Negligible focal lengths on prime lenses?

Discussion in 'Photography Beginners' Forum' started by bahandi, Dec 13, 2009.

  1. bahandi

    bahandi TPF Noob!

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    Would someone be able to educate me on the reasons why the differences between focal lengths are so "negligible" (the term negligible is borne out of pure ignorance)?

    That is, for example, why the need for 20mm vs 24mm vs 28mm? Or a 35mm vs 50mm vs 60mm?
     
  2. T-town photographer

    T-town photographer TPF Noob!

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    They all have a different effect to the film.

    Michael

    That is my best answer for what it is worth.
     
  3. bahandi

    bahandi TPF Noob!

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    Would you elaborate on "effect"? What I'm interpreting it as is how much the subject would be able to fill the frame or not.

    For example, with a kit lens, shooting something at 18 vs 55. But with such "negligible" focal lengths, why not walk closer or further?
     
  4. Dwig

    Dwig TPF Noob!

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    No one would ever have all of the primes. They pick and choose what fits their needs.

    Back in ancient times (read: before quality zooms were common) the common wisdom was that you needed a set of lenses that were spaced such that each focal length was 2-3x longer than the next wider lens in your kit. For example, back in those days my core kit of lenses were 20mm, 35mm, 105mm, & 300mm. The first two were a bit closer together than 2x but after that they were about 3x. I also had a 45mm and a 55mm but those were both special lenses, a compact pancake and a macro respectively. Some liked a kit more consistantly 2x spacing and would have a 24mm, 50mm, 105mm & 200mm set, or if the more expensive 24mm wasn't in the budget they'd have a less expensive 28mm.
     
  5. RyanLilly

    RyanLilly No longer a newbie, moving up!

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    If I understand what you are asking; Why would you need several very similar focal lengths eg. 20, 24, and 28? Then the answer is you don't need them. I think that at some point some one made a 28mm lens, and someone later on said "hey Wouldn't it be nice if this lens were a little wider, maybe a little faster?"

    I'm sure there are other design and marketing reasons that influence theses choices also. Maybe just to have a very large selection and various price points and quality, to appeal to different markets.
     
  6. JSD

    JSD TPF Noob!

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    18mm is considered wide angle, including a view that is wider than what the human eye normally takes in. Although we have good peripheral vision, nearly 180 degrees, what we see in most detail is roughly the equivalent of a 50mm lens, hence the name "normal" lens. Being able to zoom from 18mm to 55mm is a convenience, adding versatility. Sure you could move closer or further, but that may not always be possible. The ability to zoom gives you greater control of the composition of your picture, for example zoom in a little to eliminate some distracting element, or zoom out to include an attractive one.
     
  7. Derrel

    Derrel Mr. Rain Cloud

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    http://rabinergroup.com/pdfs/LensangleofviewtableLong.pdf

    lens angle of view
    On 35mm film (24x36mm capture size) 16mm lens has a 97 degree angle of view for the long side of the film. 19mm is 87 degrees; 21mm is an 81 degree angle; 24mm is 74 degrees; a 28mm lens shows a 65 degree view; 35mm shows 54 degrees; a 50mm shows 40 degrees, while 60mm shows 33 degrees; the 85mm lens shows 24 degrees, while a 100mm lens shows 20 degrees, and 105mm shows 19 degrees. A 135mm shows 15 degrees, 180mm is 12 degrees, and 200mm is 10 degrees, while 300mm is 7 degrees, 400mm is five degrees.
     
  8. chip

    chip TPF Noob!

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    wide angle lenses give you coverage. telephoto lenses give you reach. Normal lenses are for "general purpose". Zoom lenses allow you to change the focal lengths and are more flexible than fixed focal length lenses (prime lenses) but then they may not be as sharp and may be bigger and heavier. On a full frame digital (or 35mm film) camera 50mm is considered normal. Anything between 14-35mm is considered wide angle. Anything greater than 70mm is in the telephoto range. The focal length of a lens makes a huge difference. Depending on what you are trying to do, you need the right focal length lens to achieve your goal. For example, as you get more telephoto you will notice the DOF gets narrower. As you get more wide angle you will notice the DOF get wider.

    In terms of why not just walk closer to your subject, sometimes that may not be an option. If you are shooting a wild animal or a bird, they won't allow you to get close to them or they'll either run away or attack you. If you are in a room you may not be able to get the whole group in the frame unless you have a wide angle lens. well, unless you break down the building...?
     
  9. c.cloudwalker

    c.cloudwalker TPF Noob!

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    I have a 24, 28, 35, 50 and then I jump to 85. I also had a 20 but it turned out to be too wide and I sold it after about a year of barely using it.:lol:

    You can't look at it from a measurement standpoint alone. The 4 mm between the 24 and 28 may not seem much but it is 8-10 degrees (seems to depend on whose calculations you read) added to the field of view. In most cases you'd be fine but once in a while the 24 will allow you to get a better picture because you have a wall against your back.

    35mm is basically the standard lens in photojournalism. It allows you to shoot blind. Meaning the camera is over your head so as to not get just a bunch of heads in the frame. Because it is a wider angle, you will get your subject in by pointing the camera in the basic direction. And because it has less distortion than a 28 you get better images without getting too much in the frame at the same time thus, less cropping.

    The 50 came with my first camera, used it for a few months, got my 35 and basically stored the 50. Didn't sell it because it was a back up if I killed my 35.

    Always had one SLR body with a 35. And my rangefinder also had a 35 on.

    This by the way is only valid for film or full frame bodies.

    Cheers.
     
  10. shortpballer

    shortpballer TPF Noob!

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    I have a 14 24 50 and 85 and they are all COMPLETELY different. So i wouldn't call the difference negligible. I would say that even from 16mm on a 16-35 is COMPLETELY different that my 14mm 2.8L. The 14mm is WAY wider.
     
  11. bahandi

    bahandi TPF Noob!

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    wow... thanks guys. It's starting to make sense.
     
  12. t00sl0w

    t00sl0w TPF Noob!

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    starting to for me also...i hadnt considered the lenses in a way that some of you have
     

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