Can someone explain lenses...?

Discussion in 'Photography Beginners' Forum' started by LaLO929, Mar 22, 2010.

  1. LaLO929

    LaLO929 TPF Noob!

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    I've been looking into purchasing a new lens for outdoor portraits (anything from headshots to full length family photos to children) and maybe some low light indoor photos as well. As I've been researching and reviewing I've become more and more confused. Some of the lenses I've been looking at are the 50mm 1.4, 85mm 1.8, tamron 90mm 2.8 or the tamron 70-200mm 2.8. As I read on each of them it's discussed about distance between the subject & I, crop sensors, and DX stuff. Can someone help explain in newbie language what the difference between the lenses are? I feel dumb for asking but I guess this is the only way to learn, right? :blushing:
     
    Last edited: Mar 22, 2010
  2. Dao

    Dao No longer a newbie, moving up!

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  3. KmH

    KmH Helping photographers learn to fish Supporting Member

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    Crop sensor and DX are the same thing. Your D200 has a crop sensor and is called a DX by Nikon.

    Using a 50 mm focal length you have to be closer to the subject to have them fill the viewfinder, than if you use a 200mm which magnifies the subject more.

    The f-number 1.4, 1.8, 2.8 describes the maximum size of the lens opening expressed as a fraction of the focal length.

    Some zoom lenses have a variable aperture (f/3.5-5.6) that changes automatically when you zoom(less expensive to make), and some have a constant aperture (f/2.8) that don't change when you zoom (better, but cost more).

    Hope that helps some.
     
  4. NateWagner

    NateWagner TPF Noob!

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    Most of what you mentioned in your reading has nothing to do with the lenses themselves.

    the noobiest of language I can think of... hmm...

    Ok, the numbers such as 50mm 70mm 200mm are what is called focal length. This basically means how large an image appears. For example, with a 200mm lens a person will appear to be closer and larger than if using a 50mm lens.

    Crop Sensor - this can be confusing, but it is probably not something you really need to worry about. what happens here is that the part of the camera that records the image is different sizes depending on the camera. One particular size is called full frame and everything else is based off of that (because they are typically smaller).

    These smaller sensors are called crop sensors because they basically crop a portion of the image that a full frame sensor would capture in order to make their own image. With DSLR's the crop size is typically 1.5/1.6 (if it's not full frame).

    Again you really won't notice the crop factor, because you won't have a reason to. But, what happens is that when you use the 200mm lens on a full frame camera, it will take a certain image. When you take the same image on a crop sensor camera it will take effectively the same image, but crop it(really it only takes a portion of the image) thus making the cropped image appear larger and closer up. This effect makes a 200mm lens on a crop body look the same as 300/320mm lens on a full frame body.

    As far as apertures, although the f-numbers may say 1.8 that is not the only aperture you are able to use, it is merely the maximum size of the opening (it probably will let you use down to f/22 or f/32).
     
  5. LaLO929

    LaLO929 TPF Noob!

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  6. YoMoe

    YoMoe TPF Noob!

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    How is the lens you have working for portraits? I'm new but it seems like it would be a great lens for portraits. I got a 50mm 1.8 lens for sports. I do also use it for single portraits but if there is more than 2 people it really doesn't work that great because I have to move so far back to get them all in the frame. Then I'm so far away from them that it is hard to direct them and when you are too far away the quality is reduced.

    I also have a 70-200mm lens but the problem is the same. I think if you are planning on doing family portraits you need a wider angle.

    Before you spend money on a prime lens with a fixed focal length I'd set your lens to that setting. For example if you are considering a 50mm prime put your lens on 50mm and see if you can work with it all the time. Does that make sense?
     
  7. NateWagner

    NateWagner TPF Noob!

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    it all depends on what you want to do. They are all reasonably good lenses, though the price range varies a bit.

    I don't know what you have right now... but, the 70-200 is a great lens (if you go to planetneil.com he reviewed it on there good stuff) but, it's going to be more of an outdoor lens. It's relatively fast, but if you're planning on shooting people indoors you're going to have too much magnification for most of your shots. This one is also useful for outdoor portraits, and also for some sports action. It is relatively versatile.

    the Tamron 90mm is if I am not mistaken a macro lens. If so, it's good for Macro's or close up shots. This is a good lens for that sort of thing, and it can be used relatively well out doors for portraits.

    The 85mm 1.8 is known for having great IQ, however it is typically relatively slow focusing (as are most of the ones you mentioned) and again this will not be as useful indoors from close quarters. Good for portraits etc, very sharp.

    the 50mm 1.4 is probably a little faster than the 85 focusing wise, and it has the fastest aperture. Again it's going to be a little tight for indoors work (mostly) but it will be more usable there. This is a staple lens, and one that many people love and think everyone should have.
     
  8. LaLO929

    LaLO929 TPF Noob!

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    YoMoe - The lens I have seems slow, the clarity isn't so great and I want more bokeh. I will try your suggestion on my camera and see how I like it.
     
  9. KmH

    KmH Helping photographers learn to fish Supporting Member

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  10. NateWagner

    NateWagner TPF Noob!

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    your lens is slow.

    For bokeh I'm assuming you mean out of focus background. This is doable with your lens, merely put your subject close to your lens (about as close as you can while still being able to focus) and then make sure the background is say at least 10 feet away from you. This should produce plenty of "bokeh"

    oh, and use as wide of an aperture as you can, though doing the steps I gave you should be fine even with say, f8
     
  11. KmH

    KmH Helping photographers learn to fish Supporting Member

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    Bokeh is not a more or less type of thing, it's an esthetic quality.

    What you are referring to is called Depth-Of-Field, (DOF) not bokeh.

    Depth-of-field is controlled by the photographer by choosing 4 parameters:
    1. the lens aperture
    2. the lens focal length
    3. the subject to image sensor distance
    4. and the subject to background distance.
    You would benefit by playing with this online DOF calculator to help you understand a couple of important aspects of portrait photography:

    Online Depth of Field Calculator


    Until you begin to approach a full understanding of the basics of exposure, your lens purchase decisons will be based on uncorrelated, piecemeal information.
     
  12. NateWagner

    NateWagner TPF Noob!

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    ^^ +1
     

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