Superproducer Ted Hope on...

November 8, 2011

How Your Lens Choice Affects Your Subject's Appearance

A longer lens can flatten and widen a face, whereas a wider lens can pinch/pull facial features into an ugly distortion. This is true because of the varying physical distance to your subject that accompanies your choice of lens. This is not just a consideration for portrait photography, but also comes into play when choosing a lens for filming actors. For the the full size images of the thumbnails above, see photographer Stephen Eastwood's site, or watch a video of how different distances (and accompanying lens choices) affect facial geometry by LensProToGo:

Link: Stephen Eastwood Lens Distortion Photo Strip

[via Gizmodo]

Your Comment

36 Comments

My question with this has always been, shooting on a 1.6X cropped camera, wouldn't the distortion in features be the same as on a full frame sensor, with the only difference being that the cropped sensor is only using a portion of the lens thus giving it a magnified focal length?

November 8, 2011

0
Reply
Darius

My question exactly!

When I use a 35mm on a 1,6 crop sensor will I get the image corresponding with the 35mm picture above or more like the 50mm (as far as distortion concerned).

November 8, 2011

-1
Reply

to the 50mm: what matters is equivalent focal length, i.e. the angle of view of the lens+camera system, and therefore how close to the subject you have to get in order to get your desired picture

November 8, 2011

0
Reply

Crop only affects your Field of View, not Depth of Field or the optical quality. Features of an actor would be the same as above with each lens, the only difference would be that you would have to move your camera back to get the proper framing.

November 8, 2011

1
Reply
Ryan

that you would have to move your camera back to get the proper framing... which affects depth of field and optical quality!!

as for optical quality, you're blowing up the image, so any sharpness issues get blown up too

as for DoF, see here:
http://www.similaar.com/foto/doftest/doftest.html

November 8, 2011

1
Reply

No because the image would be cropped compared to a full frame, and you would end up losing features from the subjects face like the ears, chin, forehead... To get a proper frame on a cropped camera you would need to back the camera from the subject to create more room to frame decently the subject's face. That extra distance would end up flattening the perspective a little bit or a lot depending on the crop ratio.

For instance a 50 mm that is considered to render a normal perspective on a full frame camera (normal perspective meaning similar to the way our eyes work) is considered a tele-photo when used in a cropped frame. A 50 mm in a 1.6 crop factor will give you a frame size similar to a 80mm in a full frame. (50 X 1.6 = 80)

Roughly and in very lame terms a longer lens has the effect of "cropping" the field of view when compared to a wider lens. That's why this math works as a good reference almost all the times when comparing sensor sizes and lenses distances.

I didn't read this wikipedia article, but the begining seems to be right. http://en.wikipedia.org/wiki/Crop_factor

November 8, 2011

-2
Reply
mauborba

Koo, our dear master, this is terrible misconception! Cut it out or give some more accurate information!

That's not a lens who flattens/widens a face, that is DISTANCE!

I won't give links to prove that cause every one of us could do that easily.
Just take 35/50/75mm and portrait someone at a fixed distance of 5 or 6 feet using all three lenses not moving closer or father. Then crop the same facial area on all 3 pics. You'll see, it's all the same!

And for DARIUS:
It does not matter what sensor you have. Distortion depends only on a lens scheme, it's focal length and - what is above all - DISTANCE to the subject filmed!

November 8, 2011

0
Reply
PhotoRookie

yeah that guy in the video is misleading.

a 100mm lens never "becomes" 160mm. it is ALWAYS 100mm. on all cameras. it just crops differently on cameras with different size sensors. seriously, the whole conversion of focal lengths into 35 "equivalents" needs to stop. it is the source of endless confusion.

November 8, 2011

0
Reply
dv

Hear, hear!

November 8, 2011

0
Reply
Graham Kay

I do the math on lens focal length when going between crop sensor and FF cameras. For me its the easiest way to ensure that the Lens I choose has the field of view that I need for the shot.

If I I put my 50mm on my 550D and my 85mm on a 5D im going to get a moderate telephoto FOV on both. If really need them to look the same Ill have to open the apeture 1.5 stops wider on the 550D.

November 8, 2011

0
Reply
Sam

I shall add "distance" to the post, but I thought that part was obvious and implied...

November 8, 2011

1
Reply
avatar
Ryan Koo
Founder
Writer/Director

Your blog has changed a lot of lives and answered many questions for indie filmmakers. Don't be surprised if you see a juicy Wikipedia article covering your life soon. Thank you for this article.

December 3, 2011

-1
Reply

Yeah, 'A lens is a lens is a lens, and it doesn’t know what size sensor or film gate is placed behind it'
http://blog.abelcine.com/2010/05/14/a-lens-is-a-lens-is-a-lens/

November 8, 2011

1
Reply
PhotoRookie

yes, ‘A lens is a lens is a lens' and focal length doesn't change with sensor size, but I find the "equivalent focal length" quite helpful, otherwise we'd have to talk in angular terms, which is a completely new language

"my 50mm becomes a 80mm equivalent when used with my T2i" is an easy way to get a message around

"my 50mm has 25º wide FoV when used on my T2i" doesn't tell me much; it sounds narrow, but I get a much better sense of how narrow it is by the "80mm equivalent" bit

November 8, 2011

0
Reply

"PhotoRookie on 11.8.11 @ 4:56AM
Yeah, ‘A lens is a lens is a lens, and it doesn’t know what size sensor or film gate is placed behind it’
http://blog.abelcine.com/2010/05/14/a-lens-is-a-lens-is-a-lens/"

Oh but it does, as it's imaging circle (diameter) is made for the sensor size. Four thirds imaging circle is smaller than EF of course.

The focal length of a lens is irrelevant if it's imaging circle isn't known.

A 100mm lens with a 100 diameter image circle is almost square side on. A 100mm lens for four thirds is very long and thin. Light passes through these two lenses at vastly different angles, yet by the logic displayed here, they are both 100mm and therefore both the same. Clearly they are not. One is a long tube and one is a wide angle block.

35mm is just an accepted standard of reference but a 100mm lens with an imaging circle to suit four thirds is a completely different ratio to one for 35mm ff and very different from one with a circle to image MF or LF.

Even on a crop where you still use a 100mm with a 35 image circle, the crop is still only using a smaller circle, and that extra glass might as well not exist, as the lens now acts like a longer lens, with a different focal/circle ratio.

So if you use the centre of a 100mm lens on a 1.6 crop, the ratio between the focal length and the centre portion of the image circle your sensor is using, is now the same ratio as a 160mm lens where your using the full circle, so the optical characteristics are the same, the light travels at the same angle through to the sensor and the image is identical, as long as the crop sensor is moved proportionally further back to ensure the same subject is filling the frame on both cameras.

It's hard to explain, but it makes sense if you draw a lens side on, and see the rectangle ratio and mark where the light passes through the lens.

November 8, 2011

0
Reply

Thank you for this. This is fantastically useful information worth referencing over and over again.

November 8, 2011

0
Reply
Adrian Jans

I think it's overly simplistic to say "a lens is a lens is a lens", but it's similarly overly simplistic to talk in terms of 35mm equivalents. The simplest answer is, both are true.

Optically, the lens stays the same. The focal length is the same, the DOF is the same etc. But visually, the crop must also be taken into account, since that affects the distance of focus. So for the same shot, the lens is operated differently.

A lens stays the same regardless of sensor, but for different sensors, the lens is used with different parameters.

So for that reason, I really disagree with the idea that crop factors should be done away with. But I also think a physical understanding of what's going on is very important, rather than thinking crop factor is everything.

November 8, 2011

0
Reply
Luke

+1000

November 8, 2011

0
Reply

In explaining focal length to my students, I used to suggest that the next time they're about to kiss someone, they might open their eyes and really look at what they were seeing: A HUGE nose and tiny ears.

November 8, 2011

0
Reply

Luke and Dean Agar, I appreciate your thoughts, but it seems we're moving into different direction here. Let's focus on the article point and not on DOF and crop factors which seem clear.

Koo's post should better named 'How Your DISTANCE Choice Affects Your Subject's Appearance' instead of current '...LENS...' !

Look at that guy — he's constantly changing the distance and his lens choice does matter here. If he took all the photos keeping the distance constant you'd clearly see that girl's face remains the same regardless of the lens mm. Off course magnification would be different but if you crop girl's face you'll see it changes NOT. Distortion (or lack of it, depends on distance) is all the same.

That is the point! And after that we can go talking about portrait distance and lens choice.

November 8, 2011

0
Reply
PhotoRookie

Yes, it's the distance to your subject that affects their appearance, but the choice of lens affects your distance to the subject. Right? So I'm not sure how we got onto DOF and crop factor, when what the picture and video are about is geometric distortion. I'll make a semantic correction but I've never found "a lens is a lens is a lens" to be that helpful functionally (though it's of course true), given we're talking about what something looks like with the same framing (which requires different lenses AND different distance-to-subject).

November 8, 2011

0
Reply
avatar
Ryan Koo
Founder
Writer/Director

Apologies if went off topic, but there seemed to be confusion that a crop factor made no difference, which of course it does, as stated accurately in the video.

As for filming, the crop factor is very relevant. If you're shooting super 35, then to get the same distortion characteristics as the examples show, on any given lens, the camera would have to be moved back to allow for the crop factor of super 35mm.

The reason this all works is simple, although the above example is easily the best real world demo I have seen of it.

A head is 8 inches from nose to back of head. A nose sticks out 3/4 inch from the face and is say 4 inches in front of the ears.

So if the camera is 12 inches from the nose, the nose is a 1/3 of the camera distance closer to the sensor, and will image that much larger than the ears, and look horrible.

Move the cam to 8 feet from subject and that nose is now only 1/32 of the cam distance closer than the ears are, making the difference negligible, so looks more natural.

We don't see these effects with our eyes to the same degree because we see in 3D, and therefore our brains have more than just size on the image to judge distance and size of a subject.

Try looking at a persons face from 10 inches, with both eyes. They look fairly normal.

Now cover one eye, and see the distortion effect appear.

How this works in a 3D movie would be interesting, as you could get a lot closer in 3D without the distortion, but then the 2D version would suffer the distortion.

If people looked like the last example in the strip close up with our eyes, no one would kiss anyone ever again, but luckily in 3D, they don't :-)

November 8, 2011

0
Reply

Hey Koo, I can say at least for me, I was trying to respond to Darius back there. I completely agree with this article, and it's very helpful. Different lenses render different types of perspective, period! It's obvious that re-framing is going to be necessary when swapping lenses, but I don't know why people are making so much of a big deal out of it. Great article, keep them coming. Haters will be haters will be haters, as much as "a lens is a lens is a lens". Lenses don't know the size of a sensor, don't know the distance to the subject, they don't even know where the camera is pointing at, they actually don't know shit. Who should know anything is the DOP, and the relationship between lens and distance to create the best well balanced frame. People who don't appreciate this article should shut their faces.

November 8, 2011

-1
Reply
mauborba

I think the comments here have been very constructive and clarifying!

November 8, 2011

0
Reply
avatar
Ryan Koo
Founder
Writer/Director

I still am confused. For instance, the Hitchcock move where the distance from the subject either gets farther or closer while the zoom moves in the opposite direction does not yield the same field of view. There is definitely a change in perspective due to the focal length of the lens. Am I not correct?

November 8, 2011

-1
Reply
Philip

I believe the change in FOV is due to distance rather than focal length. This is a topic I've been searching for an answer to for a while now, and this whole post has been SUPER helpful! Thanks Koo, and everyone else!

November 8, 2011

0
Reply
Ethan Adelsman

Yeah, I definitely saw a lot of constructive discussions come about, but I do think some people may have misunderstood my question, which I felt directly pertained to the article. Basically I just wanted to pose the question, would her face be as narrow on a 14mm lens on a 60D as it would on the same 14mm lens on a 5DMKII. It feels like, even though the image would be magnified that the distortion should still be the same.

Apologies all around!

November 8, 2011

0
Reply
Darius

It's a common question and the best way to view it is to think of a lens and a sensor side on. Imagine the light passing through the lens to the sensor, and put a rectangle around it.

The more parallel the top and bottom rays of light are to each other, the less distortion, so light passing through the centre of a lens contains less distortion than that at the edge, so a crop cam uses the less distorted part of the lens by definition.

Barrel distortion increases from the centre outwards, and of course a lens is not uniformly distorted across it's full image circle.

Here's a random fish eye image. http://www.stankruslicky.com/546041/Fish-Eye

The very centre is not that distorted, the edge is extremely distorted, so if you had this lens on a crop factor of 10x, the final image is not that distorted where it says Hendrix, but use the whole image circle and it's fish eye.

At 1.6x the difference is of course not this dramatic, but the rule effect is the same.

Same lens, different crop factor, different distortion characteristics. A 100mm lens is a completely different lens depending on how much of it's image circle you use.

Really, all a 100mm zoom lens is, is the centre sections of glass from a 50mm, enlarged to 100mm with the outer half of glass thrown away (in basic terms)

Hope I have not misunderstood the issue, and apologies if I have :-)

November 8, 2011

0
Reply

Spot on and very interesting!

November 8, 2011

0
Reply
Darius

To further the point, the camera cannot alter the image that the lens is presenting, it can only use all of the image like a full frame sensor, or a portion of it like a 1.6crop. Therefore, even though the sensor crops the image making it appear to be closer to the subject, it isn't in fact altering the actual distance and therefore the lens's distortion remains the same even though the "distance" is altered. I think this is directly related to the article, just a little round about in method.

November 8, 2011

-1
Reply
Darius

yes

so suppose you take a fullframe camera with a 80mm and shoot one of those portraits

then, without moving your tripod, you swap to a 1.6x camera; because it crops the center, unless you want a picture of just the nose, and, given that you don't want to get any further, you'll change to a 50mm lens, thus "equivalent focal length" and how that is what determines perspective distortion, not focal length as in "a lens is a lens is a lens"

November 9, 2011

0
Reply

For me the imperative is to understand how different lenses (focal lengths) change the perspective of the subject in relation to the environment, and as a result the feel of the entire image in frame. So, for example, with a longer lens the subject will be isolated from the environment which will seem closer in distance yet out of focus. There can be a paradox of sensation in that the subject can feel both isolated and enveloped by a more general background. The same shot with a wider lens would introduce the environment as more specific, and the subject would potentially become more more isolated and "general" in the details. If the story called for a moment of isolation, the lens choice would change the feel of isolation.

At any rate, this is a big part of the fun of it all.

November 9, 2011

1
Reply
Granville

This post is getting way too complicated for everyone to understand. The number on the focal length has nothing to do with anything in this particular situation for making features on a person look different. The only things that affect your subjects appearance are subject distance and field of view measured in degrees (which is why crop factors come into play, they magnify the field of view, the focal lengths measure how long the lens is, but that is always put in relation to 35mm photography which is full frame, not motion picture film.) A medium format camera with a 50mm lens would be more like a 35mm lens on a 35mm camera and a 35mm lens on a 1/3" camera sensor would be a long telephoto lens. It all has to do with field of view and distance to the subject. So when you refer to a wide angle lens as distorting the face, it is actually referring to the angle of the field of view. Telephoto would be narrow angle lens and thus compresses the image. This is why when you want to shoot a scene and make the moon look huge in the background of a person you shoot them on a long telephoto lens from far away and compress the background and foreground together. So it is all about the angle in degrees of the field of view. Everything else has nothing to do with it unless the lens has specialty characteristics like a fisheye which makes the image round.

November 10, 2011

-1
Reply

This may be a basic question and highly off topic, but will the distortion generally show up on a digital view-finder or in the eye-piece? Yes. I am a N00b in case you were wondering.

November 10, 2011

1
Reply
Drew

Yes, Drew, you will still see the distortion...but that brings up another issue of optics...if your eye is close to the viewfinder, a distorted image (wide angle) won't look as distorted... The optics of an eyepiece may or may not compensate for some of this, depending on the particular eyepiece.

Even though I'm coming from optical viewfinders on motion picture cameras (real film), I quickly fell in love with flat screen field monitors...you can look at it at different distances (assuming you're not on a steadicam or handheld and can't really get closer or further from the screen very much) to better judge what you're seeing. I find it makes a huge difference in letting you form an objective opinion of what you're seeing as far as your aesthetic choices.

As a general comment, the 35mm "standard" is a great standard to stick with...if everyone keeps to a standard, we can all know that we're talking about the same thing! Its the know-it-all literalists who like to point out that a 50mm is a 50mm, no matter what crop factor your individual camera is using. Great...true, we get your literal interpretation and we know you're smart now...but when you're working with different directors with different experiences, if he tells you he wants a 50 and you have a 7D and it is the optical look of an 80 (in 35mm terms), that's not really what he was looking for, is it? If we keep to a standard and agree to some terms and definitions, we can communicate more clearly. There are so many crop sensors and they are all different, which can confuse people even more. (DX is 1.5x, Canon ACS-P is 1.6x...etc...) This has always been the standard, and considering the latest generation of cameras that are taking PL mount lenses, it will remain the standard for quite a while to come.

Note: I disagree about Paul P.'s comment that it's alway put forth into relation to 35mm full frame still photography terms and not motion picture terms...it depends where you're coming from. B/c of the video work done with D-SLR's, some people are coming from the still camera background, or at least the SLR lenses (the full frame standard is the standard...), but when talking with DP's, what they know isn't actually full frame, even though they may refer to it as such or think of it as such... They're talking about the 35mm academy frame (35mm run vertically, not horizontally like full frame) and always have been. So even the "standard of 35mm" is up to debate and personal interpretation.

November 11, 2011

0
Reply
Daniel Mimura

Yes. I don't know why he insisted that that wasn't the case. Changing focal length is like moving furniture around. All you're doing with changing the frame size is how big the window is you're looking into the room with. I don't get how people (especially pros) can't understand this simple fact.

June 1, 2014

0
Reply