Photo 101 - Camera Controls [Archive]

Lee Yuan Sheng

12-21-2004, 06:00 PM

Hi all! Welcome again, to another edition of Photo 101. If you've not read the <a href="http://www.digitalmediathoughts.com/forums/viewtopic.php?t=5156">previous article</a>, now would be a good time to read it, as it serves as a good primer for getting into the mindset for photography, and it'll help to understand where I'm coming from when I say something that seems to go against the conventional wisdom found in many Internet communities. To those who have read the previous article and have nodded their heads and said, I agree, but I still don't understand a lot of things - don't worry! In the following articles I'll discuss a bit on the technical bits in easy to understand terms, on what they do, and how you can use that knowledge to improve your photos. While you might not become an instant professional, with a bit of thinking, you should be able to add some valuable skills to your arsenal of photography knowledge.<!> I'll start by examining the few controls found on digital cameras over the next few articles. Some are new to the digital domain, while others come from cameras hundreds of years old. All will have an effect on your photos, but I must stress that you don't have to bother yourself with most of them if it's too much for you. Take your time to understand how they all work, and feel free to post in each article's respective thread if you need to ask questions! The Zoom Control It might come as a bit of a surprise that I'll start with this control first, instead of aperture and shutter speed controls. The reason is three-fold: not all cameras have manual exposure controls; exposure controls can be automated, but the photographer still has to make a choice with the zoom control; and the zoom control has a far greater effect on photos for most newcomers than the exposure controls. It helps the photographer to frame the photo, and I find that a poorly exposed photo is the lesser of two evils compared to a poorly framed and composed photo. The Basics Zoom lenses are basically lenses in which you can change the focal length of the lens for a given range. These are extremely handy to have, especially when most of us either have a camera that has a fixed lens or don't wish to invest in too many lenses. It wouldn't take a genius to figure out that the wide angle setting allows you to work at a closer distance as well as getting more of the view in (hence wide angle)... <img src="http://www.digitalmediathoughts.com/images/ys-dmt002-01.jpg" /> Taken at a focal length equivalent to 28mm on a 35mm film camera. ... whereas the telephoto end is used to bring distant subjects closer. <img src="http://www.digitalmediathoughts.com/images/ys-dmt002-02.jpg" /> Taken at a focal length equivalent to 400mm on a 35mm film camera. However there a couple of properties associated with focal lengths, one which is directly related, and that is the Field of View (FOV), and one indirectly related, and that is perspective. <PAGEBREAK> Field of View The FOV is a figure given in degrees used to show how much area a lens can capture. Wide angles have large values, since they capture large areas of a scene, while telephotos have a small value, since they capture small areas of a scene. Here's an illustration to give a better idea: <img src="http://www.digitalmediathoughts.com/images/ys-dmt002-05.gif" /> Image not drawn to scale. The area between the blue lines shows the area that is recorded by the lens. Right illustration shows the FOV at a wide angle, left illustration shows the FOV at telephoto. Now, what can we do with this bit of information? Well, for those of us who have been using the zoom control solely to frame our photos, there is another way of changing the size of your subjects, and that is, moving yourself! Combining that with using the zoom setting on the lens means that you can use the wide angle setting and get in close, or use a telephoto setting and step further back and still fill the frame with the subject. Let's take a look at what happens when we do that. <img src="http://www.digitalmediathoughts.com/images/ys-dmt002-03.jpg" /> Taken at a focal length equivalent to 28mm on a 35mm film camera. <img src="http://www.digitalmediathoughts.com/images/ys-dmt002-04.jpg" /> Taken at a focal length equivalent to 105mm on a 35mm film camera. As you can see, while keeping the subject at the same size in the photo, the way the backgrounds are depicted is different. With the wide angle setting, a lot of the background is captured, while using the telephoto setting, very little of the background can be seen. Granted, it won't always work (there's that wall or cliff edge, wildlife won't let you get close, or something might block your view if you stand too far away), but it means you might be able to get a more interesting shot than you'd have had you just stood there and tweaked the zoom control itself. <PAGEBREAK> For instance, getting in close while using a widey gives a good sense of the surroundings the subject is in, since wide angles have great field of view and capture a large area of the scene, and also allows for some pretty breathtaking results. <img src="http://www.digitalmediathoughts.com/images/ys-dmt002-06.jpg" /> Taken at a focal length equivalent to 20mm on a 35mm film camera. A quick reflex shot followed by a quick reflex duck to avoid getting snagged! <img src="http://www.digitalmediathoughts.com/images/ys-dmt002-07.jpg" /> Taken at a focal length equivalent to 20mm on a 35mm film camera. Conversely, since telephotos have a narrow field of view, they capture a small region of the scene, and are great at reducing background clutter. <img src="http://www.digitalmediathoughts.com/images/ys-dmt002-08.jpg" /> <img src="http://www.digitalmediathoughts.com/images/ys-dmt002-09.jpg" /> Both photos taken at a focal length equivalent to 400mm on a 35mm film camera. By virtue of needing a telephoto for bird photography, it helps in getting rid of the usual clutter in a habitat. It can work against you though when you need to get a bird in its environment! Also it's a great way of getting nice results of photos of your latest toys, especially if you have a messy table. <img src="http://www.digitalmediathoughts.com/images/ys-dmt002-10.jpg" /> Ack, messy! <img src="http://www.digitalmediathoughts.com/images/ys-dmt002-11.jpg" /> Much better. The only difference between the two was in using different focal lengths while trying to keep the magnification as close as possible. Hmm, somehow the phone in both photos looks different. Why is that so? Well, the answer lies in the next section, where I'll discuss perspective. <PAGEBREAK> Perspective Perspective is a property that isn't directly related to focal length; however the choice of focal length can affect it. To start off, I'll demonstrate how it affects your photos. <img src="http://www.digitalmediathoughts.com/images/ys-dmt002-12.jpg" /> <img src="http://www.digitalmediathoughts.com/images/ys-dmt002-13.jpg" /> I've kept the wireless mouse as similar in size as possible between the two photos, but note how the radio receiver of the mouse in the photos change. It's like they've moved or changed in size between the shots! Also note the change in the shape of the mouse. Well, what actually is happening is that the camera is capturing the differences in the distance between the objects and the camera. Let's take two objects; one in front of the other, and are a metre apart. Now, if you took a wide angle and stood two metres away from the nearest of two objects, the difference in distance between two objects is fairly significant in relation to the camera, since one object is 2 metres away from the camera and the other 3 metres away from the camera, and thus the image recorded will portray the two objects as being far apart. The close subject-to-camera distance, made possible by the wide angle, has distorted the perspective, and thus has caused what we call perspective distortion. <img src="http://www.digitalmediathoughts.com/images/ys-dmt002-14.gif" /> However, if you stand much further away, say 10 metres away from the nearest object, and framed them the exact same way as above, thus necessitating a telephoto lens, the image recorded will show them to be quite close together. The reason now is that one object is 10 metres from the camera, and the other 11 metres. Since the difference between 10 metres and 11 metres is less significant, the image recorded will reflect this, and thus, the two objects will look closer to each other than they really are. This telephoto and camera-to-subject distance combination too has distorted the perspective, and as it has made objects look closer together than what they really are, we call this effect perspective compression. <img src="http://www.digitalmediathoughts.com/images/ys-dmt002-15.gif" /> Since many make the mistake of saying the choice of focal length causes perspective changes, I'll mention it again: the actual cause in the different perspectives is in the distance between your camera and your subject, but the choice of your focal length, hence zoom setting, means the perspective of your shot will be affected since we all tend to stand closer when using wide zoom settings and stand further away when using telephoto zoom settings. (Incidentally, that's how the Hitchcock Zoom in cinematography is done; by changing the focal length while keeping the subject at the same size.) So, at wide angles, we tend to get pictures that exaggerate the relationship of distances between the various elements in the photo, and at telephoto lengths, we tend to get pictures to flatten the relationship of distances instead. Again, what can we do with this tidbit of information? <PAGEBREAK> Well, for starters, if you take a wide-angle setting and take a photo of your loved ones at a really close range, I don't think they're going to be <a href="http://bj.canon.co.jp/image/photoshooting/technihsc/camerafunction/camerafunction02_ph10.jpg">very</a> <a href="http://www.acdsystems.com/NR/rdonlyres/elwkfn3iwonu3t3yfkhzezbjcgwb4ye2sy32i4ahdsybhicvib3kml5g2z5jhcc3trteyn6sb2uxbwezscqbr43mkbc/lens-perspective01-small.jpg">impressed</a>. There'll be times where you'll want to play on the perspectives to get interesting images. Sometimes you want to exaggerate them: <img src="http://www.digitalmediathoughts.com/images/ys-dmt002-16.jpg" /> Taken at a focal length equivalent to 20mm on a 35mm film camera. I decided to highlight the towering aspects of the trees, so I chose to use the wider 20mm instead of the 28mm in my kit. Sometimes you want to flatten them: <img src="http://www.digitalmediathoughts.com/images/ys-dmt002-17.jpg" /> Taken at a focal length equivalent to 400mm on a 35mm film camera. The distance from the closet meerkat to the farthest was about a metre, but by using a long telephoto it looks like they're almost side by side. And other times you just want it to look natural: <img src="http://www.digitalmediathoughts.com/images/ys-dmt002-18.jpg" /> Taken at a focal length equivalent to 50mm on a 35mm film camera. There're a lot of things you can do with just changing the perspectives, so do experiment! <PAGEBREAK> A Small Caution: While I have mentioned possible uses for the zoom settings at each end, it doesn't mean you have to strictly follow them all the time. There's this misconception that wide angles are landscape lenses and short telephotos are portraiture lenses; it's simply not true. Here is an example of a boring landscape taken with a wide angle lens: <img src="http://www.digitalmediathoughts.com/images/ys-dmt002-19.jpg" /> Yawn. Yet another boring wide angle landscape photo. What is important is that you should use whatever that fulfills your vision, be it good or bad. If it's good, great, you've picked up something to add to your toolbox of photography skills, and if it's bad, well, like I said in my previous article, learn from your mistakes and try again. Whatever it is, don't end up as a too formulaic photographer! In Conclusion Well, that was quite a bit for just one control, but it is a fairly important one, as you can see; the zoom control has a direct and indirect influence on two ways in how a scene is portrayed in a photo. Having a better understanding of these influences will increase the options you have at your disposal the next time you approach a photography opportunity, and I hope you will get great results in your photographs!