thanks for the information. i will have to think about this whole subject of teleconverters for a while. you see, today, i just got myself an A* 400 f2.8 too and it's not quite long enough for birding even on the *istD, so i am resigned to having to use a teleconverter on it quite a lot of the time. i have the A1.4X-L and A2X-L converters too and i find them to be quite sharp, but at 40-60 ft distances, the DOF is so low wide open that it's hard to be precisely on focus without some back and forth. that means time, and that means lost pictures. i guess that is where the AF converter is best. manually get focus close and let the camera do the rest.
Yes - the little bit of AF helps, and a true AF lens, of course, would be ideal. I use my 400 f2.8 almost entirely with a TC - the only exception being when shooting large water foul like swans. That may change with the *ist-D though....
i also have the pair of current Sigma AF 1.4X and 2X converters and i find that they lose some contrast and sharpness over the Pentax Ls, and have frequent strange bokeh on top of that. i have been thinking about the 1.7X AF converter because the AF still functions somewhat but i was wondering about quality. i did do some chromatic abberation tests with the A2X-L converter mounted and the combination did very well. no visible abberation on the *istD images out to the corners.
My own tests with the 2x-L showed it to be quite good on the A* 400. to test, I mounted the lens on a tripod and put a monopod on the camera. But in the field, the results are not as good. I think that the 400 + 1.7x is the maximum I can currently work with reliably.
what do you use for a support when shooting with the 400 f2.8? right now, i have a Wimberley head on a Gitzo 1325, but it's hard to stalk a bird. instead, i pick a position and edge up a bit, but that is about all. is a big monopod good enough for this?
I have a monopod that I almost never use - it is not heavy enough for the A* 400. I use a Bogen 3036 Tripod with a 3049 ball head. Both are rated to hold 25 lbs. When walking out to locations I drop the camera, lens, flash, etc into a backpack. I put a strap on the tripod (just a standard laptop-bag strap) and sling it over my shoulder as well. It's about 30lbs of stuff - figure 13 for the tripod/head, 13 for the lens, and a few more lbs for the rest. Once at the location I mount the camera, lens, and flash on the tripod and lock it all in place, with the legs pre-set to so that tripod is at the right height when set up. I just carry the rig on my shoulder after that. It's not always easy, but it usually isn't all that difficult.
I would think the gimble head would be ideal. Can you lock it down tight? I also use this tripod for my 6x7 (these days) and for shooting in high winds were I need something heavier than the 3021, so I'd rather stick with the more general-purpose ball head. But for long telephotos, the gimble should be best.
incidentally, i mounted my *istD on an A* 1200 f8 this morning and tried to take a picture under complete overcast. my Gitzo 1325 with the Wimberley head is just not adequate to support the lens steadily. i could have tried holding and bracing more than i did, but i didn't think it was a good use of my time. this is a lens where if you can't shoot at 1/1000s or faster, you'll just get vibration blurs most of the time. i can see this lens being used on a tripod with an automatic adjusting monopod/ball head on the camera at all times.
I've never even seen the beast but 1200mm would be a whole order of magnitude over anything I've used. I really think that beginning with 300mm and up, technique really becomes critical and the challenges of technique grow exponentially and you move into longer / bigger/ heavier glass.
Hope this helps -
MCC -----
Mark Cassino Photography
Kalamazoo, MI
http://www.markcassino.com
-----
