28 February 2012

Creative Explosion - Perspective

With this, I start a new thread of articles which explore creativity in photography. Until now, most articles penned by me have been restricted to the threads "Let's get technical" and "Blasting the myths" which dealt with laying down the technical fundamentals and clearing the mist around photography resp. Along the way, I believe I have chalked out a sound understanding of photography and laid the foundation for the next generation of posts.

Simplistically speaking, perspective is the spatial distance between objects in the image, that helps you judge the spatial placement/location of the objects and their heights/forms relative to each other. Perspective is affected by the focal-length & subject-to-lens distance combination. You can alter perspective by either moving around or by changing the focal-length of the lens or both.

A wider focal length creates more depth in the image (do not confuse this with dof) and makes the objects look farther away. A tele lens will make the objects look more closely located though in actuality they may not be, thus making the image look flat (less depth). I don't have an image to depict this phenomenon right now so I'll suggest that you visit this page to understand what I am blabbering about :)

How to alter perspective?
I'd say that more than focal length, it is the subject-to-lens distance that determines perspective. After all, change in focal length is an eventuality that follows when you change the distance. Unleash your creativity with perspectives by moving around the subject and clicking from various distances while maintaining the subject's height/width the same across images. You will notice that if you kneel down and click a standing person's pic from a close distance, the person looks gigantic as compared to his/her surroundings. This attributes a larger-than-life or a heroic feel to the persona of the subject. On the other hand, if you click the same subject by standing on a stool and looking down at the subject, he/she appears dwarfed, which creates a sense of suppression.

How perspective is used in movies
This is where the director of photography in movies/sitcoms comes into play. Using a telephoto lens, the director positions the actor far away from the lens. When the director zooms in on the actor through the telephoto lens, it looks like the oncoming truck is right in the actor's tracks and is going to overrun him when in fact, they are on parallel tracks made to look superimposed because of the manipulated perspective (zooming into an object from a distance flattens the perspective, thus making things look closer than they are). Also, when the director wants to show an actress/actor along in a dense area like a forest/garden, he uses a wide angle lens to introduce more depth in terms of perspective into the frame.

So choose a position because of what it does to the perspective; then choose the focal-length/zoom. The next time you click a pic, remember the "perspective" concept and put some thought into the composition of the image. I guarantee that you will like the entire process of photography even more down this road :)

26 February 2012

Let's get technical - Focal Length

If you own or plan to own an SLR camera, you would be exposed to the standard lens nomenclatures which define your lens' capabilities. Consider for example, the kit lens on most cameras - the 18-55 lens. In a Nikon you would come across the 18-55mm VRII f3.5:5.6 lens. In this article, we will discuss what the "mm" in the 18-55mm stands for and how it affects your clicks. Note that the focal length-range is also specified on the lenses of compact digital cameras.

Focal Length
In optics, it is defined as the distance between the vertical center of the focusing lens and the focal point. As can be deduced from the below image, closer the lens comes to the sensor (focal plane), lower the mm figure goes (focal length) and wider the image.

Image Courtesy: dptips-central.com
Crop Factor
Camera bodies are basically of 2 types - full frame and cropped sensor. In case of the latter, a cropping factor comes into play, which is somewhat equivalent to 1.3. So an 18mm wide angle lens on a cropped-sensor body will yield a focal length of 18 x 1.3 = 23.4mm. Hence, if you want to harness the real power of wide angle lenses, no cropped-sensor body will give you that like a full frame body would :)

Classification of lenses
Based on the focal length of the lens, it can be classified under one of the below categories:

  • Prime: this lens has a fixed focal length. For example, the 50mm f1.8 Nikon lens
  • Zoom: any lens that has a range of focal lengths (you can zoom in/out) comes under this classification. For example, 18-55mm f3.5:5.6
  • Wide angle: a lens that provides an eventual focal length of 35mm or below is called a wide-angled lens. Please note that in case of cropped-frame camera sensors (Dx in case of Nikon and APS-C for Canon), presence of the cropping factor means that your 35mm lens is not actually an 35mm lens and hence is not a wide angle lens.
  • Super zoom/telephoto:  with focal lengths beyond 135, a lens can be considered to belong to this segment.
The below snapshot is of a Nikon Dx 18-55mm lens. So the next time you look at a lens, I hope you won't be puzzled about the meaning of these golden colored letters :)
Image Courtesy: kenrockwell.com

Prime Lenses
If you are wondering why one would settle for a prime lens, which is no less expensive than a decent zoom lens, then I can answer that for you. A prime lens has lesser components as compared to a zoom lens (sometimes a zoom lens has upto 35 lens components in it) and hence have less negative effects on the image capture process. Due to multiple components in a zoom lens, the light entering the lens is reduced by the time it reaches the sensor. Also, zoom lenses work best at the mid-range; an 18-200 lens would would best at around 125mm while it would create problems like distortion at the extreme ends of 18 and 200 mm. Also, due to architectural provisions/restrictions, a prime lens can offer you a much wider aperture of 1.2 or 1.8 mm which is almost not possible in zoom lenses (most zoom lenses have a min aperture of f3.5). A focal length of 1.8mm yields a much shallower dof which is awesome for portrait photography.

In this image, do you notice the shallow dof? The face of the guitarist is in focus while even his hands which are quite near to his face are out of focus, not to mention areas farther away (the end of the guitar and the cushions). This was shot with a 35mm f1.8 nikon lens. If i were to shoot this with an 18-55mm even at f.3.5, the dof would have been much deeper and the focussed area would encompass more of the guitar, thus stealing attention from the guitarist and confusing it with the guitar.