what would be the better choice among these

[jann1033]

which is the better (set of) lenses

Sigma 17-70/2.8-4.5 DC Macro i could use it along with the 28-80 f3.5.5 macro and 100-300mm i have now..the benefit being the wider angle plus it has a bigger aperture than what i have now but would it be enough for stuff like fireworks or other night time stuff...

or for about the same money the 18-125 sigma which i think is around f3.5-5.6 also and the 50mm f1.8 ( think that is sigma also?) ( that would be a little cheaper but once i add a circular polarizer etc not really) the benfit would be not having to change a lens very often but also it basically makes the others i have useless except the macro for the 28-80

in the past i have found the 28-80 some what limiting in the upperrange with a film camera but the 70 would 'seem" farther (? or since it's for digital does that cancel that crop factor out) and i have 100-300 for that anyway. I'd still have the macro with the one i have now......

but since i didn't like changing lens the 17-70 wouldn't help me much there would it?.mostly the 28-80/100-300 was a pain cause we like to go to the Mt's and the 80 didn't have enough zoom but the 100 awful for anything in the closer range... not sure how that would work out in actual use with the 1.6 business.

 

[Kelly Grannell]

17-70 is the sharpest one of the bunch. My copy is as sharp as Canon 17-40 L series.

 

[jann1033]

does the crop factor stll apply... it would behave ( why did i just think of mike meyers )more like a 28-100 (or something roughyly similar) or since it's the dc it is really 17-70?

 

[pisco]

Crop factor always applies.

 

[0bli0]

...why did i just think of mike meyers

oh, be-have...

yes, crop factor always applies. dc and ef-s simply aren't designed to spread the image over a full 35mm negative size horizantal plane the way other lenses are. the same crop factor reduction of view applies compared to a 35mm negative sized sensor with a lens of the same focal length.

 

[Mellie0119]

I just want to make sure I'm clear on this- no matter what lens I use on my Rebel XT, I will always have that 1.6 crop factor because of the sensor. Right?

 

[0bli0]

yes that's correct. doesn't matter what kind of lens

 

[Mellie0119]

Thanks! That's what I thought, but got a bit confused for a minute.

 

[jann1033]

Thanks! That's what I thought, but got a bit confused for a minute.

better than my terminally confused state

 

[Mellie0119]

Well, it's a first to me not to be totally lost in all the photo-technical jargon. Most days I'm just keeping my head above water and have to refer to one or two books or sites to clear up what I'm reading.

 

[jann1033]

who ever thought "the dis" would = work

 

[mhutchinson]

I just want to make sure I'm clear on this- no matter what lens I use on my Rebel XT, I will always have that 1.6 crop factor because of the sensor. Right?

...depends...

isn't the real definition of the crop that it is an occurance where the image passed through back of the full frame lens is larger and thus will over cover the sensor of a smaller sensored dSLR. So if you are using a lens that is specifically designed for the smaller sensor then technically there is no longer any crop occurring to the image because the light entering the lens is only hitting the sensor. And because the image projection is the correct dimentions and size for the sensor it is not considered a crop (or sub-component of the original).

The lens manufacturers have decided to further help the crop discussions along but not properly noting the real range on the lens and thus forcing us to perform these calcs in our heads constantly ... but notice the point and shooter owners don't have to deal with this. The Canon PowerShot S3 IS only has a 6-72mm lens but the whole world is convinced it is a vary powerful extreme range of 36-423mm .. no questions asked, no crop factor discussions. Same with every other point and shoot out there, but they are usually just know as 3X and 4X Optical zooms ...

Canon A620 is only 7.3-29.2mm
Nikon Coolpix P3 is only 7.5-26.3mm
Casio EX-Z850 is only 7.9-23.7mm

Personally I just learn what my various lenses can do on the camera I am shooting and compose my shots appropriately.

Mike