Is Lens Compression Fact or Fiction?

Photography can be confusing. I get it. I am not the sharpest knife in the drawer. Because of this, at times it helps us to actually put some of these theories and myths to the test. One of these myths is the concept of compression and, with it, parallax.

This gets confusing to me as I am sure it does for some of you. Of course, there will always be the joker that knows everything and needs to let you know he knows everything. So this post is for the average, humble photographer that can’t seem to get their head wrapped around this concept of compression, distortion, and parallax. Let’s test this out.

Definitions of the Terms

But first, let’s define some terms.

Lens compression is the idea that when you use a telephoto lens things in the background of the image will appear larger and compressed closer to the foreground. It’s a bit like the warning of your side-view mirrors on your car. An example would be if you have a row of pillars coming towards the camera. The pillars will not only appear larger but the distance between these pillars will seem to be more compressed when using a larger focal length lens.

Parallax is the apparent displacement of the position of the foreground with the background in an image. As an example, to use our line of pillars, the pillars in the background in relation to the pillars in the foreground shift to become visible. So the question would be: when you shoot an image with a telephoto lens and then change to a wide-angle lens, will the parallax effect be seen?

These two concepts are linked. To the point, you really can’t talk about one without talking about the other. So, let’s look at parallax first before we move on to compression.

Testing for Parallax

To test parallax I went out to my friendly neighborhood fishing village and made a series of photos of the Floating Mosque (it really isn’t floating, it rests on pillars over the sea). I stood in one location and shot a series of photos of the mosque focusing on the same spot in each photo.

To make the photos I used two lenses, the Fuji XF 50-140mm and my Fuji XF 10-24mm. I took five or six photos at different focal lengths just in case I need them. But in the end, I only needed one image shot wide and one image shot with a relatively long focal length to uncover this mystery.

Lens: XF50-140mm. Focal Length: 135mm. (35mm Equiv): 202 mm
Lens: XF10-24mm. Focal Length: 24 mm. (35mm Equiv): 36 mm

I then took these images and examined them for any signs of parallax. What was the verdict?

What we see is there is no parallax effect between lenses. But this will only happen if the photographer remains in the exact same spot. Why is this? Because the focal length does not change our relation to the subject. To do that we physically have to move. It’s basic physics, but we fool ourselves all the time to think there is a perspective shift between lenses used.

The only way you will see any change between the lenses we use and a shift of position between the foreground and background is when the photographer changes position nearer or farther from the subject.

Below are the same two images from above. The difference is I enlarged (a bazillion times) and cropped the 24mm photo to the same scale as the 140mm. You will now be able to see there is virtually no parallax at all. Nor is the compression any different between the two images.

135mm (202mm in 35mm terms)
24mm (36mm in 35mm terms) cropped

Testing for Lens Compression

Now, let’s move on to lens compression. I hear photographers say how a telephoto will give you more lens compression than a wide-angle lens. But I think you will see that the term “lens compression” is a bit of a misnomer. We do see compression when we use a telephoto, no doubt. But it has more to do with how, or shall I say where, we use the lens than the lens itself.

We attribute the compression to the lens when in fact it is actually due to our physical distance from the subject. As in the photos above, where I photographed the same scene with two lenses of different focal lengths but never changed positions, there was no compression, or better put, the compression was the same.

Where we see compression is when the photographer keeps the subject in relatively the same position in the frame between lens choices. Look at the images of the statue below. I tried as best I could to keep the upper body of the warrior in relatively the same position in each photo. Because I moved closer to the subject (changed spots) each time we finally see parallax and we see compression.

Photos captured (from left to right) 10mm, 35mm, 50mm, and 140mm. (15mm, 53mm, 75mm, and 210mm, respectively, in 35mm terms).

Now look at this photo:

Lens: XF10-24mm, Focal Length: 10 mm, (35mm Equiv): 15 mm, Lens Aperture: f/4.0

Now we see something else happening. Now we see lens distortion. Here you can see the distortion of the warrior’s lance and his face. This type of distortion gets worse with the use of a wide-angle lens and the closer in proximity you get to the subject the more exaggerated this distortion becomes. But that is for another article on another day.

As for compression, we can clearly see background objects appearing closer when I readjusted my position to keep the subject (the warrior) framed in the relatively same position in the frame using the telephoto.

‘Lens Compression’ is Due to Distance, Not Focal Length

Actually, “focal compression” might be a better choice of words for this effect. But let’s face it, I am not going to change the industry’s use of this term. So let’s just say, lens compression happens in proportion to the distance from your subject and that it is more pronounced or easily seen in the use of a telephoto lens.

The reason lens compression is associated with telephoto lenses is due to the fact that a longer focal length naturally causes photographers to move further from their subject, thereby increasing distance and lens compression. It is the distance that directly compresses the scene, not the lens.

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