Travel Lens - Sigma 18-250mm?

[Bios.]

Im planning to go traveling through Central America and am thinking about what lenses im going to take.

I currently have a 500d with the kit lens 18-55mm f3.5-5.6 IS, the 55-250mm f4-5.6 IS and the Sigma 105mm f2.8 macro.

Im going to be doing some conservation/research work in the rainforest so the macro lens is definately coming plus a 430ex and bracket etc. as there will be loads of bugs! I also need some length for birds/mammals etc. and surfing shots.

I was thinking about selling the 55-250 and maybe the kit lens and buying the Sigma 18-250mm f3.5-6.3 DC OS HSM as this has both of them combined. However the reviews I have read of this lens are mixed.

Having bought the sigma 105mm I have really been noticing the differences in IQ between it and the kit lens/55-250mm and image quality is starting to become an issue in lens choice.

There are many benefits of the sigma as I see it which are:

1. One less lens to take
2. Less lens changes in humid/wet/sandy conditions
3. Non rotating front element (for polariser/petal hood etc)
4. Close focusing distance (for larger than macro but still smallish creatures)

However im not sure how the IQ compares between the 55-250 and the sigma and I already have the 55-250 so im going to have to spend money that I would otherwise have to spend on the trip.

Basicly my questions are:

1. Is the IQ of the sigma that much worse than the canon lenses that it cancels out the benefits?

2. Are there any other options (maybe a better telephoto than the 55-250 with less zoom range)? Bearing in mind the price (I don't mind buying second hand) and that extra length is going to be very useful.

Any coments greatly appreciated!

 

[Light Artisan]

I had the Sigma 18-250 and it was an incredible walk around lens, loved it. I had to sacrifice it to get the Sigma 70-200 however.

Awesome lens though, sharp and contrasty! I've had 3 of the Nikon units and none of them compared to the copy of the Sigma I had.

 

[henkelphoto]

Rainforest and 6.3 at 250mm don't go together too well.

 

[KmH]

+1 ↑ ↑ ↑ ↑.

Plus, I understand the focus 'breathing' of that lens is pretty spectacular.

Focus breathing is when you are zoomed to 250 mm, but have a close focus point, you are getting a magnification factor of only 175mm or so, not the magnification of the 250mm the zoom ring is set to.

It's just one of the common issues with all SuperZoom (11x - 13.9x), jack-of-all-trades, master-of-none, walkaround lenses.

 

[Bios.]

Yes I realise the bad points/issues with this type of lens. Im not asking a straight up "is this a good lens" question.

What I want to know is: Would you take the sigma or both canon lenses?

I have thought about getting a secondhand sigma 70-200mm f2.8 APO EX DG however I would still have to regularly change lenses, carry more weight, lose IS and have less length.

 

[j-dogg]

The Tamron 18-270 VC is a wicked lens I have one. Pretty sharp through the whole range and at 270 f6.3 the VC will let you take the image at 1/10th second and come out clear. I've got one and I love it.

Travel tested, dropped, bitched at by airport security, caught in the rain, bought from a lady who was somehow convinced I was a serial killer, walked around for a full day and dogg approved.

 

[Bios.]

Done a lot of reading/trawling forums/thinking and if I sell some stuff and work more overtime I can probably get a secondhand sigma 70-200mm f2.8 and a 1.4x teleconverter. I think having some fast glass may be worth the extra weight and lens changing. I will probably only use the 1.4x with tripod/monopod.