Zoom lens question - should i?

Ok i currently have a pair of sigma zooms (bought as a twin pack when the IST D body was bought new a couple of years back)

28-80 55mm Filter Macro f3.5-5.6
100-300 55mm Filter UC f4.5-6.7

Now i see online a few lenses, also sigma

28-300mm F3.5-6.3 Aspherical (67mm) £99
70-300mm F4.0-5.6 Macro DG (58mm) £98
70-300mm F4.0-5.6 APO Macro DG (58mm) £158
70-300mm F4-5.6 APO Macro Super II (58mm) £139

I use the camera for a range - from portrait and scenic up to sports action.

I'm looking for a lens at the longer end of things, and ideally a fast lens - obviously the f6.7 at the long end of my zoom is pretty slow, and getting down to f5.6 would make a noticeable difference - but is a £100 sigma lens going to be way soft/slow to focus? Or is the price just very good because of the more modern f4 and f2.8 long lenses available?


I can't afford the 500mm f2.8 that i would love, so sticking with the real world would a £100 lens be a good buy or would it make the already soft IST D just produce pictures with no definition?



(if anyone has a tried and tested alternative then i'd love to hear, i'm open to suggestions of other brands but i know sigma is generally a fairly safe bet)

I had a Sigma AF 400mm f5.6 (non APO) and to be honest I was relatively dissapointed with it's performance, soft wide open and a real lack of contrast, then I had a Sigma 135-400mm APO (usually about £250 used) which was much better but it had a big problem with lens creep, anywhere between 5 deg's up or down and the barrel would start to slide forwards or backwords if you took your hand of the zoom ring. For long range I now have 2 lenses, a Sigma 70-200mm f2.8 EX DG (lots of money) and a Sigma EX 2x converter plus I have a Pentax 80-320mm, both are excellent performers.
For value for money the Pentax 80-320mm is a great deal, usually around the £80-£100 of that aution site.

I use a Sigma 70-300mm F4-5.6 APO Macro Super (not the II version) Primarily for its macro capability at 300mm.

I also use the Pentax FA80-320mm. If you need the long focal length rather than the macro capability, the Pentax would be my recommendation. I've had no problems regarding barrel creep with mine, but then its relatively new and not used often so its probably still tight.

I also have the Sigma 135-400mm APO lens bought new for £199. Stonking lens in my opinion.

You ought to be a ble to take your camera to a Sigma/Pentax retailer and try the various zooms for yourself. Make a few test shots at the apertures of interest and make a decision.

There is nothing soft about Pentax DSLRs. This is a piece of misinformation put about by people used to over-sharpened pictures found on a certain copier-cameras.

You can either put the sharpness setting on high, or better, leave it on medium and sharpen in your preferred image editor.

Better yet, shoot RAW.

And of course, use sharp lenses. That tends to rule out cheap Sigmas. If you are concerned about sharpeness you will have to use good lenses, ensure your technique is beyond reproach, and get used to editing your images. And, shoot RAW. It's been said before, but I'll say it again; if you want quality, shoot RAW.

Shoot RAW
Shoot RAW
Shoot RAW
If you want quality, shoot RAW.

There's a song in there somewhere.

G

I think a general rule of thumb applies here and that is . . . you gets what you pays for.

If you are on a budget and want generally acceptible photos the third party lenses may be entirely adequate for your needs.

If you want the best , perhaps with a view to selling your images then you should invest accordingly.

Pentax glass is mostly excellent but some of their products are less worthy of note. If you take the advice of this forum you'll not go far wrong.

The SMC Pentax FA 80-320mm is a superb performer. If you need a longer and faster lens you maybe ought to be thinking about a Pentax prime . . . now your talking serious money for the very fast ones.

anyone know the aperture ranges on the 80-320 pentax lens? and why do i never ever see any pentax lenses (except the 50s) on ebay? (and i already own a 50 SMC-A)

f/4.5 -5.6 ~ f/32 -38

you can always look here:
http://www.bdimitrov.de/kmp/

wrong search maybe? there are plenty of pentax lenses (& third party pentax mount lenses) on ebay; otherwise I've been buing wrong glass for the last three months...

There is an FA80-320mm on eBay at the moment from a German seller for £90.00 Buy it Now.

I find that typing "pentax lens" in the search box works best for me

You could also try widening your search to Worldwide.

Just go to "Buy", select Photography, then film camera lenses then pentax and choose between looking at them all, or just the AF or MF section.

There are hundreds available.

I tend to list digital lenses there as well, because the digital lens section mixes all the makes together and is not exciting!

and while we're talking about the sigma lenses...

what does APO, DG, EX and super mean?

ta!

Dex

From the sigma website:

ASP (Aspherical Lens)
The aspherical lens complex allows freedom of design, improved performance, a reduced number of component lenses and a compact size.

APO (APO Lens)
In order to attain the highest quality images, the APO lens has been made using special low-dispersion (SLD) glass and is designed to minimize color aberration.

IF (Inner Focus)
To ensure stability in focusing, this lens moves the inner lens group or groups without changing the lens' physical length.

EX (EX Lens)
The exterior of this lens is EX-finished to denote the superior build and optical quality, and to enhance its appearance.

DG (DG Lens)
These are large-aperture lenses with wide angles and short minimum focusing distances. With an abundance of peripheral illumination, they are ideal lenses for Digital SLR Cameras whilst retaining suitability for traditional 35mm SLRs.

DC (DC Lens)
These are special lenses designed so that the image circle matches the smaller size of the image sensor of most digital SLR cameras. Their specialized design gives these lenses the ideal properties for digital cameras, the compact and lightweight construction is an added bonus ! including compact and lightweight construction.

The Sigma 70-300 APO Macro is generally regarded as a good lens and should be considerably better quality that your current 100-300mm lens.

For zooms in that range I'd tend to stay away from anything with a maximum aperture of slower than F5.6 at the long end.