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  #1  
Old 11-26-2008, 01:55 PM
rajhema rajhema is offline
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Default Help to decide buying Aspherical lens

Greetings,

I spent a good time debating myself between buying the 2 Image stabilizer lens Versus replacing with one Aspherical lens that covers almost the same focal length. So please give me some suggestions and share your experiences so I can make the decision to utilize the 2008 holiday season.

My camera is Canon Rebel XT. Right now I have 18-55mm and 70 - 300mm lens that are not "Image Stabilizer".

I finally set myself to replace these 2 lenses with the below lenses

Canon Telephoto lens Canon IS Telephoto Lens
And
Canon IS 18-55MM Lens in place of what I have now. I know it will be expensive and but the result will be great. The con is I should carry the 2 bulky lenses all the time. Then I found the Tamron lens which almost covers the same focal length and it is lot cheaper(this is the catch).

Tamron 28-300 Aspherical lens for Canon
<a href=http://www.amazon.com/Tamron-28-300mm-Vibration-Compensation-Aspherical/dp/B000V6ON8I/ref=sr_1_7?ie=UTF8&s=electronics&qid=1227710486&sr =8-7">Tamron 28-300 Aspherical lens for Canon</a>

Now I'm struggling to settle to buy between the 2 Canon IS lenses against the Tamron Aspherical lens. What I want to know is 'the downside of buying an Aspherical lens if there is any'.

Many thanks for your attention.
Cheers
Rajesh
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  #2  
Old 11-28-2008, 05:45 AM
AdrianW AdrianW is offline
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Default Re: Help to decide buying Aspherical lens

All it means is that the particular lens contains one or more aspherical elements.

Aspherical elements can be more difficult, and therefore more expensive to manufacture. So why use one? Because it can result in superior image quality and/or weight when compared to a similar design without an aspherical element.

In reality it's a tradeoff. If all else is equal the aberrations in a non-aspherical lens are likely to be more visible, but they tend to be simpler to correct for in software/firmware.

That said, many Canon lenses have aspherical elements too. I know the 10-22 EF-S does. Not sure about the 100-400 IS, but I think it might.

The first instant drawback of the Tamron 28-300 is that it doesn't go to 18mm. 28mm may not sound very different to 18mm, but trust me it's a significant difference!

The second drawback of the Tamron is that it's a Tamron 28-300 ;) Why's that an issue? Well, historically the 28-300 has been a poor performer in image quality terms. I'll admit I haven't used the 28-300 VC which is a new design, but based on their past 28-300 lenses I'd be tempted to avoid it anyway. As a rule of thumb, the greater the zoom range, the worse the images become; there are exceptions, but don't expect miracles!

Your choice of Canon lenses seems odd to me though. The 18-55 IS is a reasonable choice, although it's not going to be massively different to your existing 18-55 (assuming it's the mk2?), the IS will help get sharper shots handheld though. The 100-400 IS is a very expensive and very heavy pro-quality lens; which seems like a strange pairing to me?

The Canon 70-300 IS (not optically the same as your 70-300) is a good mid range choice. If you fancy something less expensive consider the Canon 55-250 IS; it's intended to be the companion to the 18-55 IS.

My advice? Read as many reviews as you can, and then try them for yourself. You may find that one really fits your needs better than the rest. If you can get hold of sample images for the same subject, print them at the largest size you plan to use, and look at them closely. Can you tell the difference? If not, the cheaper lens might be the better choice for you!

I currently shoot with the Canon 300 f4/L IS, and I'm very happy with it; although there are times when I find the lack of zoom frustrating. Wildlife often doesn't lend itself to "zooming with your feet".

In reality, it's always a tradeoff between weight, cost, convenience and quality. Try and work out which factors are most important to you. For me quality is primary, then weight, cost and probably lastly convenience. The result, a bag of L-series zooms and primes.
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  #3  
Old 11-28-2008, 10:13 AM
rajhema rajhema is offline
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Default Re: Help to decide buying Aspherical lens

Adrian. My intention to get the Image Stabilizer lens for both Wide and telephoto lenses. I might have given a wrong link for 18-55. But you got the idea and gave a wonderful explanation. I will do much more lens. For now, I'm dropping the idea of Tamron and will compromise carrying 2 lens if necessary.

Cheers
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  #4  
Old 11-28-2008, 06:34 PM
AdrianW AdrianW is offline
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Default Re: Help to decide buying Aspherical lens

The Tamron's still worth considering, but I would strongly recommend testing it yourself before buying one!
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