[SA Chris]

Do they really make that much difference?

I am shopping about at the moment for a wide angle zoom lens for my Pentax DSLR and have coem up with the following

Sigma 10-20mm f4.0-5.6 EX DC HSM is £300 ish

Sigma 12-24mm f/4.5-5.6 EX DG ASHPHERICAL HSM is £425 ish

Sigma 15-30mm f3.5-4.5 EX DG Aspherical Lens  is £250 ish

So I can only conclude the 10-20 is cheaper because it isn't aspherical?

(A bit of an assumption, please feel free to correct me)

Did a bit of googling and found this.

http://www.mir.com.my/rb/photography/opinion/html/aspherical.htm

If I am not overly concerned about size or weight, does an aspherical lens have a massive impact on quality of photos?

Thanks for the help.

[dave]

unless you get 2 otherwise identical lenses you'll not know for sure how much difference the aspherical thing makes. bear in mind that a lot of the time its just marketing bullshit - they can stick 1 composite (i.e. a spheric element with a plastic layer glued on) mildly aspheric element in the design so they can market it as such. theres no reason why an non-aspheric lens of one design can't be better than an aspheric lens of another design. basically, unless you've got a lens where they updated the lens to have aspheric elements at some point i'd just ignore it. it'd be low on my list of deal-breaker factors.

for example, at 18 or 20mm my sigma is sharper than my 18-70mm kit lens which is aspherical.

the 10-20mm will be cheaper because the other 2 lenses cover full frame 35mm, and the sigma is digital only. thus needs less class, smaller, cheaper, plus its priced to compete directly with the tokina 12-24mm.  its a very good lens.

[cofe]

mine says aspherical on the bottom. i have no idea what that means. i suppose i could read that link.

[SA Chris]

the 10-20mm will be cheaper because the other 2 lenses cover full frame 35mm, and the sigma is digital only. thus needs less class, smaller, cheaper, plus its priced to compete directly with the tokina 12-24mm.  its a very good lens.

You mean the 10-20 is digital only? (they are all sigma) Does this mean I won't be able to able to use it with my old Manual SLR?

[dave]

yeah the 10-20mm is digital only.

(Technically you probably could use it on an old manual camera but the image circle won't cover the film, and you might lose aperture coupling/control).

[SA Chris]

Thanks. Avoid in other words.

[dave]

I have a 24mm prime for my manual film camera so its not a problem for me, infact its better, no lens swapping etc.

[SA Chris]

I have a prime 24mm one too, be nice to have full compatability though.

[Jim]

what lens and film camera have you got dave?
I've got an f80 which I'm going to start using again, got the 50 1.8 and am looking for another prime to go on it

[dave]

nikon FE. if you want primes then MXV got some crazily cheap AF 24mm going at the mo. i also use a 100mm 2.8 on that camera, and occasionally my old cheapo 70-210mm zoom.