sigma decision
 

Hi eveyone, I brought a canon 1100d a few months back and am enjoying learning how to use it, It has the 18-55 kit lense and I am looking to upgrade it. I was looking at the sigma 17-70 which has good reviews for the price but a friend suggested the 18-250 sigma for a similar price, too many options!. The extra zoom would be nice as I am travelling a bit so handy only having to carry 1 lense, but I am just wondering what sort of difference in image quality between the two lenses are, is it really noticable, if not the super zoom is the answer, but if the 17-70 is alot sharper it may be worth while to get 2 lenses to cover the focal range.
Any help would be greatfully accepted Thanks!!!!!!

I can't say I have experience in either of these two lenses (the 18-55mm kit lens or the Sigma 17-70mm) but....

a. you're right that having that extra 15mm focal length would be handy for the travelling photographer and,

b. the 'kit' lenses by all manufacturers all [I]have a reputation[/I] for being of a lower standard (usually less sharp) than the more expensive lenses by the same company or from people like Sigma.

The biggest difference in prices is usually the maximum aperture (f/stop), where a 'fast' lens (like f/2.8 or lower number) will allow faster shutter speeds, giving sharper pictures (less camera shake).

If I was making the decision I'd need to be convinced that the 18-250 would give me the same quality of result that the 17-70 will give.

Right off the bat, and [I]generally[/I] speaking the higher the magnification of a zoom lens the lower the quality when compared to a lens with a lower magnification because there are more elements to the lens, the light has to travel through more bits of glass and the more work the light has to do to get to the sensor the lesser the quality of that light by the time it hits the sensor.

You have the 17 - 70 which has a magnification of about 4 times whereas the 18-250 has a magnification of 14 times. I would guess that the 17-70 produces better shots than the other lens. Though I don't know either of these lenses to compare them against each other I do have a sigma 18-55 and a 50-500 and the 18-55 produces cleaner, crisper shots.

So it depends on a comparison of the end result for both lenses added to the need for a single or twin lens setup.

personally, I'd probably go for the better standard lens and then get a bigger zoom lens later as, depending on what type of photography you do most of course, you will probably use the standard lens much more than the big zoom lens.

harvmcb I can't comment on the Sigma 17-70 because I don't have one but as a rule of thumb a lens with a shorter zoom range will give better image quality compared to a lens with a longer zoom range ( as Cathus said )
The Sigma 18-250 I can comment on as it was my first lens when I got my camera , it is a very handy all in one lens which can deliver very good images in the right conditions . It's sweet spot at 18mm is about f/16 so if your shooting hand held you need a very bright day or you need to mount it on a tripod to get the best out of it , if you open up the aperture to speed things up on duller days you get noticeably softer images even at the 18mm end so when you start to zoom out things start to get softer still ( I read somewhere that the sweet spot at 250mm was out at f/40 , not sure how true this is because I've never tried it ) . The question you should ask yourself is will you be happy to loose image quality but only have one lens to carry about or would you prefer to get the best out of your camera with more dedicated lenses , I know that if I was to start over again I would buy the sharpest lenses that I could afford even if that meant waiting to save up for each lens .

If you look at my gallery all my shots are taken on either the Sigma 105mm macro or the 18-250 O/S

Mark

Thanks everyone for their advice, you read so many reveiws you confuse yourself with so many conflicting stories, I think I will get the 17-70 faster, slightly wider just shorter reach.
Thanks!!

A super zoom is always a compromise with image quality if it wasn't why would anyone buy anything else? We wouldn't have to lug a bag full of lenses around with us. I can not see the 18-250mm being any better or faster than the kit lens. If you want a super zoom get the 18-200mm there almost half the price that leaves you £160 to buy a prime lens or something.

Until I switched from the D200 to the V1, my walking around and favorite lens was the Nikon 18-105mm f/3.5-5.6G ED VR AF-S. I found it to be both versatile and reliable as well as incredibly sharp all across the range. It might not have been the longest lens on the block, but it was able to meet my everyday needs.

No matter what lens you get,when you go for the versatility of a longer reaching lens, invariably the image quality suffers.I use my Canon 60D with my EFS 17-55 f2.8 and my 55-250 f4.5-5.6.
I find the image quality of the 17-55 is fantastic and the 55-250 is very good(in the right conditions).
At the end of the day it will come down to what your requirements are--- image quality or flexibility.

Des

just seen this the 17-70os is a great lens, i have one. to be be honest IMHO a one lens does all is not the way to go.