenses than i care to admit, but I dont use them that often as i also shoot 4x5, 35mm, and digital.

Emmanuel BIGLER
16-Dec-2014, 06:13
Would the parallel lines start to become non-parallel at some point?

The problem is that the shorter the focal lengths, the easier you get into strange effects.
In principle if your film plane is perfectly set parallel to any objet located in a plane, all rectangular grids or rectangular edges will be projected on film like features with 90 angles and no trapeza-like distorsion.
Another effect mentioned by Berenice is the so-called "ice-cream cone" effect.
When you are located at street level, too close to a tall and perfectly vertical building with vertical edges like a rectangular shoe-box, even if your wide-angle lens is perfecty distorsion-free and perfectly covers your subject after perfectly setting your film plane vertical, the building can be rendered in a really non-natural effect, it will look as if the top was broader than the bottom, this is just an illusion.
So in a ideal world, architecture shots would never be taken with a wide-angle lens ;) but you often do not have enough space to allow a minimum distance for your camera.
And regarding the front/back distorsion of perspective effects and ice-cream cone effect, you could have a look at this shot I took with my 75 mm Grandagon-N lens on instant Fuji FP-100C film pack. (https://aufilmdesmots.files.wordpress.com/2014/10/201410191.jpg)
Instant film pack can be used on the Arca Swiss 6x9, but you have only access on the 6x9 ground glass for framing a smaller (about 60x90) portion of the whole final image (73 x 95 mm) ; too bad that Arca Swiss does not supply a square 90x90 ground glass for the 6x9 camera!

The building is certainly not a new world's skyscraper ;), but a only a very modest abandoned train station of a former local train line that no longer exists since 1952.
The focusing is bad so do not pay attention to the sharpness (a real shame, taking into account what the grandagon can do), but look at the geometry of the image.
I did my best to avoid any converging vertical lines. Electric poles look quite parallel to the edges of the image and verticals on the edges of the building are projectd quite vertical on the image as well.

Definitely I'm too close to the building. The house seems broader on top and looks un-natural!

I'd better take a 100 or a 135 and step back. But I could not, due to some walls and limits of a private property behind me ...

Emmanuel BIGLER
16-Dec-2014, 06:30
Dan knows about probably every 6x9 lens there is

It's time for reading again this invaluable document! Thanks again, Dan!
Unlikely lenses on 2 x 3 Graphics - part 1 (http://www.galerie-photo.com/1-lens-6x9-dan-fromm.html)
Unlikely lenses on 2 x 3 Graphics - part 2 (http://www.galerie-photo.com/2-lens-6x9-dan-fromm.html)
Unlikely lenses on 2 x 3 Graphics - part 3 (http://www.galerie-photo.com/3-lens-6x9-dan-fromm.html)

Same as a single printable pdf document
http://www.galerie-photo.com/telechargement/dan-fromm-6x9-lenses-v2-2011-03-29.pdf

Dan Fromm
16-Dec-2014, 07:51
Thanks for the kind words, Lightbender and Emmanuel.

I'm acquainted with only a small subset of lenses made for 2x3. There are so many, most of them very similar normal lenses for folding roll film cameras. Unfortunately there aren't that many readily available shorter than normal lenses for the format. There are a fair number of telephoto lenses for 6x9 that I know only from the literature. In spite of Linhof's efforts the format was used mainly by snapshotters.

Bernice Loui
16-Dec-2014, 10:25
Difference between lens geometric distortion and perspective distortion, they are not the same in any way. Indeed, the majority of wide angle or lenses with large angles of view relative to a "normal lens" are rectilinear or they tend to produce straight lines on film or imager (CCD or similar). The most common wide angle geometric distortion is barrel distortion where straight lines are rendered rounded out much like a barrel as in this example where the image on the left has lots of barrel distortion and image on the right is rectilinear.
http://hugin.sourceforge.net/docs/manual/Barrel_distortion.html

The other common lens geometric distortion is pin cushion. This is basically the opposite of barrel distortion where the lines that should have been rendered straight are now rendered curved inward on film or imager. Example of pin cushion lens distortion, image on the left has lots to pin cushion distortion and the image on the right rectilinear.
http://hugin.sourceforge.net/docs/manual/Pincushion_distortion.html

~~~~~~~~~~


Perspective distortion is quite different and not related to geometric distortion. Two examples using images taken with an iPhone set to it's widest angle.

This image is of a Lockheed SR71's tip. Note the size of this tip (actual size is about an inch in diameter) in the foreground which is rendered much larger than the body of the SR71 and the American flag that hangs side-ways on the wall which is about half the height of this building. The iPhone lens is relatively rectilinear and has some barrel distortion. The position of the iPhone camera was inches from the tip of the SR71 and carefully position to be as level as could be done hand held. If the iPhone was not level, the straight lines in this image would tilt. Rectilinear wide angle lenses will render straight lines tilted yet straight if the lens is not level and perpendicular to the subject.
https://lh6.googleusercontent.com/-UqPtq_BOTUs/VI_z2v_46hI/AAAAAAAABVU/Gqzz_a8SGso/w1368-h1022-no/Tip_SR71.jpg


Another example taken with the same iPhone at the Cantor museum, Stanford.

The front of this sculpture is about eight inches in diameter, yet as visually rendered, that eight inch round appears larger than the life size sculpture in the background of this image. The iPhone again was positioned inches away from the front of this sculpture causing it to be rendered much larger than items in the background. Another example of wide angle perspective distortion. The iPhone was also carefully leveled (hand held) to reduce the amount of tilt that would have resulted in tilted straight lines. This is the same reason rise-fall, left-right shift is commonly use to render lines straight when using a view camera. Most important, the camera position must be very close to correct and level before trying to apply any movements in the view camera, otherwise the composition, perspective and all related to how the resulting image will not be as expected and the composition after applying view camera movements will be altered at times requiring the camera position to be moved slightly to compensate for this effect.. View camera movements are very much a fine-tuning device. View camera movement can be used to several distort and alter the image rendered on film or CCD imager. It is a matter of how this tool is applied and used.

If this was a normal (normal perspective lens) lens the round front part of this sculpture ( foreground) would be similar or the same as how the human eyes would render and perceive it, that is the front part of this sculpture (foreground) would be smaller relative to the objects background. This is what changes in focal length does, alters the size of objects foreground -vs- back ground.
https://lh5.googleusercontent.com/-sfzOJSoGWrA/VI_z3GBbHTI/AAAAAAAABVY/gG3FgVxiTlo/w764-h1022-no/Cantor%2C%2BFloor%2BStone.jpg


Bernice



"On the really wide angle stuff that Bernice was talking about, I've seen non-architectural examples of the phenomenon (such as in section 6.14 in Leslie Stroebel's book on LF). But I can't wrap my head around what an architectural example would look like. Would the parallel lines start to become non-parallel at some point? "

No, pretty much all LF lenses are rectilinear.. straight lines stay straight lines. Some may have slight distortion, but i doubt anyone would notice it unless they put a ruler on the print.

Regarding a lens for you, it really depends on your price point and your patience. The best price /performance/availability will be a f8 Super Angulon or Fujinon, which you can easily find for $150. If you are patient, you may be able to find a f5.6 at that price or even a 4.5 (rodenstock) at around $200. 90mm is your best bet, but just slightly wider than normal. 65mm and 75mm are not hard to find either.

The brighter lenses are easier to focus, and have slightly more coverage, but I doubt you will need more coverage.

Dan knows about probably every 6x9 lens there is, so if you have questions, post here.
i have more 6x9 lenses than i care to admit, but I dont use them that often as i also shoot 4x5, 35mm, and digital.

quixoticcassandra
16-Dec-2014, 20:21
Another effect mentioned by Berenice is the so-called "ice-cream cone" effect.
When you are located at street level, too close to a tall and perfectly vertical building with vertical edges like a rectangular shoe-box, even if your wide-angle lens is perfecty distorsion-free and perfectly covers your subject after perfectly setting your film plane vertical, the building can be rendered in a really non-natural effect, it will look as if the top was broader than the bottom, this is just an illusion.
So in a ideal world, architecture shots would never be taken with a wide-angle lens ;) but you often do not have enough space to allow a minimum distance for your camera.
And regarding the front/back distorsion of perspective effects and ice-cream cone effect, you could have a look at this shot I took with my 75 mm Grandagon-N lens on instant Fuji FP-100C film pack. (https://aufilmdesmots.files.wordpress.com/2014/10/201410191.jpg)


Actually, I find that image quite pleasing. But I know what you mean. If anyone has Steve Simmons' book on the view camera, an unpleasant example (ie, much more ice-cream coney) is the lower left image of the California State Capitol building on p.48.

But I guess that's what a ground glass is for: checking for unpleasantness before tripping the shutter.

graywolf
25-Dec-2014, 12:49
If this was a normal (normal perspective lens) lens the round front part of this sculpture ( foreground) would be similar or the same as how the human eyes would render and perceive it, that is the front part of this sculpture (foreground) would be smaller relative to the objects background. This is what changes in focal length does, alters the size of objects foreground -vs- back ground.
https://lh5.googleusercontent.com/-sfzOJSoGWrA/VI_z3GBbHTI/AAAAAAAABVY/gG3FgVxiTlo/w764-h1022-no/Cantor%2C%2BFloor%2BStone.jpg


I have to take exception with this. If you look at that sculpture from the same distance as the camera was, you would see exactly the same thing the lens shows. The apparent change of perspective with different lenses are caused buy the distance you are taking the photo from. This is easy to verify: Simply take a shot with your normal lens, then from exactly the same place take it with your wide angle lens. Next crop the wide angle shot so its field of view is the same as the normal lens shot. No difference in perspective at all.

The mushrooming shot Emmanuel posted a link to is also not a lens distortion, but a cognitive one. Our brains know that perspective causes lines to come together in the distance, and corrects for that. When they do not come together as in Emanual's shot we see what we see as reverse perspective in his photograph. The trick there is to only correct the perspective 90% or so, then our brain sees that as normal an supplies the small amount of additional correction. Of course if you are going to measure the photo rather than just looking at it you need the 100% correction.

In cases like these we can literally not trust our eyes.

Lightbender
30-Dec-2014, 01:44
Bernice: if you look at the lines on the floors in both your pics, you will see that the lines all remain straight.

Distortion, in the form of barrel or pincushion, would cause straight lines to curve. This often occurs in wide-angle SLR lenses, because the retro-focus nature of these lenses adds this distortion, and some do a better job than others in correcting it. Rangefinder and view camera lenses rarely have much distortion at all.

Any 'mushrooming' as you say is caused by perspective, not by distortion of the lenses.