Does 50mm x 1.6 = 80mm portrait lens?

[Ken Fong]

I read the advice that more flattering portraits are achieved when the lens is at least twice the film size (35mm x 2 = 70mm), so I figure an 80mm lens is about right.

My question is: is it a bad assumption that a 50mm lens with a 1.6x DSLR crop factor equals an 80mm portrait lens? I have a feeling that the 50mm lens x 1.6 will not give me the optics of a true 80mm lens because the focal length is still the same as a 50mm lens (and thus unflattering). Can someone confirm? Is the advice to shoot at a true 80mm (ignoring crop factor) and just step back?

thanks,
Ken

[Mark Kemp]

70 mm or so is recommended for portraits as a good starting point, but it really comes down to what you like. Some people like shorter focal lengths and some longer. Sometimes you can try to 'help' the sitter a bit, for instance a longer length further away will make the nose seem shorter. I suspect that a 50mm on a 1.6 magnification will be pretty much the same as an 80mm on a film camera. Depth of field, foreshortening and other optical effects are all a function of the focal length, so if the field of view is equivalent to an 80mm all the other things should be too. However thats not very scientific, but I wouldn't get too hung up about it anyway. Whatever apparent differences there might be won't be that great, you can usually get a perfectly acceptable portrait on anything from about 35 to 100mm without magnification (the results are different but none of them looks like the hall of mirrors or anything). So in practice your personal taste will be the most important thing anyway.

[drisley]

I think you are right.
You are just losing the edges of the image, and left with a crop.

The compression would not be the same. Also, you wouldnt get the same DOF as with a true 80mm lens.

Personally I dont see any difference between in facial compression between an 85mm lens and a 135mm lens, but everyone is different.
I do however notice the difference in DOF.

If you have a look at this page, http://www.wlcastleman.com/equip/reviews/85_100_135/index.htm, you will see a comparison between the canon 85mm,100mm, and 135mm lenses with many comparison pictures. The author, many viewers, and myself have noted that there is no visible difference in facial compression, and that camera positioning and lighting make a MUCH greater difference. Others here disagree.

[Ken Fong]

Thanks for the responses. So it sounds like there is virtually no difference between using a 50mm lens x1.6 to get an 80mm field of view versus using a true 80mm lens and backing up. Distortion (nose sticking out too much) should not be a factor in the 50mm lens scenario? If this is the case, I am going to favor the 50mm lens because I think I might lose some light by backing up.

[drisley]

That is my opinion. However, like I said, many will disagree.
It's a much debated topic.

[Tom W]

Thanks for the responses. So it sounds like there is virtually no difference between using a 50mm lens x1.6 to get an 80mm field of view versus using a true 80mm lens and backing up. Distortion (nose sticking out too much) should not be a factor in the 50mm lens scenario? If this is the case, I am going to favor the 50mm lens because I think I might lose some light by backing up.

Well, close. The 50mm on a 1.6 sensor will give the same field of view as an 80 mm lens would on a full-frame 35 mm sensor or film. In other words, you can stand in the same spot and get the same image coverage with the 50 on the 10D as with the 80 on a film camera.

The distortion you speak of has more to do with position than anything else. Here's a little experiment I did using a couple of different cameras. One was zoomed to its maximum length of 22.2 mm, while the other was shot at 24 mm. Positions were changed to give a similar size to the deer's head (Ian will be so jealous).

The first picture was with the 22.2 mm focal length. This is a telephoto lens on this particular camera, due to its small sensor size. Note the perspective of the image, and the way the two arms of the chair look almost parallel. I'm about 10 feet away for this shot IIRC:

http://images.fotopic.net/?id=4170144&outx=600&noresize=1&nostamp=1

Shot #2 is of the same setting, but with a 24 mm lens on a much larger sensor - that of the 10D. While it doesn't serve as a superwide on that camera, it does serve the purpose of comparing field-of-view for portraits. I moved in considerably closer for this shot, so that the deer's head and the front of the chair covered roughly the same size in the frame as they did with the other camera. And because I was standing so close, the head of the deer looks larger, and the arms of the chair appear as if their lines would converge much sooner than in the previous shot:

http://images.fotopic.net/?id=4170143&outx=600&noresize=1&nostamp=1

The moral of the story - its where you stand in relation to the subject that gives the "big nose" impression. A narrower field of view will allow you to stand further back, and thus reduce the "big nose" effect. Thus, as far as perspective is concerned, a 50 on a 10D is equivalent to an 80 on a full frame camera.

Don't ask me about DOF though. I'm tired of measurebating.

[ron chappel]

Yes,if you back up to get the same field of view you will indeed have exactly the DOF and perspective/compression etc as an 80mm f1.8 lens! :D
The 50/1.8 became hard to find new because everyone was buying this bargain lens exactly for that purpose

Notice some people try to compare lenses without backing up to get the same field of view! That is just weird

[drisley]

Actually, if you back up and get the same field of few, you won't get the same DOF as you would on a 80mm lens on a full frame sensor.

That is one reason why many people who go from a 1.6x crop to a smaller crop like the MKII (and especially to a full frame sensor) find that it is much easier to get a background blur... because you have to stand closer to the subject, giving more background blur.

[Tom W]

Actually, if you back up and get the same field of few, you won't get the same DOF as you would on a 80mm lens on a full frame sensor.

That is one reason why many people who go from a 1.6x crop to a smaller crop like the MKII (and especially to a full frame sensor) find that it is much easier to get a background blur... because you have to stand closer to the subject, giving more background blur.

Yes! And you'll note that the 22.2 mm telephoto lens on the S-400 has no background blur at all, while the 10D at 24 has a modest amount. DOF wasn't the goal of this test, however.

Unfortunately, I have the original shots archived somewhere, so I'm not able to readily tell what aperture I used since I can't get to the EXIF data. The S-400's aperture at full tele is f/4.9 and cannot be changed (the camera uses a neutral density filter to change apparent f-stop). I will say that the only time I've gotten any appreciable background blur from the little camera is in Macro photography.

[hmhm]

The idea of using an 80mm lens for portraits on 35mm film has everything to do with the distance you stand from the subject when you take the shot. What we're talking about is "perspective", namely the rate at which objects appear to get smaller as they get further from the camera. If you try to take a portrait using a wide-angle lens, you'll end up needing to stand too close to the subject, and the parts of the face nearest the camera will appear overly prominent (the "big nose in the lens phenomenon"). You want to use a short telephoto to allow you to take a few steps back, this distance helps to "flatten out" the features of the face a bit.

In short, a 50mm lens on a 10D has the same "perspective" (or "compression", if you want to use that term) as an 80mm lens on a 35mm film camera because it has the same angle of view, and thus you'll stand the same distance from the subject to achieve the same framing.

It will _not_ achieve identical depth of field, though, the 10D will achieve the depth of field that the 35mm film camera achieves with an aperture that's 1.6x smaller (e.g. f/10 on 10D gives the same as f/16 on 35mm film camera, using same subject distance, and 50mm on 10D and 80mm on 35mm film camera).
-harry

[drisley]

I agree with you hmhm

[ron chappel]

Oops :oops: :oops: :oops:
soory-i just plain forgot about the greater DOF you get from the smaller than full frame sensor! :shock:
The above posters are of course right
In fact i think you get exactly 1.6 times more DOF-
bob atkins on photo.net has an extremely good article on this very subject.I say extremely good because he puts it SIMPLY :D :D

http://www.photo.net/learn/optics/dofdigital/

[Ken Fong]

Thanks everyone for the confirmation. Tom, your illustration is great...I have greater clarity now.

On the other extreme, how does one shoot those photos of the dogs with exageratingly large noses...and how do you get them to look into your lens like that?

[chris.bailey]

a lot will depend on how big a space you have in your studio. Mine is somewhat cosy so I use a 50mm 1.4 for torso shots and an 85mm for head and shoulders. Full length I reach for the 17-40. Out of these I like the 85mm as you can get the background nicely blurred.

[ron chappel]

The big nose look is from either of two things
A fisheye lens will do that-you've likely seen tons of pics done that way.

But also ANY wide lens that lets you focus really close can do it too.There is a really good way of actually seeing how this works-just get yourself REALLY close to something ,a dogs face for example,and you'll see that the nose looks really long while the rest of the face is miles away
This is called perspective distortion and is the exact opposite of the flattening distorsion you want in most portraits

not sure why i can't make the image apear,here are links instead

These are just a cheap fisheye adapter,but a close focussed wide angle lens will have a very similar effect

http://www.photo.net/photodb/photo?photo_id=2470728&size=lg

http://www.photo.net/photodb/photo?photo_id=2470756&size=lg

[Jakov]

a lot will depend on how big a space you have in your studio. Mine is somewhat cosy so I use a 50mm 1.4 for torso shots and an 85mm for head and shoulders. Full length I reach for the 17-40. Out of these I like the 85mm as you can get the background nicely blurred.

All true, here is a shot with 50mm f/1.8 @2.8 distance about 3m from model.. Nice, but for a headshot 85mm is much better choice
http://img78.photobucket.com/albums/v255/nenad/Slika_018.jpg

Hope this helps you to decide.

[drisley]

:shock:

[Olegis]

I didn't do any "proper" model shooting with the 50mm yet, but from what I've shot on a local food festival - the 50mm is one great performer for torso+shoulders+head shots :

http://www.pbase.com/image/29624777.jpg

http://cakili.image.pbase.com/image/29624787.jpg

http://www.pbase.com/image/29624798.jpg

You just need to get closer for a tight head shot - which I guess will bring the nose out a little bit. I have to try this one day. Anyway it seems that with the 80mm lens you'll be able to fill the frame and keep the perspective more easily.

[Ken Fong]

Wow! Nice work. Did you use a flash bracket?

[drisley]

Very nice Olegis and Jakov!

I've tried both the 50mm and 85mm on people, and I see no difference in facial compression. (DOF is usually nicer on the 85mm though). I believe that the angle is much more important when it comes to facial features.

For example, the facial features in Olegis' first shot above seem more subdued because of the direct angle. Although the second and third images are not the same subject, the angle shows more facial depth and more prominence in the facial features.

[Olegis]

Wow! Nice work. Did you use a flash bracket?

Nope, I didn't use a flash at all. All the photographs at the food festival (http://www.pbase.com/olegis/tasteofcity&page=all) were shot with available lighting.

For example, the facial features in Olegis' first shot above seem more subdued because of the direct angle. Although the second and third images are not the same subject, the angle shows more facial depth and more prominence in the facial features.

In order to study the influence of the 50mm vs 80mm focal lengths I'll have to shoot a comparison sometimes ... Poor girlfriend 8)

[Jakov]

:shock:

For a second seemed to me I did something wrong, and then saw your 2nd post..

Well I'm new to all this DigitaL stuff

go dital go!