The Bell Tower Problem

I shoot of a lot of Architectural photographs of churches that have a bell tower. A particular problem arises when I want to make a two point perspective shot of the building, with a wide angle shift lens with an angle of view greater than 28mm. (It is not always possible to back off and shoot with a longer lens.)

The main building looks fine, but the bell tower often has a strange perspective, due to the two point perspective lines laying on different planes. Here, below is a shot of the Pieve in Vigoleno, shot with just vertical perspective correction.

The bell tower looks strange. This is not distortion. The picture obeys all the rules of two point perspective.

A method I use, and which you will not find in many texts that explain the use of shift lenses, is to use diagonal shift. In the case of this church, the sensor plane should be parallel with the façade and bell tower front. Then using diagonal shift the church is framed to our liking.

The result is the shot below, taken from the same position.

The result is a much more natural looking picture.

I returned sometime later to make a more dramatic blue hour shot.

When the bell tower is on the front face, diagonal shift is not generally needed. This is St Clement's Church, Old Romney

This exaggerated two point perspective example shows that the two point perspective vanishing lines are coplanar. This is why the bell tower does not seem distorted. Chiesa di Sant'Ambrogio,Uscio, near Genoa.

Sometimes, diagonal shift, is useful to reduce the two point perspective effect when you cannot take a one point perspective view for reasons of space. S. Giorgio, Parma

The shots above were made with a shift lens. The same corrections can be made with post processing software, at the cost of losing large areas of the picture. This is a corrected shot made from the first picture in this post. 

There is another problem with old churches with bell towers. The church below was built almost a thousand years ago, on the side of a mountain. It has weathered a few earthquakes as well. The foundations are probably almost non existent. In time the bell tower had moved out of plumb. The church itself has walls that lean. 

There is no optical way of  correcting all the effects of time, that this building has suffered. I just have to live with the strange distorted look of the church, particularly, the bell tower in this shot.

S Paolo Vendaso, Fivizzano

Exploring Perspective

Here are a few thoughts about one of the most useful tools we have, to give the impression of depth in a photograph.

Previous cultures understood pictorial perspective, but in its mathematical form, linear perspective is generally believed to have been devised about 1415 by the architect Filippo Brunelleschi (1377–1446) and codified in writing by the architect and writer Leon Battista Alberti (1404–1472), in 1435 (De pictura [On Painting]). 

But, Brunelleschi, Alberti, and others only understood one point perspective, the simplest pictorial form of perspective. We have just one point where the sightlines converge. Central perspective, however, is so violent and intricate a deformation of the normal shape of things that it came about only as the result of prolonged exploration and in response to very particular cultural needs. Curiously, the distortions imposed by perspective on the real, tactile world are so successful that modern viewers only note them when pointed out.

If we construct a perspective drawing, or use perspective in a photograph, the angle of view is a question of proportion, that can be explained by tracing an image on a window whilst looking through a small hole at a fixed distance. A simple illustration explains the concept nicely. It is obvious that the angle of view and the steepness of the sightlines are infinitely variable. 

Quoting a pamphlet on the use of perspective in Renaissance painting, published by the British National Gallery, we can understand that sometimes we need to depart from pure geometric, or mathematical models:

“Optical illusion does not necessarily depend on mathematical absolutes and, with a few important exceptions such as Piero della Francesca, it seems that painters were more concerned with achieving a level of visual plausibility than with the rigorous application of theoretical models. Perspective was designed to fulfil the needs of the picture (not vice versa), and a series of other conditions and criteria were at stake: the knowledge, skill and aesthetic preferences of the artist, the demands of patrons, the ways in which the site might determine the viewpoint, and the requirements of the subject matter. Thus, a painting which has often been considered a perspectival manifesto, Masaccio’s ‘Trinity’ fresco, has been shown to bend the rules of one-point mathematical perspective, probably because it looked better that way”

Construction of a One-Point perspective drawing 

Sight lines for Leonardo da Vinci's The Last Supper

Simple 1 point perspective

Two-point perspective, necessary to show objects set at an oblique angle to the viewer, took another century to evolve. The first known diagram of the two-point perspective by Jean Pélérin, in his De Artificiali perspectiva (1505), which was also the first printed treatise on perspective. With two-point perspective, there are two vanishing points on the horizon line. This creates the illusion of depth and space

Simple 2 point perspective

Two-point perspective is probably a much more useful, than one point perspective, if we want to create an illusion of a three-dimensional object in a photograph. But it is harder to control and unwanted perspective effects can creep in to make a picture look unnatural. 

Three-point perspective is a type of perspective that uses three vanishing points. It is used to draw objects that are above or below the viewer’s eye level, such as skyscrapers or bridges. In three-point perspective, the lines that are parallel to each other in the real world converge to three different points on the horizon line. Three-point perspective is closely connected to two-point perspective, and is generally unwelcome in Architectural photography. Three-point perspective often appears as “key stoning” in a photograph. 

Simple 3 point perspective

I have introduced the most simple cases, to show how the basic principles of perspective drawing and photography using perspective effects . We can see in the drawing below that we can have many vanishing points in a scene. But most of the time one or two point perspective for the main subject are sufficient.

The principle piece of furniture obeys two point perspective. Think of all the secondary objects as separate entities using two or three point perspective in this case.

Let's look at some real world examples. With Aldo Rossi's Ossario in Modena as an example. I made three pictures with one, two and three point perspective. 

1 point perspective

2 point perspective

3 point perspective

When we look at a reasonably low building like the one above, our brain applies key stone correction, and we see the vertical walls as being vertical.

A shift lens can help us produce pictures with one or two point perspective. It allows us to shift our eyesight convergence point in any direction. 

Upward shift moves the single convergence point upwards

But we can also shift the convergence point both upwards and sideways, to keep the horizontal and vertical line s parallel, and create un unusual perspective effect

Exaggerated 2 point perspective for dramatic effect. 

2  point perspective

This shot has multiple vanishing points

Nikon 28mm -400mm Lens Review

 

Nikon have Just released the rather interesting 28mm-400mm zoom lens, which I can see as being pretty useful in a number of situations.

I had some doubts about firmare match with my Z7, but when I was reassured that everything would work well, I took the plunge and bought this lens. I wanted something with a bit more reach for detail shots and also travel. I tried my Sigma 100-400 on my three legged monopod to see if it was usable a 400 at long shutter speeds, but it did not work out, The VR in the Sigma is pretty lame. So it is out for Architectural details

I skived off this afternoon, to see what this lens can do. Nothing artistic. I had an hour to shoot some stuff in town with the 28-400. I like to test out new gear in real life situations. I have done some minor tweaking and some keystone correction. I did not find the aperture limiting in the old church. I just used a higher ISO. I did not find F8 limiting for this sort of photography.

Wow, the first try-out pictures just to see how this lens handles impressed me. This lens like the 24-200 before it has already exceeded my expectations. The pictures are nice and crispy sharp and the IBIS/VR let me get some sharp shots at 400mm with a 1/30 shutter speed. Distortion is corrected in camera and is done well.

My Z7 with this lens is not particularly heavy and I do not think carrying it around over my shoulder for a few hours will present any problems. Certainly nicer than carrying a camera bag with two or three lenses around.  

I think this is going to be very practical for hiking in the mountains, as it is quite light, when combined with the 14-30. For my more specialized photography, like Architecture, I will still be using a bag full of specialized lenses, as this lens does not do everything well  .

On my big screen they look nice and sharp with lots of detail. I think optically it is better than the 24-200 even in the corners. Im sure if I made some 100% enlargements of the corners I might see something less than sharp. But like most modern lenses they look fine on a big screen at normal viewing sizes. Things like contrast can be tweaked in post.

For those interest in photography rather than pixel peeping, this is a great lens for when you do not want to carry a bag full of gear. 

Here are some examples.

I had a chance for a quick walk along the River Po. The light was not perfect and I was with my wife, who gets impatient if I stop too long to take pictures. Here are the pictures I took. I have done a bit of quick post processing on these shots. 

Are Shift Lenses Still Useful?

 Some time ago I was becoming bored with the mostly scenic photography I was doing, mostly during hikes in the Apennines. Slowly my photography shifted towards architectural subjects, and initially like most photographers, I corrected the geometry of the buildings in post. 

I have always been fascinated by cameras with movements, which allow the manipulation of geometry. Indeed, I had an expensive to feed 5x4 camera back in the nineties. As my interest in Architectural photography deepened, I slowly put together a collection of  shift lenses. Here are a few thoughts about perspective control lenses.

The first myth to get out of the way is that these lenses are hyper expensive. The still valid Nikon 28mm and 35mm PC lenses can be found second hand in good condition for about €300. My early shift lens photography was done with a Nikon D700 and a Nikon 28PC, which cost me less than the cost of a good  lens bought new. I lost nothing when I sold the glorious D700.

The Ghiara Reggio Emilia

I picked up my Nikon 24 TS and 45mm TS for less than €1000 and the excellent Laowa 15mm Zero D shift, cost me a little over €1200. Sure these more modern lenses are not cheap, but compared to the long lenses used by  photographers photographing the natural world, shift lenses are about average or even cheaper than most specialised lenses.   

Secondly, there seems to be a very common belief, that with the powerful photo editing tools we have today, the shift lens has become redundant. I believe this quote from James Ewing from his textbook Follow the Sun. A book  aimed at professionals and students and considered a standard text destroys this myth.

Castel Arquato PC

"You might ask yourself "Do I really need an expensive tilt shift lens" Can't I just correct the perspective later in Photoshop?" The answer is yes you could correct it later, but the tilt shift lens allows you to see and feel the perspective of the images you are shooting. The final crop and ultimately the entire composition will be totally different in a shot that is corrected in post. If you cannot see the image while you are shooting you cannot control the composition and therefore you cannot effectively interpret the building. Correcting the perspective during post production causes a significant loss of sharpness and detail. The Tilt shift lens gives you accurate, sharp controlled images."

I think this says it all.

I can add from experience that it is almost impossible to judge how much extra framing space needs to be left, to take into account the area lost when correcting in post

Traditionally due to the fact that the camera needs to be absolutely level when using a shift lens, a tripod needs to be used when using them. The mirrorless camera has liberated the shift lens from the tripod. With the viewfinder level it is now possible to hand hold the camera whilst using these lenses. IBIS is lets me close down the lens too. This is brilliant for those places where tripods are not allowed, or when you do not want to carry one about. I often use my 24PC alongside my 24-200 for general travel photography.

San Francesco Bologna

But after getting the technical arguments out the way, the thing I most enjoy about using these lenses, how it slows me down to really look at what I am looking at, and what I am trying to convey with the picture I am making. I now tend to spend more time photographing fewer venues, when I visit a place, which I believe makes my photography a little deeper.