Introduction guide to photography

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Johnmcl7
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Introduction guide to photography

Postby Johnmcl7 » 25 Apr 2009, 03:09

This is my second attempt at writing a photography guide, this time I'm going to try a more practical approach rather than get bogged down in the terminology. I make no claims to expertise in these areas, just some familiarity with the basics and as another disclaimer, there are a lot of Jake pictures here as he's a willing subject who doesn't mind his picture being published online

Minimum shutter speeds

This seems as good a place to start as any as getting too low a shutter speed is a common reason for poor results in a photo.

Camera Shake

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One of the main reasons for pictures to turn out blurry is that the shutter speed is too low for the focal length the lens is set to - some cameras are good at giving warnings that the shutter speed has dropped too low but others will tend not to, particularly SLRs which assume you are checking the shutter speed constantly. The general rule of thumb to avoid camera shake is to have the shutter speed at 1/focal length (equivalent) or more, while this is very general in that some people can do slightly better and some slightly worse in practice it's a fairly good way to judge your shutter speed. What this means is if I'm shooting a camera with an equivalent focal length of 28mm to 120mm if I'm shooting at the wide end then I'm aiming for a shutter speed of 1/30 or more whereas if I'm shooting at the telephoto end then I need a much faster 1/120 shutter speed.

Something to be particularly aware of is that by this formula, the longer the focal length the higher the shutter speed you need but also for most camera lenses they have a smaller aperture which means they let in less light. In the example above that camera lens at 28mm has an aperture of F2.8 which lets in quite a lot of light however when it's zoomed in to 100mm the maximum aperture drops to just F4.9 which means it's letting in almost four times less light. On top of that to get a reasonable sharp picture you need a shutter speed four times faster, the net effect is that if you want to change from 28mm to 100mm you're going to need to have a reasonable amount of light otherwise you're going to end up with blurry pictures.

I'll go into how to squeeze more light into the camera through its settings later on, for now however there are some basic tricks to avoiding camera shake. The most obvious one is simply to brace yourself better, leaning against a wall or lying flat can usually help you stabilise the camera better and achieve a sharper shot. Most cameras have a burst mode where they take a series of shots in row, if you're just on the edge of getting a sharper shot it's worth using the burst mode as there's a good chance that in the sequence you'll end up with a slightly sharper shot.

Once the shutter speed drops to below 1/10 no matter how good you are at holding the camera it's unlikely you're going to be able to take decent shots, if the light level has dropped this low it's time to start looking for a rock, post or similar to place the camera on or use a tripod if available.

A popular technology available for most cameras to help avoid camera shake is image stabilisation which comes under many different names, Panasonic call it Mega OIS, Nikon call it Vibration Reduction but it's all the same basis. There are two forms of image stabilisation, one is lens based IS and one is sensor shift IS. In lens IS system an element within the lens automatically moves to compensate for any movement in the camera body which means that the image at the sensor remains steady even if the camera is moving. The advantage of this stabilisation system is that you can see the effect of the stabilisation in the viewfinder and it tends to be slightly more effective on telephoto lenses. In a sensor shift stabilisation system the actual camera sensor itself sits on a floating platform which moves automatically to compensate for the camera movement, although you can't see the effect in the viewfinder this system has the advantage that it works for every lens you attach to the camera.

In reality both systems work well and it's a featre which is very much worthwhile to have on your camera. The gains are dependent on the setup you are using although on average it's around one to two stop improvement (allowing you to shoot two to four times slower and keep a sharp image) Here's an example of it in action - both of these shots are taken at 100mm equivalent, ISO 400 with one at 1/6 second and the other at 1/8 second. You can clearly see how much sharper the stabilised shot is:

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There are a few points to be aware of and the first is 'fake' stabilisation systems - some companies advertise their camera as having 'digital image stabilisation' or similar, in reality this not a mechanical stabilisation system at all but instead a method of boosting the shutter speed by increasing the sensitivity of the sensor. This is something of a con as pretty much all digital cameras are capable of this it's just they don't offer it as a fake feature.

In terms of us, image stabilisation has its limits - for wide angle lenses it's less effective, hence those who offer lens based IS systems don't offer stabilisation for their wide angle lenses. Additionally IS systems can only correct camera shake, they can't stop subject motion which means if anything in your picture is moving it's still going to be blurry. One of the main issues to be aware of with image stabilisation systems is that they should be disabled if you are moving the camera while taking the shot such as panning the camera sideways to take a picture of a racing car. If the IS system is fully enabled then it will attempt to correct the sideways motion of the camera and actually blur the shot. Some cameras do offer the facility to only stabilise vertical movement and disable horizontal correction to stop this happening.

Subject Motion

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No matter how well you stabilise the camera, if your subject is moving too quickly you're going to end up with a blurry shot - in the above shot you can see that everything in the shot is reasonably sharp with no blur as the 1/50 was plenty of the focal length however Jake is just a blur as the shutter speed was nowhere near fast enough to freeze his motion. There's no real rule of thumb here aside from the faster your subject is moving, the faster a shutter speed you are going to need. If you're shooting a relatively static group of people then you'll get away with 1/50ish shutter speeds as long as no-one makes any quick movements, frequently someone will turn their head or move their arm just as the shutter trips which will just be a blur in the final picture despite the rest being sharp.

If you're shooting any sports you should be aiming at 1/500 or higher to freeze the motion, checking your pictures to see if you need to go higher yet. Dogs and similar tend to move that bit faster which means in turn you're probably going to need a shutter speed 1/1000 or 1/2000 to be fast enough. Racing cars or similar can be more tricky, unlike say an athlete moving along there is no actual motion within the car as it's a solid object. As you're panning the camera to follow the motion of the car this will mean the relative motion isn't much and freezing the motion of the car with a high shutter makes it look like it's sitting parked. Here are a couple of shots demonstrating this:

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Believe it or not this is a very fast Porsche ripping up the Nurburgring, as I'm used to shooting fast little spaniels I went for the same tactics and shot this at 1/2500. Rather laughably the car looks like it's parked on the track when it was actually racing by.

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In this shot I was panning the camera sideways and used a much lower shutter speed of 1/250 which you can see works far better in conveying a sense of speed. While the background and the car wheels are blurred, it works far better for this type of shot.

Here's a couple of examples where a really fast shutter speed was needed, Jake is moving rapidly through the water which in turn creates a considerable amount of motion within the water itself:

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The first one is shot at 1/2000, the second at 1/2500 and in both you can see how the very high shutter speed has completely frozen the water.

Automatic vs manual camera control

I've talked about choosing an appropriate shutter speed but before advising on how to get that shutter speed it's worth going over the basics of camera operation. Each company has a different way of implementing the various modes but at a basic level there are four modes - P, A, S and M. P stands for Program Auto where the camera chooses both the aperture and the shutter speed and is a fully automatic mode. A is for Aperture priority mode where you choose the aperture (the iris which allows a certain amount of light through the lens) and the camera automatically chooses the shutter speed. In S mode which is Shutter Priority you choose the Shutter speed and the camera chooses a suitable aperture. Both A and S modes are semi-automatic. M is Manual mode where you do it all yourself choosing both the shutter speed and the aperture value, the camera will normally attempt to assist by telling you whether it thinks you are over exposing or under exposing.

Commonly there's a raft of other modes, confusingly it's not uncommon to see both a P mode and an auto mode - the difference between these two depends on the camera, in some cases P mode still allows you to choose WhiteBalance and ISO whereas 'Auto' modes lock all options down. Scene modes give preference to certain settings to suit the scene such as a small aperture for landscape shooting (everything in focus, no need for high shutter speeds) or setting the shutter as high as possible for a sports mode. It may be that the auto mode has limits such as not dropping below 1/4 second shutter speed or not increasing the ISO above 400 which are bypassed in scene modes.

So how does the camera choose the right settings when it's in one of the automatic or semi-automatic modes? At the most basic level the camera measures the amount of light coming into its systems and chooses an appropriate shutter speed to try and avoid under exposure/over exposure. By default most cameras will measure the entire scene take note of the dark and bright areas and try to choose a shutter speed which prevents the dark areas going to black (underexposed) and the bright areas going white (overexposure). However there are a wide range of exposure options that allow you to tell the camera how you want to measure exposure such as only measuring values from the centre of the scene (where your subject is).

In a fully automatic setting where the camera chooses both aperture and shutter, as it knows the focal length you are shooting at it will try and give you a usable shutter speed using the 1/focal length rule. Some cameras currently can be even smarter and will try to analyse motion in the scene and opt for a higher shutter speed if it thinks it necessary. In a semi-automatic mode such as Aperture priority as the camera only has control over the shutter speed it will simply try for a balanced exposure.

Which mode should you use? There's no real answer to that although further on I'll go into some more detail about the benefits of shooting in aperture priority mode, from reading the above you can probably see the benefits of shooting in shutter priority mode. Personally I tend to stick with aperture priority as the aperture setting has a large effect on the final picture but you still have automatic exposure. I tend to only use manual mode when the camera cannot work the exposure on its own such as during fireworks or shooting the moon.

Underexposure, overexposure and the histogram

Firstly a quick intro to these terms before going into further detail, underexposure is where the picture is too dark as the shutter speed wasn't fast enough and didn't let in enough light. Overexposure is where the shutter was open for too long and let in too much leading to an image which is too bright. The histogram is one of the most useful tools for judging exposure, it's a graph which plots out all the values in your picture. For each fully black spot (completely underexposed) it will add a value to the column at the far left and for every fully white spot (completely overexposed) it will add a value to the far right. Therefore for a balanced exposure you want to avoid either of these and simply have a curve which has a maximum somewhere in the middle.

All the following pictures were shot using aperture priority with the autoexposure set to measure the whole scene. First up, an underexposed picture:

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Clearly Jake is far too dark here, the camera has chosen a higher shutter speed due to the bright sunlight reflecting off the water.

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This is the histogram for the above picture, you'll notice that there's a reasonable number of values in the middle which represent the properly exposed water however that steep part on the far left shows that Jake was badly underexposed.

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This time Jake is overexposed, one of the reasons I'm using him yet again for examples is because his coat plays havoc with the cameras' auto-exposure systems as parts of him are bright white and reflective and others are very dark. In this case there's more dark areas in the shot which the camera has exposed well however the bright sun has overexposed most of the left side of the picture.

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This time on the histogram most of the exposure isn't too bad however the large portion on the far right means there's serious overexposure. The next shot has a balanced exposure, no deep shadows or blown highlights which can be seen in the histogram as there are no peaks at the extreme sides:

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Most camera will offer a histrogram in the playback modes and many compacts will actually give you a live histogram while shooting. SLRs tend not to have this feature due to their design which blocks the main sensor aside from liveview modes. Another useful tool cameras and software have is showing shadow (underexposure) or highlights (overexposure), this is the overexposure shot with the view highlight option enabled:

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The large red areas show the large overexposed area at a glance, similarly underexposed areas can be marked in blue. The Olympus cameras on the other hand show the under and overexposed portions as flashing areas to make it easy to identify them on the small camera screen.

Fortunately you don't need to change to manual exposure, most cameras offer the facility to slightly change the exposure in their automatic modes known as EV compensation (Exposure Value) which is usually shown as a button marked with a - and +. By setting negative EV compensation you can set the camera to choose a slightly faster shutter speed than the one it automatically chose or by setting positive EV compensation the camera will use a slightly slower shutter speed. In the first shot with Jake in the water I should have set postive EV compensation by +2/3 stop or even a full stop which would have the effect of halving the shutter speed. In the second overexposed picture I should have dialled either -1/3 or -2/3 of a stop exposure compensation to just slightly increase the shutter speed to prevent it being so overexposed but without underexposing the black areas.

This following shot was taken at night where the car and nothing else was lit up by the light coming from the garage which I wanted to try and capture. I fired the camera up and took the following shot:

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As most of the area is dark (the final version was cropped) the camera went for a slow shutter speed which has overexposed the light on the car. In this case I didn't want any of the background which meant I had to set the EV compensation to -3 stops (bordering on needing manual mode) to get this version:

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All cameras are different and getting the right exposure will be dependent on the camera and need some experimentation. Generally I've got a good idea where my cameras will overexpose and underexpose and adjust accordingly. By shooting raw (effectively a digital negative) it is possible to make small exposure corrections after the picture has been take to recover highlights and bring back the shadow detail.

One of the difficulties is that in some cases it won't be possible to capture the scene without overexposing one portion or undexposing another - this is what's known as the dynamic rang eof the camera, generally the larger the sensor the more the dynamic range they can capture. The dynamic range is the difference between the underexposed areas and the overexposed areas, cameraphones tend to have very limited dynamic range which means they blow out highlights very quickly as well as blackening shadow portions.

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This is a picture taken late evening with no exposure compensation, the sky is overexposed and too bright but the hill area and the beach are underexposed.

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Dialling in negative exposure compensation shows the sky properly however the detail is completely gone in the beach and the hill area

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Alternatively setting positive exposure compensation shows the beach and the hills far better but the sky is now completely lost.

There are several solutions to this issue but they're really outwith the scope of this guide, in this case I set the camera to a bracket mode (where it rattles of five shots, two under exposed, two over exposed) and then combine them afterwards to get a better balanced exposure for both the sky and the beach. This is a relatively poor example as I'm still trying to get the hang of the exposure blending however if you ignore the obvious saturation issues, halo and the glitches in the water you can see the benefits for the exposure:

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Aperture

Changing the aperture of a camera lens changes the amount of light that the lens allows in which will increase/decrease the shutter speed of the camera and will also change the depth of field. The aperture is controlled by a set of blades within the lens, when the lens is set to its maximum aperture known as 'wide open' the blades are completely retracted to let the maximum amount of light through, the smaller the aperture chosen the more the blades close down into the lens to limit the light coming through.

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This is an old Pentax 50mm manual lens with a maximum aperture of F2, wide open you can see a large amount of light is allowed through but as the lens is stopped down the iris blades close down further until only a pinhole of light can enter the lens.

Aperture is measued in f-stops with each complete f-stop measured as letting in half as much light as the previous f-stop. Changing a lens from F1.4 to F2 will halve the light reaching the camera which means the speed will drop by half, changing to F2.8 will drop the shutter speed in half again. Alternative starting at F8 and changing to F5.5 will double the shutter speed and changing to F4 will double the shutter speed again. The smaller the F-number the wider open the lens is and the larger the F-number, the smaller the lens entry is.

Changing the aperture value also changes the depth of field which is the area within the picture that is in sharp focus. Generally the wider the aperture f-stop (small f-number) the smaller the depth of field - a very shallow depth of field will place the subject in sharp focus but the background will be blurred which is often desirable especially when shooting portraits. However at other times a larger f-stop is desirable when a large area of focus is needed such as when shooting landscapes. This is where shooting in aperture priority mode is useful as the camera does not know what type of shot you are taking and will simply choose a 'safe' aperture - if there's a reasonable amount of light it will probably go with an aperture of around F5.5 and widen it as necessary. If I'm walking along and taking pictures of Jake I'll usually want a wide aperture to either blur the background or to increase the shutter speed but then if I want to take a shot of the landscape I'll stop down to around F8 to increase the depth of field as I don't need a fast shutter speed any more.

Thinking about minimum shutter speeds, widening the aperture is clearly one of the main ways to increase the shutter speed. There are two issues with increasing the aperture with the first being the shallow depth of field. In some cases this can be desirable but at other times it isn't as it can mean that portions of the subject are out of focus while other parts are in sharp focus.

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In this example, the eyes are in sharp focus but the nose is out of focus due to the very small depth of field.

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In this shot I've intentionally stopped the lens down to F5 to give me some more depth of field and instead pushed up the ISO to keep the shutter speed reasonable. Technically the lens was capable of shooting over twice as fast however due the bikes coming towards me it meant it was difficult to get them in sharp focus as they were quickly moving through the small depth of field.

The other issue with increasing the aperture is that your lens may not open that wide as a wider aperture generally makes the lens larger, heavier and more expensive. Kit lenses in particular tend not to be able to open very wide particularly at their long end. One potential solution is to consider a prime lens which is a lens with a single focal length. While you lose the flexibility of being able to zoom you normally benefit from a wider maximum aperture, a smaller size, higher quality and lower cost. Take a look at these two lenses:

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The lens on the left is the Zuiko Digital 50mm F2 and the large one on the right is the Zuiko Digital 35-100mm F2. The 50mm lens is simply tiny in comparison to the large zoom lens which has to make many compromises to have such a constant large aperture, at around 350 pounds the 50mm is around a sixth of the cost of the large zoom lens. The 50mm F2 is still fully weather sealed and despite the lower cost is considered one of the sharpest lenses on the market and also produces virtually no distortion. While the 35-100mm is a superb lens I still frequently use the little 50mm lens simply because it's small and light making it comfortable to use and discrete. The 35-100mm is far from subtle and the weight whether on the camera or in the backpack is a real killer after a couple of hours.

ISO

The ISO setting refers to the sensitivity of the sensor and is similar (but not equivalent) to ASA ratings for film. Each time you double the ISO you increase the amplification on the sensor which allows you to double your shutter speed as the sensor becomes more sensitive to light. The disadvantage to increasing the ISO is that you also increase the amount of noise in the picture which once at very high ISO's becomes very intrusive.

The ability for a camera to handle high ISO is largely dependent on the physical size of the sensor, the current high ISO king is the Nikon D3/D700 which even at ISO 6400 can still produce pictures with very little noise. Cropped sensor SLRs can't manage quite the same performance but they are usually still usable up to around ISO 1600. Compact cameras with their very small sensors normally have virtually no ISO overhead and even at their base ISO 100 there can be evidence of noise. Increasing the ISO either leads to massive amounts of noise or large amounts of noise reduction which obliterates the noise but also removes all the fine detail in the picture.

Due to the increase in noise some people are very wary of ever putting their ISO up however if you are struggling to get enough light into the camera leading to pictures suffering from camera shake or subject motion then at times increasing the iso is going to be only available option if you're already at your maximum aperture. While you will introduce more noise into the picture this is something which can be reduced in post processing through one of the many noise reduction software packages however correcting camera shake/motion blur afterwards is very difficult.

Most cameras do offer an auto-iso system along with automatic aperture and shutter control where the camera will also choose a suitable ISO speed. As always the implementation varies depending on the manufacturer and it's well worth checking how your camera handles ISO speed as I find auto-iso on many cameras to be poor. My friends were showing me their new Sony A300 SLR with which they were generally pleased with however in low light the results were not good, looking at the very low shutter speeds it was clear their shots were suffering from camera shake. The camera has a stabilised sensor and being used on full auto mode it had set the aperture as wide open as possible however the auto-iso had only gone up to ISO 400. As a cropped sensor SLR it could comfortably handle a far larger ISO up to ISO 1600 or even 3200 to get a sharper shot as the blurred shots were of little use.

Alternatively some cameras are not conservative enough with their ISO settings, the Panasonic LX2 is a small compact camera which is not very good at high ISO - at ISO 100 there is noticeable smearing from the noise reduction which means ISO 200 is really as far as it should be pushed. However the auto iso will frequently jump to ISO 800 even when it's not quite needed. The older Olympus SLRs had a very poor auto iso setting in that it never moved from ISO 100 unless a flash was attached.

Minimising noise is partially handled with noise reduction software in post processing however it can also be reduced when taking the picture. Noise is most evident in underexposed areas which means when taking pictures at high ISO leaning towards overexposure will generally reduce the noise.

Using a flash

There are going to be times that even when the the aperture and the ISO are maxed out you still cannot get enough of a shutter speed for the shot you are taking. This is when a flash can be useful as the pulse of light it produces allows a higher shutter speed as well as often producing a more even light across the subject. Some people are put off using a flash due to the very harsh and direct light it produces as well as lighting up people's (or animal's eyes) leading people to try and use available light and high ISO instead.

Going into detail about flashes is a guide in itself but there are a few basic tips which can signficantly improve the usefulness of a flash. The first is probably the most obvious and that's to buy a dedicated flash, all SLRs have hotshoes and many bridge cameras do as well. In most cases it's best to choose a flash made by the same company as the camera body as this will ensure full compatibility allow the camera to tell the flash what aperture, iso setting and focus distance the camera is using to accurately calculate the flash power. A dedicated flash offers more power and with a moving head it allows you more fleixibility to bounce the flash off a ceiling or wall to reduce the harshness of the light. You can also mount a diffuser to soften the light coming from the flash and give a more even, pleasing light to your subject.

When using the flash it's also worth keeping the ISO reasonably high and the aperture wide open, by doing so you lessen the need for a flash which means the light created by the flash blends in better with the rest of the shot. For example if I'm getting too slow a shutter speed even at ISO 1600 I'll tend to mount the flash but rather than drop to the base ISO of 100 and stop down the aperture I'll normally go to ISO 400 where the noise is still minimal and keep the aperture as wide open as I can get away with.

Up above in the exposure section I detailed exposure compensation, the flash also has a similar control which usually looks the same aside from the addition of a flash lightning bolt. Changing the flash compensation allows you to force the camera to either reduce the power of the flash or increase it. If you're trying to minimise the effect the flash has on a scene and you have some existing light you can use then it's worth trying out reducing the power of the flash.

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This picture is a classic example where the flash has been poorly used, the light is very harsh against the dark background giving that 'caught in the headlights' look. The scene looks far darker than it actually was due to the low iso setting used when firing the flash.

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This picture is much better balanced, this was taken using a dedicated flash gun at ISO 400, F2.8 and a Lightsphere fitted to the flash.

Misfocus

Due to many different factors another common cause of blurred pictures is simply because they are out of focus either because the camera locked onto the wrong portion of the scene or the subject simply moved from the optimal focus area. There is a vast difference in the autofocus systems across different cameras however there are some general tips to be aware of.

The first is to simply to be familiar with the autofocus system in your camera as they all tend to have their own quirks and benefits. One of the main sources I see of misfocus is cameras that attempt to be too clever and use a large area of the picture to autofocus rather than a small point in the centre. The problem here is that the camera will tend to lock onto where it can find good contrast which may well not be your subject. If you're shooting a plane in the sky or a shot where there's only one subject in the picture and the rest is comparatively blank then an all points AF system will do a good job however if you're shooting a scene with many objects in it then it's probably better changing to a single AF point or small AF area so you know what the camera is going to lock onto.

You need to be very aware of your depth of field as while cameras will often warn you when the shutter speed is dropping too low, I've never come across any which give any warning when the depth of field is too shallow. The longer your focal length, the wider the aperture and the closer your subject the shallower your depth of field which means you need to be all the more careful with your focus. If I'm shooting a subject at 100mm with the aperture set to F2 I know that much focus accuracy is absolutely critical otherwise there's a good chance I'm going to end up with a poorly focused shot. However if I'm shooting at 7mm with an aperture of F8 the depth of field is so vast that accurate focus doesn't really matter.

The depth of field goes across the scene which means if possible you should try and track a subject sideways as they're likely to remain within your depth of field. However if the subject is moving forward and back they are going to be moving into the out of focus areas which either means you need to refocus or stop down your aperture to increase the depth of field.

Both contrast detect AF systems in compact cameras and phase detect AF systems in SLRs are looking for strong contrast as this is how they focus. When composing your shot always aim for something which has a strong contrast which will ensure the camera can get a quick, accurate lock. Trying to focus on an area with very little contrast such as a blue sky or the side of a building with a flat texture will cause the AF system to hunt longer for focus and will usually end up not managing to get a lock or focussing incorrectly.

If you're shooting something which is moving along a fairly certain path and you're having difficulty tracking the subject it's a good idea to set a focus trap - half press the shutter on an object or area you know your subject is going to cross and hold the camera there then press the shutter full down the moment your subject enters your focus trap.

White Balance

The human eye is extremely good at dealing with low light which can be difficult when judging exposure as when you shoot with the camera it's actually far darker than you realise. White balance is something else we do very well and again which cameras do not, although we don't realise it we automatically recolour the scene so that white is always white. Cameras attempt to do the same through automatic white balance - they either measure the scene through a dedicated WB sensor or more commonly they try and guess the white balance by looking at the colours in the scene.

In scenes with natural lighting the auto white balance systems will generally do a good job however in artificial lighting they struggle and will usually choose too warm a white balance which produces the orange cast you can see in the picture above. Most cameras offer the option to choose the white balance setting from a range of predefined values which are usually Sunny, Cloudy, Shade and some indoors lighting. If you're shooting outdoors then autoWB systems are ok but if you're shooting indoors without a flash normally you need to set the WB manually.

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The first shot was taken with auto white balance which has given the picture a strong orange cast, on the next shot I manually changed the WB preset from auto to Tungsten which gives far more accurate colour. A word of warning though, make sure you change it back! If you take a picture with the flash enabled or a scene lit by natural lighting you'll instead find yourself with a strong blue cast.

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The first shot was due to me leaving the WB preset to indoors lighting (which still catches me out from time to time), as the building was lit by natural light I changed the WB preset to auto which captured the colour correctly.

One large advantage of shooting raw is that you can change the white balance afterwards which means if the camera setting was wrong it doesn't affect the final picture. If you're shooting jpeg it's not quite so easy to fix the incorrect colours however most image editing programs will allow you to set the colour balance back to what it should be.

Shooting raw

A raw file is essentially a digital negative - when shooting jpeg the camera takes the data from its sensor then passes it through a processing pipeline applying white balance and any presets you have chosen such as saturation, contrast and sharpness to produce the jpeg file. The problem with this process is that it actually throws away a lot of information in its conversion from the 12 or 14 bit raw file in producing the 8-bit jpeg. By shooting raw you gain considerable flexibility primarily through being able to under/overexpose the picture and being able to set the white balance. This means if you have a picture which has slightly blown highlights and some dark shadow areas you can often pull back the detail in these areas to give a better picture.

The downsides are that not every camera supports raw and due to the larger amount of information stored in the file they take up more space and can take longer to write to memory card particularly with compact cameras which can be particularly slow. You also have to post process every file to produce the jpeg although it is normally possible to batch process raw files into jpegs, essentially doing the same as the camera does. There are limits to how much detail you can pull back from highlights and some shadow detail may be too dark to bring back as when lifting the exposure it shows a large amount of noise. While there is a standard for raw files (DNG, Digital NeGative) in practice most companies choose to go with their own implementation which means if you try to process a raw file from a newer camera with an older piece of software it most likely won't work. Adove are particularly bad for this as they only allow the updated versions of their raw processor to work with newer versions of Photoshop - in this situation it is possible to batch convert the original raw files to another similar format (TIFF or DNG) then import them into the editing program.

In terms of motion blur it's still important to get the correct shutter speed as once the shot is blurred even if you increase the exposure when importing the file into a raw processor it can't fix that. However it is possible to underexpose slightly to increase the shutter speed and then brighten the image by increasing the exposure when importing the raw file.

I have to admit I've been quite lazy with raw shooting and I've tended to rely on the out of camera jpegs. However more recently I am taking the time to shoot more in raw when I know the extra exposure latitude is something I'm likely to need.

Creative control - taking advantage of your camera

One of the main questions I was asked when writing the previous guide was why shoot using manual settings if the results from automatic seem fine. In many cases particularly with current day cameras the automatic settings do an extremely good job of choosing the appropriate shutter speed, ISO and aperture. However the camera still does not know what you are shooting and can't change its settings to optimise for different shooting scenarios.

As mentioned earlier depth of field is a signficant portion of a picture, in some cases you will want a very shallow depth of field but other times a greater depth of field. As the light drops the camera will need to start pushing the aperture wider and the ISO higher but as both bring their own disadvantages (less depth of field for aperture, more noise for ISO) you need to balance each control against the other. At times I need a greater depth of field but still a higher shutter speed (such as shooting motorbikes on a cloudy day) so in this case I'll push the ISO up and take more noise but keep the aperture stopped down to keep the focus. On automatic the camera would either keep the shutter speed too low or it would widen the aperture too far. At other times I may be wanting to keep noise as low as possible and instead will widen the aperture right up to get the shutter speed I'm looking for.

If I'm shooting a portrait shot in good light I'll also widen the aperture to maximum to gain a very shallow depth of field and provide a pleasing background blur - as I don't need the super high shutter speed this would end giving me, the camera on automatic would tend to leave the aperture stopped down.

There are times when you may intentionally want to slow the shutter speed right down for a certain effect such as blurring the motion of water or on a night shot using a very long open shutter to capture light trails.

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To let in as little light as possible the aperture here is set to F22 and ISO 100, the shutter was left open for 60 seconds to capture the light trails of the vehicles moving by. Despite pedestrians walking in front of the camera none of them show on the final shot as they didn't reflect enough light

Image

This is another shot where I wanted a longer shutter to blur the motion of the water although as the sun was still going down I couldn't get away with the same settings as in the previous picture. Again the camera was set to F22 and ISO 100 to let as little light through but I also deliberately set the EV compensation to +2/3 to slow the shutter down leading to very obvious overexposure. When importing the raw file I dropped the exposure by 2/3 stop to correct the overexposure which may seem a little pointless however if I hadn't overexposed I'd have had less blurring on the water which I didn't want. This is the underexposed raw version:

Image

The next shot is a wide aperture portrait:

Image

As the sun was bright there was technically no need to widen the aperture as the shutter speed was at a reasonable speed already and on automatic the aperture would have been kept somewhere in the middle. However as I wanted a soft background I intentionally opened the lens wide open.
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Re: Introduction guide to photography

Postby EviL Ras » 25 Apr 2009, 03:22

WOW!!! You're some kind of legend John! Thank you so much for spending time on this for us all! You're teaching me a lot more than my books are!
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Re: Introduction guide to photography

Postby sayed » 25 Apr 2009, 21:16

Some stunning pictures John. Have to reiterate EviL Ras gratitude.
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Re: Introduction guide to photography

Postby EviL Ras » 25 Apr 2009, 22:40

HA! and you lot think i just +1! };o)
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Re: Introduction guide to photography

Postby Advocate » 27 Apr 2009, 11:15

Very nice guide John, well thought out and very comprehensive. Will no doubt be using this as a reference on my iPhone when out shooting on occasion.
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Re: Introduction guide to photography

Postby steffcip » 27 Apr 2009, 17:23

WOW John
great guide....now I can learn more....maybe :lol:
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Re: Introduction guide to photography

Postby jurassicjim » 28 Apr 2009, 10:02

Superb guide, thanks!

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Re: Introduction guide to photography

Postby Roadshow » 28 Apr 2009, 10:12

Excellent guide John. Took me back more than 25 years to when I did 'O'-level photography, only you are better than my teacher was at explaining the concepts. With you in charge I might have done better than get a 'C'.
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Re: Introduction guide to photography

Postby Fodder » 28 Apr 2009, 14:10

Excellent. Especially like the +/- Ev tip for lengthening exposure. Wanted to do that a while back and was digging around for some ND filters to achieve it. Must get my head 20 years on in photo technology!
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Re: Introduction guide to photography

Postby Dr Who » 09 May 2009, 08:53

Thankee koindly sorr.

The missus hasn't used an SLR for years and I sent her the link to your post and she found a good refresher - she says you write well John!
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Re: Introduction guide to photography

Postby jurassicjim » 04 Sep 2009, 13:32

Just re read this on my way down to liverpool and in anticipation of my new cameraand lens. Thanks again john, good to have something that explains everything in simple terms with examples.

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Re: Introduction guide to photography

Postby Combat Marmot » 20 Sep 2009, 20:40

Thanks for the guide John, I've read it a few times now.

For further reading I picked up a copy of "The Ultimate Guide to Digital Photography" in WHSmith (a large one, couldn't find it in the smaller stores). It seems fairly good with some info on white balance as well as correcting/altering images using the gimp/photoshop. It's clearly aimed at those unfamiliar with technology in general as there's a section about what you might want in your PC; it is very basic in some areas but even so I've found it fairly useful, and at £8 it's a lot better value than most photo magazines that seem to have very little technical content indeed. Admittedly a lot of the editing content could be found online and one complaint I do have with the magazine is there isn't a part dealing with correction of converging verticals in images.

So all in all, reasonably good for those who are just starting (like me) but poor value for those with experience as I doubt you'd learn very much from it.

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