Lenses

Discussion in 'Photography Beginners' Forum' started by Leigh, Apr 29, 2007.

  1. Leigh

    Leigh TPF Noob!

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    :confused: :confused: I've read lots of threads from people wanting help with buying a new lens and to me (a complete and utter noob and not at all technicaly minded) all the posts seem to be filled with numbers. What on earth do all these numbers on a lens actually mean??:confused: :confused:

    I want to buy a macro lens for doing close ups and improving my portraits but honestly havent got a clue where to start.

    All help aprreciated.
     
  2. GYFÄP

    GYFÄP TPF Noob!

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    Hey, thanks for posting! I'm kinda in the same situation ;)
    Anyone? Help?
     
  3. agonzalez

    agonzalez TPF Noob!

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    Focal length, max aperture, etc... try doing a search, it has been explained several times. :)
     
  4. DSLR noob

    DSLR noob TPF Noob!

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    DSLR Noob's lens buying guide.

    How a lens is named(Canon, others are similar)

    Canon------------50mm------------f/1.4------------USM
    ^manufacturer----^focal length----^max apertrue--^feature, in this case, a USM ring focusing motor

    For landscaping you want the middle number to be as low as possible. The max Aperture is better when it is a low number as well.
    Nikon uses a few lettering systems to indicate featers in the lens name such as VR (vibration reduction) ED (low dispersion glass) etc.

    Focal length guide(variable "L" for length):
    L < 28 it is considered wide and would be good for landscaping, somehting around 14 to 21 would be ideal. It is also good for taking pictures in cramped spaces. One can also emphasize the size of a building.

    30> L < 80 Is considered a midrange lens. Good for portraits, photos of cars, etc.

    L < 80 Is a telephoto, good for taking pictures from a distance. Lengths above 250 are great for nature photography of animals that'd be scared when you approach closely. think a telescope for your camera.

    Aperture Guide usages and benefits.
    A low aperture number or a high aperture (the lower the number the higher the aperture, don't ask). A high aperture (like 1.8) means that the aperture blades in the lens can open up to a very large hole to let light pass through. Thus you can take a picture in a low light situation, without a shutter speed slow enough to make camera shake a horrible reality. The positives, being able to use faster shutter speeds, brighter viewfinder, interesting blurring of the objects not focused on (called bokeh, and is achieved with a shallow DOF [depth of field] ). Downside, fully opened lenses aren't as razor sharp as usual, shallow depth of field can be a bad thing, (i.e. let's say you focused on a bench 30 feet in front of a building, this bench has really nice aging wood and beautiful woodgrain, but the building also has a detailed antique feeling. You want to capture both. well if your aperture is wide open at 1.8, when you focus on the bench, the building turns into a blurry series of dots of light[you see them in movies in the background or foreground a lot].

    Using a smaller aperture (lower MAX is still preferred in buying a lens but this is a usage tip) can be good because more is in focus. you would be able to take a picture where the bench and the building, are in moderately good focus (naked eye probably couldn't tell the difference). Downsides to this are, longer shutter speeds, possibly needing a tripod, darker viewfinder, and if too high, once again losing razor sharpness on the most focused object.

    Most lenses work best (for razor sharpness) at around F/8.

    Here is just a feature yo might see someday when looking at lenses.

    Macro- indicates a life-size magnification. In other words, you can focus close enough to a small object, filling the frame, and it would take the picture with the object in life size proportion to your sensor. think, if you sensor is the size of a postage stamp, and you take a picture of a bug that fills the entire postage stamp, then when you uploaded the image, that poster stamp image makes a 40 inch high res Monitor sized digital image, and in theory, a 40 inch bug in full detail!


    Focal length diagram of how a telephoto sees compared to a wide angle. (Variable "C" for camera, lines represent everything camera can see, not the shape of the lens) Both cameras are pointed at a red Corvette.


    Telephoto, 150mm
    [​IMG]
    ......|...........|.........
    ......|...........|.........
    ......|...........|.........
    .......|.........|..........
    .......|.........|..........
    .......|.........|..........
    ........|.......|...........
    ........|.......|...........
    ........|.......|...........
    .........|.....|............
    .........|.....|............
    ..........|...|.............
    ..........{C}.............


    Wide angle 28 mm
    [​IMG]
    \.........................../
    ....\.................../....
    .......\............./.......
    ..........\......./..........
    ............{C}............

    On the telephoto, notice the accuracy to fill the frame with a small portion of what the camera is pointed at, but at high magnification (imagine the lines at the end of the camera's sight being edges of a picture frame, the photo is the same size, just stretch or squish the image into that perspective. this camera sees from a few feet in front of the bumper to just in front of the rear tire of the car.


    On the wide angle, it captures a lot of what it is pointed at, more than what your eye can pick up (eye is about a 50mm), but everything in the picture is smaller to fit. Once again picture is same size. This image captures the car and the entire parking lot

    Always research a lens before buying it. Just because it has the focal length and aperture you want doesn't mean that the image quality is great. ask here before purchasing!

    Aperture diagram.
    This is a bad example because I rarely take photos with a large depth of field but here is aperture at 2.8
    [​IMG]
    See how the girls are both in focus, as is the front of the table to the rear of the table?

    Well here is another photo at 1.8
    [​IMG]
    look at the table the can is sitting on. Notice how an inch of depth is in focus. Everything an inch behind the can is blurry everything an inch in front of the can is blurry. Making the can stand out, a desired effect in this instance. The soft background is called bokeh and is visually pleasing without its sharp lines and harsh contrast.
     

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