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Old Jun 13, 2008, 3:44 AM   #1
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hi

Seeming as the Canon 450d doesnt come with the 55-250 IS lens as a bargin twin deal i may as well look at other zoom lens's and buy trhe 450d with the kit 18-55 IS lens

1. Will i miss much by having a gap in the lens length if i get the sigma ie a gap between 55 and 70mm

2. this sigma lens is tempting as it has 1:2 macro also (i understand the lens wont let in as much light compared to a dedicated macro lens)
Can anyone give me a good reason to pick one or the other?
If the sigma isnt IS then thats a big minus, and image quality is important to me, and the extera zoom of the 300mm is attractive


thanks


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Old Jun 13, 2008, 6:15 AM   #2
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1. Will i miss much by having a gap in the lens length if i get the sigma ie a gap between 55 and 70mm
No - The 18-55 IS kit lens is already a fantastic bargain
-> You can zoom from 55 to 70 by walking closer a few steps

2. this sigma lens is tempting as it has 1:2 macro also (i understand the lens wont let in as much light compared to a dedicated macro lens)
Can anyone give me a good reason to pick one or the other?
If the sigma isnt IS then thats a big minus, and image quality is important to me, and the extera zoom of the 300mm is attractive
Which Sigma?
If you really miss the 55-70 then this Sigma may be right for you: http://www.sigmaphoto.com/lenses/len...mp;navigator=6
-> OS is Optical Stabilization in Sigma term

or this Tamron: http://www.tamron.com/assets/vs2/pdfs/a20.pdf
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Old Jun 13, 2008, 6:32 AM   #3
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What kind of photography are you interested in?
As wildlife is quite demanding on the lens and 300mm is usually too short and most 'low-cost' 70-300mm is usually not very sharp at the long end of the travel

-> Don't worry about not having much light in macro as most macro are done with flash anyway (if you know what you're doing)... As most macro are shot with the lens step-down to increase the sharpness and depht of field!
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Old Jun 13, 2008, 8:54 AM   #4
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i cant find the lens i saw now lol darn.

i love taking macro, but also want to take all typs of images.

I dont mind the 55-70 gap, as youve explained that now.

question.
some lens's ie 70-300 quote 2 f stops, i guess this is top and bottom of lens range, but some only quote one f stop for a 70-300, does this really mean the light coming is is the same at both ends?

also some lenses say macro but dont quote the ratio like 1:4 or 1:2, why is this, surely its important?
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Old Jun 13, 2008, 9:02 AM   #5
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Aperture as expressed as f/stop is 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 will 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 nothing but motion blur, even at higher ISO speeds if you subject is moving. To put things into perspective, a lens with f/2.8 available is exactly 4 times as bright as a lens that only has f/5.6 available.

For many indoor conditions trying to shoot moving subjects without a flash, even f/2.8 may not be bright enough. Then, you may need to use a brighter prime (fixed focal length versus zoom, since you can find brighter primes versus zooms).

Lenses are rated by their largest available apertures (smallest f/stop numbers). But, most lenses can be set to use apertures of f/22 or smaller.

When you vary the aperture, you're controlling the iris in the lens (which like a pupil in your eye, can be opened up to let in more light or closed down to let less light in). So, this impacts the shutter speeds you'll need for proper exposure (since more or less light is getting through to the sensor).

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).

Quote:
also some lenses say macro but dont quote the ratio like 1:4 or 1:2, why is this, surely its important?
The word Macro is used very loosely in product descriptions for lenses. Some people don't consider a lens to be a "true" macro lens unless it's 1:1. But, the trend is to use the word Macro in a product description, even if it's maximum reproduction ratio is only 1:4. ;-)

When comparing lenses, make sure to keep in mind that the max reproduction ratio quoted is when you're at the longest focal length and closest focus distance. So, keep your desired working distance in mind when comparing lenses.

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Old Jun 13, 2008, 9:30 AM   #6
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P.S.

Due to a "qurk" with the forums software, the description line for the thread is not visible unless viewing a list of threads within an individual forum. So, it's a good idea not to use it unless you repeat the text in your posts (that's why NHL was wondering what Sigma lens you're referring to).

As far as that particular Sigma (Sigma-70-300mm-f/4-5.6 APO DG Macro), it's got a rep for being a tad softer on it's 300mm end. But, that's true for all of the budget zooms with that focal range. The APO version of it does have the better reputation, and it is considered one of the best budget zooms available.

A close compeitor would be the Tamron 70-300mm f/4-5.6 Di LD Macro (and it's newest version is also has a 1:2 macro rating). It's a bit less expensive lens compared to the Sigma APO you're looking at.

Neither are going to have image quality quite as good as a a bit better lens like the Canon 70-300mm f/4-5.6 IS USM Lens would have (not the cheaper Canon 75-300mm f/4-5.6, which is not a very high quality quality lens by most reports). Or, if you wanted to step up to an even better lens that reaches out to 300mm, look at a lens like the Sigma 100-300mm f/4 EX DG HSM.

But, depending on the use for the images and the viewing/print sizes desired, you may find the image quality to be just fine with one of the budget 70-300mm zooms. Most lenses are a bit sharper when the aperture is stopped down a bit from wide open anyway (which you'd be able to do in brighter lighting outdoors). So, the differences between lenses are not as great when using one like that, depending on your expectation of quality (which can be very subjective).

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Old Jun 13, 2008, 9:48 AM   #7
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Here are two well known sites with lens reviews you may want to look at when comparing lenses:

http://www.photozone.de/

http://www.slrgear.com/reviews/index.php

For older lenses, this site is a good bet for MTF charts (which never tell the entire story about a lens).

http://old.photodo.com/nav/prodindex.html

You can also get to it via http://www.photodo.com

But, the new site is much harder to navigate from my perspective, since it's tough to see a list of lenses from a given manufacturer that have MTF data with them. Fortunately, they kept a copy of the original site online, which is my previous link with old in front of the address.

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Old Jun 13, 2008, 10:55 AM   #8
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simonbratt99 wrote:
Quote:
also some lenses say macro but dont quote the ratio like 1:4 or 1:2, why is this, surely its important?
This is because it's a zoom lens so the ratio is variable as one changes the zoom setting - On some macro zooms theses ratio numbers are engraved on the lens barrel so as the barrel moves in and out their macro ratios are indicated correspondingly
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Old Jun 13, 2008, 10:58 AM   #9
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thanks jim,

It is hard to judge what lens will be acceptable to you, as you said, everyones expectations are different, and indeed people eye sights are different.

Thats why standard images taken with each device are handy to compare, like dpreview do for showing noise. Noise is one of my pet hates, so thats a big consideration now im selecting my 1st dSLR and why the canon 450d (for the money) is my top runner.

I will check out those sites, hope they have comparitive images taken


cheers
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Old Jun 15, 2008, 11:34 AM   #10
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I recently purchased the 450D with the twin lens, although I purchased the 55 - 250mm IS separately for £170.

I upgraded my camera from a Panasonic FZ30, so I know where you are coming from regarding your hatred of noise. I must say, it is one of the biggest plusses that I have noticed since using the Canon, noise, even in low light is so much less, I hardly notice it.

With regards to the Canon 55 - 250mm IS lens, well I am very impressed, given the price, that said I have no experience of the other lens mentioned, but the 70 - 300 IS lens are still considerably more expensive, so for the price this IS lens is excellent.
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