I could be wrong but from what you say it sounds like this is a group tour? If so the best possible protection is to stay with other members of the group at all times. Criminals have no qualms about targeting those who look like easier targets if they are on their own, but they will think twice and generally steer well clear if you're in a group.

The comments were intended to be light hearted and not intended to offend. I apologise if they did not come accross that way. In general I find people pretty friendly on these forums and a bit of banter often arises but is rarely intended in a mean-spirited way.

I have the Tamron and have handled the Sigma, albeit not in the Pentax mount. I don't find the zoom ring on my Tamron too tight at all, but it is a little tighter than my other zooms so it may be a matter of taste. I wouldn't hesitate to recommend the Tamron based on my own experience, and I do not personally feel that the Sigma is worth the extra cost. YMMV.

Tamron

Pros: Smaller, lighter, cheaper, and according to certain reviews/opinions, sharper.

Cons: Noisy AF, Rumored BF/FF problems in some copies (I personally have not had any problems), acceptable build quality - but only just (meaning if it was even just a little bit flimsier, it would worry me. As it is I can cope).


Sigma

Pros: Quiet AF, much better build quality.

Cons: Larger, heavier, more expensive, possibly not quite as sharp.

My three main zooms are all pretty sharp.

• Sigma 8-16mm F/4.5-5.6 DC HSM (according to some reviews, the sharpest UWA available)
• Tamron SP AF 17-50mm F/2.8 XR Di II LD ASL (much discussed here already)
• SMC Pentax-DA 55-300mm F/4-5.8 ED (also had a mention)

In fact I'd highly recommend this combo to anybody, as far as I can tell it's the most cost effective way to get all the way from 'ultra wide' to 300mm all with excellent sharpness - and believe me I have researched this exhaustively, as I'm not exactly rich so I make every penny count when it comes to the gear I buy. (There are usually cheaper ultra-wides available than the 8-16 but right at this moment in time it's available on SRS cheaper than the others. That may not last).

Okay there is a 5 mm gap between the 17-50 and 55-300 but you're unlikely to ever miss it. (If you really must take a shot at 53mm then take it at 50 and crop it a tiny bit, or if possible zoom with your feet).

It's a good bit larger than the kit lens, sure, but you have to expect that from an f/2.8 zoom. It is actually significantly smaller and lighter than the other f/2.8 standard zoom alternatives - i.e. the Sigma 17-50 and the Pentax DA 16-50.

Perhaps the OP intends to photograph military bases, nuclear submarine pens, weapon test sites and such.

B.T.W. I saw an American tourist here (in Edinburgh) actually lugging around a 645D the other day. His camera equipment was certainly not unobtrusive. I briefly considered mugging him but decided against it. (I've never mugged anybody before, but then I've never seen anybody carrying a 645D around before either).

Yes, it certainly does help. It helps because, and only because, other bidders are indecisive. My point is if you don't want to*, or for some reason can't bid at the last minute then the only way you can possibly win is to be decisive and bid your maximum straight off.

*Some folks seem to feel it's "cheating" to snipe.

I have been known to snipe when 'appropriate' so to speak... however if you know exactly how much you're prepared to pay there is no need to cancel, unless you're bidding on several items at the same time when you only really want one, of course. When I bid it tends to be on rare items I can't get hold of through normal retailers, for such items the likelihood of several being up for sale at once is quite low.

I don't buy stuff to resell, generally speaking. If I did I'm sure I'd take full advantage of all these indecisive bidders and snipe constantly.

For my part I've purchased around 140 items on eBay over the years and bid on goodness knows how many, and eBay has never once autobid over my stated maximum. I really doubt they would let a bug like that creep in because the autobid system is really the heart of eBay, or should be, if used properly.

In all honesty the way many (possibly most) people go about bidding on eBay simply baffles me. Used properly (the way the people who designed it intended it to be used) you should only ever bid once, and it should be the maximum amount you're prepared to pay - let the autobid system take care of the rest. Some people seem to think that if you bid this way you'll end up paying more for the item, but that isn't how it works - autobid will never bid higher than necessary to keep you ahead of the next highest bidder. There is no real advantage to withholding your highest bid until later, and there is the severe disadvantage that you might well lose the item to a 'sniper'.

A lot of people whine about snipers, i.e. last second bidders who outbid them to win the item. If you use the system as it's intended and bid the most you're prepared to pay straight off you cannot possibly be beaten by a sniper unless they're simply prepared to pay more than you are. Snipers are not taking advantage of 'faster internet connections' or being able to 'be there for the close' when other people might not be able to as the complaints often state. Nobody's internet connection is fast enough to beat the autobid system, nor is anybody unable to bid because they're not there, as long as they let the system do it for them! The only thing snipers are taking advantage of is other bidders' indecisiveness. Another reason to be decisive and use the system as it was intended.

If you find it hard to decide on the maximum amount you'd be prepared to pay, think of it this way - what's the lowest amount you definitely would NOT be prepared to pay? Got it? Okay, bid a penny less than that. Not a pound, not ten pence, just ONE penny. Remember than unless another bidder is prepared to match you pretty closely (or outbid you) the likelihood is you will not end up paying as much as your maximum bid.

Yup I think whatever method is used for limiting the shots to 800 pixels wide on the forum isn't too great at retaining sharpness. It's probably just whatever is built into the browser you happen to be using. I usually use GIMP to resize my own shots and I find it's quite excellent at retaining the sharpness. As a result I'm quite lazy and don't usually use USM but I should probably get into the habit as it would make the resized images sharper still.

As for focusing, this is the first time I've used such a wide lens so I'm not yet used to judging how the depth of field will come out at such short focal lengths. I know you get a much larger depth of field at the same aperture than with longer focal lengths, but I think in a few shots I may have overestimated just how much larger! I'll get used to it with practice.

Perhaps it's just novelty value but the extremely exaggerated perspective in that one was one of the things I liked about that shot.

I was considering one of the 10-20s but SRS dropping the price of the 8-16 to £375 made my decision for me. I have to wonder if it will stay at that price for long... it seems to be about £175 cheaper than any other UK retailer I could find!