Monday, April 30, 2012

Telephoto


Here is a great example of what effect a Telephoto lens adds to photography. Everyone who watches the news on TV, especially a report from a war correspondent, or even more commonly, a clip from a sportscast has seen this, so it's pretty common and boring, but if you're a budding photographer, especially  one with a super long zoom on your camera, this is for you. This shot will show extremely well how to put your super-zoom to best use (or more importantly I think, how to avoid it's mis-use).

I wasn't using a "zoom" lens here, just as a side note. I was using a fixed length telephoto lens of 200mm focal length (one of my newest 20 dollar acquisitions - a Pentax SMC Takumar 1:4-200). With my 1.6 crop-factor Canon, this is equivalent to 200mm X 1.6 = 320mm... another example of how easy "camera math" really is! For those of you with long-zoom compacts, that's the same as having a "12X Zoom" extended all the way.

So, now that we've got all the math out of the way, let's look at the picture. The most obvious clue that this is a really long-zoom picture is how all those telephone poles are so close together. This picture actually covers three city blocks in distance! The red awning and the couple walking on the right is located at a street corner that is three blocks away from the Sackville Train Station seen on the left. Yet in spite of that, the detail in the background is about equal to that in the foreground. This is called "distance compression", and it is the most important distortion factor of telephoto (or "long zoom") lenses.

In this photo, the effect works well - you can almost imagine a news clip of a military vehicle lumbering along a road in the Iraq dessert. The repeating poles also add an optical illusion of motion here. The long-zoom is what allows news photographers to get close to the action while remaining  a very safe distance away, and the distance compression is the distortion from reality that results.

If you really want to attain distance compression distortion in a picture, this would be a rare thing. The reason it works here is because of the motion effect created by having three blocks worth of telephone poles receding into the background of the moving truck. But be careful - if you're not yet used to distance compression and you have a super-zoom on your camera, you might think that you're composing a great shot of a subject by zooming in on it from a great distance, but when you look at the final product, you'll find that everything within 1 Kilometre distance has the same emphasis as your subject, which often looks weird and distracting. I now own three super long lenses, because of my fortune of getting them so cheap, but in general, I have little use for them, because in general, I do not shoot news or sports. I think this is also the reason why the Classifieds have so many long-zoom lenses for sale... people soon discover that you get much better shots by getting up close and personal, rather than getting lazy and making your camera cover the distance.

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