What's with the numbers?

Discussion in 'Beyond the Basics' started by jocose, Dec 19, 2005.

  1. jocose

    jocose TPF Noob!

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    OK, so I'm still trying to figure out what to buy. I'm pretending like I have a clue, saying crap like "I'm thinking about the 18-70mm lens." But the simple fact is that I have really no idea what that means.

    The camera I'm looking at comes with an 18-70mm, someone has suggested that if I get that, then I should also get a 70-300mm, and I'd be set.

    Now Hobbes and Daniel are saying that I would be just as good with a 50mm. So what do these numbers mean? I know that literally, it has to do with the focal point hitting the film/sensor, but what do the numbers mean? And isn't one that has a sliding range better than a fixed one? That is, wouldn't the 18-70 DO what the 50 does?

    Thanks.
     
  2. Chase

    Chase I am now benign! Staff Member Supporting Member

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    Think of it in comparison to point and shoots when they talk about having a 4x or 10x zoom, etc.

    A 18-70 will give you a fairly wide angle to something near our normal view of the world. A 70-300 will give you "normal" view up to a nice telephoto zoom for far away subjects. A 50mm is similar to our normal view as well, but is fixed and offers no zoom. The great thing about the 50mm is the amazing quality they offer. Generally speaking, fixed lenses tend to offer higher qualilty than zoom lenses. It really comes down to how picky you are going to be. :D

    Does that help a little?
     
  3. zedin

    zedin TPF Supporters Supporting Member

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    However keep in mind (in your situation at least) that nikon digital cameras have a smaller sensor area then a 35mm frame of film. What this means is that for all intensive purposes a 35mm lens is 'normal' (aka same size/proportion as your eye sees). This is due to a 1.5x factor over a 35mm film due to smaller sensor. Most folks suggest a 50mm fixed prime because their optics are supurb and the normal aspect is good for tons of compositions. However on a digital nikon it would be equivilent to a 75mm lens (aka things are 1.5 times bigger in viewfinder then naked eye). This isn't much of a change but can definitly crop out some background depending on what you want.

    In all actuality I would suggest just getting the kit lens and then try it out for awhile. Lenses won't really get any more expensive so you can pick up a prime lens (35mm or 50mm) later with no real downside.
     
  4. danalec99

    danalec99 TPF Noob!

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    The main number(s) denotes focal length. Here is a link to a comparison of different focal lengths. You can opt for an extreme wide, wide, normal, long or very long, depending on the type of work you do.

    Then there is the f/stop...
     
  5. Jeff Canes

    Jeff Canes No longer a newbie, moving up!

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    I like zoom lens personally for the flexible, as for fix lenses being better IMO that is more about cost. The high-end zoom lenses are fabulous. But, if those type of lenses are not in your budget, then yes a very good 50mm f1.4 would be better then a low-end zoom 24-85mm 3.5-4.5f
     
  6. danalec99

    danalec99 TPF Noob!

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    The 18-70 is not 'wide' as the 50.

    the aperture number of the 18-70 is f3.5-f4.5.
    whereas the widest aperture number of a single focal length 50mm that we suggested for you is f1.8. f1.8 is a scenario where the opening in the lens is wide open, therefore letting in more light, which would aid in low light shooting. If it is not a concern for you, forget about the 50, for now. Play with the 18-70 and eventually you will know which ones to add.
     
  7. Rob

    Rob TPF Noob!

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    Yes the kit lens zooms approximately around the same length as the 50mm, so it covers that focal length. However, the lower f-stop rating (the width) of the 50mm lens make it more useful for achieving depth-of-field effects in your shot and give you more light for those darker moments.

    The biggest reason to get a prime lens in my mind is that it's going to be sharper than a zoom. It's the only way to get the best out of your camera. 18mm isn't really that wide, considering the crop factor of a Nikon DSLR and 70mm isn't that long. A standard lens is very cheap and is capable of producing awesome work and teaching you more than a thing or two.

    It's my personal opinion that these mid-range zooms are a hindrance to people starting photography with an SLR. You don't need to be worrying about zoom when you're already worrying about exposure, aperture, composition, foreground, background etc. Zoom with your feet at these focal lengths. Honestly there's nothing that a 70mm lens can reach that a 50mm can't really and don't you want those extra 2 or 3 stops of light?

    Rob
     
  8. hobbes28

    hobbes28 Incredible Supporting Member

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    I personally like the fifty because it is a lot like your natural vision and it has such a wide apeture (the 1.8) so I can shoot in lower light. What I like about the focal length is that I already know what my composition in my picture is going to look like before I put the camera to my eye. With my 18-70, I have an idea of what it will look like at both ends but could have to move around some or make adjustments and the like. It's kind of petty but it's one thing I love about it. Another thing is that the 50mm is so sharp but, like Jeff said, it's because I don't have a really expensive zoom lens that delivers the same quality.
     
  9. danalec99

    danalec99 TPF Noob!

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    Totally agree. Just did not want to impose my opinion. With the 50mm, you are confined to just one focal length therefore helps you to focus more on the composition and exposure.

    When I first ordered my first dslr, I did not get the kit zoom along with it. I got the 50 even before I got the camera! :)
    50 would defenitely be an awesome way to start.
     
  10. jocose

    jocose TPF Noob!

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    Hey everyone, thanks so much for the info...sadly, I think I'm more confused now than before ;) Now I don't know what to do as far as lenses.

    As some of you might recall, I posted a thread a while back about getting my bro-in-law's camera (see over here). He has a 50mm and a 70-300mm, but both are manual focus and both are for a 35mm, not digital. How would this impact me? If I'm understanding correctly, the 50mm on the 35mm isn't 50mm on the DSLR, right? I was also told that these 2 lenses would mount onto the DSLR, but wouldn't work as well as a 500mm or 70-300mm built for the DSLR. But, since I have them anway, should I still consider them when looking into new lenses? Will someone at my level really tell the difference betwixt the 70-300mm for a 35mm on a DSLR?
     
  11. Rob

    Rob TPF Noob!

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    There's two issues here young Jo.

    Firstly is the crop factor. The sensor on a digital camera is not the same size as a 35mm film frame. It's a bit smaller. Therefore you get the centre of the image cut out at that size.

    [​IMG]

    If you look at the above picture and look at the "full frame" compared to the 1.6x box you get the comparison. A 50mm lens is still a 50mm lens and takes pictures in exactly the same way as a 35mm film camera. There is no telephoto effect and the lens does not become longer. However what does happen is the equivilent of you taking a pair of scissors to a 6x4" print and cutting the middle bit out (as in the picture above). This is the effect it has on your lens. Some people explain this as a 50mm lens turning into an 85mm lens, but this isn't in the slightest bit helpful (IMO).

    The second issue is that you are trying to use an older lens on a newer camera. It will physically fit, but the Tamron you have and the prime lens will probably not allow auto-focus or in fact auto anything (I would think). It is possible that the lens won't work at all, but is likely it will just be manual and you will have to set the settings on the body (annoying) manually every picture you take. I'm sure someone here will have the real story on this exact model, but I would say it's not a great lens, so don't bother.

    Hope this helps

    Rob.
     
  12. crawdaddio

    crawdaddio TPF Noob!

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    On the advice of folks on this forum I bought an Nikon N80 35mm with a nikkor 28-80mm and 70-300mm kit.
    I also bought a D50 to quickly re-learn how to compose and expose. I also bought a nikon 50mm f1.8 as people are suggesting you do here.
    As a novice myself, I will tell you that after about two weeks with this setup and about 1500 shots, I like the 50mm lens the best.
    The 28-80 is nice for quick impromptu shots where I don't really care to spend alot of time on moving and framing. The 300mm is a great zoom but I don't even know how to use it well yet. But the 50mm just seems to take crisper pics, forces me to move and compose and pay attention to manually photographasizing, and the big aperture (1.8) is great for DOF and time exposure (which I love!).
    All three of these lenses work well, but I would take the advice here and get a 50mm f1.8 (or f1.4). You'll be glad you did, and they're only about 100 bucks;)

    Hope I helped as one noob to another(?)

    ~DC
     

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