Sigma 28-200mm

Hi guys and gals. I've got an old sigma aspherical 28-200mm lens that i purchased a good tens years ago as an all rounder for my old pentax mz. At the time i was very happy with this lens and have some great shots on the old fuji velvia to prove it. However, now that i pull this old heavy beast out and attach it onto my K10 i get nothing but pathetic shots. Weak contrasts and colours and out of focus. I am sure there is something that I can tweak on my K10 to make it work well, but what. I like the idea of keeping this lens as a zoom, rather than forking out more money to buy a 50-200mm Da. Any suggestions?

I have a similar lens (Sigma Aspherical IF 28-200mm) and have done quite a few shots with it on film and digital SLR bodies. My lens has the magic ability to not focus correctly on my K10D body particularly over 80mm focal length. I am running firmware/software version 1.30 on my K10D and all my pentax lens work perfectly fine on the same body running the same software. What firmware/software are you running on your K10D body?

I spoke to Pentax and they suggested speaking to Sigma as Pentax cannot support Sigma products. Sigma offered to have a look at my lens which I will do as soon as I can. I find the problem is intermittant and both Pentax and Sigma had not heard of any problems with my lens/body combination.

I always think a lens that covers alot of ground is going to have more elements so lens designers will always have to balance extra elements losing optical quality over the advantage of covering more focal length with one lens.

Just to complicate matters the glass composition for new digital lens also allows for the fact that light will have a greater chance of being reflected back from the sensor to the lens so if you have tried all the setting in addition to the latest K10D firmware from Pentax then I suspect you might find the same as me where the performance is not what you expect.

I hope this helps at least. I am saving for the new Sigma 18-250mm lens to replace it.

Sigma "reverse engineer" their lenses as they avoid paying Pentax for licensing, so existing Sigma lenses may show anomalies in their performance on new Pentax bodies. If it can be upgraded then Sigma may be able to re-chip your lens, but next time you get a new body there might be different problems.

I've settled long ago on just buying Pentax lenses, which is fairly well known around here!

Those old film-era Sigmas are pretty dire compared with modern lenses. (I speak from experience.)

Ditch it as soon as you can, and you won't regret it.

G

Trust me George, I am saving for the new Sigma 18-250mm lens.

Thanks for the advice and your own personal experience with these lenses. I have found however that at all focal lengths apart from 200mm it lacks optic quality and performance in all areas. The last update I performed on my k10 was a year ago, to support SDM. I probably should check to see if there are any new updates. Think i might ditch it, as john says, your better off sticking with pentax lenses. If i had the money i'd go a 50-135 SDM now, but may have to settle for a 50-200 WR.

Hi guys does anyone know where I can find in UK company that is fixing Sigma's lens, specially 28-200mm IF. Works fine but I have something on one of the glasses(looks like little fungie
On photos you can't see any points or whatever, but I just want have it clean

You could try asking here, he did a great job of cleaning a 200mm prime for me a while ago and charges very fair prices.

Thanks Matt. I hope he'll manage to clean that Sigma.

Pawel

Fungus isn't generally terminal, I've had a few lenses with it now and it doesn't seem to damage the coatings. The trick is to make sure you get all of it and don't let too much dust in while the lens is open. I was willing to open and clean a brace of cheap 50mm "spares or repair" lenses which came up pretty much mint, but I entrusted my 200mm prime to a professional as it was a bit too expensive to risk wrecking it with my attempts!

The 50mm is also a lot simpler to work on - the fungus was nearly always on the front element of the rear group, so I simply unscrewed the front group, cleaned the fungus off with a cotton bud dipped in vinegar, polished it dry with another bud and then reassembled.

I rang to Alan and says would be able to do. Anyway I'm still looking in my local area shop that would be able to clean it. But Alan seems to be pro in that case. Thanks for info one more time.

PS. I had spare 35-80mm where had cracked focus ring, decided to open it myself. How people manage to build such a precise construction!