Many of us photographers in the Seattle area have an obsession with capturing a photo of the moon and the Space Needle. I have seen some spectacular photos. I have also seen critics suggest that the photos are "fakes." Some claim them to be composites. Some say things like, "the photographer telelphotoed the shot." I hope to show here that the photos are real. And while a telephoto lens helps out, it is not the reason or cause of the effect.
It's Not The Lens
First, let's talk about "telephoto compression." A common expression about a situation that does not exist. The focal length of a lens determines its power or magnification. A longer lens magnifies more than a shorter lens. And it magnifies everything in the scene equally. If the camera remains in the same position, the size relationship between the objects in the scene remains the same. If the focal length is 4x longer (for example switching from a 50mm to a 200mm) everything is 4x larger. No compression takes place. You can easily demonstrate this by taking a photo with the 50mm lens and then from the same spot switch and take a photo with the 200mm lens. Take both photos into your computer and crop them the same. You will see that the perspective is the same. No compression!
It's The Distance
Now, if you were to take a photo with the 50mm lens and then switch to the 200mm lens and move the camera back to get the subject to be the same size as it was with the 50mm then you will see a compressed scene. But switch back to the 50mm at the 200mm distance and compare and see the same perspective. It's the distance, not the focal length, that creates the compressed look.
From the same camera position the area of the scene that is common to all focal lengths shows the same perspective. Shorter lenses show more of the scene, while longer lenses come in tighter. A longer lens is effectively cropping the image in-camera. The longer/telephoto lens doesn't compress the scene, it just enlarges the area that was compressed by distance.
The Incredible Shrinking Space Needle
My friend Rebekah posted this on Facebook, “I’m kind of obsessed with this optical illusion from the window of my new floor at work. When I first get off the elevator the Space Needle looks ginormous, and as I walk towards the window it gets tiny. My teams might be questioning my sanity as I keep walking back and forth going “whooaaah…”
My response to her was, "May I borrow these to use when discussing perspective? It is all relative. The closer you are to your subject, the smaller the background elements will appear. The further you are from your subject, the larger the background elements will appear. In this case, the 'subject' is actually the window. While at the elevator, the window and the space needle are relatively closer to each other than to you. But as you approach the window the window gets progressively closer and larger, while the space needle remains the same distance and size.
"I am assuming that in the first photo, with the large needle you had to crop in quite a bit on the photo or that you had to use a longer focal length lens to fill the frame.”
Her response, "You're welcome to use this John! You can even come by my office for a better quality version sometime if you want . You're right that I had to zoom in on the first one... and I was just using my iPhone so the quality isn't as good as if you used a lens for it."
So, thank you, Rebekah. Here are my photos after taking her up on her offer to have me visit her office.
All three images were made with a 24mm lens, but from three different distances from the window. The first one, as you enter the office is around 20 meters from the window and the Space Needle fills the window frame. The second image is taken from about 5 meters away from the window and we see that the Space Needle seems smaller. The third image is taken right at the window, so the window frame doesn’t appear in the photograph.
However, if you look more closely, you will see that the Space Needle is actually the same size in all three images. It is the window frame that has gotten larger as I got physically closer to it.
As you walk out of the elevator into the hallway you see the space needle and your mind “zooms” in on it, with the rest of the office falling off into the periphery. We take for granted what we see. The Space Needle looms large, filling the window. Our brain conveniently dismisses the rest of the office.
Our camera, on the other hand, doesn’t have a brain. It just records what is actually in front of it. When we look at the first photograph we do notice all the periphery. But we also have the ability to “zoom in” on the photograph taken near the elevator and concentrate on the Space Needle via one of two ways. First, we can take the photo made with the shorter focal length lens into Photoshop and crop in to eliminate the distracting peripheral elements. Or we can take another photo using a longer focal length lens to come in closer by magnifying the scene. Notice that either way, cropping or using a longer lens, the relationship between the elements of the scene (the perspective) remains the same. The cropped version has greater depth of field, but at a tremendous loss of quality as a result of the center portion of the image having to be enlarged. The telephoto version has less depth of field (look at the lamps and furniture inside the office), but has greater image quality. The same “compression” of the scene is recognizable in the area of the scene common to both the 24mm and the 105mm images, showing that it is not the lens that causes the compression, but rather the distance between the camera and the subjects.
In the case of the first set of images above, the Space Needle remained relatively the same distance from the camera while the camera to window distance changed. Let’s say that in the first photograph the Space Needle was 800 meters away and the window was 20 meters away from the camera. In the second photograph the window was now 5 meters from the camera and thereby four times as large as when 20 meters away. But the Space Needle is now 785 meters instead of 800 meters away, an insignificant change in the distance. So while the window grew dramatically in size as we approached it, the Space Needle remained the same size.
In this case, with the camera remaining at a stationary distance from the window and space needle we actually zoomed in, which has the same effect as cropping. In a zoom, the relationship between the elements in the scene remain the same, they all get larger (zooming in) or all get smaller (zooming out) at the same rate. This is not a natural way to look at things. And this brings me to the the saying that photographers often here, “you should zoom with your feet, not with your lens.”
I have a problem with this statement. I totally agree with the concept that you should move around your subject—get closer, move back, go higher or lower, move left or right—to give a different perspective. But you cannot zoom with your feet. Zooming assumes a static camera position and the same rate of change in the size of all the elements in the scene. As soon as you move your feet the relationship between elements in the scene starts changing. You are no longer zooming, but, to borrow a term from the film industry, you are making a dolly move. This is a much more natural movement. When you move in closer to your subject the items behind your subject will get smaller. And consequently when you move back away from your subject the items behind your subject will get larger.
This may sound counter-intuitive at first, so let’s go over that again. Basically, the closer you are to your main subject when making a photograph, the smaller the background elements are going to appear. As you move back, away from your main subject, the background elements will look larger (scene compression). It does not matter what focal length lens you use. People throw around the term “telephoto compression” because this is more noticeable in photos made with long lenses. But the reason is not the lens itself, but the situations when longer lenses are used. We tend to use long lenses to magnify a part of a scene when we photograph at longer distances from our subjects.
As illustrated in the third set of images above, if you crop in or if you use a longer lens from the same camera position the compression in the area of the scene that is common to both the cropped short lens photo and the uncropped long lens photo will be exactly the same. Quality of the image will be very different, but the perspective will be the same.
In these particular photographs the subject is actually the window in the office. Let’s look at them again, in reverse. 
Now we are starting at the window. The window is too close and too large to be in the frame of the photograph. By stepping back about 5 meters we can now see the window as well as the Space Needle. Notice that the window got smaller, but the needle remained the same size. Then we move back to 20 meters and now the window is even smaller in the frame and now about the same size as the Space Needle (which is still the same size it was in the first photo). By moving back, away from our subject (the window), we have made the background element (the Space Needle) look larger.
Somewhere up above I mentioned the film term "dolly." There is a move in film called a dolly/zoom, sometimes also called the Hitchcock Effect. Here the camera is moved towards or away from the subject while the lens is simultaneously zoomed at the same speed. The effect can be shocking or subtle. One of the more subtle uses of a Dolly Zoom is in the film Goodfellas with Robert Deniro and Ray Liotta sitting across a table in a diner. As they are talking to each other the camera is rolled (dollied) back away from the actors and the lens is zoomed in so that the actors remain the same size but the scene going on in the background across the street from the diner gets larger. You can find this clip on YouTube .
So, what about those moon photos! We will take a shot at the moon in Part 2.