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Old Apr 26, 2011, 1:14 AM   #1
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Default What is the purpose of getting different lens ?

Hi all ... Well I recently purchased the Nikon D3100 with the 18-55mm lens .. I'm not curious, what do you get by getting different lens ? As far as I can tell, they just let you zoom more, in simple SLR-n00b terms .. I mean with my 18-55mm lens, there is hardly any zoom available .. Or am I not zooming in properly ? Like I just know that manually rotating the lens changes the zoom, and the zoom I'm getting with the 18-55mm is not much at all ... Do I need the 55-200mm lens for more zoom capability ?

Also, what other advantage do you get by having different lens ? Just asking as someone who is absolutely new to SLRs, what's the point in spending $100s on a lens when in just $300 you can get the Panasonic FX35 which has an 18x zoom, which is awesome ... ?

Can someone explain to me the purpose of lens, and what secret powers they hold ?
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Old Apr 26, 2011, 1:19 AM   #2
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well a long zoom will let you reach out to subject that you can not get to easily. Something like the 55-300 is a good option. Better reach the the 55-200. And not that much more.

A big aperture prime like the AF-s 35 1.8 will let you shoot better in low light when you can not use a flash.

A macro lens will let your shoot very small things is that is a type of photography you are into. Also the big aperture will let you work with shallow dof shots, where the back ground has a nice blur effect.

A big aperture zoom will let you shoot indoor action where you need fast AF.

So it come down to giving you more option for different kinds of photography with different lenses. There are lot of different situation certain lenses are better for.
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Old Apr 29, 2011, 12:23 PM   #3
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Yes, longer zoom is obviously one of the primary reasons for getting another lense

While larger aperture may not be a necessity for everyone
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Old Apr 29, 2011, 12:49 PM   #4
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Originally Posted by ahmadka View Post
Also, what other advantage do you get by having different lens ? Just asking as someone who is absolutely new to SLRs, what's the point in spending $100s on a lens when in just $300 you can get the Panasonic FX35 which has an 18x zoom, which is awesome ... ?

Can someone explain to me the purpose of lens, and what secret powers they hold ?
A lens is a tool. Just like a hammer or screwdriver is a tool. Some lenses are designed to do specific jobs while others try to be jack-of-all-trades. In simplest terms, it might be helpful to see some types of shots your current kit lens won't let you take. These are just some minor samples - there are countless other samples. BUT, I caution - there are hundreds of lenses available. You should always buy a new lens based on need and deficiency of current gear. No need to go out and buy a 400mm f5.6 lens if all you do is take family snaps in the house.
Wide aperture prime lenses - these lenses have a very shallow depth-of-field (DOF) so your subject is in focus but the background is not. See if you can reproduce this type of shot with your current lens:

Wide aperture / fast focusing lenses. In addition to shallow DOF, wide aperture lenses (f2.8 or wider is usually considered wide aperture) allow for faster shutter speeds in low light. Combine that with a lens that also has a focus motor built in that focuses extremely fast (not all focus motors are the same) and you can track moving subjects and make low light action photos. Again, try to re-create a shot like this (indoors, running & throwing) with your current lens:

Along the same lines - now we have yet another lens that is wide aperture (so background is blurred from shallow DOF), fast focus motor but also has longer focal length so you can take the photo of someone 25 yards away instead of 25 feet away:

Now, as I said the above shot had several lens characteristics: The fast focus motor allowed the shot to be in focus. A slower focusing lens might not allow for the shot to be in focus. The f3.2 aperture created a more blurred background (an f6.3 aperture would have the background more in focus). The fact that at 300mm the lens is still sharp enough to produce a good photo is also a differentiating factor. There are other less expensive 300mm lenses but they won't be as sharp at 300mm. But they exist because people need more affordable options.

And then we have shots that require even longer focal length because the subject is even further away. They still have to be reasonably sharp though and in the case of moving subjects have to have good focus motors. Again, try taking this type of shot with your current lens:

It's also worth noting again that even at the same focal lengths, the quality/sharpness of lenses are different. A tamron 28-75 2.8 is going to be a sharper lens than your current kit lens for example. Or, in my case - my canon 24-105L is sharper than the kit lenses canon sells with their DSLRs (although the 24-105 is a kit lens in some configurations for the 5dII):

There are all sorts of jobs where a tool different than your current tool will do a better job. The problem is: the better tools are usually specialized. So you want to buy that tool only when you know you're going to be performing that job a lot. As nice as my 70-200 2.8 tool is it's a poor tool for indoor family birthday parties (70mm is too long on the wide side) and a poor tool for birding (200mm is too short for many birds). And while my 85mm 1.8 is great for shots like the shallow DOF one I posted above - it's way too short to use for a night football game. Or too long to use to take group shots indoors.
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Old Apr 29, 2011, 1:32 PM   #5
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Also, I find the Nikon 18-55 to not be quite as sharp as some other lenses.

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Old Apr 29, 2011, 2:44 PM   #6
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I just want to mention that the 55-200 VR in the OP is a terrific second lens. It has excellent optical properties for such an inexpensive lens, is light as a feather, and takes the same size filters as the 18-55 he already has. If the OP is feeling that he can't zoom as far as he might like, this is a very good addition to his kit.
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Old Apr 29, 2011, 9:47 PM   #7
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Here is an example with the 55-200 taken at 200mm f6.3 1/320 sec. Wasn't anticipating the action shot as was focusing on the chicks, and when the adult is in the nest, relatively still. Since f5.6 was the lens maximum aperature, would have bumped it and the ISO for a little faster shutter, but it worked out OK.

Typical of a telephoto, it brings the background in, and blurred due to the relatively shallow depth of field considering the distance between the nest and trees. It also required manually focusing on the nest (before the osprey entered the picture and just the chicks) as auto focus wanted to focus on the trees and blur the nest.

Oh, and no shutter lag like on a P&S.

Last edited by tizeye; Apr 29, 2011 at 10:02 PM.
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