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Old Jan 5, 2008, 9:23 PM   #1
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Just purchased an Xti body, now I need help with the right lense combination for a home, kids, sports and wildlife.

I am considering the Tamron for all in one vs the SIgma

AF18-250mm F/3.5-6.3 Di II LD Aspherical (IF)

18-200mm f3.5-6.3 DC OS

Or should I try a two lense combination:

18-50mm f2.8 EX DC Macro HSM (Sigma) or similar kit lense that retails for $149.00

In addition too






Tamron Zoom Normal-Telephoto AF 55-200mm f/4-5.6 Di-II LD Autofocus Lens for Canon Digital SLR



What combination should I opt. for? This forums advice is always welcome.




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Old Jan 5, 2008, 10:25 PM   #2
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The Tamron 18-250mm lens has received excellent reviews. Based on that, I purchased the lens, and have been very pleased with the one lens solution strategy.

Sarah Joyce
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Old Jan 5, 2008, 10:38 PM   #3
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Thanks for the reply, that is the way I am leaning toward.

Can you tell me where are the reviews of the tamron 18-250?
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Old Jan 6, 2008, 2:30 AM   #4
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http://www.photozone.de/8Reviews/len...anon/index.htm

http://www.bobatkins.com/photography...on_18_250.html

the tele end is going to be a bit slow during dim lights. Probably wont help in sports unless a flash can be used.


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Old Jan 6, 2008, 7:32 AM   #5
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I agree that the Tamron 18-250mm lens with its almost 14X zoom range does represent a lens where some compromises have been made to get a physically small lens with a great optical range.

I have come to the point where I am reducing the size of my kit and I find a single lens solution rather attractive. If you understand the compromises and can deal with them, then the Tamron 18-250mm lens may offer what you are looking for in a single lens solution.

Sarah Joyce
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Old Jan 6, 2008, 1:36 PM   #6
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I agree Joyce,

I understand that I will have to comprimise for an all in one solution.

Sports in low light is a very difficult solution, I will need a prime lense in the near future. Thats what makes this lense so attractive, I do not wish to carry around three lenses a flash.

Another ? The tamron does not have OS, is it truly necesary? My wife has a problem with moving the camera body when pressing the shutter on point and shoot cameras.
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Old Jan 6, 2008, 1:47 PM   #7
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Angel-

There is an easy formula: take a look at the focal length and put a 1 over it to get the shutter speed. Example: on the Tamron 18-250mm lens convert it to normal 35mm terms by multiplying by 1.5. Therefore, if the lens reads 100mm, that =150mm in 35mm terms. So you will need a minimum shutter speed of 1/150th.

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Old Jan 6, 2008, 2:06 PM   #8
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Can I apply this formula to most conditions?

Ex: apeture priority, Shutter priority and other settings.


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Old Jan 7, 2008, 10:16 AM   #9
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Quote:
...sports...
I've seen some of your baseball photos under the lights taken with a Sony DSC-F717 in the past (some of them were shot at ISO 800 and pushed to much higher ISO speeds by brigtening underexposed images later in software to get faster shutter speeds).

Don't expect to be able to do that using a lens like that Tamron 18-250mm. It's just not bright enough for low light sports. Ditto for the 55-200mm (too dim for night games).

The lens on your existing Sony DSC-F717 has a widest available aperture of f/2 available on it's wide end, dropping down to a widest available aperture of f/2.4 on it's long end.

That's roughly 7 times as bright as the Tamron 18-250mm by the time you zoom in much with it. That Tamron has a widest available aperture of f/6.3 on it's long end.

IOW, if you were getting shutter speeds of 1/350 second with the Sony at ISO 800 and f/2.4, you'd be down to around 1/50 second using the Tamron at ISO 800 and f/6.3 (the widest available aperture on it's long end) for the same exposure. In fairness, the Tamron is a longer lens. But, the widest available aperture drops off pretty fast as you zoom in with this type of lens. It's a dim lens.

Also, because it's a dim lens, AF speed may suffer in less than optimum lighting (it's not a very fast focusing lens, and the AF Sensors won't be able to "see" very well through it in lower light).

So, even though you have ISO 1600 available with the XTi, it's not going to make up for the difference in lens brightness (each time you double the ISO speed, the camera can use shutter speeds twice as fast for the same lighting and aperture). You'll just get a lot of blurry photos trying to use the Tamron for night games (because shutter speeds will be too slow to prevent blur from subject movement).

That Tamron is best suited for very good light.

You're going to want a zoom that can maintain f/2.8 throughout it's focal range to try and take shots of night games like you were taking with your Sony DSC-F717. For example, a Sigma 70-200mm f/2.8 EX DG HSM is a popular choice for this purpose. It's around $800 at online vendors.

I just wanted to make sure you're aware of the differences, since I know you like to take photos at night games under the lights with your Sony, and you'd be wasting your money trying to use a Tamron 18-250mm lens for that purpose. Ditto for the 55-200mm (it's not bright enough for night games).

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Old Jan 7, 2008, 10:40 AM   #10
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P.S.

Aperture as expressed as f/stop as a ratio between the focal length of the lens and the diameter of the aperture iris opening. So, smaller f/stop numbers are larger openings.

With a prime (non zoom) lens, you will see one aperture listed.

With a zoom lens, you usually see two apertures listed (the largest available aperture at wide angle zoom setting, and the largest available aperture at the full telephoto zoom position). When in between the widest and longest focal length of the lens, the largest available aperture will fall somewhere in between the apertures shown.

Some higher quality zoom lenses can maintain a constant aperture throughout their zoom range (with f/2.8 being the most common). A lens that can maintain f/2.8 throughout it's focal range is a must have for some types of shots (i.e., night sports in a stadium under the lights). Otherwise, you're going to get motion blur, even at higher ISO speeds if your subject is moving.

The aperture scale in one stop increments (with larger than f/1 apertures theoritically available) goes f/1.0, f/1.4, f/2.0, f/2.8, f/4.0, f/5.6, f/8.0, f/11, f/16, f/22... With each one stop move to a smaller aperture (represented by higher f/stop numbers), you will need shutter speeds twice as long for proper exposure for the same lighting and ISO speed (only half the light gets through compared to a one stop larger aperture).

Here is a handy online expoure calculator that you can use to get anidea of the relationship between lighting, aperture and ISO speed (shown as film speed in the calculator).

http://www.robert-barrett.com/photo/...alculator.html

If you want to shoot night games (and I noticed you were doing that with your DSC-F717), you'll need a brighter lens (for example, a Sigma 70-200mm f/2.8 or Canon 70-200mm f/2.8 ).

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