lens perspective

Perspective (yet again!)

One word…, “DISTANCE”

Here we go again! Let’s start with the lesson drilled in my my college photography professor, Ed Sculley:

 
Pick the camera to subject distance that gives the perspective you want, then select the focal length lens to fill the frame appropriately
— Ed Sculley
 

Wise words! They harken back to a favorite Ansel Adams quote:

 
A good photograph is knowing where to stand
— Ansel Adams
 

For this post I define perspective as the relationship between the elements in a photograph. In a portrait that would be the size of the nose compared to the eyes compared to the ears, compared to the background. In an outdoor scene it might be the tree in the front yard compared to the house compared to the mountains in the distance.

Let’s start with the portrait. All too often I see articles claiming to show how lenses affect the look of a face. You’ve seen them, too. They show a photo made with a short wide angle lens where the face narrow with a big nose and then a series of photos with longer lenses where the face is flatter and flatter as the lenses get longer and longer. But what they don’t tell you is that not only did they change the lenses, but they also moved the camera. And moving the camera is what caused the changes in the looks. The lens just determines what is in the frame at the various distances.

Think of changing lenses as cropping your image in camera. All lenses show the same perspective at the same camera to subject distance. By putting on a longer lens you are magnifying the central area of the frame. If you don’t move the camera everything in the photo scales equally—the perspective remains the same. Let’s imagine a scene where you have a person in front of a window. with a tree outside. If you switch from a 50mm lens to a 100mm lens everything in the scene (the person, the window and the tree) all become twice as large in the frame, but their sizes relative to each other remain the same. If, on the other hand, you move the camera closer a more natural change occurs. The person in the front gets larger while the elements in the background appear smaller. The act of moving in might require us to change to a shorter lens to fit everything in the frame. But it isn’t the changing of the lens that altered the perspective, the move did that. The lens just determined what would fit into the frame.

Start with our view of our subject by a window with a tree outside as seen with a normal lens.

Start with our view of our subject by a window with a tree outside as seen with a normal lens.

Leaving the camera in the same position, a longer lens magnifies everything in the scene equally. But the relationship between objects remains the same.

Leaving the camera in the same position, a longer lens magnifies everything in the scene equally. But the relationship between objects remains the same.

If instead of changing lenses we move the camera closer the subject in front gets larger while the background elements appear smaller. The size relationships all change.

If instead of changing lenses we move the camera closer the subject in front gets larger while the background elements appear smaller. The size relationships all change.

 
The closer the camera is to your subject the smaller the background elements will appear
— John Cornicello
 

As you move back away from your subject the objects in the background get larger in relation to the size of the subject—compressing the scene. Longer lenses force you to move back, leading one to think that it is the lens that is doing the compression. In reality it was moving back that compressed the scene. The longer lens magnified the subject to fill the frame better.

This is why you cannot “zoom with your feet.” Cinematographers tend to use prime lenses and move the camera (dolly in or out) to change the size relations in the frame. A zoom tempts you to keep the camera in one position and zoom to change size. But this is an unnatural look. In our 3-D world perspective changes as we move closer to and further from the objects around us. In a moving image a zoom instead of a dolly move just doesn’t quite look or feel right.

Don’t take this to mean I am against zoom lenses. Quite the opposite. I think they are very useful, especially in still photography, if used correctly. With a zoom lens you can position your camera exactly where you want it and then fine tune the framing to avoid or limit the cropping that you would need to do in post-processing.

And I do encourage you to move your feet. Step to the left or the right. Take a step in or back. Get down on the ground or up on a ladder. These all give you a different perspective. And you can do this with a prime lens or a zoom lens.

This all started a few days ago when my wife showed me this “great demonstration of lenses” in an Instagram post. I felt bad that I had to tell her it was all wrong. So I quickly made these crude illustrations to clarify things. The video on the left shows photos made with the same 16mm lens at various distances and resized to show how the drawing of the face is affected by the camera to subject distance. In the video on the right the camera remained stationary while the lenses were changed to show that the lens doesn’t alter the drawing of the face.

Here are side-by-side comparisons to help get the point across. The images in the first set were all made with a 24mm lens at different camera to subject distances and resized to maintain the same head size.

24mm lens at various distances

24mm lens at various distances

This images in this next set were all taken from the same distance with different focal length lenses and resized to maintain the same head size.

Different lenses from the same distance show the same perspective

Different lenses from the same distance show the same perspective

One more example to show that telephoto compression is a fallacy. Here we have a scene from a railroad station in Kyoto, Japan photographed with four different focal lengths from 18mm to 400mm. As you can see, the area of the scene that is common to all four images (in the magenta box) is exactly the same. The longer lens just isolates the central area, but the perspective is the same as in the wide angle photo. If you were able to enlarge the 18mm photo to match the size of the 400mm photo the quality would be terrible, but the compression (perspective) would be the same.

For more entertainment, please visit my post about the Incredible Shrinking Space Needle.

Well, enough early morning rambling for now. I hope you got something useful out of this.

Until next time, Cheers!
John
(Oh, yeah, please buy my book! THANKS!)

Perspective (AGAIN!)

Here we go again!

First thing. Distortion and perspective are not the same. In lenses "distortion" is defined as an aberration where the corners of an image projected by the lens pull outward (pincushion) or the corners pull inwards (barrel). Distortion is independent of focal length. It is controlled in the design of the lens and is affected by the placement of lens elements and the placement of the aperture diaphragm inside the lens. It cannot be corrected by anything you do with your camera. It is built into the lens. Post-processing software often provides tools to help correct distortion. Most lenses are corrected as much as they can be for distortion. Rectilinear lenses attempt to keep straight lines straight across the image plane. Wide angle rectilinear lenses do have a characteristic of stretching objects at the edges of the frame. this comes from trying to fit a very wide almost unlimited view onto a fixed size image sensor (or film). This is usually most noticeable when the camera is in very close to the subject. The cure for this stretching is to use a fisheye lens! But that introduces a whole set of other issues for another discussion.

An interesting point about this "wide angle distortion" is that it only affects 3-dimensional subjects. Let's take an example of a tennis ball photographed with a wide angle rectilinear lens. If the tennis ball is in the middle of the frame it appears perfectly round. If it is move off to a corner of the frame you can see that it gets stretched out into an oblong shape. However, if you make a print of the centered ball and put the print in the corner of the frame in place of the actual tennis ball the ball in the print remains round. 

2-tennis-balls.jpg
3-tennis-balls.jpg

But enough of that, it is just a distraction from what I want to talk about. If you want more information about lens distortion I invite you to take a look at this article from Zeiss

On to Perspective!

I seem to be on a perpetual quest to help photographers understand the affect on perspective caused by camera to subject distance and how it is not related to focal length. Perspective here is defined as the relationship between objects in the scene. Objects closer to the camera appear larger than objects farther away. Objects closer to the camera also appear farther apart from each other than do the object farther away. It doesn't matter what focal length lens you use. All lenses show the same perspective from the same camera position.

So, you ask, what about telephoto compression? Isn't that caused by using a long lens? No! Go back to the previous paragraph. Looking at it from the other direction, it says that objects further away from the camera appear to be closer to each other than objects closer to the camera. Focal length doesn't affect that. Focal length affects magnification and the field of view (how much of the scene fits into the frame). You don't even need a camera to see how this works. Go someplace that has a series of similar items spaced out evenly in front of you. Maybe a long stretch of road with street lamps or something like that. Stand a foot or two from the first object and notice the distance to the second object. Pretty far apart. Now concentrate on the 8th and 9th objects. They look closer together and more similar in size. There is your compression. Of course, you took your camera with you anyway. So put the camera on a tripod and take a photo with a short lens and another photo with a longer lens.

Take those two photos into your favorite photo editor and crop the photo taken with the short lens to match the image taken with the long lens. You will see that for the area of the photo that is common to both focal lengths the perspective (and compression) are the same. When we want to show this compression we, of course, will pick a longer focal length lens as cropping optically maintains image quality as opposed to digital cropping or making an extreme enlargement from film. Changing the lens just changed the magnification, though, not the perspective.

Here is a set of images from a train station in Kyoto, Japan. All were made from the same camera position at various focal lengths rom 18mm to 400mm.  Notice that perspective in the area outlined in purple, which is common to all of the photos, remains the same.

People, too!

The same thing happens in our portrait work. From the same camera position your subject will look the same (except for size) if photographed with a 10mm lens or a 100mm lens. Take a look at the following image. It shows a studio scene made with a 10mm lens on a full frame (35mm) digital camera. The camera is fixed on a tripod at 58 inches from the mannequin. If you drag the slider from the right side to the left you will reveal an image taken with a 100mm lens and resized down to match the size from the 10mm lens. Notice that the perspective on the face is exactly the same from both lenses, despite the vast difference in focal length.

Here we see the same setup photographed with an 85mm lens next to the setup photographed with the 10mm lens. Again, the perspective is the same.

85mm lens, not cropped

85mm lens, not cropped

10mm lens, cropped 

10mm lens, cropped 

Here is a set of photos made with the following lenses: 100mm, 85mm, 50mm, 35mm, 24mm, 20mm, 16mm, 15mm fisheye, and 10mm. Despite the extreme barrel distortion bending everything but the center of the image, even the 15mm fisheye shows the same perspective on the face (see below).

100mm, 85mm, 50mm, 35mm, 24mm, 20mm, 15mm, and 10mm from the same camera position 58 inches from the subject

Here are the 85mm and the 15mm fisheye cropped to the same framing...

85mm full frame

85mm full frame

15mm fisheye cropped

15mm fisheye cropped

For another take on this, please visit my previous post about the Incredible Shrinking Space Needle that is an excerpted from my book, Anatomy of a Studio Portrait, which is available on Amazon

And a quiz of sorts... 

This is also from Anatomy of a Studio Portrait.Can you tell what focal length lens was used for each of the above images?

From left to right, top to bottom: 200mm, 135mm, 105mm, 100mm, 70mm, 57mm, 38mm, and 24mm.

 

 

To round things out, all of the photos in this set were made with the same 24mm lens, but the camera to subject distance was changed attempting to maintain the same size head in each image. Distances are 20 inches, 24 inchces, 28 inches, 39 inches, 51 inches, and 60 inches.


What about full frame vs crop frame?

Easy enough. Same setup with two cameras. Full frame (Canon 5Diii) with a 50mm lens and a 1.6 APS-C (crop) frame (Canon EOS M5) with a 35mm lens. Camera to subject distance is the same (36 inches) in both photos. The facial features are the same.

50mm lens on full frame camera

50mm lens on full frame camera

35mm lens on APS-C "crop frame" camera

35mm lens on APS-C "crop frame" camera

Let's take it further and compare the 50mm lens on full frame with a 10mm lens on crop frame...

50mm on full frame again

50mm on full frame again

10mm on APS-C cropped to match

10mm on APS-C cropped to match


I hope this helps explain how distance affects perspective. Yes, you can get very widely different perspectives by using different focal lengths, but that is when and because you move the camera. Telephoto (long) lenses tend to make us back up away from our subjects making the scene look more compressed. Wide angle (short) lenses invite us to move in closer to our subjects making the scene feel more wide open. It is our moving in and out, though, that changes the perspective. The focal length of the lens then determines how much of the scene will be captured.

For even more on this topic, please visit the Understanding Camera Lenses article at Cambridge In Colour. And take a look at the other tutorials there. Sean McHugh does a great job at explaining photographic concepts with text, illustrations, and calculators.

Cheers!
John

 

It is NOT the lens!!

It's the DISTANCE, %&^^^##

Here we go again. If you have read my harangues about this before you can go ahead and skip this one. But again I see photographers talking about lenses and perspective and blaming the lens. Even back in 2012 I was talking about the camera adding 10 pounds to people. So, let's try this again. All lenses show the same perspective from the same camera position.

Wide angle lenses don't expand a scene and long lenses don't compress a scene. The area of a photograph taken from the same camera position with the two lenses that is common to both photographs will have the exact same perspective, which includes the look of the drawing of the face in a portrait. What short lenses do is tempt us or allow us to move in closer to the subject. What long lenses do is make us back up away from the subject to fit the subject in the frame. But that is your decision. The lens suggests things, it doesn't dictate them.

 
Don’t let the lens dictate your camera position. Find your position, then pick the lens that fills the frame appropriately.
 

Let's look at two photographs. One was taken with a 24mm lens, the other with a 105mm lens and they were cropped to match the same size. Can you tell the difference?

Yes, there are some obvious giveaways. The 24mm photo has more depth of field (you can see it in the hair) because the subject was magnified less in the 24mm original. But in general, the look of the face is the same with both lenses. How can that be??? It is because the distance between the camera and the subject didn't change. That distance is what determines the look of the face. Don't blame the lens!

Above you can see the full frame and cropped images from three different focal lengths, 24mm, 50mm, and 105mm with the camera 24-inches from the subject. The perspective is the same in all three.

 
Just because a wide angle lens tempts you or allows you to move in close doesn’t mean that you have to!
 

Below is the same series, but this time from 86-inches away. Again, the perspective is the same for all three lenses. But it is different from the set above because the DISTANCE changed, not because of the lens.

Now let's go back to the slider. This time the two photos compared below are taken with the same lens (24mm), but at two different distances (24-inches and 48-inches). Now you see a big difference in the perspective. But these are made with the same lens--how could that be? It is the DISTANCE.

I really hope that this helps clear up the question about lenses and perspective and adding ten pounds to the subject and on and on and on. 

Yes, it is not practical to make a portrait with a short lens and then have to crop in and enlarge it. But again, that isn't the fault of the lens. You picked the wrong size wrench from your toolkit.  Don't blame the lens.

Thanks!

 

 

Do you still think it is the lens?

Photographic Lenses, Perspective,
and Distortion

Yes, another in the series about lenses, perspective, and distortion. This time it is about wide angle lenses used up close. For example, if you photograph a group of people with a short lens and fill the horizontal frame with the group you will find that the people on the right and left appear to be stretched out.

Pop quiz! Why does this happen? Do you think it is the wide angle lens causing the situation? Or is it the distance between the camera and the group of people?

I think the popular answer is going to be "the lens," but I also think that with a few photographs I can show that the lens is NOT the issue. In these photos, the (full frame) camera was stationary with a 16mm lens on a tripod. I photographed the mannequin head straight on, then I moved it to the left and right sides of the frame, still facing straight forward. I then combined the three in Photoshop. The images are layered straight over each other, with no cropping or other manipulation.

perspective_1.jpg

You can clearly see the distortion of the mannequin head when moved out to the far edges of the frame. And, of course, our first inclination is to blame the use of a wide angle lens. But is the lens to blame? Let's look at another set of images...

perspective2.jpg

We start with the same image that ended the first series of photos for reference. Then we see a photo with a PRINT of the original photo in the same position as the head on the left. Take note that the head in the print does NOT show the "wide angle" distortion that the actual head shows.

This shows us that the distortion is not from the lens. The reason we see the distortion on the three-dimensional head is that we are so close to those people on the edge of the frame and at such an acute angle that the lens is seeing both the front and the side of their heads at the same time. The 2-dimensional print, in the same position as the head is rendered straight--there isn't a side of the head to show in the print.

This is something you can easily try for yourself. Hang a photograph on your wall. Put your widest lens on your camera. Position the camera straight on to the wall with the photograph centered and take a photo of the photo. Then move laterally to the left or right so the hanging photograph is on the edge of your frame. Make sure the camera is still positioned straight on to the wall and take another photo. Repeat the same with a 3-dimensional object (a lamp, a statue, etc.). Do you see the same amount of distortion in the 2-dimensional photo as in the 3-dimensional item?

If I was to keep the same 16mm lens on the camera and backed up to a suitable distance I would not be at that strong of an angle and would only see the faces straight on. The distortion would be gone, but the people in the image would be much smaller with a lot of empty space around them. The fix for that? Use a longer lens, which will magnify the people more to fill the frame. The longer lens doesn't fix the distortion we saw with the short lens, it just magnifies the scene when you are further away from the subject by providing a narrower angle of view.

So..., what do you do if you are in that situation where you have a group of people to photograph and you can't move back? Have the people on each end of the group turn in towards the other subjects so that they are more straight on to the camera. It won't be perfect, but will help. Next time try to arrange to take the photo in a larger space that allows you to back up.

This goes back to the basics of perspective in photographs. The camera to subject distance determines the perspective (the relationship between items in the photo) and the lens focal length determines the magnification or how the subject fills the frame. One of the best descriptions of how this all works is in a book from the 1930s called Pictorial Composition in Photography by Arthur Hammond. A good read if you can find a copy. Check out Chapter V  on "Linear Perspective."

Here is a list of some of my previous articles on lenses and perspective:
Seeing Ourselves In Photos
Seeing Ourselves Part 2
Depth of Field
Lens "Compression"
Aperture and Depth of Field
Aperture and Portraits

Thanks!
John