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I have a really 'noobie' question about lenses.

Discussion in 'Native Lenses' started by banana101, Apr 17, 2011.

  1. banana101

    banana101 Mu-43 Regular

    57
    Mar 5, 2011
    London
    I've got to grips with most of the terms used for lenses and for the camera i.e aperture, the f-points, ISO etc etc but I still can't get my head around the whole '20mm' '80mm' etc :( can anyone explain it to me :redface:
     
  2. Gwendal

    Gwendal Mu-43 Veteran

    300
    Jun 6, 2010
    Focal length : the higher the figures, the narrower your field of view and the closer things seem to be. Let's say you want to capture a whole building : you will want the shortest possible length, around 15mm for example. If on the contrary you want to capture a wild animal that's far from you, you want a longer lens, for example 200mm. Also note that the shorter the lens, the more distortion you get - buildings that seem to fall back etc ; so if you're making a portrait, you'll prefer to stand back from the person and use a rather long lens. And finally, note that the same lens will give different fields of view on different sensors - typically, a 50mm lens on a m43 camera will give the field of view a 100mm lens would give on a full-frame camera.
    I hope it's clear - the best way to get your head around this is play with a zoom lens and browse through the forum's "Sample images archives" for native or adapted lenses : Native Lens Sample Image Archive - Micro Four Thirds User Forum and Adapted Lens Sample Image Archive - Micro Four Thirds User Forum
     
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  3. Spuff

    Spuff Mu-43 Top Veteran

    652
    Dec 5, 2010
    Berkshire, UK.
    Is that so?
    The Panasonic 20mm is not what I understand as 'long' and that is an ideal portrait lens.

    I think this page is quite good and explains things very clearly:
    http://www.hypergurl.com/blog/photography/numbers-on-lens.html
    (becomes not relevant to m43 at the end)

    and this page goes more in depth:
    http://www.cambridgeincolour.com/tutorials/camera-lenses.htm
     
  4. Iconindustries

    Iconindustries Mu-43 Hall of Famer

    The panasonic 20mm when used on m4/3 camera's has the same field of view as 40mm on full Frame. 50mm is pretty close to the same focal length as our eyes. So hence it's a good portrait lens because it's relatively close to 50mm. Most great portrait lenses you find are 50mm, as it looks the most natural to our eyes.
     
  5. Gwendal

    Gwendal Mu-43 Veteran

    300
    Jun 6, 2010
    OK - I admit my mistake on the concept of portrait lenses (but point out that Understanding Camera Lenses mentions that the "medium telephoto" range ie 70-135 is ideal for portraiture ;-) )
     
  6. kevinparis

    kevinparis Cantankerous Scotsman

    Feb 12, 2010
    Gent, Belgium
    actually in 35mm film photography the classic focal length for portrait lenses was in the 85-105 mm range - it allowed you fill the frame without sticking the camera in somebodies face, or a achieve a fuller portrait and have some separation from the background.

    Every major system manufacturer would have a 85/1.8 in their lens range. I have ones from Nikon, Canon, Contax and Olympus

    The Panasonic 20mm is a bit wide for a portrait lens - wider angle lenses tend to distort the features

    K


    in micro 4/3 the 50mm lens sort of serves the same purpose taking into account of the doubling aspect of the smaller sensor - hence the popularity of using legacy 50mm lenses
     
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  7. Before we get too off-topic with debating what is a portrait lens, the focal length of a simple, single element lens is a physical property that refers to the distance behind the lens that it will focus light to a single point. Think of a magnifying glass, where you can focus a point of light to the degree that it can actually start to char wood or burn paper. The distance the magnifying glass is from the surface is equal to the lens' focal length. While a camera lens is made up of multiple lens elements, the combination of these elements has a focal length just as a single lens does.

    When related to cameras you only really need to know how to relate focal length to field-of-view or angle-of-view. As long as you know what FOV a particular focal length will give you, that's really all that matters.
     
  8. Alanroseman

    Alanroseman Super Moderator Emeritus

    Dec 21, 2010
    New England
    I'm in Kevin's camp here.

    The standards for 35mm "perfect" portrait being 85-105mm.. I'll extend that traditional viewpoint to the well regarded FL of 135mm.

    This is one of the very best reasons to collect 1 or 2 real favorites in your legacy lens collection.

    Any nice 45 - 58 mm legacy lens ie. Canon, Nikon, Rokkor, Hexanon etc et al. instantly transforms itself into a perfect portrait lens when placed on your µ43 body.
    The focal length of the legacy lens being "doubled" when used on your µ43.

    So in effect, a 55 mm Rokkor, becomes a perfect 110mm portrait lens, same with all. 45mm Hexinon being transformed into a nice 90mm portrait lens on your Oly or Panasonic body.

    Cheers, Alan
     
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  9. Spuff

    Spuff Mu-43 Top Veteran

    652
    Dec 5, 2010
    Berkshire, UK.
    Ah, waded in with partial knowledge again, wrong I was.
    Would it be true to say that the Panasonic 20mm is regarded as good native portrait lens for m43? I've gained that impression. Is that more because of the low light speed?
     
  10. The 20mm can be used for portraits, but it is not a 'classic' focal length for portraits. Part of the reason why the 85-105mm (in 35mm film terms) is preferred is due to the perspective these focal lengths give of the human face. A longer focal length will tend to flatten a face. A shorter focal length will distort a face and give the subject an unnaturally big nose.
     
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  11. Pan Korop

    Pan Korop Mu-43 Veteran

    479
    Mar 31, 2011
    Phare Ouest
    Portraits? Zoom!

    ... and even 180mm for tight close-up framing.

    This is why the "ideal portrait lens" to me is a fast, AF, medium telephoto zoom. A 70-200/2.8 in 35mm comes close. Working distance remains fixed, say 2~2.5m (6~8 ft), and you "crop" with the zoom. Aperture doesn't change, so you can work with any strobe setup.

    Except a 50 mm comes in handy when you want to show the person in situation, like at work, or with its hands (picture Mona Lisa?).

    So, my dream lens would be a 25-100 or 25-75mm f/2.0 :43: native (i.e. AF) lens. Keep on hoping :rolleyes:
     
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  12. kevinparis

    kevinparis Cantankerous Scotsman

    Feb 12, 2010
    Gent, Belgium
    the zuiko 50-200 makes a nice portrait lens - though its a bit big for a micro 4/3 camera

    3591575893_bf3afab7c4_z.
    Rex by kevinparis, on Flickr

    3590648948_c768ef60ae_z.
    simon by kevinparis, on Flickr

    K
     
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  13. Spuff

    Spuff Mu-43 Top Veteran

    652
    Dec 5, 2010
    Berkshire, UK.
    I see.
    Those portrait shots to my relative newcomer eyes I would certainly see as a zoom/long lens shot.
    And come to think of it the 20mm people shots I've seen are probably more full body/multiple person.
     
  14. kevinparis

    kevinparis Cantankerous Scotsman

    Feb 12, 2010
    Gent, Belgium
    just to clarify for the original poster

    the focal length of a lens determines how much of your subject is captured by the camera.

    The smaller the focal length the wider the view or the bigger the focal length the more your image is magnified.

    The size of the sensor/film also has an effect on this as well

    In traditional 35mm film - or of a full frame digital camera like a Canon 5D or Nikon D700, typical focal lengths were as follows

    Ultra wide angle: 10 to 20mm - used for architectural and dramatic effects
    Wide Angle: 24/28/35mm - landscapes, photojournalism
    Normal: 50mm - general photography
    Telephoto: 85/105/135mm - portrait, some sports
    Extreme Telephoto: 200mm up to 1000mm - sports, wildlife

    In micro 4/3 cameras, because the sensor is half the size, then all these numbers get halved

    so in micro 4/3 for example , the Panasonic 14mm, gives you the same view as a 28mm lens would on a 35mm camera - so the 14mm is a wide angle lens.

    Now as a lens doesn't know what camera it is attached to, and it cant change its focal length, if you put a 50mm lens on a 4/3 camera, it will give you the same view as a 100mm lens on a 35mm camera - in other words a telephoto lens.

    hope this helps


    K
     
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  15. Tom Swaman

    Tom Swaman Mu-43 Veteran

    Same Info in Different Words.....

    Here is the same info with a bit of historical perspective and a few fifferent words. I hope it helps some of you.

    In the days of olde when things like "aspheric, ED, etc. were not invented and lenses were designed by man rather than by computers, a camera normal lens was typically selected to have a focal length approximately equal to the film diameter, now sensor diameter. Hence, the 3:2 format of a full frame 35mm camera had a film diameter approximating 43mm. So, normal lenses are typically said to fall in the 45 mm to 55 mm focal length range.

    These normal lenses, like most lenses are not perfect in producing images. They suffered from aberrations, distortions and short working distance. Lens/camera designers found that many of the undesireable image distortions and short working distance could be avoided by using a longer focal length lens for portraiture such that its focal length was about 2 to 3 times that of the normal lens or about 90mm to 150mm.

    Perhaps the most important things that the longer focal length portrait lenses afforded photographers included, but was not limited to minimization of the unflattering affects of barrel distortion, increased working distance to make portrait lighting easier without "melting" the model and allowing the photographer to better locate their camera without being in the face of the model or blocking the light.

    Today, whether or not necessary, we continue the name of portrait lens when the focal falls in the approximate range of about 2 to 3 times the sensor/film diagonal in its effective aspect ratio. In reality, there is nothing magic or sacred about these names or numbers, only the results count.

    Have fun,
    Tom
     
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  16. sphexx

    sphexx Mu-43 Regular

    54
    Feb 19, 2010
    Harrogate, Yorkshire
    There is an interactive focal length demo on Nikon web site at:
    Nikon | Imaging Products | NIKKOR Lenses Simulator
    Obviously it does not cover µFT but I think it may be useful.
    The best interactive demo I have seen is:
    cameraDemo
    but it only relates to exposure.

    Richard
     
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  17. ~tc~

    ~tc~ Mu-43 Hall of Famer

    Oct 22, 2010
    Houston, TX
    This is not exactly true. Distance to subject causes distortion. Wide angle lenses tend to be misused by people getting very close to the subject in order to fill the frame for a head/shoulders portrait. Here's an article with pictures showing the effect and how to avoid the problem

    Micro 4/3rds Photography: Using the Lumix 20mm as portrait lens

    Longer focal lengths avoid the problem by forcing the distance to subject to be far enough due to the restricted field of view.

    Here is a graphic depiction of the effect of focal length on field of view
    Olympus Zuiko lens field of view comparison
     
  18. kevinparis

    kevinparis Cantankerous Scotsman

    Feb 12, 2010
    Gent, Belgium
    good link.... but stand by my original assertion.... :)


    if you fill the frame with a headshot using the pana 20mm you will get distortion... moving away and cropping is a work around

    I know and you know that wide angles shouldn't be used for portraits... certainly if you a beginner

    K
     
  19. Pan Korop

    Pan Korop Mu-43 Veteran

    479
    Mar 31, 2011
    Phare Ouest
    Sorry but no, no and no. In the 19th century already, the Cooke triplet solved most of these problems. 1902 Tessar just solved the last one. And, by the way, it was already computed, if by hand: Abbe's law is math, not grind the glass and hope. As for working distance, hence perspective, the Italian Renaissance had already coined the rules... And a turn of the centuries Kodak Cirkut camera shot perfect 360 panoramas before anyone came to software stitching: how to get a really wide angle shot with none's head distorted!
    In short: even before silver halide photo took over Daguerreotypes, they weren't Flintstones.
     
  20. Pan Korop

    Pan Korop Mu-43 Veteran

    479
    Mar 31, 2011
    Phare Ouest
    Yes, mostly. Hence my advocacy of zoom lenses for portraits: fixed distance, different framing.

    Plus being off the lens axis. Sphere in center of a 14mm (7 mu43) lens frame looks undistorted. In the corner, looks like a rugby ball...
    I shot portraits (full body) with 24 mm lenses, head off-center and they were OK. But I cheat: 24 shift lens frames off-center, but the mug-shot remains in the optical axis. Basic view camera technique applied to modern gear...