Lenses (Part 3) – Prime or Zoom?

This next post builds on where Part 2 left off. We have seen that a lens can be categorised, broadly, as being either within the wide-angle, standard/normal or telephoto category, depending on its focal length. However, there are lenses out there that change their effective focal length. These are called “zoom” lenses, since, you guessed it, they can zoom in/out. Where such zooming capabilities are not available, the lens is referred to as being a “prime” lens.

A first point of clarification needs to be made: what a “zoom” lens implies is that the lens can vary its focal length in between two fixed extremes – its widest and its most zoomed in. It is important that one does not assume that a zoom lens is the same as a telephoto lens. In fact, one can have zoom lenses with a range of focal lengths that only cover the “wide-angle” category, for instance a lens that goes from 10mm to 18mm, like the Canon EF-S 10mm-18mm. Also, you can similarly have “standard zoom” lenses, like the typical “kit lenses” provided with a new camera. Here, the zoom range would cover focal lengths falling within the standard/normal category of lenses. Also, you can have some that are telephoto zoom lenses, such as lenses that go from 70mm to 200mm. Finally, you can have zoom lenses that span across different focal length categories, starting out as a wide-angle and zooming in to telephoto focal lengths. Examples include lenses that go from say 18mm to 200mm.

The major advantage presented by zoom lenses is in the form of versatility: with a zoom lens attached to your camera, you can be shooting a landscape one moment (e.g. at 24mm), a portrait the next (e.g. at 50mm) and then a zoomed-in shot of a bird on a perch some distance away (e.g. 100mm). Whilst this of course depends on the focal lengths available to you, it is of course much easier to accomplish this with a zoom as opposed to having three separate prime lenses. For starters, you save time in the form of not having to change lenses. This also lets in less dust onto your camera sensor, an added advantage.

Given such versatility, why would anyone need “prime” lenses? To recap – prime lenses are all those lenses with a fixed focal length. Common examples of prime lenses are virtually all camera lenses in smartphones these days, albeit with a few exceptions that incorporate a lens that can zoom optically. Some of you might say, “hold on, I can zoom on my smartphones”… and that would call for another clarification. There are two methods whereby one can zoom, namely optical zoom and digital zoom. Optical zoom is a method whereby the lenses are physically moved to increase or decrease magnification – it is thus a mechanical type of zoom. On the other hand, digital zoom is a software-dependent zoom. In digital zoom, what the software does is to “crop” in on the image, enlarging the centre portion to simulate zooming in. By doing so, you are presented by a more zoomed in image, but this comes at the expense of image quality as some areas of the photo are “discarded”. Note: I will be expanding on this in future posts dealing with megapixels, cropping and other image-quality related aspects.

With that out of the way, we can go back to the role played by “prime” lenses. What advantages do prime lenses offer over zoom lenses, if a zoom lens can cover any given focal length, plus vary this according to the situation? A number of advantages, in fact…

First off, image quality is generally superior when it comes to prime lenses. The reason is simple – prime lens are constructed to be good at doing one thing, that is, taking a picture at a single, predetermined focal length. On the other hand, zoom lenses have to be good at doing this at various focal lengths. Needless to say, it is easier to construct a high-quality lens with a fixed focal length than it is to construct one with a variable focal length. This simplicity often translates in optical qualities that are superior when compared to zoom lenses set at the same focal length. For instance, comparing the quality of photos taken by a 50mm prime lens, to an image taken with a standard zoom set to the same focal length will more than likely show better results in favour of the prime lens.

Secondly, prime lenses generally have larger maximum apertures, and this also links to the construction argument above. In fact, the simpler construction parameters behind prime lenses permits designers to include wider maximum apertures in prime lenses as opposed to that technically permissible in zooms. This is not to say that there are no zooms with wide maximum apertures, but it is a known fact that primes, on the whole, are equipped with wider maximum apertures. For instance, it is common to find prime lenses with maximum apertures that vary between f/1.2 and f/2.0, whilst commonly zooms top up at f/2.8. There are, of course, exceptions, such as the recently launched Sigma’s 18 – 35mm f/1.8 lens. However, such zooms are few and far in between, whilst it is almost the norm for primes to have such wide maximum apertures.

There are other advantages too, such as that generally, prime lenses tend to be cheaper and lighter, although these do not hold true across the board. When this is the case, it generally stems from the fact that the construction is less complex, requiring less elements and components, thereby making it cheaper to produce and lighter to carry around.

As you can see, there are advantages of using both kinds of lenses, and choosing amongst the two is generally down to what you value the most. Is versatility more important to you than image quality or wide apertures? Then you probably would be better off with a good quality zoom lens. Are you constantly finding yourself wanting enhanced image quality and better low-light performance? Then you probably need to invest in some good prime lenses. Depending on what you’re after, there are lenses out there ready to play their part…provided, of course, your budget allows for it!

 

 

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Lenses (Part 2) – Focal Lengths

In Part 1, I introduced the theme of “lenses” by providing a definition of what a lens is, and presenting two “concepts” relating to lenses – the “zoom factor” and “focusing“. Today’s entry deals with the former.

For starters, let’s clarify one thing. In photographic terms, the preferred term to refer to the “zoom factor” of a lens is focal length. In other words, a lens’ focal length represents that lens’ ability to make objects appear bigger, smaller or life-size on the camera’s film or sensor. In other words, focal length can also be said to represent the “magnification” properties of the lens.

Focal lengths are denoted in millimeters, “mm“, format, for instance 24mm, 35mm, 50mm, 70mm, etc. The “mm” reflects the “angle of view” of the lens, in other words, how wide or narrow a view can be seen by the lens. The rule is as follows: the smaller the “mm” number, the wider the angle of view is. So for example, a 24mm lens is wider than a 70mm lens. Let me explain…

Recall the “funnel” metaphor used in my previous post… A funnel with a very wide (top) opening will of course “catch” more water if left out in the rain than one with a narrow opening, since it would have a larger surface area. The same is the case with lenses trying to “catch” light. The wider the lens is, the bigger its angle of view (AoV) would be. In practice, it doesn’t mean that wider lenses are in fact physically wider, rather, it means that they are able to modify light that is coming from a wider area in front of them than would be possible with another “narrower” lens. The diagram below should help explain this pictorially.

A comparison of the effect of having a wider/narrow AoV.

A comparison of the effect of having a wider/narrow AoV.

In the diagram, the dotted, red lines represent two light rays entering into the lenses at their widest extremities. You can notice the difference between the first lens, with a 30-degrees AoV and the second one, with a 90-degrees AoV. Of course, the image from the first lens (30) would show a more “zoomed in” image, at the expense of “breadth” in the final image. In fact, only three of the subjects show in the final photo. On the other hand, the second lens (90) would show a more wider view, at the expense of size – there are in fact more subjects showing, but these appear smaller in the photo when compared with the first photo.

As seen in the diagram, the lens focal length will heavily influence what photos you can or cannot take. Suppose for instance you want to shoot a picture of a flying aircraft during an airshow. The higher the plane goes, the smaller it will appear to the naked eye. This implies that we would need to “zoom in” further to get a picture whereby the aircraft is sufficiently large to make the image useable. For such a scenario, a lens with a large focal length would come in handy, for instance a 200mm lens. By way of a practical example, such lenses are used in binoculars to enable you to make far away objects appear larger.

On the other hand, if you want to take a picture of a large group in a small room, you would typically need to be “zoomed out” and as far back from the group as possible, in order not to leave out anyone from the final picture. What you need, here, is a wider angle of view, that is, one with a small focal length, such as 16mm. Real world examples of wide-angle lenses are “peep-holes” in doors.

Since lenses’ focal lengths determine what they are best used for, in photography, lenses are generally “categorised” according to their focal length. Wide-angle Lenses are lenses that offer a wide (duh!) angle of view and typically include anything less than 35mm. Standard or normal lenses offer angles of view that are neither very wide nor very narrow, and typically these include lenses that go from 35mm to around 60mm. Finally, telephoto lenses are those offering a very narrow angle of view, and would include all lenses above 60mm. Their “zoom factor” is inversely proportional to the angle of view, i.e. wide-angle lenses make objects look smaller than they look like with the naked eye, standard lenses approximate the same size as seen, whilst telephoto lenses make objects look bigger than what we can see unaided. Note: In truth, the effective angle of view, i.e. what will actually be seen by the camera’s sensor/film, is also affected by the size of the sensor/film in your camera. This theme will be addressed later – for now, it suffices to know where to “classify” a lens if you only have its focal length to go by.

Finally, you might ask whether all lenses fit in one of the above categories. Incidentally, if a lens can vary its effective focal length (zooms in or out), what does that make it? For that, you’ll have to check back again as that’s the theme of the next post: Lenses (Part 3) – Prime or Zoom?

 

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Lenses (Part 1) – Introduction

By now, if you’ve been following this blog, you should know a bit more about how cameras work, how an exposure is made, and how to juggle between the various exposure modes. We also covered a number of tutorials dealing with the exposure triangle and obtaining a “correct exposure” for our photos. If any of the above is not ringing enough bells in your grey matter, then you can easily go back to the respective tutorials by clicking on the relevant bold text above. If, on the other hand, you wish to delve into another theme, you’re in the right place. This entry will introduce the theme of lenses.

First off, let’s define what a “lens” is, as otherwise the entire entry would be pointless. Some definitions from the world-wide web follow:

  • “a piece of glass (…) with curved sides for concentrating or dispersing light rays“…
  • light-gathering device of a camera”…
  • “a lens focuses (…) the direction of movement of light”.

In layman terms, a lens can thus be said to be an object (typically made of glass) that allows light to enter from one side, and exit from the other in a “modified” way. What the lens does, in fact, is to “bend” the light towards a particular direction. What this does, in photographing terms, is help you “paint” a picture on your film or sensor, (the latter “record” whatever light touches them). To use a metaphor, you can look at the lens as a “funnel” that moves a large body of water (light) from its top part down towards a very narrow exit at its bottom, into a container of your choice (the sensor or film).

In a camera, the lens is needed to make the objects you want to photograph “appear” on the film or sensor. The lens can make the object look bigger, smaller or life-size, depending on the type of lens it is. In layman terms, we often refer to this as the “zoom” factor of the lens. You might be familiar with notices on cameras that say it has a 3x zoom or a 10x zoom. Most also immediately acknowledge that the higher the “zoom” factor, the further away the lens can see, or the bigger an object can be made to appear on the camera film or sensor. So far so good.

A second important point to make is that the picture “painted” by the lens can either be “blurred” or “sharp”. Again in layman terms, the sharper the image looks, the more “recognisable” the object will be. On the other hand, if it is blurred, then the edges that make up the shape of the object would not be well defined, making it harder on the viewer to identify what is being seen. The process of interacting with the lens to make an image appear sharper is referred to as “focusing“. For now, it suffices to know that most cameras carry out focusing on their own if you half-press the shutter button. Other cameras also allow you to focus “manually”, typically by turning a ring on the lens, or pressing dedicated buttons on your camera. What focusing does to the lens is to move it backwards or forwards in small increments until the image becomes sharp on the film or sensor.

So, this introduction presented two concepts: “zoom” and “focusing“. Is knowing this enough for you? If you’re only after day-to-day snaps, it should be enough. However, if you want to take photography more seriously, there’s much more to know about lenses than what we’ve covered in this introduction.

Thus, you can expect more blogs on this theme as follows:

  • Lenses (Part 2) – Focal Lengths
  • Lenses (Part 3) – Prime or Zoom?
  • Lenses (Part 4) – Other Properties
  • Lenses (Part 5) – Specialised Lenses & Tricks

I hope this introduction has piqued your curiosity and I look forward to see you around again for the next posts. Of course, feel free to post comments if you have questions or suggestions!

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Exposure Modes

As promised in my last post on the “correct exposure”, this next post deals with the different “exposure modes” on your camera. You might be in a position where your camera does not feature all of these modes, so if you can’t find one (or more) particular modes on your camera, you might want to check your user manual.

So – what are exposure modes? In brief, we can describe these as the camera setup that you will use to make your exposure, i.e. take your photo. Each setup, or exposure mode, will allow you a different level of control over the camera, depending on what your “priority” is. Let’s go over the options.

1. Automatic: Simple really- automatic means a process that is carried out without human intervention. All you do in Auto-mode is to point and shoot. It’s the simplest of exposure modes and the one where the least amount of effort is needed from the photographer’s side. Its primary advantage is the fact that it frees you from the technical aspects of photography and allows you to focus exclusively on content. Its biggest disadvantage, however, is that losing control over the technical aspects more often than not ends up limiting the photographer’s options to express his/her creativity.

2. Program Mode: In most cameras, this is referred to as P-Mode, you might have a “P” as one of your options in the camera’s control wheel/dial. What P-Mode gives you is a more “involving” auto-mode. What you get, in this mode, is an automatic combination (camera decision) of Shutter Speed and Aperture that should result in the desired exposure level, typically based on the scene’s “correct exposure”. The camera will thus be doing most of the work, but you are allowed an input to influence how dark / bright the final image is through exposure compensation. In P-Mode, you are generally allowed to do the following:

  • Increase/Decrease ISO
  • Introduce Exposure Compensation
  • Shift” the Program, that is, cycle between available sets of Shutter/Aperture. For instance, for a shot taken out in the sun, using ISO 100, f/16 and 1/100″ would result in the same exposure if taken at ISO 100, f/8 and 1/200″, or at f/22 and 1/50″. In some cameras, you are given an option to choose (shift) the most ideal combination of Shutter/Aperture to best suit your creative intent.

3. Aperture Priority: Things are getting interesting – in A-Mode (or Av-Mode in some cameras), you determine the “Aperture Value”, that is what aperture you want to “force” the camera to use. This is why the mode is referred to as aperture priority, as in this mode your priority is the use of a given aperture value irrespective of what the other settings are. Here, the photographer is telling the camera that the important factor is the depth of field required, and as you should recall from one of my earlier posts discussing the exposure triangle, this is determined by the aperture used. In this mode, you determine the following three items, and your camera chooses the appropriate Shutter Speed to give you the exposure required. The controllable elements are:

  • The Aperture Value you want to use.
  • Increasing/Decreasing ISO
  • Introducing Exposure Compensation.

4. Shutter Priority: This is similar to A-Mode, but here your main focus, or priority, is the Shutter Speed. In S-Mode (or Tv-Mode in some cameras), you determine the “Time Value”, that is the length of time you want to “force” the camera to leave the shutter open. Here, the photographer is telling the camera that the important factor is the length of time to be captured, and this is of course determined by your Shutter Speed, as discussed in another of my exposure triangle posts. The photographer using this exposure mode would thus want to concentrate on ensuring absolute control on the degree of “motion” captured above all else. For instance, the emphasis would be to capture light streaks of passing cars, or else to freeze an athlete in mid-air during an acrobatic movement. Both images require a primary focus on using the correct shutter speed. In this mode, you determine the following three items, and your camera chooses the appropriate Aperture Value to give you the exposure required. The controllable elements are:

  • The Shutter Speed or Time Value you want to use
  • Increasing/Decreasing ISO
  • Introducing Exposure Compensation.

 6. Manual: This is the total opposite of the Automatic mode – here you have FULL control over all camera variables – that is, you tell the camera exactly what settings you want used for a given shot. For each image you shoot under M-Mode, you have to make all the important decisions vis-a-vis the Shutter Speed, Aperture, ISO. Before taking the photo, the photographer is “aided” by the exposure gauge in real-time, which tells him/her how bright / dark the image will turn out on the basis of the selected settings. The savvy photographer reads this output and corrects the settings used accordingly, and then makes the exposure. This mode is certainly the one which gives the photographer the greatest creative freedom, but it is also the most complex exposure mode to use.

So – which mode should you use? That depends, of course, on what you’re after. There’s nothing wrong in shooting in Automatic mode or P-mode most of the times, but you might find yourself limited as your technical ability and appreciation grows. Switching to Av-/A- or Tv-/S-Mode should help to give you a greater level of control whilst leaving some decisions to be made by the camera ‘on the fly’. But if this is still not working out for you, M-mode should present you with a carte blanche for you to do whatever you wish.

 

 

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The “Correct Exposure” – Part 3

This post is a continuation in the series of “Correct Exposure” series. We will deal with “exposure compensation” in this post, and it’s best that you’re familiar with what we’ve covered in my earlier tutorials, in particular the first two parts in this series, (click here and here for a refresher, if needed).

On to the subject at hand… what is “exposure compensation”? In simple terms, one can describe exposure compensation as being a man-made “interference” with the camera’s decision-making process. As you might recall from my previous post, the exposure meter is a gauge that tells you the extent of brightness or darkness being recorded in the image, and whether or not your image should be exposed properly, or correctly, given the selected settings (aperture, ISO, shutter). The way the camera “decides” this is to make a computation on the basis of the light that is coming into the camera. This computation is designed in a way to show a “correct exposure” reading if the light coming into the camera produces a particular shade of grey if it is “mixed” together. If the result is a darker grey, the camera indicates that the image is underexposed, and if it’s brighter, it shows an overexposed reading. Where does our interference come in then? How can we introduce exposure compensation, and why would we want to?

For starters, let’s clarify one thing. The camera, on its own and irrespective of how good it is, is no guarantee of a good photo. It is almost insulting to a good photographer to be told “wow, that’s a great photo – you must have a good camera.” Why? Simple really – no camera on its own can take a good picture. You need a photographer, and, preferably, one that knows what he or she’s doing. One area where this really matters is in knowing when the camera’s exposure meter is “lying” to you. In such circumstances, one needs to “compensate” for this lie, by overriding the camera’s decision. Let me present you with an example.

Suppose you’re taking a picture of a dark object placed on a dark background. In such a situation, much of the light coming into the camera is going to be dark. In fact, most times, it will be so dark that if you mix all the light (and colour) coming in, the result would most definitely be a grey that is darker than that required for a “correct exposure”. In such situations, if you DO take a picture based on the camera settings recommended by the exposure meter, your image would end up looking much brighter than what is in truth the real situation. In such situations, you need to tell the camera that you need an underexposed image, and this is done by using the exposure compensation button/dial on your camera. (Most cameras allow you to do it, refer to your camera’s guide for more specific instructions). By telling the camera you need to underexpose, the settings recommended by the camera are adjusted to let less light in, generally resulting in a more “true” photo of the subject than if you had used correct exposure. Check the images below, for instance.

 

correctexp_vs_expcomp

 

The image on the left is what the camera “suggested” would be a correct exposure of a black joypad on a black laptop case. As you can see, there’s very little “black” in the image, despite both items being black in colour. When I took the photo on the left, the exposure meter read “zero”, but does that imply that the camera was right? Would the manufacturer of the joypad be happy that his product is shown as grey when in fact it is black? I doubt that. That’s why I had to use exposure compensation. On the right, I used a 3-stop, negative exposure compensation, and the ISO was lowered to 400, (which is one half, of one half of one half of 3200, the original setting). The image, obviously, turned out much darker, but at least it’s definitely more correct than the “correct exposure”, right?

The same principles apply when photographing a scene or subject that is made up of a lot of white/bright elements – but this time round the exposure compensation should be on the plus side – that is, you need to tell the camera to let in more light so that you end up with the proper exposure needed. Examples include a photo of a white subject on a white table, for instance – with so little grey or dark items showing, the resulting picture would definitely be an underexposed image if you use the camera’s recommended settings. By dialing in some positive exposure compensation, you will get a better image for sure.

So, to recap:

  1. The Correct Exposure is sometimes not ideal – for very dark scenes or very bright scenes you will probably need to use exposure compensation.
  2. When shooting a scene that is predominantly dark, use negative exposure compensation.
  3. When shooting a scene that is predominantly bright, use positive exposure compensation.

Finally, using exposure compensation is only possible when you’re shooting in Aperture Priority, Shutter Priority or Program exposure mode. When using Manual exposure mode, you control all three factors of ISO, Aperture and Shutter Speed and thus need no “compensation” per se – you just have to change the settings you want to get the image exposed to whatever level you want it. Under the other modes however, exposure compensation is used as described above, to tell the camera to over or under expose the image as desired. We’ll cover “exposure modes” more in depth in my next post if you want more detail!

 

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The “Correct Exposure” – Part 2

If you’ve read Part 1, you should now be more familiar with the exposure meter, and how to read the information it displays. In a nutshell, you should know when your current settings will result in a correct exposure (zero-reading), an underexposed image (negative reading) or an overexposed image (positive reading). What we still haven’t covered is how to react to this information, and that is what this Part will address.

This is where the three factors of Shutter Speed, Aperture and ISO come in again. We will be assuming full control over these three factors for the purpose of this blog – this will make understanding the changes being made easier. Our second assumption is that we’re starting off with the following settings:

ISO: 100  / Aperture: f/8.0 / Shutter Speed: 1/100th of a second.

Now – suppose your current settings are showing an exposure meter reading of “-2”. What this is telling you is that if you shoot your image with these settings it will be underexposed, by two (2) stops of light. You might remember from my earlier posts that one “stop” of light less than required means that you need to double the amount of light coming in. Two stops of light less than required means that you need to double the amount of light coming in, twice – that is, two multiplied by two, which is equal to four. If you’re already dreading all the mathematics, fear not. The exposure meter will rescue you. In case you can do the math, you will probably know right away what you need to do, but if you don’t, let’s quickly recap on how to get rid of underexposure and make the image brighter:

  1. Increase your ISO
  2. Slow down your shutter speed
  3. Make your aperture wider.

The next question arises – by how much should I increase the ISO, slow down the shutter or widen the aperture? The answer is in the “-2” signal. Yes, that’s right – we need to let two more stops of light in. You can go about this as follows:

Keeping both shutter and aperture constant, your first option is to increase the ISO; by doubling the ISO from 100 to 200 you would get one more stop of light in, and another stop more would double it again from 200 to 400. By simply raising the ISO from 100 to 400, your reading (from the same scene) should show that you now have the correct exposure. But – suppose you don’t want to increase the ISO, because you want to avoid having more noise in the image (click here for a refresher), what else can you do? In that case, you have to turn to the other options.

A second option is to slow down your shutter speed by two stops – that means having a speed that takes four times more time to close the shutter. Our starting point was 1/100th of a second. If we want twice as much light to come in, the shutter speed must be half that time – so we go down to 1/50th of a second. But that would still be one stop less light than we need – so we need to go down another stop, to 1/25th of a second. With that shutter speed, and the ISO and aperture retained at 100 and f/8.0 respectively, we should get an exposure reading of zero, correct exposure once again! But – do you remember what you risk when doing this? No? You might need to revisit this for more detail. In brief, what a slower shutter speed can lead to is camera shake, resulting in blurry images as a result of movement of the subject, your hands, or both. In our example, the shutter speed required on f/8.0 and ISO 100 would be 1/25th of a second – a relatively slow shutter speed if you’re hand-holding your camera, as it’s difficult to stay perfectly steady enough for that “long”.

This brings us to our third option, which is to open your aperture wider, and let more light inside your camera. Same principle applies here – two (2) more stops of light are needed so the aperture needs to widen from f/8.0 to f/5.6, and that would let in twice as much light. We need more than that though – we need to double the amount of light once again to increase another stop. This means you have to go from f/5.6 to f/4.0. By doing this, we would have let in four times more light and the exposure reading with f/4.0, ISO 100 and 1/100th shutter speed should be zero – correct exposure. What does this do your DoF, however? As discussed in more detail in this post, it makes your depth of field much more “narrow”, meaning you have much less in the image that appears sharp and in focus. Whilst this is not always a bad thing, it might ruin a shot for you if you want front-to-back focusing in your image, for instance when you’re photographing a large group and there’s some distance between the front and the back row of people.

So, the million dollar question arises – what is the right thing to do? The answer is simple really – it depends. It depends on your creative intent, it depends on your equipment limitations, as well as on the type of subject you’re photographing. In the example above, you can have a fourth option, which is to mix and match as needed, for instance, increasing one stop by using a higher ISO and increasing the other stop by widening the aperture. The settings would read ISO 200, f/5.6 and 1/100th of a second. Those settings would still give you a correct exposure, and potentially lead you to a better picture. The trick is in knowing what each change will give and take from your image, and then select accordingly. There’s nothing like practice to learn these things, so it’s time for you to grab your gear and go shoot something. Switch to Manual exposure mode, and enjoy experimenting!!

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The “Correct Exposure” – Part 1

I have talked in the preceding posts about three key factors in taking photographs, or “making an exposure”. These factors were the Shutter Speed, the Aperture and the ISO Sensitivity. For a refresher, you can click on each of these terms to re-load the respective post explaining the term in detail. Otherwise, I’ll assume you’re familiar with what each of these factors is doing to your final image, both in terms of how much light is let in or “detected” by your camera, as well as in terms of the effect it has on your final image.

This post is a first in a series that will look at the three factors again, focusing on how these work together. After all, if you want full control over your final product, you will need to have each of these factors under control, or at least working within parameters that you want these to be. To this end, this post will talk about getting a “correct exposure”, in other words – an image whereby the “right” amount of light has struck the film or sensor. In more layman terms, the image must look neither too dark, nor too bright – think Goldilocks for comparison purposes! How do we go about this? Read on…

First, we need to understand how to “read” our camera, as that will tell us when our settings (choices) will result in a correct exposure. You might have noticed that your camera can display a horizontal line with numbers written from left to right, typically going from say -3 to 3, with zero in the middle. On my Canon 70D (and pretty much on several other Canon DSLR models), the exposure meter looks like this:IMG_3170

That is an important gauge and one that you should be very familiar with if you want your images to look OK after you press the shutter. That gauge is the “exposure meter”. Think of it as a thermometer – instead of detecting heat, however, it detects how much light is going to be registered in the final image. If the camera detects that just the right amount of light is coming in, the meter will read zero (0). If less light is coming in than that needed, the indicator will be on the negative numbers, and vice versa. Your job to get the correct exposure is to get as close (or on) the zero in the meter. In most cases, at least. But let’s forget about the exceptions and the artistic choices – in general terms, that zero is good. But, what exactly is it telling you?

What the zero is saying is the following- the camera’s processor (call it its brain, if you wish) is showing you the result of a very quick computation that mixes together all the light coming in. Given that light carries different colours (in different degrees of brightness), mixing all these up leaves the camera with just one colour – much like when you mix together different paints. The result, with paint, is that you end up with just one colour of paint, and depending on the colours you mix together, that shade is either dark, light, or somewhere in between, right? Same happens with the light coming into the camera. When this is all mixed up, the camera knows that the correct amount of light for a “correct exposure” should result in one predetermined shade of grey – no pun intended here! Depending on how far off the resulting shade is, the exposure meter will show you a number that is either negative (for under-exposed, “dark” images) or  positive (for over-exposed “bright” images), respectively. Therefore, if the grey is darker, you need more light to come in for you to get the correct exposure, and vice versa – if the grey is brighter, you need to reduce the amount of light coming in.

So, the next quetion arises – where do the three factors come in, in all of this? This question will be answered in Part 2 of this series, which will cover how we can manipulate one or more of these factors to get as close to the desired exposure, which, as hinted above, is generally the “correct exposure”, a reading of zero on the exposure meter that is.

So – let’s recap to conclude:

  1. The “Correct Exposure” is based on a calculation done by the camera that should give you an image that looks “right” – that is, neither overly bright nor too dark.
  2. There are circumstances where the “correct exposure” as given by the camera is in fact NOT what you’re after – but this will be discussed in later posts.
  3. An exposure reading on the negative side means your image is under-exposed – you need more light.
  4. An exposure reading on the positive side means your image is over-exposed – you need less light.

See you again for Part 2 and thanks for following my blog!

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Exposure Triangle (Part 4) – ISO Sensitivity

Welcome again to my blog – this is the fourth post in the “Exposure Triangle” Series: you can read the other posts by clicking their title from the main page or clicking here: Part 1, Part 2 or Part 3. This fourth, and final, entry will focus on ISO (or film) sensitivity – in other words, how quick a film or sensor reacts to light coming into the camera. As covered in more detail in my earlier posts, the more sensitive a sensor or film is to light, the quicker it will go from black to white.

For clarity’s sake – keep in mind that every image starts off as a fully black picture until light starts coming in. Colours are registered on the film or sensor during the time the shutter is open. If an excessive amount of light goes into the camera, the part on the sensor or film that received excessive light will be “burnt out” and it registers as white. If all the sensor or film receives excessive light, than all the image simply becomes a totally white rectangle.

Now, it should be simpler to understand sensitivity – it essentially means how quickly your image will transition from a black-image state to one whereby colours are registered and possibly have areas completely burned to white. The higher the ISO, the quicker this process will take place.

That should have already been made clear in my earlier posts – what we didn’t discuss, however, was the trade-off we must keep in mind when using a higher ISO. This trade-off comes in the form of “digital noise” or “grain”. I’ll focus mostly on digital noise, given that most of you are likely using digital cameras anyway. I can go all technical to describe noise, or stick with simple methods – I’ll go for the latter…

So – what is noise? Essentially it can be described as imperfections in the image that are a result of a sensor (or film) that “misread” the real picture out there. The quicker a sensor tries to register light (and colour), the more likely it is that there are “errors” or misreadings in the process. As a result, the higher the ISO goes, the more the final image loses detail, colour accuracy or both. That is the side-effect that higher ISO leads to, and it goes without saying, it’s a bad thing. Check the uploaded image below (you can click on it to enlarge it). This is the same image taken at ISO 100 and ISO 3200. Can you spot the noise and imperfections? Can you spot the loss of detail in the image?

Noise Comparison

So – why would you want to use higher ISO? Well, there are situations where it is inevitable – if light levels are low and you cannot increase them, then more often than not an increase in ISO would be one of the options that you have to consider. How high should you go? That depends, and it depends on what other factors you can and you want to control. But that question, dear readers, will be the theme of the next post – that is, what to change, when, and why. In other words, it’s time to start seeing the exposure triangle in practice now!

Recap of this post:

Higher ISO = Faster transition from Black to White BUT more NOISE.
Lower ISO = Slower transition from Black to White BUT less NOISE.

Thanks and come back later for more!

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Exposure Triangle (Part 3) – Aperture

So far, we’ve talked about the three main elements in the exposure triangle, and looked in more detail into Shutter Speed. Our next stop is with the “Aperture”. If you don’t remember the theory from the first post in this series, you can read the post all over again by reading again the How it’s Made post or the Exposure Triangle introduction. If you don’t feel like reading these articles again, just keep in mind that the Aperture is a variable-diameter hole in a lens-construction, which we can make wider or narrower, depending on whether we need more light (wider) or less light (narrower) to enter the camera when we make our exposure (by pressing the shutter button).

As with the Shutter Speed, which we covered in Part 2 of this series, using a wide or narrower aperture is not just a decision based on how much light we want to get in our image. There is another factor to take into consideration, and that factor is “depth of field”. This post explains this phenomenon, hopefully in simple enough terms for everyone to understand.

So, what is Depth of Field? In simple terms, Depth of Field (DoF) can be defined as referring to the area in front of and behind a subject in focus. The DoF available to you is not something static – it changes on the basis of the Aperture value selected (although not exclusively). As a general rule,  (and assuming you are focusing on a subject), the wider the aperture is opened, the shallower the DoF becomes – that is, you will have a very small area in front of and behind of the subject focused on that also appears in focus, with the rest looking more blurred. On the other hand, the narrower the aperture is, the larger the area in front and behind of the focused subject becomes. Let’s look at an examples, as it’s best this way!

DoFDemo

Above are two photos, side-by-side of the same scene. In both images, focus was locked on the red plant. Notice how the background is clearly more blurred in the wide-aperture shot. The main difference between the two is in fact the result of a different Depth of Field available – in the first image the aperture was f/1.4, a very wide Aperture in photographic terms. The other image is f/8.0, which translates to a difference of five (5) “stops” of light.

Now, this might get technical – what five stops of light implies is that the amount of light coming in at f/1.4 is substantially more than what is coming in at f/8.0. For clarity’s sake – One (1) stop of light more equals to twice as much light coming into the camera, and of course, one (1) stop of light less equals to half as much light coming into the camera. So how much is five-stops of light more? Easy – That’s 2 x 2 x 2 x 2 x 2.  Or for the more mathematical among you, 2 to the power of 5. The answer is 32 – which means that f/1.4 allows 32 times more light into the camera than an aperture of f/8.0. Or else, we can say that f/8.0 allows 1/32 times the amount of light to pass through when compared to f/1.4. The maths is reversible.

If the above lost you, remember the essential stuff:

  1. Wider aperture = More light, Shallow (less) Depth of Field.
  2. Narrow aperture = Less light, Wider (more) Depth of Field.
  3. One (1) “Stop” of light more allows double the amount of light to enter the camera.
  4. One (1) “Stop” of light less allows half the amount of light to enter the camera.

Hope this was informative and leave comments or queries if you have any doubts!

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Exposure Triangle (Part 2) – Shutter Speed

So, you’ve read Part 1 and are eager to learn more, right? That’s great; you’re in the right place dear reader and thanks for visiting again.

Today, you’ll find out more about one of the three key factors discussed in Part 1: Shutter Speed. Specifically, you’ll find out more about the benefits and trade-offs of using a fast or slow Shutter Speed. As demonstrated in Part 1, each of these factors controls how bright or dark your final image will look, but what we didn’t cover in Part 1 is the effect that these changes make on the quality and presentation of the image.

So, what is the effect that changing Shutter Speed introduces? Let’s recap first – in Part 1 we saw how a longer exposure, (that is, one where the shutter stays open for longer), results in a brighter image because more light is let in. If this is what you’re after, then that’s a good thing, right? But suppose for instance you want to photograph a sprinter running from your left to your right. In such a situation, a long exposure (slow shutter) would not be the most recommended way forward, even if we wanted a brighter image. The reason being that the longer the shutter stays open, the more light goes in. What this translates to is a blurry image of everything that is moving in the photograph! Since the sprinter is not static, the camera will register his movement on the film or sensor, and the longer the shutter speed is left open, the more blurred the image would look. In such situations, we need to “freeze motion” if we want to get a sharp picture of the sprinter. To do so, we need to use a fast shutter speed – that is, a very short timeframe for the shutter to open and close down again. Speeds to capture such “action” shots are typically over 1/200th of a second – so remember: action shots typically need motion to be frozen so go for fast shutter speeds.

"Freeze" Movement

“Freeze” Movement

On the other hand, suppose for instance that you want to photograph a seascape and make the sea look like a smooth and milky surface – the way to go is to use a sloooooow shutter speed. And by slow, I mean really slow. Most times, you’d have to use a shutter of at least 1″ (second), but I have been in circumstances where the shutter was set at 30″ or more. It all depends on how much light is available at the time of the shot. And if you think 1″ is a fast time-frame, try holding a camera steady for that long whilst taking a picture, and you’ll realise that your end result would probably be a very blurry image as a result of “camera shake”. (So as a side note to keep in mind with slow shutter speeds – use a tripod or rest your camera against a steady surface). Where else would you want to use a slow-shutter speed? Well, in many situations actually, so long as you know what you’re after. Essentially, slow shutter speeds allow more light into the photo and smoothen movement, rendering anything that moves as a blurry “ghost”. Slow shutter speeds can be used when your camera is steady and you’re photographing a still life or static object, it can be used to shoot fireworks, lightning strikes, seascapes with smooth seas, night landscapes, and anything where light-streaks are desired. If you’re unfamiliar with any of these terms, remember – the Internet is your friend. Search any of the above and you’ll see plenty of examples of photographs that, in most probability, were shot with a slow shutter speed. So the rule here is easy – if you want to capture movement, the shutter must be slow, that is, go for a long-exposure.

Motion Blur

Motion Blur

Of course, I’m sure that this blog might have raised as many questions as it could have answered, so if that’s the case, leave comments and send me your queries and I’d be happy to answer. As a recap, I’ll make it simple to remember:

  1. Action is fast, so go for a fast shutter speed.
  2. Movement takes time, so give it time by selecting a slow shutter speed.

One final comment – don’t take my word for it. Try it out. Make mistakes. Learn by doing – and when you get the hang of it, break the “rules” and see what happens. Sometimes, you’ll find artistic possibilities increase when you leave the rules behind you and make your own! Enjoy experimenting!

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