Otto Mode I: Thoughts on Photo Composition

To become an expert in using something, it is neither necessary nor sufficient to understand how it works. But lately, I've been feeling like Otto von Chriek ... thinking about light a lot.

The things that define a photograph fall in two categories:

• Composition, or framing
• Illumination
• Capture

Composition is what we choose to photograph. The diagram below shows an inhabitant of Flatland composing a photograph.

For the two-dimensional world, three things define composition.They are shown in red, blue and green in this picture.

• The red circle shows the camera position.
• The blue wedge shows a combination of two things:
  • The camera direction, which is the bearing of an imaginary line down the center of the wedge.
  • The angle of view, which is the angular size of the wedge.
• The green doughnut shows the depth of field, which is the range of distances that our photographer wants to capture.

The golden (okay, yellow) area is where the green and the blue intersect. The final photograph is an one-dimensional projection of this two-dimensional area as seen from the red dot.

In our own three-dimensional space, the same idea applies: only, what was a circle becomes a sphere, and the photograph is now a two-dimensional projection of a three-dimensional volume. The definitions are upgraded somewhat:

• The two-dimensional camera position can be represented as (x, y) in some Cartesian coordinate frame. In three dimensions, this becomes (x, y, z).
• In two dimensions, the camera direction could be represented as and angle θ (-180° ≤ θ ≤ +180°), from some reference direction. To represent it in three dimensions, we need to introduce a new angle φ  (-90° ≤ φ ≤ +90°). The direction would be expressed as (θ, φ). It may be easier to think of φ as the 'latitude' and θ as the 'longitude'.
• In two dimensions, the angle of view could be represented as a single angle α (0° ≤ α ≤ 360°). Now, the angle becomes a solid angle. If we fix the shape of the 'window' to be a rectangle of a given aspect ratio, this solid angle can be expressed as (α, β), where, α is the angle subtended by the diagonal of that rectangle at the centre of the sphere, while β (-90° ≤ β ≤ +90°), is the orientation of the diagonal of the rectangle with respect to the 'line of longitude' passing through its midpoint. In general, if the shape 'S' of the window has a rotational symmetry of order 'n', we have -180°/n ≤ β ≤ +180°/n. If the window happens to be circular, β is irrelevant.
• The depth-of-field doughnut becomes a hollow ball in three dimensions. In both cases, however, it is defined by the radii of the near and far bounding sphere or circle: u_n and u_f

So the composition of a photograph is a function F(x, y, z, θ, φ, α, β, S, u_n, u_f). The control of some of these parameters are entirely up to the photographer, irrespective of what camera he uses:

• The position co-ordinates x, y & z are decided by where the photographer has chosen to be
• The angles θ, φ & β are actually how the photographer chooses to hold and point his camera

Some parameters, however can only be controlled if the camera supports such a control:

• The shape S is actually decided by convention—it is usually a rectangle of aspect ratio 16:9, 4:3, 3:2 or 1:1.
• The parameter α may be available for control as 'zoom'
• The parameters u_n and u_f are usually not adjustable individually, but may be available for control jointly.
  
  • When focusing the camera manually or automatically, what is being adjusted is a quantity u₀ that is:
    
    • For u_f  < ∞, the harmonic mean of u_n and u_f (defined as u₀ = 2/(1/u_n+1/u_f).)
    • For u_f  = ∞,
  • And the actual depth of field u_f - u_n can be controlled indirectly though a number of other parameters, each of which have some other side effect.

Is it really that hard? More to the point, after taking all the trouble to be there at (x, y, z) do I, the casual Sunday photographer, have to worry about (θ, φ, α, β, S, u_n, u_f) as the golden moment t flashes past?

The interesting thing about the angle of view is that from any picture, we can extract other pictures as long as the 'wedge' of the extracted picture is entirely contained in the 'wedge' of the original picture. So if we manage to capture an 'all around' view—often called a 'spherical panorama', technically a 360°×180° or 4π steradian view—then the camera direction becomes irrelevant, and we can subsequently extract pictures with whatever direction and angle of view we want. We could forget about θ, φ, α, β and S when we are taking that shot.

If the picture captured is a flat image, a two-dimensional projection of the three-dimensional view selected, we cannot later extract pictures that have a depth-of-field that is entirely contained in the doughnut of the original image. And conventional capture techniques (such as film and common digital image sensors) are such projections. If, however, we somehow capture a light field, we can extract those pictures at our leisure. We need no longer worry about u_n and u_f at the golden moment t!

Recent buzz seems to suggest that both these ideas may come to a neighbourhood store soon. Today most panoramas are created from multiple images taken with a sweep of the camera, but there is this ball, with 36 small cameras mounted on it, that takes spherical panoramas instantly. And there is a light field camera from Lytro that proudly invites us to 'focus later'.

Maybe in the not too distant future, a casual photographer can just get to (x, y, z) at time t ... and take a picture without bothering to compose!


$X$

Inside the Camera

A camera,  a wonderful device that brings two pieces of magic together:

1. Casting a real image of the subject on a surface
2. Capturing that image for posterity

Seeing an image of an object on a screen is magical enough: I've got a 'wow!' from my children when I've shown them an image of some commonplace luminous or brightly illuminated object projected on a wall using a magnifying glass, or on the tracing-paper screen of a home-made pinhole camera.

Now, in everyday life, we don't see real images too often. The images we are used to seeing are virtual images which can't be cast on a screen and shadows, which can.

So how do real images happen?

Let's take a very simple case of an object (imagine it is luminous or brightly illuminated if that will help) and a flat screen. We will have a sharp real image of the object on the screen if we can set things up such that:

1. For each distinct point $A_i$ of the side of the object facing the screen, there is a corresponding distinct point $B_i$ on the screen such that each and every ray of light falling on the screen that originated at $A_i$ falls on the screen at point $B_i$.
2. No ray of light originating from any other point (on the object, or elsewhere) passes through $B_i$.

How can this be done?

One way is to put, between the object and the screen, a thin, opaque plate with a pinhole $P$ such that the plate is perpendicular, at $P$,  to the line joining the mid-points of the object and the screen. This way, for each $A_i$, the point $B_i$ is where the extension of the straight line $A_{i}P$ intersects the screen. All rays originating from $A_i$ other than the line $A_{i}B_{i}$ are physically blocked by the plate.

The pinhole works by eliminating light: the images it creates are therefore faint. But it is so constrained because it handles only light traveling in straight lines. A better method to create a real image would be to have a contraption that bends the light rays in such a way that a much larger fraction of light rays that originate from the same source point $A_i$ (some of which otherwise may not even have touched the screen) are bent just right so as to pass through the same destination point $B_i$.

Either of the arrangements illustrated in the following diagram would do this:

Here, we have an object $A_{0}A_{1}$ of height $h_A$ that forms and image $B_{0}B_{1}$ of height $h_B$. In each of the two diagram, we have something--a device--to bend the light rays, and we show that device as a thick grey line. The center of our contraption is designated $P$, and the line perpendicular to it at $P$ is called the axis. Our object and image are both perpendicular to this axis.

When we use a pinhole, an image is formed irrespective of the distance $u$ between the object and the pinhole, and the distance $v$ between the image and the screen. With the methods suggested by the diagram, however, this is no longer the case.

First, we consider the red ray: the one that originates at $A_1$ and passes through $P$. For the type of device for which the left-side diagram is applicable, this ray proceeds in a straight line through $P$ to the other side: just as it would have been for a pinhole. For the type of device for which the right-side diagram is appropriate, this ray is reflected at $P$ just as it would have been in a plane mirror.

Next we consider the blue ray. This one originates at $A_1$ and proceeds parallel to the axis up to $X$, where it is bent by our contraption. From $X$, this ray travels in the new direction until it intersects the red ray. This point of intersection is $B_1$, which is by definition the point where all rays from $A_1$ converge. On the way, the blue ray intersects the axis at point $F$.

A little geometry now. Irrespective of whether we choose to look at the diagram on the left or the one on the right, we can see that triangles $\triangle P B_0 B_1$ and $\triangle P A_0 A_1$ are similar, so $h_B / h_A = v/u$. We can also see that triangles $\triangle F B_0 B_1$ and $\triangle FPX$ are similar, so $h_B / h_A = (v-f)/f$.

To these two observations, we can apply a little algebra to get the well known formula: $$\frac{1}{u} + \frac{1}{v}=\frac{1}{f}$$ We can also obtain another useful result: $$\frac{h_A}{h_B} = \frac{u}{f} - 1$$ The point $F$ is called a focus of our device: a beam of light parallel to the axis will, after hitting our device, converge at the focus. The value $f$, being the length $PF$, is called the focal length of our device. It is not possible to obtain a real image of any object for which $u \lt f$ (we get a virtual image instead).

Turns out that such a device can be built in many ways. The ray diagram to the left can be satisfied by:

• Using refraction at a curved boundaries between media that have different refractive index values, with a convex lens (biconvex, plano-convex or positive meniscus) placed between the object and the screen. This will collect all light rays that hit the lens. For a converging lens, $f$ depends on the geometry of the lens and the  of the material it is made of: the refractive index in turn depends on the wavelength (roughly, the colour) of the rays of light.
• Using refraction within a single medium with gradually varying refractive index, with a gradient index lenses. This will collect all light rays that hit the lens. The focal length $f$ depends on the geometry of the lens and the variation of the  refractive index of the material it is made of
• Using diffraction, with a zone plate (ideally, a 'sinusoidal zone plate', a.k.a. 'Gabor zone plate' or GZP) placed between the object and the screen.  This will collect roughly half the light rays that hit the zone plate—the other half will be blocked by the plate itself. For a zone plate, $f$ depends on the geometry of the plate and the wavelength of the plate: for a given geometry, it is inversely proportional to the wavelength.

The diagram to the right can be satified too:

• Using reflection, with a concave mirror placed such that both the object and screen are on the same side (the reflecting side) of the mirror. This will collect all the light rays that hit the mirror, minus any that are blocked by the screen or the object (whichever is closer to the mirror). For a concave mirror, $f$ depends only on the geometry of the mirror.
• Using a combination of reflection and refraction, with a converging lens with one side silvered. This will work pretty much the same as a concave mirror, except that $f$ will now depend both on the geometry and the wavelength as in a lens.

Note that the thickness and shape of the lens or mirror is ignored here: this is because all of this works under that approximation that lens is very thin, or the concave mirror is very shallow.

Pinholes, zone-plates, curved mirrors and lenses have all been used for photography at some time or another. Today, pinholes and zone plates are alive in a class of artistic photography. Concave mirrors remain the mainstay of photography as used in astronomy, and can also be found in some telephoto lenses.

However, it is the lens that rules the roost when it comes to image forming in photography. One possible reason for this is the ease with which lenses can be combined in a 'compound lens'. This allows us to fine tune optical properties such as the focal length and its variation with wavelength.

Actually, all types of optical elements—lenses, mirrors and zone plates—can be combined in an optical path between the object and the screen. And not all the elements in such a combination need to be able to cast a real image by itself, either—it is perfectly possible to throw in a diverging lens or a convex mirror (these have $f < 0$) or even a plane mirror or reflecting prism (these have $f = \infty$) into the mix if that is what is needed. But it is more convenient with a lens because it can be inserted into the straight line path between the object and the screen without blocking any part of the light path.

So how do these combinations work? Consider two converging lenses, of focal lengths $f_1$ and $f_2$ placed along the same axis, at a distance of $w$ from each other. Like the following diagram:

It can be shown that the focal length $f$ of the combined setup is $$f = \frac {f_1 f_2} {f_1 + f_2 - w}$$ If we consider a beam of light parallel to the axis coming from the left and hitting this combined setup, it would converge at a point that is at a distance $f$ to the right of the second principal plane, which is at a distance $s_2$ behind (to the left of) the second lens, where: $$s_2 = \frac {w f_2} {f_1 + f_2 - w}$$ If we consider a similar beam coming from the right, we'll find that it converges the same $f$ to the left of the first principal plane, which is $s_1$ to the right of the first lens, where $$s_1 = \frac {w f_1} {f_1 + f_2 - w}$$ The distance $t$ between the two principal planes is, then: $$t = \frac {-w^2} {f_1 + f_2 - w}$$ Even though this compound lens can no longer satisfy the 'thin lens' approximation, it turns out that the equations $1/u + 1/v = 1/f$ and $h_A/h_B = u/f-1$ will still hold, with the proviso that $u$ is measured from the first principal plane, while $v$ is measured from the second principal plane.

These equations hold even if any or all the lenses are diverging lenses, that is even if $f_1$ or $f_2$ or both are negative. Irrespective of whether any of $f_1$ or $f_2$ is negative, the final $f$ has to be positive if the combined system is to cast an image.

Let us count the blessings:

1. The two lenses can be made with materials of different dispersion (variation of refractive index with wavelength) so that the combination can have a focal length independent of colour. We get achromatic lenses.
2. Given an object and the screen at fixed positions with respect to one another (i.e. a constant $u+v+t$), by simply adjusting $w$ it is possible to change the focal length of the combination, thus changing the image size $h_B$ cast on the screen. In other words, we get zoom.
3. It is possible to design a compound lens such that the second principal plane that is even before the first lens in the light path. This lets us have a camera with a focal length that is larger than the size of the camera itself, if so desired. This can be done, for example, with a converging left-side lens such that $f_1 \gt w$ and a diverging right side lens such that $-f_2 \gt f_1 - w$. This is the principle behind most telephoto lenses.

Let us now look at an aspect we've been side-stepping so far. While the screen can accurately be considered a two-dimensional plane, the same cannot in general be said about the object. Whatever we are photographing is usually three-dimensional, so when we've cast its image on the screen for any given $u$, only that part of the object that intersects a plane at distance $u$ from the lens will be exactly 'in focus'. For everything else, the focus would be somewhere in front of or behind the screen: on the screen, they will be 'out of focus'.

In general, an out-of-focus point of light will be a patch of light of the same shape as the aperture through which the light hits the lens. In cameras, this shape is usually a circle, or a regular polygon when an iris-diaphragm is in use. The size, as in diameter, of the patch will be proportional to the distance the screen is from the actual in-focus position for that point. It will also be fainter the farther it is from the in-focus position, the brightness being inversely proportional to the square if this distance. These patches of light merge with each other, and make out-of-focus images blurred.

Images captured by a camera are meant to be seen by the human eye, which cannot resolve more less than about 1 minute of arc that is about 0.0003 radians. This means that any shape that subtends an angle of less than this cannot be distinguished from a point.

For a given captured picture, this angle is dependent on the size the image is scaled to when viewed, as well as the distance the picture is viewed from: for example, say a 24mm x 36mm capture is printed at 10cm x 15cm, and is viewed from a distance of 50 cm. An angle 0f 0.0003 radians will be subtended by 0.15mm (50cm x 0.0003) on the print, which will be 36 microns (0.15mm x 24mm / 10 cm) when captured. If the same picture is printed at 30cm x 45 cm, the same 0.0003 radians will be some 12 microns (0.15mm x 24mm / 30cm) when captured.

Ultimately, the resolution of the image when viewed is limited by the image as captured. Film will resolve down to the grain size, which is anything from 0.2 to 2 microns. Digital sensors will resolve down to the pixel size, which is a function of the 'sensor size' and 'megapixels' parameters: today, it is anything between 1 to 10 microns.

This tells us that some amount of 'out-of-focus' is acceptable, whether we define it from the resolution of the capture technology, or from the point of view of the print size and viewing distance. The  maximum acceptable size of the patch of light in the image corresponding to an out-of-focus point is called the circle of confusion.

In the diagram above, the diameter of the circle of confusion is marked as 'c', while the diameter of aperture that lets light in is marked 'd'.  In the picture, the point $u_0$ is perfectly in-focus at the screen, while points up to $u_n$ on one side and $u_f$ on the other side are acceptably out-of-focus. With simple geometry, it can be shown that: $$u_n = \cfrac {du_0f}{df+cu_0-cf} \qquad\qquad u_f = \cfrac {du_0f}{df-cu_0+cf} \qquad\qquad \cfrac 1 {u_n} + \cfrac 1 {u_f} = \cfrac 2 {u_0}$$ Any object lying between $u_n$ and $u_f$ will appear to be in focus. The distance $e$ between the $u_n$ and $u_f$ is called the depth of field. $$\begin{align}e &= u_f - u_n \\ &= 2u_0 \cfrac {\left(\cfrac{c}{d}\right)\left(\cfrac{u_0}{f}-1\right)} {1 - \left(\cfrac{c}{d}\right)^2\left(\cfrac{u_0}{f}-1\right)^2},\qquad f\le u_0 \le H \\ &= u_n \cfrac { u_n - f } {\cfrac{H}{2} - u_n},\qquad f \le u_n \le \cfrac{H}{2} \\ \end{align}$$ Here, $H$ is the hyperfocal distance defined as: $$H = \left(\frac{d}{c} + 1\right)f$$ When $u_0 = H$, we get $u_n = H/2$ and $u_f = e = \infty$.

It should be noted that this depth of field shrinks quickly for points farther away for the axis: these points would cast elliptical patches of light on the screen instead of circular ones, and such patches would only be indistinguishable from points if the longer (transverse) diameter of the ellipse is less than $c$. This diameter will be longer the further the point is from the axis.

As $u_n$ goes from $f$ to $H/2$, $u_0$ goes from $f$ to $H$, and $e$ increases monotonically from $0$ to $\infty$. Beyond this, no point beyond $u_0$, even if it is at infinity, can cast a patch of light larger that $c$, so the depth of field stays $\infty$. Simply put, if we focus on a more distant object, we get a larger depth of field.

Let's consider the focal length $f$ next. It can be seen that as long as $f \le u_n \le H/2$, as $f$ increases, the numerator $u_n - f$ decreases and the denominator $H/2 - u_n$ increases. The net result is that as $f$ increases, $e$ decreases. That is, if we use a larger focal length, we get a smaller depth of field.

Next we look at the aperture diameter $d$. It is evident that as $d$ increases, $H$ also increases, and consequently the denominator of the expression for $e$ increases. Therefore, as $d$ increases, $e$ decreases. In other words, if we have a larger aperture, we have a smaller depth of field.

Finally, we come to the $c$, the diameter of the circle of confusion. And this is where we have to step very carefully ... for what would changing $c$ actually mean? If we take the simplistic approach of keeping $u_n$, $f$ and $d$ same, a smaller $c$ will result in a smaller depth of field ... but is that what we are looking for?

If, however, we go back to the original definition of 'circle of confusion', we see that $c$ is, in fact, a specified fraction of a specified length dimension of the capture frame. This is easier understood for digital sensors: if we take two capture frames of different sizes but the same megapixel resolution, it is easy to see that pixel size in the larger frame will be larger. For example, if we consider a 4:3 12 megapixel sensor, its resolution is 4000 x 3000, and thus the pixel diameter will be 1/4000 the width of the capture frame size.  Thus, changing $c$ will mean changing the size of captured frame: such as the film format, or the digital image sensor size. Now, what exactly do we wish to keep the same? Let's say we want the 'same picture' in the two capture frame sizes. Since the DOF will be different, it will obviously not be the exactly the same picture, so let us interpret 'same picture' to mean 'same composition and same brightness of image'.

Suppose the new capture frame size is $n$ times the old one: the height and width each have been scaled $n$ times. This multiplies $c$ by $n$, or $c_{NEW} = n \cdot c_{OLD}$.

Since the frame size is proportional to $c$, multiplying $c$ by $n$ will multiply the area of the image by $n^2$. We want the brightness of the image, defined as 'light per unit area' to be the same, we need $n^2$ times light to be admitted. The amount of light admitted is proportional to $d^2$, so in order to keep the image brightness the same, we need to multiply $d$ by $n$ too: $d_{NEW} = n \cdot d_{OLD}$.

This leaves the ratio $c:d$ unchanged.

To keep the 'same composition', we have to multiply the image size by $n$ as well. To do this, we need to change $f$. But by how much? If the new $h_B$ is $n$ times the old one, the new ${h_A}/{h_B}$ is $1/n$ times the old value. As $h_A/h_B = u/f - 1$, this means ${u_0}/{f_{NEW}}-1 = ({u_0}/{f_{OLD}}-1 )/n$.

Now let us take another look at the expression for $e$ expressed in terms of $u_0$. We can say: $$e=2u_0 \cfrac{z}{1-z^2},\qquad z=\left(\frac{c}{d}\right)\left(\frac{u_0}{f}-1\right), \qquad 0 \le z \le 1$$ Since ${c}/{d}$ is unchanged, this means $z_{NEW} = {z_{OLD}}/{n}$. Now, as $z$ increases from $0$ to $1$, the value $\frac{z}{1-z^2}$ increases monotonically from $0$ to $\infty$. Since $n \gt 1$ implies $z_{NEW} \lt z_{OLD}$ and vice-versa, if we use a larger format, we get a smaller depth of field.

Enough about depth of field. But while talking about it, we've mentioned brightness of the image, so let's dwell on that for a moment.

This brightness is something that can be expressed, roughly, as 'light per unit area' on the screen where the image is projected. Considering that this light originates at the object being photographed which is a distance $u$ away. Consider also that the sum total of light that falls on the screen is that which comes in through that circle of diameter $d$ at the first lens: so far, we've considered this to be the size of the lens itself, but it could equally well be an hole, an aperture, with a $d$ we can select, placed just before the lens.

From the law of inverse squares, the light per unit area available at the position where the aperture is proportional to $1/u^2$. This means the amount of light actually admitted is proportional to $d^2/u^2$.

Suppose we happen to be photographing the same object from different distances $u_1$ and $u_2$, using the same capture frame size. Let us say we want to have the same size of image, and get the same brightness for both the images. So what do we have to do?

Since the brightness has got to be the same, we must have ${d_1}^2/{u_1}^2 = {d_2}^2/{u_2}^2$. As the image size $h_B$ has got to be the same as well, from the relation $h_A/h_B + 1 = u/f$, we can see that we have to use use different focal lengths $f_1$ and $f_2$ such that $u_1/f_1 = u_2/f_2$. Combining the two, we can see that if we want the same image brightness and same image size, we need $f/d$ to remain the same.This ratio is called the f-number, and will play a starring role in what we are going to talk about next.

This brings us to the other bit of magic inside the camera: the capturing of the image that has been cast on the screen.

This is deeper magic. For close to two centuries, this magic was done using chemistry, with photographic plates and film that depended on the properties of a magic element ... silver!

Exposure to light causes many silver salts, notably the silver halides AgI, AgBr and AgCl to break down, releasing metallic silver. This is the basic chemistry used in photography.

Take s sheet of good quality white paper—soaked it a solution of NaCl (salt), dried, coated with a solution of AgNO₃ (silver nitrate) and dried again—and, placing a few coins on it, expose it to bright sunlight for half an hour or so. The paper would have darkened, except under the coins where the sunlight couldn't reach it. The shadow of the coins would have been captured on the sheet of paper (making not a photograph, but what is known as a photogram).

What happened? Well, AgNO₃ + NaCl → NaNO₃ + AgCl for starters. The AgCl, being insoluble in water, is precipitated on the paper. Subsequently, light breaks it down to metallic silver, which is what made the paper dark.

When we take a snapshot, however, we certainly aren't exposing our film for half an hour to sunlight! When the silver halide (which is in the film) is exposed for a fraction of a second to an image which is much less bright in comparison to direct sun-light, the breakdown of the silver halide is far from complete. After the exposure, some 'grains' of the halide will have a few atoms of silver in them, and many others will have none. Areas of the image that were brighter will have a larger proportion of grains containing free silver atoms.

There is another interesting property of silver halides that helps us here. Certain chemicals will break down a silver halide crystal to release all the silver in it only if the crystal contains some atoms of metallic silver to start with. This is called 'developing' the image.

The image that we get after developing is evidently 'reversed', with the bright portions of the object rendered dark on the image and vice-versa. This won't do for the final product, obviously. To get it 'right', we first ensure that when capturing the image in the camera, the silver halide is coated over a transparent base: historically glass, and polyester film today. Then:

• If we want our final print on a paper base, first a 'fixer' such as a solution of Na₂S₂O₃ (sodium thiosulphate or 'hypo'),  (NH₄)₂S₂O₃ (ammonium thiosulphate) or KCN (potassium cyanide) is used to wash away any remaining silver halide—so further exposure to light has no effect on the image. (If we want our photogram of the coins to be permanent, we should do this too!) Next, a photogram of this 'negative' image is taken ...with a halide coating on paper this time. It is developed and fixed, and we have a printed photograph.
• If we want a transparency (slide), we can get it with a 'reversal' process. In this case, we would treat the developed film with chemicals that would remove the silver, leaving the remaining halide intact. Then the film would be treated with another kind of chemical (called a 'fogging developer'), one that would convert all silver halide to silver. This is a 'positive' slide that we want.

Photochemical reactions are usually sensitive to the wavelength (colour) of the light, and the response is like a step-function: there is a maximum wavelength over which the reaction won't happen. Silver halides are actually sensitive to the shorter wavelength part of the spectrum: blue, violet, ultraviolet and beyond. It turned out that adding certain dyes to the halide could 'sensitize' them to longer wavelengths too, giving more natural black-and-white photographs.

All of this gives us only black-and-white photographs. But

cc

Holidays by the sea

I've always liked holidays by the sea.

It is not so much the 'sun, sand and surf' that I indulge in: I don't actually enter the water as much as that, and being a brown-skinned Indian, getting a sun-tan isn't a priority.

I've always liked the sea for the view. Somehow, I get the feeling of standing at 'the end of the world' when I'm at any sea-shore (beach or not).

Here's a few of my pictures that bring back pleasant memories. These aren't so much photos of the sea: rather they evoke a sense of proximity to the sea when I look at them.

This one is actually a scan from a print. It was taken from our ground-floor room at the Taj Exotica, Goa in June 2006. Looking west over the Arabian Sea.

This one was taken from our room at the Ashok, Pondicherry in June 2010. Looking east over the Bay of Bengal.

This last one was from the entry to the beach at the Leela, Goa in May 2011. Looking west over the Arabian Sea again.

The cameras I've had

More than thirty years ago, I was growing up in middle class India. Photography, then, was a somewhat expensive hobby for a kid not yet out of school.

The first camera I had access to was my mother's Agfa Click III. It took 120 format film rolls, and made square 6 x 6 (cm) negatives. Black and white film was all I (and my parents) used in those days. We didn't shoot a lot:  the price of film and processing was a bit too steep. And our prints would mostly be 6 x 6 as well: enlargement was costly business.

It was a simple, robust mechanical device with nothing electrical in it at all. No batteries, for one!

It had a fixed focus lens. It had a lever to the left of the lens to choose between three preset aperture options: a small aperture for 'sunny', a larger aperture for 'cloudy', and an even larger aperture with a yellow filter. There was no iris: the lever operated a kind of rotating diaphragm which had these three circular holes of different diameters.

The shutter release was a lever too, mounted to the right of the lens. There was a single shutter speed on offer: that was all that a purely mechanical system, and a rather simple one at that, could do.

There was a knob to turn the take-up reel to advance the film. After taking a snap, you turned it anti-clockwise, while keeping an eye on a round red-glass window on the camera back, which showed the frame number (printed on the film backing) as it came sliding by. There was no interlocking: if you forgot to turn the knob, the shutter would still click, exposing over your previous snap. And if you hadn't advanced the film enough, the shutter will click equally promptly—giving you overlapping frames. The only protection was that the knob wouldn't turn the other way.

Interestingly, there was no rewind crank—there was no need for one. When the film got over, it was all wound around the take up reel, which you took out for processing. The pay-out reel was now empty—you took it out, and put it into the place vacated by the old take-up reel.

There was an optical viewfinder, through which you looked to compose the shot. There was no flash, but there was a hot shoe for one. And that was it!

Years passed. Some time in my undergraduate days, I bought an Agfa Snapper 35, a basic 35 mm camera.

This, too, was a purely mechanical device: no batteries yet! Not even an in-built flash (though there was a hot shoe.) The shutter release was now a button, and the film was in a 135 format cartridge instead of on a bare roll. By now, color film was commonly available, so I shot in color.

The film advance mechanism was a thumb-wheel. You turned it till it stopped with a 'click' at the next frame—and what's more, it was interlocked so that if you didn't do it after a shot, the shutter won't click for the next one. The 135 cartridge now necessitated a film rewind crank, for use when the roll ran out.

This was still a fixed focus camera with a single fixed shutter speed. Like the Click III, it had three aperture settings: 'sunny', 'cloudy' and 'flash'. The 'flash' setting had an aperture that was apparently the same size as 'sunny',  but this setting would additionally trigger the flash hot-shoe.

This camera also had a lens cap, which you had to remember to take off. You just looked through the viewfinder, clicked ... and hoped.

More time passed. I now had a job, one that took me to the United States for months at a time. This was the early nineteen nineties, and for a young middle-class Indian guy, this was consumerist heaven.

In these trips, I took quite a lot of photos with disposable 35mm cameras, usually Kodak. I'd get the pictures developed and printed at the neighborhood supermarket, and it all worked out swell!

I also bought a couple of regular cameras. The last of those was a Focal PC620D. The obvious difference between this and the Snapper 35 was that this camera needed batteries.

A pair of AA cells was needed to drive a motorized film transport system. The film would automatically advance to the next frame after every shot, and automatically rewind when the film ran out.

The same AA cells also powered a built in flash. It could be set to 'off'. It could be set to 'fill-in', in which case it would fire every time. It could also be set to 'auto', where the camera decided when to fire the flash. The auto-flash logic used the inputs from two sensors in the camera:

1. One sensor would read the DX-coded ISO rating of the loaded film cartridge
2. The other sensor would measure the ambient illumination: a basic light metering mechanism

Another feature was a 'date-back' that could mark each shot with the date and time.This had its own battery: a button cell.

Otherwise, it was an ordinary fixed focus, fixed aperture and fixed shutter speed 35mm film camera with an optical viewfinder. One advantage over the Snapper was that, instead of a separate lens cap, there was a sliding lens cover that wouldn't allow the shutter to click when closed. 

Eventually, in 1998, I got myself a  Samsung Maxima Zoom AF Fuzzy Logic (this may of may not be the same as their AF Slim Zoom model: photos on the Internet appear identical except for the shade of the plastic, but I can't tell for sure). As it turned out, this ended up being the most advanced 35mm film camera I owned.

This has all the features the Focal PC620D had—the quartz date-back, the motorized film transport and the auto flash. But it had more.

This was the first camera I owned that needed a shutter 'half-press'. Because it had auto-focus. The focusing mechanism was active infra-red, which would work for 20 ft or so. I guess this range was good enough, because beyond that, the depth of focus would stretch to infinity anyway. There was a button to deliberately focus at infinity.

Speaking of focus, in this camera the focal length could be varied between 35 and 70mm at the press of 'W/T' buttons (another first for me). In other words, it offered 2x zoom (optical of course.) Specifically, this was power zoom.

This camera also used its light sensor for more than just the auto-flash decision: it had auto-exposure. It probably had a fixed-sized circular aperture (given the focal length, the f-number was fixed.) It would therefore choose the appropriate exposure by varying the shutter speed under electronic (microprocessor) control.

Actually, the microprocessor is what made this camera different from my previous ones. The obvious visible difference was the user interface: instead of per-function switches, this camera had a basic menu system displayed on a black & white LCD screen. There were two buttons to navigate it: a 'flash' button to cycle between the flash options, and a 'mode' button to cycle through everything else.

The microprocessor allowed it to offer many software controlled features. I haven't actually used most of them, and I have lost the manual, so the list below is partly from memory and partly from the manual of another similar camera from Samsung:

1. A 'bulb' mode, where the shutter would stay open for as long as the shutter button was depressed.
2. An optional pre-set exposure compensation of +1.5EV
3. An automatic zoom function where the camera itself took a guess at composing the picture--that was the 'fuzzy logic' bit I suppose.
4. Timer features: to take a shot after so many seconds, or to repeatedly take shots every so many minutes, and so on.
5. Multiple exposures over the same frame by not advancing the frame after a shot (I could get this for free with the Click III, but not after that!)

This was actually quite a capable camera for amateur use. I regret I didn't completely tame it in its lifetime, but there was a reason. Film.

The film and its processing was much more affordable now, of course, but the cost of each frame wasn't zero. An illustrative number would be, say 10 rupees per snap, considering the film, its development, and the first print (which I always got, not being very good at judging a negative.)

So I didn't really experiment. I used it a lot for snapshots, though, to capture a lot of memories. It stayed with me from 1998 to early 2007. It is still with me, but it doesn't work any more.

Circa 2001, somewhat by mistake, I acquired my first digital camera—a Fujifilm Finepix 2600 Zoom. It recorded 2 megapixels, had a 3x optical zoom, would shoot video (without sound), and was quite a capable camera for its time. It even had an optical viewfinder—something which compacts of today usually omit. But as it turns out I didn't use it much.

It's shape was somewhat awkward. It was too thick for me to hold comfortably. It was powered by 2 NiMH AA rechargeable cells, and one set of charged cells didn't last anywhere as long as the battery of my Samsung film camera. It used a 32 MB SmartMedia card for storage, and  60 photos or less would fill it up.

All this would have been acceptable (after all, I was used to 36 exposure film rolls) but for the real killer: the labs around where I lived used to charge simply too much for prints from digital cameras! Many times more than prints from film, actually. Maybe they were trying to make up for the cost of film and development that they were losing out on? But whatever the reason, this resulted in the camera not seeing much use. Which is a pity, because it isn't a bad camera. I still have it, and it works well enough.

In 2007, the Samsung broke—and for a couple of years I fell back on a Kodak KB-12 that happened to be lying around the house. This was a very basic 35mm film camera. Compared to my my old Snapper 35, this one had only a single aperture, and a built in flash that would fire every time (unless I'd removed the batteries from the camera, of course! The batteries weren't needed for anything else.) The lens was protected by a sliding lens cover that locked out the shutter when closed (as in the Focal PC620D).

Later, in 2008, I got a Nokia E71. It is a smartphone with a reasonable digital camera: 3.2 megapixels, and auto focus. While I've used the phone extensively, I've not really used it as a camera that much. If fact, it's only recently I figured out that it's camera was, in fact, auto focus, and that the 'T' key did what a 'half-press' does in other cameras. I sincerely hope that I'll use it more effectively henceforth. Being 'the camera that's always with me', it has taken quite a few unusual photographs for me: such as a top-view of a Shinkansen, or ice-fields of Greenland from an airplane window. 

Finally, in 2009, I went digital. I got myself a Canon Powershot A2000IS. It shoots 10 megapixels, has 6x optical zoom, and is a lovely compact camera overall. It takes 2 AA alkaline cells, which I get everywhere, and a pair lasts reasonably long. It shoots only in 'auto' and 'program', however (which was good enough for me to begin with.) Unfortunately, like most compacts, it does not have an optical viewfinder. You are supposed to compose using the LCD, but this can be difficult when out in the sun.

With digital, I began experimenting. And this year (2011), looking for a bit more control and a somewhat larger sensor, I acquired a Nikon Coolpix P7100. It shoots 10 megapixels too, and has a similar 7.1x optical zoom. But I now have Aperture Priority, Shutter Priority and Manual modes available, and a built in neutral-density filter should I need one. Also a bigger sensor—about twice the area of that on the A2000IS. And I got back the optical viewfinder!

For now, I intend to keep using both the P7100 and A2000IS. I've resisted the urge to upgrade to a DSLR because I didn't really want interchangeable lenses.

This year, I've also bought a Canon Powershot SX230HS for my wife (who needed its 14x zoom to take pictures of birds) and a Nikon Coolpix L23 for my daughter (entry level price, and pink). And a Genius G-Shot 501 (basic & even cheaper, fixed focus) for my son. That's quite a lot of cameras!