[Des]

I am not a mad photographer, just trains, scenery and models (of trains).

Hi Mark, from another Victorian.

Are you really looking for a long lens (xx-300mm) for trains and model trains? Not my expertise, but I would have guessed that the DA 18-135 would be a more suitable range for these things? And as people have said, that lens is quite fast-focusing, it's weather resistant (WR) and the image quality is very good for such a versatile lens. And it's reasonably priced - around $A250-300 for a used one in VGC. The DA 16-85 is sharper in the corners and edges, but it's a lot more expensive, and you would miss the extra 50mm at the long end. (Weather resistance also relies on a WR body, and the K20D isn't, but if you do upgrade the body it's likely to be to a WR model.)

But if it's a longer lens you are after, one of the Pentax DA 55-300 models is hard to beat. The new PLM one won't work with the K20D (or anything up to or including the K-5ii), but the image quality from the previous screw-driven DA 55-300 f4-5.8 models is comparable anyway. (The DA-L, DA and DA WR 55-300 f4-5.8 are optically identical except that the WR has newer coatings.) There's a WR version on Gumtree at the moment for $200 - looks a bargain to me (Pentax 55-300mm WR Lens | Lenses | Gumtree Australia Brisbane North East - Ascot | 1170269471). There's also someone in Torquay selling a what looks like a non-WR version who might take $150-$200 (https://www.gumtree.com.au/s-ad/torquay/digital-slr/pentax-kx-camera-white-1...bag/1169932092).

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Last edited by Des; 01-07-2018 at 08:09 PM.

[audiobomber]

Des, the K20D is weather-resistant and tough as nails.

[mikesbike]

Since you have the DA-L 18-55mm, which is the lowest build quality in Pentax, yet with the same optics as the next step up, but it won't go any wider than 25mm- I agree that your next setup would be well-served with a new DA 18-135mm f/3.5-5.6 DC WR as well as the HD (High Definition coatings) DA 55-300mm f/4-5.8 WR.

There would be some overlap, but so what? You would not need to change lenses as often, except when you need to go to extra long-range. And the DA 18-135mm is exceptionally well-built, has a very quiet, DC driven, fast, accurate AF, and is very compact for its zoom range. The overlap would not be a waste in another way- from 70-200mm, the HD DA 55-300mm f/4-5.8 can hold its widest aperture at f/4-4.5, while the DA 18-135mm can hold to that up to 70mm (Still very good), so when you need that extra aperture speed in that range over 70mm to 200mm, you will have it in the DA HD 55-300mm f/4-5.8 WR. It uses the standard screw-driven AF, but it is also very well built. It has been tested by independent labs as being superior to the 55-300mm lenses of other brands, even all the way out to 300mm. And other brands do not offer a lens having a zoom range of 55-300mm that features WR construction.

Imaging quality in zoom lenses tends to diminish gradually towards the longer end of the zoom. With the DA 18-135mm, the central image area has been tested excellent throughout its entire zoom range, which is exceptional, while the edges of the image area are what diminishes starting around 55mm, and its aperture speed after 70mm. Keep in mind, as one goes more into the tele range, the edges tend to become less important in most cases anyway. However, with these two lenses, if the situation arises where the continuation of edge sharpness is important, just switch to the DA HD 55-300mm f/4-5.8 WR and you've got it available. You would also have a complete WR system over a very wide zoom range, in just two lenses.

[Des]

Des, the K20D is weather-resistant and tough as nails.

Thanks for the correction Dan. Yeah that underlines the worth of looking for a WR lens for it. I agree with everything @mikesbike said.

[Laidlaym]

Hi Mark, from another Victorian.

................ There's a WR version on Gumtree at the moment for $200 - looks a bargain to me (Pentax 55-300mm WR Lens | Lenses | Gumtree Australia Brisbane North East - Ascot | 1170269471)..

Not any more, I just bought it. Thanks for finding it for me.

Mark

[Cee Cee]

I have a K20D & K30, I have the sigma 100-300, not a great lens, it gathers dust in a cupboard somewhere. If you get the 55-300 I don't think you will regret it at all, I'm very happy with mine,
you may not think you need 300m but once you have it you'll find how useful it is.

oh, I should read more carefully, I see you just purchased one - good move & best of luck, cheers

[Des]

Not any more, I just bought it. Thanks for finding it for me.

No worries, Mark. Hope you enjoy it.