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Old Jan 18, 2007, 5:49 PM   #11
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The Sigma will give you about a 25.5mm - 105mm which is a great range and the MTF charts on the sigma site look great. How much is this lens gonna cost you?
Im kind of new to DSLR's but the 25.5-105 out of a 17-70 is only thefield of view isnt it? The magnification is still equal to that of a 17-70 right? I've seen the 1.5 factor quoted all over the web and it seems to be a little misleading. The only advantage I can see using a film lens with the 1.5 factor is the possibility of the "sweet spot" of the lens hitting the sensor. Other than that it would seem to me that the 1.5 crop factor would be a bad thing. Narrowing the field of view with out the added benifit of the extra magnification associated with a longer lens Just my opinion
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Old Jan 18, 2007, 6:16 PM   #12
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I have had the 17-70 on my Konica Minolta (now owned by my father) and no on my Canon 30D and think it is a very good quality lens indeed!!! I didn't even bother with either kit options for the Canon just went straight to this as I have always been able to get great results with it.

style="BACKGROUND-COLOR: #000000"I also like the look of the Sigma 18-200 with OS but am concerned about the performance of the lens due to the large range covered. When we see the price on it as TC3 says getting a new body might be worth considering if you are thinking of OS/IS etc. It is one thing that was nice about my KM5D but not essential for what I shoot (sports) so not too worried.
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Old Jan 18, 2007, 11:49 PM   #13
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Spiritbro77 wrote:
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CptOfGondor wrote:
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The Sigma will give you about a 25.5mm - 105mm which is a great range and the MTF charts on the sigma site look great. How much is this lens gonna cost you?
Im kind of new to DSLR's but the 25.5-105 out of a 17-70 is only thefield of view isnt it? The magnification is still equal to that of a 17-70 right? I've seen the 1.5 factor quoted all over the web and it seems to be a little misleading. The only advantage I can see using a film lens with the 1.5 factor is the possibility of the "sweet spot" of the lens hitting the sensor. Other than that it would seem to me that the 1.5 crop factor would be a bad thing. Narrowing the field of view with out the added benifit of the extra magnification associated with a longer lens Just my opinion
Ok basically I think it works like this. All lenses are labelled in 35mm Film Size terms. If you stick a 17-70mm on a film camera..you'll see a 17-70mm view. But because dSLR sensors tend to be smaller than film size, it only records the light coming through the center portion making ti seem like you had a longer lens. Yea, in most cases the centre part is nicer. The extra telephoto effect is nice though.

As for you NatureAdmirer, don't be so easily led astray but a couple of photos. The technicals (MTF graphs) aside, the best thing is to read lots of lens reviews to get people's culmulative opinions on the lens. I don't really think the 200 end will do you any good. Its considerable softer and slower (f6.3) and Ira might be right about that Optical Stabilizer function. Know this, the majority of your shots fall into the wide angle to moderate tele/portrait and the Sigma 17-70mm suits this very well and the MTF charts are backed up with very good user lens reports!
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Old Jan 19, 2007, 4:08 AM   #14
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CptOfGondor wrote:
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Ok basically I think it works like this. All lenses are labelled in 35mm Film Size terms. If you stick a 17-70mm on a film camera..you'll see a 17-70mm view. But because dSLR sensors tend to be smaller than film size, it only records the light coming through the center portion making ti seem like you had a longer lens. Yea, in most cases the centre part is nicer. The extra telephoto effect is nice though.
Nope, lenses are measured based on their focal length which is not dependent on the type of camera you are using.

Have a look at this link http://www.paragon-press.com/lens/lenchart.htmwhich will explain what focal length means.

The size of the sensor will change how much of the available field of view is recorded by the sensor/film.

Lets take a couple of examples based on a lens which has a 50mm focal length (looking at the above link again there are some examples of shots with differing focal lengths using a film camera - 35mm).

With the Canon S3 IS the 50mm lens setting on that will give the 35mmequivalent of 300mm so this is a good telephoto length.

With a dSLR with a 1.5x Crop (the most popular amongst the manufacturers) then the 35mm equivalent is 75mm which would be a short portrait length/shot telephoto.

With 35mm film or something like the Canon 1D or 5D cameras (which are know as full frame) then 50mm is 50mm and is roughly what the eye sees.

With Mamiya ZD medium format digital camera whichhas a crop of approx 0.65 then the 50mm lens is approx 32mm in 35mm equivalent.

So we have one length lens but 4 different results. The reason that the 35mm equivalent is used is that most people can relate to this (after all a lot of us have come from shooting in film) however it is arbitrary and any standard could have been used.

The new digital lenses designed for the APS-C size sensor (1.5/1.6x crop)can be better than those for film as the designers were building them with the awareness that only the middle section of the lens is going to be used. This is not always the case but worth considering and you can get the idea of this by looking at MTF charts.

Hope that helps a little.

Mark
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Old Jan 19, 2007, 1:09 PM   #15
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TC3 wrote:
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SteveB wrote:
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My Sigma 17-70 is miles better than my kit 18-55 lens in terms of quality of image. I couldn't believe how poor the kit lens was in comparison to my previous camera's lens on a x10 zoom Olympus C750, so I just had to get something better. It's sharp at all apertures, zero PF and focuses quick. Problems? No quick shift, hardly noticeable very slight red/orange cast easily tweaked out but nothing's perfect.
Dont knock the lens. I and many others on dpreview have got some great results with the kit lens. Dont knock something just cos u might not have what it takes to get the best out of it!
I know what it takes to get the best out of the kit lens, and mine isn't good enough, sorry. f8 is its sweet spot, and mine is still fuzzy, no definition at all and needs tons of sharpening to get anything reasonable. 2MP consumer cam results out of a 6MP DSLR. I bought the 50-200 shortly after getting the K100D and saw immediately what the camera could really do, so that's why I got the Sigma for wideangle. I got a lemon kit lens basically.
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Old Jan 19, 2007, 1:45 PM   #16
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You definately won't be dissappointed with the Sigma 17-70. I quickly sold my 18-55 kit lens to help finance the Sigma 17-70.

Honestly I think the later 18-55 kit lenses weren't as good as the earlier production ones because my kit lens wasn't that great. Focus to infinity was terrible. My older FA28-70 f4 and F35-70 lenses were optically far better then that kit lens.

Regardless my Sigma 17-70 blows away my old kit lenses. This is my experience, others may differ.
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Old Jan 19, 2007, 2:27 PM   #17
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I think where my confusions lie is the difference between the field of view and the magnification. Lets take a 300mm prime for example. Now if I'm thinking correctly..... on a 35mm camera the field of view and the magnification is normal for a 300mm lens. However when mounted on an aps sized sensor camera with a 1.5 crop factor, the field of view and the cropping of the pic taken would be 450mm sized but the magnification, the "bringing closer of the subject" would be equal to a 300mm right? The magnification remains the same for what ever camera you place the lens on, the only thing that would change is the field of view?
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Old Jan 19, 2007, 3:31 PM   #18
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Correct

Kjell
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Old Jan 21, 2007, 1:43 PM   #19
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Thanks for the explanation of the magnification issue. I do have one question which has only a little to do with this post, but what does LBA stand for?

Glenn
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Old Jan 21, 2007, 3:01 PM   #20
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Glenn-

It means Lens Buying Addiction.

MT/Sarah
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