Apertures

 

Within every lens there is an aperture, which like the iris in the eye, can be opened and closed to vary the amount of light that is allowed to pass though to the recording medium.

Below are two pictures of the same lens, one with the aperture fully open, and the other with the aperture nearly closed:

f2.8	f32

As you can clearly see the lens on the left has the aperture wide open which would allow the maximum amount of light to enter the lens, useful where there is little light, where as the lens on the right has the aperture nearly closed and therefore reduces the amount of light entering the lens.

The amount of which the aperture is open can be used to determine the depth of field, or the amount of the foreground and background of the subject that is in focus.

Below are two diagrams showing a representation of the depths of field for the two apertures above:

f2.8

f32

As you can see the first aperture has a shallow depth of field, which would be suitable for portraits, where you would only want the subject in focus with the background thrown of of focus.

The second aperture with its deeper depth of field would be more suitable for landscapes, where you want everything in focus.

 

Controlling the Aperture

When taking of apertures we talk of stops, or f stops. The lens aperture is usually specified as an f number, the ratio of focal length to effective aperture diameter. A lens typically has a set of marked "f stops" that the f-number can be set to. A lower f-number denotes a greater aperture opening which allows more light to reach the film or image sensor. The photography term "one f-stop" refers to a factor of √2 (approx. 1.41) change in f-number, which in turn corresponds to a factor of 2 change in light intensity.

Below is a diagram showing some of the different f stops in relation to the opening and closing of the aperture:

Each lens has its own range of aperture f stops, with lenses the lower f stop values (f 1.2 and f 1.4) demanding far higher prices than starting lenses with slightly higher f stops (f2.8, f3.2 and f4.5), because they allow far higher shutter speeds whilst keeping the sensitivity lower to ensure clearer images. Zoom lenses usually have two lower f stops listed as these cover the different focal lengths available (minimum and maximum), although more expensive zoom lenses may carry a single high aperture, f4 for example, across the whole zoom range.

A typical lens will have an f-number range from f/16 (small aperture) to f/2 (large aperture) (these values vary). The maximum aperture (minimum f-number) tends to be of most interest (and is always included when describing a lens). This value is also known as the lens speed, because it is proportional to the square of accepted light, and thus inversely proportional to the square of required exposure time (i.e. using a lens with f/2, one can take pictures at one quarter of the exposure time necessary using a f/4 lens). Lenses for 35mm cameras can have f-numbers as low as f/1.2.  These are known as "fast" lenses because they allow in more light and therefore reduce the exposure time

Prime lenses (non-zoom lenses) have a fixed focal length (FFL) and large aperture and are favoured by professionals, especially by photojournalists who often work in dim light, have no opportunity to introduce supplementary lighting, and need to capture fast breaking events.

Zoom lenses typically have a maximum aperture (minimum f-number) of f/2.8 to f/6.3 through their range. A very fast zoom lens will be constant f/2.8 or f/2, which means the relative aperture will stay the same throughout the zoom range. A more typical consumer zoom will have a variable relative aperture, since it is harder and more expensive to keep the effective aperture proportional to focal length at long focal lengths; f/3.5 to f/5.6 is an example of a common variable aperture range in a consumer zoom lens.

Shutter Speeds

 

The shutter speeds are controlled by the camera, as opposed to the apertures, which are controlled by the lens. 

The range of shutter speeds vary from camera to camera, but many of today’s cameras have a fastest shutter speed of 1/8000 of a second, usually referred to 8000th, with the slowest shutter speed of 2 seconds and / or bulb. Bulb is a term for the shutter remaining open for as long as the shutter button (or remote release or control) is pressed.  Shutter speed, or more literally exposure time, is measured in seconds but often marked in reciprocal seconds. A typical exposure time for photographs taken in sunlight is 1/250th of a second, typically marked as 250 on a shutter speed setting dial. In addition to its effect on exposure, shutter speed changes the way movement appears in the picture. Very short shutter speeds are used to freeze fast moving subjects, for example at sporting events. Very long shutter speeds are used to intentionally blur a moving subject for artistic effect.

Fast shutter speeds are normally used to capture action, for example a footballer kicking the ball that scored a goal or a fast jet flying past, in both cases where the subject is fast moving but for the photograph it is essential that the subject is captured with no or very little movement. Although excessively fast shutter speeds can cause a moving subject to appear unnaturally frozen. For instance, a running person may be caught with both feet in the air with all indication of movement lost in the frozen moment or a helicopter is captured with its rotor blades seemingly frozen and motionless.

Below are two photographs showing how a too high shutter speed can ruin a photograph:

1/200’	1/45’

As you can see the first photograph looks false because the helicopters rotor blades are frozen by the high shutter speed, where as second photograph looks better as the motion of the rotor blades is captured.  Although the second photograph looks better extra care must be taken due to the use of such a low shutter speed whilst using a high focal length, to avoid camera shake.

Slow shutter speeds are often used in low light conditions, extending the time until the shutter closes, and increasing the amount of light gathered. This basic principle of photography, the exposure, is used in film and digital camera, the image sensor effectively acting like film when exposed by the shutter. As opposed to faster shutter speeds, movement can be captured, also slower shutter speeds can be used for a more artistic image.

 

7/10’

Generally, a good rule of thumb for knowing the slowest shutter speed you can use with a particular lens, without using a tripod or any anti-shake technology, is to use the focal length of the lens as a guide to the slowest shutter speed. For example, a 300 mm lens can be hand held at shutter speeds of 1/300th of a second and faster. Note that the minimum hand held speed should never be below 1/60th of a second without image stabilization assistance from your camera or lens, or without the use of a support, like a tripod. Although like any rule of thumb this can be broken for several reasons including the inability to use a tripod (at a concert or a museum for example where a tripod would not be allowed).

Like the use of apertures, shutter speeds can be used creatively, for example a photograph of a waterfall or river taken with a very slow shutter speed and a tripod, can create a picture which looks very different to a photograph taken with a fast shutter speed which would freeze the motion of the droplets.

With mechanical shutters common shutter speeds are: 1/8000, 1/4000, 1/2000, 1/1000, 1/500, 1/250, 1/125, 1/60, 1/30, 1/15, 1/8, 1/4, 1/2, 1, 2, and bulb, although with modern cameras with their program modes the camera creates it’s own shutter speeds, for example 1/350 and 1/750.

When things go wrong

 

It is a fact of life that even though we take care of our equipment that one day something will go wrong, and this is not just in the case of digital photography !

Camera Issues

Today's cameras are far different from those used 30 years ago, no longer, or seldomly, being built in metal cases, today's cameras are carbon Fibre based, sometimes with an internal metal chassis.  This makes the cameras pretty tough and able to handle some bashing, but too much bashing and its a case of a new camera !

Lenses

Although the cameras themselves may be strong they still use fragile glass optics, so if one of these are damaged that can spell the end for that lens.

Lenses are very prone to getting dirty, so using a lens cloth on a regular basis can save a number of hours on a photo editor removing the marks caused by lens dirt.

Sensors

Sensors in DSLRs can also become dirty, as fine specs of dirt and dust can enter the camera whilst the photographer is changing the lenses.  The sensor is very delicate so tools like a hurricane brush (a large blower brush - without the brush) can often blast any dirt off the sensor.  For more stubborn dirt tools like the 'sensorklean' can be used to remove dirt from the sensor itself.

Batteries

Always remember that a camera without batteries, or recording media (memory cards, film) is nothing more than a very expensive, and heavy, monocular !

Spare batteries should always be carried, and checked prior to setting out - preferably the previous night - to ensure they are fully charged.

 

Media Issues

A common issue will film based cameras, especially those with motor winds, is when the photographic film comes away from its cassette in the camera.  This happened to me once whilst taking photographs at the Burton Carnival (yes a long time ago !), when after taking some photographs of a street performer, I heard a strange noise coming from the camera.  After finding somewhere dark to check, I carefully partly opened the camera back to see what had happened, which to my horror is was what I suspected, the film had come away from the cassette.

Once I got home it was a case of using a film changing back, which is a light tight bag with elasticated arm slots, and after putting in the camera and an empty film case, I zipped up the bag and by touch only I opened the camera and carefully fed the film out of the camera's spool and carefully placed it into the empty film case.  Taking both the film case, which I sealed with black tape, and the empty film cassette to Chris Goodhead for careful developing.

In today's digital camera memory cards take the place of photographic film, but problems can arise, sometimes through the photographer !

 

Deleted and Lost Images

When taking photographs it is easy to look at the photographs on the camera's LCD screen and decide if you want to keep the images.  People sometimes choose to delete a photograph themselves, only to regret this later.

Sometimes there can be a camera or memory card issue and the memory card can become unreadable by both the camera and a computer.

It is handy to understand how computers handle data on a disk, DVD, memory card, etc.

Both computers and digital cameras use a system called FAT, which stands for File Allocation Table, to know what is on the disk or card, and where it is, which I will compare to an index in a book.  When a computer, or digital camera, deletes a file it simply removes its entry from the index, instructing the device that extra space is now available, without actually removing the pages from the book.

In these cases recovery software, installed on a computer can often recover the lost photographs, videos, etc. The reason I put the etc at the end is that the recovery software can recover any type of file that is on a computer, memory card or USB drive.  These work by looking at the index and then the disk, or memory card, and listing all the files that don't have entries on the index, and if the files can be recovered.

One piece of recovery software that I use is called Recova, and this software can be run from a USB drive, so that it can recover lost files on any windows based computer, not just your own.

 

 

The way Recova, and all other recovery software works is that they scan the disks or memory cards for files that are missing the file header entry in the FAT (or the index of the disk, or memory card) and presents a list to the photographer, together with if the file can be recovered (sometimes because the camera (or computer) believes there is free space available it might overwrite the photograph that was deleted.

It is important to note though that sometimes photographs, etc cannot be recovered, for example if the memory card develops a serious fault.  In this case it is time to get a new card.

Personally I always carry spare cards, so if one develops a possible fault, I can change to another card and prevent loosing too many photographs.

 

Computer Issues

It is ironic that as I type this my computer is recovering from a boot issue !

Errors to arise, hard disks can fail, power supplies can damage a computer if they are affected by an electrical storm, etc so it is important to back up your computer !

Always remember my sum:

Tomorrow   =

Too late

 

Hard Disk Failure

Back ups are one thing everyone hates to do, it means the computer cannot be used for up to 18 hours, it’s not enjoyable, etc, but it can save you a lot of trouble !

There are a number of back up solutions available, one of which is Genie Backup Manager:

This software allows you to make full back ups and partial back ups (selected areas, files, etc) including scheduled back ups.  These back ups can be made to several DVDs, external hard disks, network drives or even to internet based servers.

It is important to note that there is a difference between back up software and imaging software.  Back up software allows the user to choose to restore everything or only selected files, whereas imaging software usually only allows a full restore, which might overwrite files that have been updated since you last image was created.

Back ups can also be encrypted to protect the data,  as it would be pointless in using secure passwords on the computer, only to leave the back ups unprotected !

Crucial information can always be backed up to DVDs, USB devices etc every night if necessary.

 

Electrical Storm Damage

Many people think that lightning storms only cause damage at remote places, or somewhere else, trust me they don’t !

Spike and Surge protectors can protect you computer equipment in most cases and sometimes even carry a basic insurance for any equipment attached to them that is damaged due to a spike in the power supply (as would be the result of a lightning strike on the power supply, or to the building).

These devices come as individual plug in devices that you plug your computer power into before connecting to the mains, or as trail sockets that can protect several devices and even telephone and USB connections.

 

Power Failure

In this country we are lucky that we have a pretty constant electrical power supply, but in some cases even this can fail, workers cutting through mains cables, fires at substations, disputes, etc.

It is good practice to save your work on a regular basis, so that in the event of a power failure the amount of work that is lost is reduced.

Also UPS, or Uninterruptable Power Supplies, can be used to filter out the power supply, like a spike and surge protector (see above) and provide a few precious minutes in the event of a power failure for you to save what you are working on and shut the computer down properly.

It is important to note though that these UPS are very expensive, and might only give you about five minutes power.

Types of Photographic Lens

 

The one biggest advantage of a SLR is the ability to change the lens on the camera.  It is this ability that extends the functionality of the camera far beyond anything that can be accomplished with a fixed lens camera.

Below are some of the different types of photographic lens:

Zoom Lenses

Zoom lenses are lenses where the focal length of the lens can be varied, allowing the photographer to zoom in to a subject, isolating them in a scene from some of their surroundings, or zoom out to include other elements into the photographs.  Often today's cameras come with a kit lens with a zoom range of 18 - 55mm, this lens takes the place of the traditional 50mm lens.

This lens with its small zoom range provides some scope for the photographer, giving them some limited opportunities with the camera, prompting the photographer to buy additional lenses.

  

Above is a typical 'kit lens'

A more useful zoom lens is shown below:

This lens, a 70 - 300mm zoom lens is sometimes referred to as a tele-photo zoom lens, which offers a wider range of focal lengths covering popular tele-photo lenses.

A super zoom is a zoom lens that covers a very wide range of focal lengths ranging from wide angle to tele-photo, within one lens body.

The lens above is a Tamron 18-200mm 'super zoom' lens, which has become my standard lens as it offers such a wide range of focal lengths.  On my previous SLR, a Canon T70, my super zoom lens was a Vivitar 28-210mm lens which I found enabled me to capture scenes how I wanted them, but also allowed me to zoom in on individual features when I wanted.


Zoom lenses are good general purpose lenses which offer a wide range of possibilities, but some of the more expensive lenses offer larger apertures of f2.8 for the whole focal range, giving these lenses the advantage in low light situations or when faster shutter speeds are needed.

Tele-photo

Tele-photo lenses are fixed lenses, which offer higher focal lengths than prime lenses, often larger than the focal ranges offered by larger zoom lenses, but have larger apertures than zoom lenses can offer.

One of the team, Suzy, has a 800mm tele-photo lens !

Above is a 500mm tele-photo lens, which is not an easy lens to use due to its length.  For this lens you would have to use a support (tripod or monopod).

Another way of providing this focal length, but in a more compact form is a catadioptic mirror lens:

This lens, whilst more compact, has a disadvantage of having a fixed aperture of f8, which reduces its uses in low light.  For this type of lens you would have to use in a stop down mode.

This lens provides this high focal length, within its short wide body by using a series of mirrors (hence its nickname 'mirror lens'), which reflect the incoming light towards a small mirror at the front of the lens,

this reflects the light back towards the camera, this procedure is how such a large focal length is produced within a small lens body.

Often these lenses use the universal 't mount' system, whereby the lens has a thread which is connected to the camera via an adaptor, which can easily be changed allowing the lens to be used on different makes of camera, by changing the adaptor without having to buy a different lens.


These lenses can be used to take photographs of wildlife, at a safe distance, or aircraft in flight, where large focal lengths are needed.

 

Wide Angle

These lenses are the opposite to tele-photo lenses, where shorter focal lengths are needed.  These lenses have focal lengths of around 15 - 28mm.

These lenses are far shorter than tele-photo lenses, and sometimes offer smaller apertures.


These lenses are used for landscape, architectural, and some travel photography as they allow the photographer to include more scenery into the photograph.




Prime lens

These lenses are fixed focal length lenses, but have large apertures of f1.2 and above.

These are seen as some of the traditional lenses where the photographer would carry an assortment of different lenses, where today many of these lenses would be encompassed within one zoom lens.


These lenses are usually used for specific types of photographs like portraits.

Macro Lenses

These lenses are specially designed with close focusing for taking close up photographs of nature, and textures.

These lenses are specialist, although some lenses, in particular zoom lenses, feature a macro mode, where they can focus at close range for macro photography as well as their normal use.


These lenses are specifically designed for macro photography.

Fish Eye 


These lenses can be seen as extreme wide angle lenses, where due to the very low focal length of the lens, there is a distortion in the final photograph:

In these cases, this distortion is used in an artistic form, or sometimes just to include more than a normal wide angle could manage.

The fish eye lens above is in fact a fish eye zoom lens with a focal range of 10 - 17mm, with the lower end of the focal range creating the more pronounced fish eye effect.

Post Production

For these portraits I wanted to crop them tightly and convert them to black and white.

For this I used Serif's Photo Plus X3, and its black and white filter:

Post production is where the differences between digital photography and traditional film photography become very apparent.

With traditional film photography, much of this work, like dodging and burning, has to be carried out in a dark room, although sometimes prints can be edited outside the darkroom, and then the print is re-photographed to produce a new negative. 

With digital photography, software applications such as Adobe's Photoshop, Corel's Paintshop Pro, Serif's Photo Plus to name four software packages are used to edit the digital files on a computer.  Although the range of software is very limited on the Apple Mac computers.

Adobe Photoshop is seen as the standard to which many photographic editing software is measured against.  This application is available for both windows based pcs and Apple Mac computers.

Week Two

At the beginning of this lesson, Steve discussed the making system and the different options available.

Then Steve had a one to one meeting with me to discuss what options I was looking to study.  Steve did say about choosing a theme, which I will have to think about, and discussed the different units that I would need to achieve a diploma.  Steve did discuss the time required to complete the modules and we felt that this would be achievable given the work done on the previous modules.

Different Types of Digital Camera

There are four types of digital camera:

Compact Cameras

These range from the basic click and shoot cameras, to more advanced compact cameras which offer different ISOs, more program modes, manual mode, RAW capture.  These cameras have fixed lenses, in that you cannot change the physical lens, but many of these cameras do feature zoom lenses, which would sometimes cover many of the lenses you might need especially as some cameras feature up to 10x zooms.

My first digital camera was a compact camera, a Fujifilm Finepix 1400 Zoom.

This camera is between the point and click and the more advanced cameras.

Bridge Cameras

The next type of camera is the bridge camera.  These cameras are called bridge cameras because they bridge the gap between compact cameras and SLR (single lens reflex) cameras.

These cameras also feature fixed lenses, but offer higher zoom ranges, up to 30x, and offer more features and allow the photographer to be more creative.

Above is the Fujifilm Finepix S7000 bridge camera, like the one that I own, that I moved on to after the Finepix 1400 zoom.

This camera offered RAW capture using Fujifilm's RAF format, as well as a larger zoom range and far more control over the final photograph with metered manual mode.

Single Lens Reflex (SLR) Cameras

These cameras offer total control with more manual control, interchangeable lenses and a wide range of accessories.

  

The Pentax K10D shown above has the battery grip, which not only holds a second battery but also includes a second shutter button and front and rear e-dials for changing the shutter speed and aperture, whilst the camera is held to the photographer's eye.  This accessory is very handy as not only does it provide these features but can also store a second SD memory card (not directly accessible from the camera), and a Pentax remote control, but makes portraits and portrait style photographs easier because it provides a more natural way of holding the camera as opposed to simply rotating the camera and twisting the hands in order to access the camera controls.

The ability to change the camera lens makes these cameras more versatile than any other type of camera.

A newer form of interchangeable lens camera, similar to SLRs but sometimes referred to as micro systems.  One example of these is the Olympus Pen camera, shown above.

Medium Format Cameras

These are the larger cameras, offering resolutions of 40 megapixel for more professional photographers, and are very expensive.