Why Zooming With a Lens and With Your Feet Produce Different Images

You will often hear proponents of prime lenses tell fans of zoom lenses to simply "zoom with their feet." However, zooming with your feet will not produce the same image as zooming with your lens, and understanding the difference will give you lots of creative capabilities for taking more powerful images. This helpful video will show you the difference and the impact it will have on your photos.

Coming to you from Mark Wallace with Adorama TV, this great video shows the difference between zooming with your feet by getting closer with a shorter focal length and zooming with a lens by using a longer focal length. This difference is often leveraged by photographers to create telephoto compression (or in the opposite direction to exaggerate perspective). For example, a landscape photographer might use a 200mm lens to bring a mountain range closer together and create the illusion of them almost piling on top of each other. On the other hand, a wide angle lens might be used up close to exaggerate the relative distance between two objects. It is an important creative concept that has a significant impact on your images, so be sure to give the video above a watch for the full rundown from Wallace! 

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9 Comments

John Adams's picture

One word is enough: COMPRESSION.

John Adams's picture

No you have it wrong. Zooming in is COMPRESSION, not perspective. Learn the difference.

Deleted Account's picture

Perspective is the term given to the geometric relation of things in one's field of view. Compression is the name that we have arbitrarily given to the artifact of perspective that comes from the observer being at a relatively greater distance from a grouping of objects, such that their angular subtenses are approximately equal, i.e. the perspective of the observer is that the objects when foreshortened into two dimensions appear to the observer to be close together and of the same size. They are not two different things. The same thing happens with your eyeballs as you get closer and further from a grouping of objects, with the same focal length. We notice it more with telephoto lenses because we can fill the field of view. The same is true of "distortion" with wide angle lenses. Both distortion and compression are merely descriptions of the effect of perspective on our perception. I thought your reply to be unnecessarily harsh given that it was also not really correct.

John Adams's picture

You're absolutely incorrect. There is a very good reason for the term "compression" when zooming in on things. It is absolutely different from a perspective. Your perspective is simply your position in a three dimensional world in relation to an object, with or without optical lens compression. Both things are completely different.

Deleted Account's picture

Well I am not going to argue with you. But the optical physics is quite simple. I have a Ph.D in engineering and worked on electro-optical systems for 35 years. I know of where I speak. If you take a 50 mm lens at the same distance as a 200 mm lens, and then crop it in to the same field of view, you will get the exact same picture. The only difference in the original images is the total field of view, not the rendering of any part of the field of view. The "compression" effect comes from distance from observer to object, regardless of focal length. It is simple lens geometry and it is based on 3-d to 2-d angular projection, which is perspective.

I you zoom the 50 mm with your feet to get the same frame fill, you have changed your perspective, and thus the angular projection gives more differentiation in perceived size/orientation and relationship, so it will look different, i.e. not "compressed". Again because the perspective is different.

If you don't want to believe me, here is an easy to understand article from a completely independent source:

https://nofilmschool.com/2018/05/lens-compression-myth-whats-really-happ...

In the interest of full disclosure, I should state that this is not true for extreme macro photography, in which the focus distance is the same as the focal length of the system. In this case, the rays at the outer circumference of the lens have to be bent to a different angle dependent upon focal length, so different focal lengths will render the image slightly differently. In reality, this is due to the fact that the outer circumference of the lenses actually have different perspective. In the extreme, hypercentric systems can see behind objects, but these are gloriously strange systems. Normal photography, in which the minimum focus distance is multiples of focal length, needn't concern itself with these esoteric cases.

John Adams's picture

>distortion.

I have watched this video and I think they are not entirely correct in the sense that lens compression should be called perspective compression. It's entirely obvious that everything around you is a state of perspective, this isn't up to a debate. This is just masturbation with words that doesn't prove nor disproves anything.

Deleted Account's picture

Okay. If thinking in terms of lens compression makes it easier for you and helps your photography, then sally forth and go in peace. As an aesthetic concept, 'compression and distortion' are simple and useful mnemonics to help one think about how to compose a shot and make a lens choice. I just had an objection to you being uncivil to Mr. Bugnone when he was correct. I, like Don Quixote, am on a mission to civilize. My interest was merely to educate, not to argue.

John Adams's picture

Okay thank you but I just don't agree that perspective is what compresses your image. I mean everything all the time, everywhere, is in perspective in relation to your field of view. We all know that. It's not like I just discovered that perspective exists. When I walk around with my eyes in my head why isn't everything I see from my perspective compressed? It isn't right, I need a telephoto lens to do that or some kind of telephoto eyes :)