How Your Lens Choice Affects Your Subject's Appearance

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?

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

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!

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/

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

"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.

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

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.

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.

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.

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.

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?

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!

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.

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.

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.

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.

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.

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.