More on perspective

My last post here was about why we might not like what we look at in photographs. And one of my readers, Maximilano da Costa asked a great question. what about taking a photo from 18" with a 100mm lens and then from 60" with the same lens.

Well, the  lens I used here, a Canon 70-200 f/4L, with a Canon 500D closeup lens on it would only focus in as close as 22" so I tried Maximiliano's test at 22" and 60". I hope that is close enough.

Anway, Maximiliano asked if those two images would look the same. I didn't expect that they would. My whole premise is that perspective is determined by camera to subject distance, not by lens.

So, let's take a look at the results...

Camera 22" from the subject's eye

Camera 60" from the subject's eye

I think you can see that the look of the face is quite different between the two. As "promised," the image taken from 60" is much flatter in appearance. Hence looking a little wider/heavier. Here they are side-by-side...

Click to enlarge

Can you see the difference? The image taken at 22 inches has a nice gentle curvature of the cheek as it wraps around from the nose to the ear. The one at 60" is flatter.

This being the internet and all that, I know someone is going to suggest that maybe it is the optics of a zoom lens, even if both images were taken at 100mm. Or someone may suggest that adding the 500D close up filter to allow the 70-200 to focus so close are affecting things. I can assure you they are not.

But in the sense of full testing, I pulled out an old Tamron 90mm macro lens that could focus at 18 inches and repeated the tests. I think you will see the same results...

Camera at 18" from subject's eye

Camera at 60" from subject's eye

 And the side-by-side for closer comparison...

Click to enlarge

Please, don't just take my word for it. What I really want you to do is to go out and try these things yourself. Just because a book says it is so, or some photographer on the net says it is so doesn't mean they are always correct. 

So, go out and take some photos of the same person or mannequin (they tend to hold still longer for a better comparison) and see what happens as you move around them and move closer and further away. And then try a higher or lower camera angle than you usually use. Experiment. These don't have to be images that you show to anyone else. They are references for yourself.  Write your own photography book using the tests you run yourself.

Thank you Maximiliano for asking your question. I love questions. Please post yours in the comments if you have some.

John

Seeing Ourselves In Pictures

The folks at PetaPixel posted a short video from a Ted Talk by Duncan Davidson called "Why do we hate seeing photos of ourselves."

While I agree with Duncan's main premise that part of the issue is that we are used to seeing a mirror image of ourselves, I think it goes deeper. Some of the comments on the post touch on more issues, such as the image being static and missing "micro-expressions." I agree with those, too. But I think the static image and micro expressions are more related to the retouching that we do. In real-life interactions we don't notice little zits, scars, pores, etc. as the face is moving and our eyes are moving around the face of the person we are talking to. In the captured still all of these things stand out to us in a big print, but I don't think we see that much detail in the small image on the back of the camera that is referenced in the video.

I think there is another issue that wasn't brought up in the talk or the comments. That is the camera-to-subject distance. As photographers, we are constantly instructed to be at least 36" inches from our subject. Many instructors tell us to be 5 feet or 6 feet away. This is supposed to give a "better" or more pleasing perspective. And that may well be so. In many of our social interactions we are probably around 2 to 3 feet or more away from the people we are talking to. At least in the US culture. Yes, there are cultures where it is more common to be only inches away from the people you are talking to. But I don't have experience photographing in those places. I'd be interested in hearing from people who do usually stand "in each others' face" about how subjects react to seeing their photographs. In the case of most of the subjects I work with we are used to seeing other people from a bit of a distance.

But how do we see ourselves? I usually see myself in the bathroom mirror. How about you? Today I measured the distance from my eye to the mirror when I'm standing at the sink. That was 21". I checked with my wife, Kim, and she said she is usually looking in a makeup mirror. We went and measured and found she was 9" from the mirror.

If you have been following some of my earlier blog posts about perspective, you will remember that the closer you are to your subject, the more narrow their face will appear. When you are just inches away from your subject their nose is relatively much closer to you than their eyes and ears. The ears seem farther away, making them smaller, making the face seem narrower.

So, my additional premise on this is that we all seem to look heavier to ourselves in photographs that are taken from greater distances. Other people will think the photo looks good because they are used to seeing us from those greater distances. And in a mirror we are always looking at ourselves at eye level. The woman in Duncan's photo was also photographed from above. She probably has never seen herself in a mirror from that view.

A few weeks ago a question came up on Quora that I was compelled to reply to. That was about why the camera "adds 10 lbs." to people. You can read my response there.

Here are some photos to help illustrate. All of them were taken with the same lens (Canon 24-105mm) set to 24mm at different distances, from 18" to 60" (measured from the mannequin's right eye to the focal plane mark on the top of the camera). They were then cropped so that the face is approximately the same size in each frame...

Here are the 18" and 60" images side-by-side...

I think you will agree that in the closer photos taken at 18", 21", and 30" make our subject's face appear thinner. This is how you would see yourself in the mirror. As we then move back to 48" and 60" away the face starts to flatten out and look a little heavier. To someone really concerned about their appearance, it might see more than a little heavier. That extra 10 pounds that we get from being further away.

As noted, all the above images were taken with a 24mm lens. This is to show that it isn't the lens that does this, but is instead the camera-to-subject distance. Look back at my previous perspective articles for that rant. Don't blame the lens!

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You may be asking yourself about the difference in the appearance of the backgrounds. The lighting is the same (a Westcott Apollo Orb on camera left with a home-made crinkled aluminum foil covered reflector on the right). What is different is that from the greater distance we are only seeing the middle of the backdrop right behind the mannequin's head. When in closer the field of view is wider and we are seeing the edges of the backdrop and see the falloff of the light. Here is a quick diagram to help explain the field of view...

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To help illustrate that this is not lens focal length related, this next image was taken by zooming the lens to 105mm without moving the camera after the 60" image from above. You will see that the perspective is exactly the same as in the 24mm at 60" image above.

Here they are side-by-side and then overlayed on each other in Photoshop in Difference mode.

Click on the image for a larger version

Notice that only the very edges of objects are highlighted as different between the two images. That is most likely because the depth of field is different between the two and the quality of the 105mm image is better because it isn't cropped in so much (losing resolution). But the look of the face is the same in the photos with both the 24mm and 105mm lenses.

Here is a little experiment for you the next time you are standing in front of the bathroom mirror. Lean in real close to the mirror and study how your face looks. Then slowly pull back away from the mirror while carefully observing the look of your face. Notice that the perspective flattens out as you back away, which gives the impression of being slightly wider, which we translate into appearing those ten pounds heavier.

And one more question... Do you like photos you take of yourself with your phone camera? What is the distance you can hold your phone away from your face to take those photos?

I'm not suggesting that you change to photographing from closer in or with shorter lenses, But do experiment with it to help understand what is happening. Find your style and go with it.

Please share your findings in the comments below.

Thanks!
John

Is it in Focus?

I recently wrote about lenses and perspective. In there I mentioned following up with a post about depth of field. I assume that most of my readers are familiar with the term. If you need a refresher, I suggest starting with this Tutorial from Cambridge in Colour.

The main control we have over depth of field is the aperture of our lenses. Wide open (lower number f/stops) we get less depth of field. As we stop down (larger f/numbers) the depth of field increases. But stopping down the lens can have negative effects, too. Small apertures lead to an effect called diffraction that lowers the image quality. Think of what happens when you put your finger over the end of a faucet. The smooth flow of the wide open faucet turns into a wild spray. So, you can stop down too far and get a lot of depth of field, but with an overall loss of image quality. What aperture you start to suffer diffraction at will vary with sensor size and specifications. Too much math to go into here, so I suggest you take a visit to Cambridge In Colours excellent tutorial on diffraction. While there, read all the other tutorials. This guy is good!

I just wanted to cover some of the questions that might come up when looking at the images in my most recent post about focal length and compression. Consider these two images

24mm at 48"

85mm at 48"

They were both taken at f/5.0, but the top one, taken with a 24mm lens shows the grid patter in the background more in focus than the lower image taken with the 85mm lens. Well, of course. We've all been told over and over that you get more depth of field with a shorter lens. But is that really true?

It is partly true. In this case it is true because the images were taken from the same camera position and the one taken with the 24mm lens was cropped in from this original 

24mm not cropped

So, we do see more depth of field, but at a considerable loss in resolution. The image taken with the 85mm lens is 3744x5616 pixels, while the crop from the 24mm lens is only 995x1492 pixels. That's fine for a 3x5 print or for use online. But not for much more. If you need to print an 8x12 or larger the lack of pixels is going to be a much bigger issue than the extra depth of field you gained by using a shorter lens--unless that non-cropped version of the photo is really what you wanted.

What if you decided to move in closer with the 24mm lens to get the subject to be about the same size in the frame? Then you do get your full 3744x5616 pixel image. But it is a very different image. The look of the subject is totally different as seen here...

And the depth of field has shrunk back to where it was with the 85mm! What's with that? The shorter lens is supposed to give more depth of field, isn't it? Yes, when used at the same camera to subject distance. But when you move in to get the same framing you counter that.

The fact of the matter is that focal length alone is not a contributing factor in calculating depth of field. You need to combine focal length with the camera to subject distance. So, it is more like magnification in the original image is the contributing factor. If the main subject is the same size on the sensor with a long or a short lens the DOF will be approximately the same.

Let's look at these images, which were all taken at f/22...

35mm full frame

200mm full frame

35mm cropped

For these the camera was moved to try to maintain about the same size head in both frames (same magnification). Here we see that the images taken with the 35mm lens and the 200mm lens exhibit similar depth of field. The yellow text on the black disc in the background is blurred about the same. The overall effect of the 200mm vs the 35mm appears that the subject stands out more in the 200mm version. But that is more about the limited field of view behind the subject. The blurriness is about the same in each, but there is a lot less background to be noticed in the photo taken with the 200mm lens. In the photo taken with the 24mm lens there is a lot going on in the background, and despite being equally out of focus there is more context available for our brain to tell us what is back there (fence, table, my wife Kim, etc.).

And overall, the image quality on the 35mm photo is lower, as seen below...

200mm full frame, no cropping

35mm full frame, no cropping

Both of these images were taken at f/22. As noted in the last post, the perspective is the same (camera and subject weren't moved, I just changed lenses). But if we enlarge the center section of the 35mm shot we get this...

35mm cropped to same framing as the 200mm

Here we can see the 35mm image has more depth of field (the text on the black disc is not as out of focus), but suffers a lack of contrast and overall loss of edge detail that I am chalking up to diffraction. Here is another comparison. This time both images are taken with the same lens in the same position, but one is at f/16 and the other at f/2.8. While the f/16 version has greater depth of field, the f/2.8 version appears more crisp and contrasty. I admit I added to the challenge here by working in less than ideal conditions with strong backlight. But this is a situation we often find ourselves in.

f/16

f/2.8

Anyway, I just want you to stop and think about the generalizations we hear every day as we learn about photography. Telephoto compression, stopping down for better images, focal length and depth of field, etc., etc. All of them have an element of truth to them. But they are often only half the story.

I end this as I started, by suggesting you visit the Depth of Field and other tutorials at Cambridge In Colour where they go into great technical details.

And after that please go out and do your own experiments. Then share what you learn in the comments here.

Thanks!

Lens "compression?"

Or, why should you get up and move around when making a photograph.

Just a quick question... Which compresses a scene more, a short or a long lens? Don't be so quick to come up with your answer. In each pair of photographs below one was taken with a wide angle lens and the other with a telephoto. Big thanks to one of my favorite models* for obliging me here.

24mm lens at 48 inches

85 mm lens at 48 inches

35mm lens

200 mm lens

While the lens was changed between each image, the camera and subject were stationary. If the camera to subject distance stays the same, the perspective (relationship between objects in the scene) stays the same. The wide angle lens lets you get more of the scene into the frame. The telephoto lens lets you fill the frame more selectively. But for the part of the scene that is common to both the perspective will be the same.

Here's what the original full frame images look like from the short lenses. The images taken with the longer lenses were not cropped.

24mm at 48 inches, no crop

35mm, no crop. Same distance as with the 200mm

However, if you do move the camera, things change dramatically, as seen in each of these non cropped images. By moving in close to fill the frame with the 24mm lens we get a much different drawing of the face than we do filling the frame with the 85mm lens. It isn't the lens, however, that is causing the different looks--it is the camera to subject distance. The lens just lets us fill the frame the with the subject's head at the different distances.

24mm at 12 inches

85mm at 48 inches

Getting physically closer to the subject slims the subject's face by making the relationship between nose to eyes to ears stretch out. As you take your camera and move back away from your subject the nose/eyes/ears are all relatively closer to each other, resulting in a flatter overall look which makes the subject look wider.

This works outside as well as in the studio.

35mm cropped from the image below

35mm full frame

Compare the 35mm** crop here with the 35mm crop in the third image from the top of this post to compare the compression. Same lens, but different camera to subject distances.

Keep in mind that objects close to the camera will appear larger in your photographs. But it is all relative. At 48 inches away your subject's nose, eyes, and ears are all relatively the same distance from your camera. When you move in so the nose is only 12 inches from the camera it is relatively a lot closer to the camera than the eyes and ears, so the eyes and ears are proportionally further away and look much smaller.

Consider this illustration (not to scale)...

In reality (above)

What it appears like from being in close

Pay attention to the relationship between the yellow and green shaded areas above. Note that close or far, the green shaded area remains the same size. In this illustration I have shown the green area as nose/eyes/ears at 12 inches and 48 inches. However, you can also think of the subject as a rock, trees, and a mountain and 12 feet and 48 feet. What I want you to see is that you move closer to or further from your subject the elements in the scene maintain their relationship between each other (nose/eyes/ears or rock/trees/mountain). No lens is going to change that relationship. If you switch from a 100mm lens to a 20mm lens without moving the camera, everything in the frame is rendered at 1/5 the size it was before. The relationship between those objects stays the same, but we see more of their surroundings.

At the top we see the camera to the nose is 12" and to the eye is 13" and it is 16" to the ear. When we pull back those numbers change to 48", 49", and 52". The tip of the nose to the ear in each situation remains about 4" and isn't going to change whether we're close or far away, or whether we use a short or long lens. What has changed is the yellow shaded area. Up close that 4" is relatively similar to the 12" camera distance. The ears are 1/3 again as far from the camera as the nose is. Moving back that relationship changes so that the ears are now relatively the same distance from the camera as the nose is (just 1/12 again as far). The further you move back from your subject the more pronounced the effect. Hence the appearance of "compression" or flattening of the view caused by backing away from your subject.

As noted, the same thing happens in landscape photography. Just substitute rock/trees/mountains for nose/eyes/ears. Move in close to an object and it becomes big in the scene and everything behind it starts to fall away in size. But if you back up far enough the relationship between the objects gets tighter (compressed). It doesn't matter if you have a short or long lens, the compression is the same. What the lens choice does is allows you to get more into the frame (short lens) or to zero in on a particular part of the scene (long lens).

If you stand in one spot and use a zoom lens the perspective stays the same. In many cases this is exactly what you want, and there is nothing wrong with that. But if you take the opportunity to move around your subject and change the camera to subject distance, whether with a prime lens or a zoom lens, you open yourself up to more variations and possibilities. Move in close to emphasize size differences and select a shorter lens to take it all in. Move back to de-emphasize size differences and select a longer lens to bring it all closer to you. You could use a short lens and get the same compression, as shown above, but that leaves you with tiny subjects that you will need to blow up to billboard size to recognize, with an inherent loss of quality.

You have probably noticed differences in the depth of field and overall image quality in the outdoor examples. I'll discuss that in a future post. For now, just start moving around and view things in different perspectives.

Then come back and let us know what you discovered in the comments below.

Thanks!

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*I use a mannequin for these examples for a variety of reasons. One is that I can make sure the model doesn't move between camera setups. Another is that I hope the audience won't be distracted by the look of the model and facial expressions that might otherwise influence the look of the image.

**The short lens used in close was actually zoomed to 32mm. Oops! But it doesn't change anything about the lesson.

More On Aperture and DOF

This is a follow up to my recent post about the effect of aperture on the look of a portrait.

There, I mentioned that changing focal length would not affect the depth of field if the camera was moved to maintain the size of the subject in the frame. I didn't have any images prepared then to demonstrate this at the time. I got a chance to create those images last night and present them here. Click on each image to load a larger version that will be easier to study.

 Above we see three photos that were taken with 135mm, 85mm, and 35mm lenses all set to f/2.8. The camera was moved closer with the 85 and even closer with the 35 to make the mannequin head be about the same size in each. If you look closely you will see that the depth of field is about the same in each. The perspective is different in each because the camera was moved (not because of the lens change).

Many photographers go for a lens in the 85 to 105mm (full 35mm frame) range for portraits because they put you at a distance from your subject that gives a nice drawing to the face with pleasing relationship between the features on the face and head (nose, mouth, eyes, ears). If working with a smaller sensor camera look for lenses with similar angles of view for that format (such as 50-65mm on cameras with a 1.5 or 1.6x multiplier).

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In the second set of photos everything is the same as the first set, except that the aperture was set to f/22. Again, you can see that the depth of field remains the same, even though various focal length lenses were used (135, 85, and 35).

You may also be surprised to see that the face looks the thinnest in the image taken with the wide angle lens. This is what happens when you move in close. With any lens the objects closest to the camera appear larger than objects further away. When in so close with a short lens the nose is relatively closer to the lens than the cheeks, eyes, and ears. So they fall away and look smaller. When you move back with the longer lens the nose, eyes, and ears are all relatively closer to each other than to the lens, so the face flattens out and they all appear at a similar size. This is due to the camera to subject distance, not the lens, even though this is often erroneously called "telephoto compression." See the fourth set below for more about that.

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In this third set of photos the camera remained stationary. The top image was taken with an 85mm, the middle is 135mm, and the bottom is 35mm. Here we can see that the size of the mannequin head is very different between the images and the depth of field changes drastically between because of the difference in magnification from each lens (all set to f/2.8)

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In this final group we again have images taken with the 135mm, 85mm, and 35mm lenses, this time all set to f/5.6. As in the third set, the camera remained stationary and the lenses were changed.

In these last two sets of images you should be able to see that the perspective remained the same even though the lenses were changed. The relationship between the head and the background is the same in each. If you cropped in on the 3rd image in this set the perspective would match the 1st image in this set. But the depth of field is different. Remember that when the camera to subject distance is set and the lens is changed the perspective of the area of the image that is common to each image is the same. The camera to lens distance determines the perspective. The focal length determines what fits into that frame.

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One of my favorite Ansel Adams quotes is "good photography is about knowing where to stand." I think that many people misunderstand this quote. They might associate it with Jim Richardson's quote "if you want to be a better photographer, stand in front of more interesting stuff."  But what I believe Ansel meant was that you need to find the location to set up the camera that gives you the perspective (relationship between items in the scene) that you want, and then you select a lens focal length that fills the frame the way you want. Too often people pick the lens first.

I really don't like the mantra of "zoom with your feet." Zooming implies making the scene smaller or larger while maintaining the perspective by changing focal length without moving. If you move your feet the perspective changes. So you CANNOT zoom with your feet. I'm not saying it is a bad exercise to select one prime lens and learn how to use it by moving around. If you want to make good and interesting photos, do find your location by moving your feet, but then select the appropriate lens to fill the frame of your camera. Maybe the frame should be "move your butt!" And a zoom lens is the perfect lens for this, as you can frame exactly as you want. Zoom lenses got a bad reputation in the 1970s when the quality wasn't nearly as good as prime lenses. Zoom lens design has come a long way since then and today's zooms come very close to the quality of prime lenses. That said, I often use prime lenses instead of my zooms, but this is primarily because of the weight of a good zoom. The primes are easier on my shoulder, elbow and wrist.

One more thing. Something that I learned during the exercise of preparing this article is that it really is difficult to manually focus a wide angle lens. I've always heard that short lenses were more difficult to focus, but it reallyshowed here. The following set of images were taken with the same camera/lens (35mm at f/2.0) combination. A was manually focused through the viewfinder. B was manually focused using Live View at 10x, and C was autofocused. Maybe autofocus isn't such a bad idea....

Perspective (again)

I've been seeing some tweets and Facebook messages about how lenses affect perspective and the drawing of the human face. My argument is that the lens doesn't cause the different look, but rather the distance from camera to subject does. The lens focal length just determines the angle of view or what fits into the frame. I could refer you to my previous blog post from this year on this. Or the one before that in 2009. Or even a post from 2007. But no, I'm going to write it all up again for your enjoyment.

I'm not saying that you should photograph everything with a short lens and then crop later to get your composition. But I am saying that you should determine your camera to subject distance to set your perspective and the relationship between items in the photograph and then select the lens focal length that fills the frame appropriately. Don't blame your lens(es) for perspective distortion (expansion or compression of the scene).

Here is a set of 3 images. I'm using a mannequin here instead of human so that there would be no movement between the photographs. One was taken with a 200mm lens, one with a 35mm lens, and one with a 16mm lens. The fourth image takes the 200mm and the 16mm images and combines them in separate layers in Photoshop. I then set the blending mode to "difference" to show how the two images compare. The pixel and noise structure of the two images accounts for the variations inside the facial area. But if you look at the outline of the face, you will see that it is exactly the same in both images. Changing the focal length did not change the perspective. Can you tell which image was taken with which focal length lens?

200mm and 16mm images overlayed
on each other in Photoshop's "Difference"
blending mode. The facial shape and
features are the same.

Here are the full frame originals to show the size differences due to the various lens focal lengths...

200mm lens from 8' away

35mm lens from 8' away

16mm lens from 8' away. Notice that
the relationship between objects
in the scene are the same even with
the widely varied focal lengths used

And to round out the comparison, here are three photos taken with the 200, 35, and 16mm lenses where the camera to subject distance was changed to try to maintain the approximate same size of the face in the frame.

200mm lens from 8' away. Facial features
are flattened. Nose, eyes, and ears are
all similar in size. The face appears slightly
wider than "normal"

35mm lens from about 2' away. Facial
features are more pronounced. The nose
is larger than the ears. The face is
narrower than "normal"

16mm lens from a few inches away.
Facial features are even more distorted.
The nose comes forward, the ears are
much smaller. The face is much narrower
than "normal"

Once again, I'm not suggesting that you take your portraits with a short lens from far away and then crop. I just want to show and help understand that camera to subject distance is what affects the perspective in a photograph. Too often the lens gets blamed for this. Select the appropriate lens for the situation.

Remember, a shorter lens doesn't cause the perspective change. But it does allow you to move in closer so that you get that distortion. And a long lens doesn't compress depth. Blow up the center section and you will find they match (like in the first three images above). Photographs taken with different focal length lenses, but from the same camera position, show exactly the same perspective in the section of the scene that is common to all the different angles of view of the various lenses.

Thanks for putting up with this again!