Need Help with Lens choices

Guys...

Really would appreciate another "set of ears" on deciding which lenses to buy. I will purchase two lenses for my camera in the next few days. I have a Canon 10d and want to buy either the Canon 17-40 f/4L or the Sigma 15-30 f/3.5-4.5 and either the Canon 70-200F/4L or the Sigma 70-200 f/2.8.

I will use the WA zoom in (I think) the Jonah C10D housing with appropriate port for u/w photos and also for land photography. I will use the long zoom for nature/wildlife photos.

From the reading I have done it seems there are mixed opinions on which lens is better in each case. The cost of the pure canon vs. pure sigma option is with-in $100 of each other so either way I will be spending about the same amount of money (assuming I buy the same brand of both) so that doesn't really cause me to fall either way. This appears to be purely a quality/functionality issue.

My thinking: (my wife tells me this is very dangerous)

Sigma 15-30 is a little wider but is bigger/heavier and is not weather sealed or HSM and has fixed lens shade and no option for filters

Sigma 70-200 is one stop faster but is also bigger/heavier and not weather sealed

neither is "canon L"

Wondering if there is an advantage to keeping a pure canon system (camera and lenses) or if there is any issue using sigma lenses on the 10d. Also wondering if the the fact that the canon lenses are weather sealed vs the sigma lenses which are not is a big consideration. Wondering too if the fact that the sigma WA does not except filters will cause me much frustration (circular polarizer for landscapes etc.) and whether the fact that the sigma WA is not HSM will be an issue.

For the 70-200, wondering if f2.8 vs F4 is really that big a deal considering that digital gives me the flexibility to bump up my ISO at any time if necessary.

I know there are several questions here. I appreciate any opinions shared.

Thank you,

If you're going to use a WA zoom underwater, it is very important that it accept diopters. You may need a diopter to get best results behind the dome port you plan to use.

The Canon WA zoom does and the Sigma does not.

Cheers

James

Maybe not relevent but...

I've noticed that the Sigma lenses tend to be faster but they also take a larger filter size than the big name lenses. If you want several filters for a given lens, you may end up spending more in extra filter costs than you saved on Sigmas.

I would also be careful to check if the Sigma can fit in the housing you intend to use. It is a large lens and may not fit through the bore of all port systems.

One diver on my last trip was using the 15-30 in an Aquatica D100 with an extender. I don't know how good it was.

The longer end of the Canon 17-40 would be useful if it's the only lens you'll have.

Over the past few months I made similar decisions. I chose the Canon 17-40L over the Sigma 15-30, because of the size of the Sigma, and the lack of a flat front element (no filters). I also chose to get a Canon 70-200 over the Sigma 70-200, but in the end went with the 2.8 IS version of the Canon. Right before I bought the 2.8, I had decided to go with the Canon f/4 over the Sigma, but at the last minute decided I really wanted the IS version. If there was an f/4 IS, I would have gone with that.

As Craig also mentioned, the extra 10mm on the tele end meant more to me than the extra 2 mm on the wide end.

Guys,

Thanks for all of your help. I sincerely appreciate it.

I decided to go with the canon lenses. I ordered the 17-40 and 70-200 f/4 from Badger Graphic. The 17-40 is in; waiting for the 70-200, which I 'm told will be in in a day or two. Hopefully these will ship by the end of the week.

Now for that housing...