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Photography Question 
Rob Francis

Portrait lens focal length


After fumbling around for a while I have taken a real shine to candid and eviromental portraits, I wanted to take this up a level and have decided to look for a prime portrait lens.

What im a little stuck on is the 1.6x crop factor.

I know that it is recommended that for this sort of picture to use a fast lens F1.4 - F2.8 in a 50mm, but on my 20d a 50mm becomes 80mm so would I be better looking to get a 30mm prime instead ? (30 x 1.6 = 48mm)

If anyone could also give me some makes/models and any feedback on the lenses that would be great.


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5/23/2007 5:20:27 PM

Bob Fately   Actually, Rob, in traditional 35MM format the standard portrait lens is 85MM or sometimes 105MM, so a 50MM lens with that crop factor of 1.6 should make for a very nice portrat length.

The reason this focal length is often used for portraits is that it allows for the filling of the frame with head and shoulders yet allows the photographer to stand 6-8 feet back, giving the subject more space to feel comfortable.

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5/23/2007 5:42:40 PM

Rob Francis   Ok , thank you very much.

I had heard so often that a 50mm lens was condsidered a portrait lens but in retrospect that was from digital photographers so it all makes sense now

Any recommendations for a lens ?

Im looking at the Canon f1.4 50mm USM at the moment. is there any alternitives I should consider ?

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5/23/2007 5:56:23 PM

Bob Fately   Actually, that might be the ideal lens - you want the fast glass to minimize DOF so backgrounds get blurred and are not distracting to the eye.

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5/23/2007 6:02:29 PM

Debby A. Tabb
BetterPhoto Member Since: 9/4/2004
  This kind of question Lens for Portraits comes up alot so from a previous post:

I find it best to work with my 200mm
when doing portraits 100-300 is recommended, you do not want to be switching lens alot in a portrait sitting and you are working with a space that allows you little control of your background.
Typical "portrait" lenses are therefore between 90 and 135 MM long.
most professionals use 70-200/2.8 or 80-200/2.8 zooms as portrait lenses,
or better yet 100 or 105 macro.
A lot depends on where you want to start and you pocket book.
I hope this helps,
Debby Tabb

* In my reg portrait sitting camera bag I have:
Nikon D200 and Fuji S2
Nikon 24-120mm 1:3.5 Vr Lens
Tamron 28-300 AF 1:3.5 macro lens
Tamron 28-200 AF 1:3.5 macro lens
on site extras:
Polarizes, soft focus and Centre Soft and asst. other filters depending on the job.

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5/23/2007 10:29:36 PM

Darren J. Gilcher
BetterPhoto Member Since: 9/1/2005
  Debby, is part of the reason portrait lenses are longer also due to the fact that shorter lenses up close distort the subject a little like a fish eye effect? Obviously with a 50mm lense the effect would be slight but while the crop factor makes the 50mm equivalent to an 80mm the camera is still too close to the subject so the longer lense puts the camers farther away from the subject. Am I in the ballpark with this assumption?

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5/23/2007 10:43:10 PM

Pete H
BetterPhoto Member Since: 8/9/2005

The word "portrait" probably needs to be defined. LOL
Dictionaries are poor (IMHO) in rendering a proper definition.

Generally though, it is the capturing of a persons face and/or body, be it in a drawing, painting or photographically.

With that said; the lens choice will be one of personal preference and modeling mode desired. (Head & shoulders..Face..Full body)..etc

Longer lenses (100mm +) are good choices as they "flatten" the persons face and limit the depth of field. (i.e) Eye sockets won't look so deep or a nose looking too big.

There are many photographers who use the shorter lenses for portraits as they seek a different look or perspective. 18-28mm lenses are not unheard of in portrait work, but these are usually for special effects portraits.

You will want a series of focal lengths when shooting portraits.

Personally, I see no reason to go with just ONE prime for all your portrait shooting. By doing so, you lock yourself into a (range) and eventually a cookie cutter approach.
You'll find yourself forced into changing (YOUR) distance to subject and probably missing many magical moments.

A prime is ok for a studio only setting; but even that is limiting. I like to move around, change the shooting angle at times etc....I don't want to worry about moving closer or further away from my subject..Or tripping over something as I look thru the viewfinder! LOL

Personally I like 50-200mm for outdoor use and maybe 28-135 for indoors.

All the best,


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5/24/2007 4:36:52 AM

Alan N. Marcus   Hi Rob,

Consider this long winded explanation.

Ideally what focal length we use should be based on our desire to render an image as distortion free as possible. Our subjects and editors seem to prefer images that display reduced distortion as these renderings prevail i.e. they sell and win contests. When we choose a lens that is too short, distortions creep in and the nose is rendered too big and the ears too small. On the other hand, if we choose a lens that is too long, facial features appear compressed. In either case a facial rendering is compromised due to improper prospective. You should also know that photography is an art form and sometimes images win because they are seemingly enhanced by out of place prospective.

Technically a camera generated image will be distortion free if the viewing distance is exactly the same as the taking focal length. While at first glance this seems a ridiculous statement it is completely factual. It is for this reason that slides are often inspected using a hand held viewer. These convenient viewers are equipped with 2Ē (50mm) magnifying lens, the same focal length used on most fixed lens 35mm cameras.

Now you need to know, for distortion free viewing, we must take into account display size. When we make a print or view on a projection screen or monitor, the size of the display i.e. the magnification must be taken into consideration. Consider an image taken with a 35mm camera equipped with 50mm (2 inch) lens. Generally an 8 x 10 print is made; this enlargement is produced using a magnification that works out to be about 10x. Now the viewing distance becomes 2 inches x 10 = 20 inches, which is the ideal, distortion free, viewing distance. Portraits are generally viewed mounted and framed and on the wall thus the viewing distance averages 40 inches. For this reason a 105mm taking lens, mounted on a 35mm camera is considered best. When using cameras other than 35mm, the same math applies.

Letís look at your 20D in the same light. You camera sports a sensor chip thatís 62% smaller than a 35mm film frame. The 35mm frame is 24mm height 36mm length 43.3mm diagonal measure. The 20D is 15mm height 22.5mm length 27mm diagonal measure. Thus 27/43.3 =0.62 or 62% smaller. Stated another way, 43.3/27=1.6 the conversion factor your camera vs. the 35mm camera.

Applying this wisdom we can calculate the ideal focal length for portraiture using the 20D as 105 x 0.62 = 65. Thus the 65mm is the midpoint focal length to consider for portraiture.
Again, photography is both a science and an art. You are free to use any lens that suites your taste.

Alan Marcus

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5/24/2007 7:40:35 AM

Christopher A. Vedros
BetterPhoto Member Since: 3/14/2005
  Darren - Your assumptions are correct.

Rob - The Canon 50mm f/1.4 is a very sharp lens that works well for some portraits and other general uses. I also use the 85mm f/1.8 sometimes, and I also use my f/2.8 zoom lenses sometimes. Like Pete said, there's no reason to stick with just one lens.

The focal length that works best for a given portrait will depend on several factors, including: how many subjects are in the photo, how much of the body do you want visible, how much of the background do you want visible, how far back from the subject do you want to move, how far back from the subject can you move with the room you have, etc.

If you have a zoom lens, or can borrow one, get a friend to help you do a test. Set up or find a typical portrait setting that you would like to use. Position yourself at what you think is a comfortable working distance from the subject, and see what focal length on the zoom will give you the framing that you want for the portrait. Take some shots moving in with shorter focal lengths, and moving back with longer focal lengths to see how the image is affected. Take notes on what focal lengths work best for you.

Good luck,
Chris A. Vedros

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5/24/2007 9:34:38 AM

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