adrianpd

I have been using this lens on my Nikon D500 with great results. However if I add a 1.4 Extender it will not focus but hunts continuously. Any suggestions. I haven't tried it on my D850. Would it be any better.

randave2001 Loc: Richmond

I had the same issue some time back with a Canon 100-400mm f4.5-5.6 and a 2x extender. What happens is that the aperture changes by two stops with this extender. So, when you are shooting at full zoom of 400mm you are effectively shooting at f11. There is not enough light for the auto focus to work with and therefore it will hunt. I even tried it with another photographer's 1.4x extender and it behaved the same way at the long end of the zoom (effectively f8). My only choice was manual focus which can be a bit problematic for things like BIF photography.

imagemeister Loc: mid east Florida

NO, you need to get closer -OR- maximize your IQ and CROP and use well applied pixel enlargement software if necessary ...

CHG_CANON Loc: the Windy City

Have a look at page 99 of your D500 user manual as well as consider the effective aperture of your variable aperture lens when the extender is attached and the zoom focal length increases. Your D850 manual should have a similar chart and possibly a different specification on the minimum aperture size.

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

As Larry said (Imagmeister) you need to get closer to your subject. If a 600mm lens on a D500 (effective angle of view equal to 900mm) isn't getting you the results you are looking for, then you are too far away.

You can capture good fine detail with this lens, but not at great distances. Cropping your image may help a bit, but between the smaller sensor and the tiny bit of softness at 600, you may not be happy with the results with cropping. Adding an extender only makes the softness more evident, as well as exacerbating any movement on your end and any other flaws in technique or gear. Manually focusing a lens with a max aperture of F6.3 is hard enough. When it becomes F9 it's even harder. The issue of what constitutes adequate support enters this discussion as well. Hand holding or using a really light duty tripod and head is pretty much out of the question.

I disagree that pixel enlargement is a viable strategy. It will enhance edges and better correct anti-aliasing on inclined and circular edges creating a cleaner, "crisper" appearance, much like micro-contrast adjustments, but by expanding the number of pixels by making more space in between the pixels and using interpolation to fill in the spaces, you will end up with more pixels and no corresponding loss of detail, but it won't add more detail. Image resizing is not a solution for adding fine detail that wasn't captured to begin with, but it will make a large print look better.

Your solutions are then to either get closer, or get a sharper faster lens that will give you a max aperture of F5.6 with a 1.4 TC on it, along with a Gitzo, RRS, Induro, LeoFoto or ProMedia Gear tripod with a minimum top leg section diameter of 41mm - and these will cost you $1000 or more. If you are using a gimbal, then you can scale back the tripod a little bit, and maybe use a $600 Feisol CT-3472 with a 37mm leg.

Kmgw9v Loc: Miami, Florida

Why not the 850?

blue-ultra Loc: New Hampshire

Revet Loc: Fairview Park, Ohio

I have the same combination of lens and camera and I have never had a problem focusing even in low light (to my amazement). I use the Sigma TC-1401 with my set up

lrjames Loc: Lacey Washington

You can tune the 850 to the lense it is a marvelous camera by tuning it you take most of the softness out at 600 on the sigma

carl hervol Loc: jacksonville florida

what is BIF?

Tim Stapp Loc: Mid Mitten

Birds In Flight