Hibler Loc: Oklahoma

I have a Olympus E-M1
What Lens should I look at for taking Wildlife
Thanks

SuperflyTNT Loc: Manassas VA

If you’re looking for reach the Panasonic Leica 100-400 cant be beat.

wdross Loc: Castle Rock, Colorado

Along with SuperflyTNT's suggestion of the Panasonic 100-400, there is the Olympus 40-150mm F2.8 Pro (with 1.4X teleconverter, 56-210 f4), Olympus 14-150 f4/5.6, Olympus 400 f4 Pro IS, Panasonic 200 f2.8, and Panasonic 100-300. And next year, there will be the Olympus 150-400 f4.5 Pro IS (188-500 f5.6 with built-in 1.25X teleconverter and 375-1000 f11 adding on the 2X teleconverter and, per Olympus, handholdable). Most of these will not be cheap, but all will be great lenses for your needs.

SuperflyTNT Loc: Manassas VA

I also have the Olympus 14-150 and 75-300, both are good. The 14-150 is my walk around lens and it covers almost everything.

Jeffcs Loc: Myrtle Beach South Carolina

Olympus 300f4 pro with both Olympus 1.4 or the 2.0 converters
Can’t be beet for size quality sharpness

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

Minimum 300 mm. Better if it reaches out to 500mm, even better if it can reach 700 mm.

wdross Loc: Castle Rock, Colorado

With the 300 f4 and the 2X teleconverter he can achieve 600 f8. That would be equivalent to 1200 in 35mm angle of view terms. If he waits until next year and gets the new 150-400 f4.5 along with the 2X teleconverter, he will be able to shoot up to 2000mm handheld in 35mm angle of view terms.

fetzler Loc: North West PA

Panasonic 100-400mm also consider 100-300mm. Olympus 300mm.

dsmeltz Loc: Philadelphia

Depends on the wildlife. BIF, bird feeder, back yard deer, bears at half a mile, owls in trees at night, African safari?

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

A 2X converter on any lens is not going to offer optimum image quality, I would not recommend that to anyone. What is a 150-400 4.5 lens?, I know of no one who manufactures such a lens.
Many camera's will not auto focus at f8. Or, they will focus slower or hunt for focus which can lead to bad images or out of focus images. No camera is going to auto focus with a 2X on a f4.5 lens.
Hand holding a 2000 mm lens is less than desirable.
I found it difficult to find anything in your post that will be helpful to the OP. It is filled with information that will result in flawed images.

azted Loc: Las Vegas, NV.

I have the penny 100-300, and I found it to be very sharp at 300. I think it is quite a bit less money than the one quoted above.

Architect1776 Loc: In my mind

That length 100-400mm is my favorite for this.

Hibler Loc: Oklahoma

Thanks to everyone

wdross Loc: Castle Rock, Colorado

Olympus (and Panasonic) has a way of being very innovative.

The 150-400 f4.5 lens is a part of their 100th anniversary celebration even though it will come out in January or February next year. From the more reliable rumors I have found, supposedly there will not be just one set of IS in the lens but two sets of IS. How this is possible and also work is beyond me. This would put two sets of IS in the lense plus the 6.5 stops of IBIS. And Olympus states specifically that it will be handholdable with the 2X teleconverter. I would have never thought that I could handhold my camera at arms length over my head, while viewing the articulated screen, and getting 4 out of 4 shots at two second exposures. But I have the shots to prove that it can be done. I have no doubt that Olympus has done it and will make handholding at the 2000mm angle of view not only possible but desirable.

This is helped by the lense being only about 16" long and about 4.5" in diameter. My estimate for weight is 4 to 5 pounds. We will find out just how acturate my measurements as determined from the side by side comparison of the lens to existing lenses in photographs.

And you are right that the 2X is not likely to be perfect with the lense. It will probably work better with the 1.4X and the newer E-M1X focus system unless the upgrade for the E-M1mkIII will match or go beyond what the E-M1X does. I suspect the A.I. will come into play here and make it much easier for focusing at f11 and smaller. And even if the OP only wants a 1000mm angle of view, he will not need to buy a teleconverter. That 1.25X teleconverter will already have been built into the lens and will allow the 1000mm angle of view at f5.6.

I know you might not find my post helpful, but I know there will be a lot of photographers that would like a lens capable of a 300mm to 1000mm angle of view in a size of 16" long, 4.5" diameter, and only 4 or 5 pounds. All the OP has to do is wait until next year to find out what will be possible for sure.