I just went to bangkok in last weekend and found that it was so inconvenient to change lens when traveling. Also, it is too heavy.
Can anyone recommend lens that cover most range? how about 18-250? i dont know which one is good.
i don't really like not having the benefit of changing lenses when travelling, i suppose it depends on how serious you are. you need to maintain a balance between what you need, as opposed to carrying your entire lens collection on your back like a pack mule.
i could give you many reasons for why you should want to change lens:
1) option of uwa, no all-in-one lens is going to give you anything in the region wider than 18mm, which is definitely useful for many locations.
2) limited fastness of lens, at best f/2.8 for zoom lenses i think.. there are situations where you might need f/2.0, or even f/1.4. rare, no doubt, but like i said, depends on how serious you with regards to photography on the trip.
3) image quality.. as much as megazoom lenses have improved since their conception.. still lagging behind.
4) size, street situations, 18-250 is still going to give you more attention than a simple flat lens. don't even need to be pancake, like a 28mm manual lens is so small
if you must have an all-in-one, i think the best compromise is 17-50 f/2.8 , tamron, or 16-50 f/2.8 DA*.. most versatile i guess.
18-250, 18-270, possibly doable, but for that price, i rather bring two, 18-55 kit lens + a telephoto zoom.
here's what i usually bring, i don't think it's particularly painful, since i have done 4 hour walks with it without rest or water.. sigma 10-20 + 28mm + 50mm + 70-300mm. on trips where i don't even think i might walk that much i will bring 2 bodies (one modified for IR), the previous + 18-55 kit lens.
some people have suggested an all prime set up..
it is not that incovenient to change lens using a shoulder bag or a hybrid bag.. all you need is practice, and the desire to get photographs that you can be proud of.
but like i said, if you are looking more to have a great time with your family, and capture memories, then 17-50 f/2.8 will be a good choice. and of course, it's your choice in the end.