Sigma 50-500mm and a converter

[hughredcanary]

Hi
Happy new year
Using a Nikon D200 and the Sigma 50-500mm 1:4-6.3 AP0 DC HSM D lens with a KENKO N-AF 1.5 teleplus SHQ converter what focal dissidence will it give me I normally shoot at ISO 400 in good light I can shoot at f4 ok, so with the KENKO N-AF 1.5 teleplus SHQ converter upping ISO to 800 will I be able to shoot a f4 If no what would be the ISO to shoot with the converter to shoot at f4 I hope this make sense
Hugh
http://hughsphotoshop.com/

[jdepould]

You'll probably run into AF problems. Officially, Nikon says a lens has to be f/2.8 or faster to get good AF using a TC.

[marxz]

changing ISO will not affect AF sensitivity because the AF points on SLR's are a separate system using their own pre imaging sensor (ie the af points are actually their own COSM sensors that are built in to the camera (usually in the penta prism) receiving light that is bounced off the mirror.

As such they are independent of any imaging sensor settings.

You'll probably find that in anything other than good daylight you will run in to autofocus issues, and even in strong daylight you may want to manually select the center focus point and focus on a strong contrast area of your subject - either that or use manual focus

either way may be problematic given the 2x converter used at 500 will give you a 1000mm lens which even at f8 has a depth of focus may only be a few mm deep - so if you focus on the beak of a bird at 10 - 50 meters away to get a strong contrast line you might find the eyes to be out of focus.

note that using my Bigma with a 2x converter (and a 1.4x) things start to get very soft towards the long end (500 pre converter settings).

Nice for taking BIG sunset shots not so hot for birding

[bertone61]

using the TC 1,5 will reduce your maximum aperture from f4 to f6, so you won't be able to shoot at f4.