Hi Brian -

I know absolutely nothing about the 500mm lenses you mention above but as you know, I have been to Horicon Marsh a few times over the last few months. I used my 100-400mm and I didn't have as many keepers as I would have liked! Some worked ok as more of a landscape shot with a bird in the distance if you know what I mean. A few worked out with the cropping not doing to much damage. If you are hoping to get some decent shots of that middle section on I think it's Dike Road, that will be difficult with a 400mm lens.

This shot is slightly cropped I think taken on a very foggy morning but you get the idea of how far the GBH still is with the 400mm ...


Just me & nature on a early foggy morning by Denise Trocio ( www.dtrociophotography.com), on Flickr

This one is cropped alot more ...


IMG_4248 by Denise Trocio ( www.dtrociophotography.com), on Flickr

You can take a look at my flickr site if you want for more shots taken there. The 400mm length works well for the birds on the road & in the trees.

I have tried a 1.4x II on my 100-400mm and shots weren't too bad, I just couldn't adapt to MF quickly enough before the bird was gone.

I'm very interested what others have to say about the 500mm lenses listed above and in what you decide. I have thought of ditching my 100-400mm every time after leaving the marsh and getting a 500mm but as you, I couldn't decide on which less expensive one to get.

Good luck with your decision!

Denise