Confused About Lens Lengths

Discussion in 'Photography Beginners' Forum' started by gunghorjc, Apr 6, 2010.

  1. gunghorjc

    gunghorjc TPF Noob!

    Joined:
    Mar 27, 2010
    Messages:
    23
    Likes Received:
    0
    Location:
    Michigan, U.S.A.
    Can others edit my Photos:
    Photos OK to edit
    I can't really seem to find a "direct" answer w/ google, and I've looked in the stickies for this board and can't find them there either.

    So I'm confused how lens lengths affect the type of photos you'll produce. I'll be purchasing my digital SLR within a month and I'm debating going with just the kit lens to start off, or with another one as well.

    Does the longer lens (i.e. 300mm) allow you to get a great depth of field for scenic shots? Or are the longer lenses for more extreme close ups for flowers, bees, bugs, etc?

    I hate to be redundant if I this has been asked a gazillion times but it is something I'd like to know. Any links anyone could supply that explain it would be really awesome too! Thanks. :)
     
  2. DerekSalem

    DerekSalem TPF Noob!

    Joined:
    Aug 8, 2009
    Messages:
    660
    Likes Received:
    10
    Location:
    Cleveland, OH
    Can others edit my Photos:
    Photos OK to edit
    Well long confusing story short...the bigger the maximum length (300mm in your example) the more it can zoom. There's a lot of math involved in figuring out exactly how the number correlates but the bigger the number, the more zoomed in.

    For depth of field your looking for a lower f number (like f/1.8). Lower numbers mean a bigger aperture on the lens
     
  3. Vinny

    Vinny TPF Noob!

    Joined:
    Mar 14, 2010
    Messages:
    667
    Likes Received:
    1
    Location:
    New Jersey
    Can others edit my Photos:
    Photos OK to edit
    The longer the focal length, the closer the object appears to be. Also the longer the focal length the objects that you are looking at appear to be closer together. A lens has a minimum length that it can focus to and you can zoom in howerever much as long as you remain at that distance. The exception being a macro lens - it's function is to focus close distances.

    I would advise going to the library if you can and get a photography book but Nikon has a lens selector to show what it's like: Nikon | Imaging Products | NIKKOR Lenses Simulator
     
  4. pbelarge

    pbelarge TPF Noob!

    Joined:
    Feb 11, 2010
    Messages:
    2,680
    Likes Received:
    0
    Location:
    New York
    Can others edit my Photos:
    Photos OK to edit
    Gung
    this is strictly my advice, I am sure there are others who may not agree, which is fine.

    If you can afford not to purchase the kit lens, I would look to buy a different lens. The $64,000 question then would be...which lens.

    So, you have to ask yourself what you want to shoot.
    Landscape, wildlife, macro, night, portrait, glamour, architecture, abstract, weddings, etc...
    There are some lenses that overlap some of the types of shooting, and then there are lenses that are very specific, such as macro lens.

    You can follow this google link Google , which will help you get started in your choice of lens.

    Take a look and get back to the site there are some guys here who are really knowledgeable with lenses.
     
  5. JSD

    JSD TPF Noob!

    Joined:
    Aug 9, 2009
    Messages:
    138
    Likes Received:
    0
    Location:
    Colorado
    Can others edit my Photos:
    Photos NOT OK to edit
    Does the longer lens (i.e. 300mm) allow you to get a great depth of field for scenic shots? Or are the longer lenses for more extreme close ups for flowers, bees, bugs, etc?

    Longer lenses such as a 300mm are often used for subjects that cant be gotten close to such as wildlife, and have less depth of field than shorter lenses. Wide angle-shorter- lenses such as 24mm have much more depth of field. Often, but not always, short lenses are used for scenics/landscapes becasue of their huge depth of field. Macro lenses are for getting really close as with bugs and flowers, and have very little depth of field even when stopped down to a small aperture such as f16. Remember: The smaller the aperture the bigger the f- number (i.e. f16) and the more depth of field. Larger aperture= smaller number (i.e. f1.8) and less depth of field. BUT: f16 on a 300mm does not equal f16 on a 24mm in terms of depth of field. Hope this helps...JSD
     
  6. SrBiscuit

    SrBiscuit TPF Noob!

    Joined:
    Apr 22, 2008
    Messages:
    2,721
    Likes Received:
    44
    Location:
    NH
    Can others edit my Photos:
    Photos OK to edit
    the faster the lens the better DOF.
    but even zoomed all the way, with the ap wide open, a slower lens should still get decent DOF...provided your subject is well in the foreground. (the bokeh might not be ideal)

    keep in mind too that if youre shooting with a crop body the length will be multiplied by roughly 1.5x. i.e., a 300mm lens on a 1.5 crop body will be 450mm.
     
  7. KmH

    KmH Helping photographers learn to fish Supporting Member

    Joined:
    Apr 9, 2009
    Messages:
    38,223
    Likes Received:
    5,003
    Location:
    Iowa
    Can others edit my Photos:
    Photos OK to edit
    Depth-of-field is a function of several factors:
    • the apparent lens focal length
    • the lens aperture
    • the subject to image sensor distance
    • the subject to background distance.
    Lens for making closeups of bugs are quite specialized and the good ones are expensive. They are known as macro lenses though some lens makers use the term as a marketing aid more than as a true description of a lenses capabilities.
    Many of them have focal lengths from 60 mm up to about 200mm. The longer focal lengths for macro lenses mean the lens can be further from the subject so as to not scare it off or to make lighting it easier.

    The longer focal length non-macro lenses offer what is called more 'reach' or magnification, like shooting sports from the sidelines or making images of birds of prey in flight. Generally, as focal length increase so does lens cost.
     
  8. --ares--

    --ares-- TPF Noob!

    Joined:
    Aug 17, 2009
    Messages:
    152
    Likes Received:
    0
    Can others edit my Photos:
    Photos OK to edit
    Not to throw this thread off topic, but does focal length and range have any direct bearing on magnification? Or does it change from lens to lens?
     
  9. Nameless

    Nameless TPF Noob!

    Joined:
    May 25, 2009
    Messages:
    37
    Likes Received:
    0
    Location:
    NYC
    I would have to disagree with this slightly because I think it is dependant on which camera/kit the OP buys. The Canon 7D kit comes with a 28-135mm IS, which is a pretty good lens for someone starting out. The Nikon D90 kit comes with a 18-105mm VR, which is also pretty decent for the money.
     
  10. gunghorjc

    gunghorjc TPF Noob!

    Joined:
    Mar 27, 2010
    Messages:
    23
    Likes Received:
    0
    Location:
    Michigan, U.S.A.
    Can others edit my Photos:
    Photos OK to edit
    Thanks everyone for the replies! Really great information.

    As to what kit, I'm still debating between the Nikon D3000 kit or the Canon Rebel 350D kit. Both come with a an 18-55mm lens I believe.

    I guess what I'm really getting at. How do you determine what lens for how far away you are from a subject? Such as if the subject is 100, or 200 feet away.
     
  11. chaman

    chaman TPF Noob!

    Joined:
    Apr 7, 2010
    Messages:
    11
    Likes Received:
    0
    Can others edit my Photos:
    Photos OK to edit
    I would suggest to get the kit lens and start shooting, and shooting! You want to start right away, right? Then as you gain a bit more experience consider a zoom lens or a better all around alternative. My advice...whatever you do, get a 50mm prime lens...!
     
  12. Derrel

    Derrel Mr. Rain Cloud

    Joined:
    Jul 23, 2009
    Messages:
    35,456
    Likes Received:
    12,795
    Location:
    USA
    Can others edit my Photos:
    Photos OK to edit

    Within a format, like APS-C, or FX digital, or 645 rollfilm or 120 rollfim,and so on, the shorter a lens is in focal length, the wider its angle of view, and the lower its magnification. Focal length of a lens is computed and specified with the lens at Infinity focus; as a lens is focused closer, it typically will lose focal length--sometimes quite a bit, especially in the case of macro lenses, or lenses which are corrected to deliver flatter field and better close-up performance. So, when talking about focal length, it must be measured with the lens at Infinity focus.

    The relationship between focal length and image size is directly linked. A 25mm lens will produce an image that is half as large as a 50mm. A 50mm lens will produce an image one-half as large as that of a 100mm lens, and a 200mm image will produce an image size that is twice as large as that of a 100mm lens. So, the relationship in Image size is direct, when the different lens lengths are used on the same camera format.

    It's important to note that the optical industry has about a 10 percent maximum tolerance in labeling on lenses and MANY lenses cary specified focal lengths that are a slight bit off in their actual, measured lengths; a 300mm labeled single focal length lens may actually be a 285mm lens, or a 307mm lens when measured critically. Same with wide-angle lenses, and zooms like 24-70mm, which could easily be a 25.1-68mm or some such thing.
     

Share This Page

Search tags for this page

lense lengths