Architect1776 Loc: In my mind

It is a unique and superb lens then add the incredible close focus capabilities and there is nothing close to it.

bleirer

COHappyHiker

Wow!

PHRubin Loc: Nashville TN USA

Here is a thought right out of the box.
For additional reach, an APS-C camera body narrows the FOV by a factor of 2.56 (1.6L X 1.6W). Far less expensive then that lens, and you would have 2 options.

Notorious T.O.D. Loc: Harrisburg, North Carolina

Thanks. I may look for a higher mp body one day. I will see what else Canon comes out with. I was shooting trains today with sun and partly cloudy skies. 1/1250 to 1/2000, f/8 and ISO 800-1000. So sounds like the 5Dsr would handle the ISO needs for my daytime shooting just fine. Thanks!

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

The heaviest 600mmF4 was the Nikon AF-S II which was 10.7 lbs, but the current Canon 600mmF4 is most certainly hand-holdable. It's only 1/4 lb heavier than a Sigma 150-600 Sport - and I know of many bird photographers that use the Canon hand-held, and some are senior women.

Do you have a link to your images? I'd love to see them.

Blurryeyed Loc: NC Mountains.

I think that I would consider the 600/4 II before even thinking about the 800mm. Both the 500/4 and the 600/4 in the latest versions have lost a lot of weight making them easier to use handheld but I can't speak to that personally because I have never shot with the newer lenses. You should consider a few things, if you are planning on using that 600 with an extender you will need to use a tripod not only for the weight of the lens but if you are going to be shooting a 1200mm lens stability become paramount.

I let go of my 500mm f/4 and replaced it with the 300mm f/2.8 II with the 2X extender and have been quite happy with the new set up. The 500mm I had was not the new one and it was too big and heavy to handhold for any length of time, that is not to say that the lens could not be used handheld but in short time it became a real burden. I have found the 300mm f/2.8 II to be an extremely sharp lens even with the 2X extender, I have no regrets in fact I think that the 300 with the extender is possibly sharper than the 500/4. Weight wise it is much more comparable to shooting with my 100-400II than the 500mm, there really is no comparison, but like I said the newer versions of the 500 and 600mm Canons have been totally redesigned and are much lighter.

Had I been able to afford it I would have gotten the 400mm f/2.8 II but it was beyond my budget. If budgets were of no concern I think that the 400mm f/2.8 III would be in my line up, I would think that lens with the use of extenders that is all the lens one would need.

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

The current Nikon 600 f4 went on a diet at 8.4 lbs. the current Canon is 6.71 lbs. and the new Sony is 6.7 lbs. Yes, they are lighter, but the Canon 400 f4 comes in at 4.6 lbs.
I would rather shoot with the 400 for 4 hours than the 600 any day. But then again, I am not as young as I used to be.
For me, the Canon 600 is not hand-holdable, 20 years ago it would have been.

imagemeister Loc: mid east Florida

Are you doing high action ?? or BIF ??

imagemeister Loc: mid east Florida

NO - IMO.

With the Canon system currently, and for the weight considerations to get to 800mm, I would be trying to use the 400 DO II with 1.4 and 2X and I would be using the 5DSR or the new 90D. Rather than using the 2x, my preference would be trying to just use the 1.4X and CROP and use well applied pixel enlargement software if needed for larger printing. Hopefully, Canon will be improving the AF of their mirror less.

Of course the ultimate answer IMO is the 400 2.8 with extenders - the 800 native prime, not so much.
.

amfoto1 Loc: San Jose, Calif. USA

What you might want to try instead is getting one of the new 32.5MP 90D.... an APS-C camera sensor is sort of like a 1.6X teleconverter, but without the light loss to an actual teleconverter... Plus the 90D has higher resolution than your 5DIV or 1DXII.

Your 100-400mm II on a 90D would "act like" a 160-640mm f/4.5-5.6 on your full frame cameras. Add the 1.4X to the lens and it will act like 224-896mm f/6.3-8.0. Plus, the 90D can autofocus that lens/teleconverter combo... In fact, if your 1.4X is the III version, the 90D will be able to AF with 27 of its 45 autofocus points.

Hmmm..... $1200, 1.5 lb. camera? Or a $13000, 10 lb. lens (plus a hefty tripod to sit it on)?

Edit: While lighter than the 800mm, the EF 600mm f/4L IS USM III is still 7 lb., costs the same as the 800mm and is going to require as sturdy tripod. There isn't a "III" version of the EF 500mm f/4 IS USM yet. The "II" actually weighs slightly more than the 600/4 III. But at least it "only" costs $9000!

Personally, with the trend toward mirrorless right now... and the trend away from DSLRs... I'm not sure how much I'd invest in EF lenses. Sure, the EF lenses can be used on the R-series cameras via an adapter (adding a little weight and length). But there will be RF versions of these lenses in the not-too-distant future, I'm pretty sure.

Blurryeyed Loc: NC Mountains.

The prices that we have seen on the RF lenses have been significantly higher than their EF equivalents if that trend holds I can't imagine what the prices will be on the big white RF primes. According to DXO mark the 600mm f/4 II is just a hair sharper than the 400mm f/2.8 II and I suspect that the 400/2.8 III is sharper than either of those two lenses. People have mixed feelings about DXO and their ratings. I will say that I pretty much used my 500/4 on a gimbal and rarely handheld because of the weight, the 600mm weighs in at about 8 1/2 pounds and the new very expensive 400/2.8 III is just over 6 pounds which actually becomes much more usable hand held. Personally if I could afford it I would go with the 400/III but that is a heavy investment.

I have the Canon R and don't find there to be any difference in focusing performance between my one RF lens and an EF lens adapted to the mirrorless camera. The R itself has suffered focusing problems that are still being addressed with firmware updates, the next update 1.4 is supposed to further address AI Servo problems that have been a big issue for me when using the R.

tlmly

The Canon 600 F/4.0 with a 1.4 extender will give you an effective focal length of 840 mm with THE SAME F/5.6 F-stop as the Canon 800 mm. It also gives you more flexibility than just the 800.

The image quality of the new Canon Super telephotos with the current version extenders is very good. Here is a link to a recent image of some herons from a long way away with the 800 series II paired up with a 1.4x III. I used a 7DII for this image but I will also use my 5DIV.

https://www.flickr.com/photos/tim_lumley/48266371656/in/dateposted/

aellman Loc: Boston MA

Sounds like a classic GAS attack to me. >Alan

davidrb Loc: Half way there on the 45th Parallel

Photography is the epitome of "trade offs". We all want perfection, but settle for less when the bills come due. There are several ways to get 800mm in focal length. Start with the EF800 and work down in price to the EF 100-400. Find what you will accept and shoot it. Personally, I shoot the 100-400 using a 2x TC, the 400 f/4.0 DO and a 2x TC, or the 800mm lens by itself. The EF 800 at f/8 is as sharp as any other. It also weighs 10 lbs. I may try shooting it next week using a monopod. I also may go with a lighter 500mm and a TC. A small group is going after elk next week and one of the other guys uses the EF600mm v iii on a monopod. We worked the Shenandoah Natl. Park in June and he used that rig all week. His lens is slightly heavier than 6 lbs. "Is it worth it?" doesn't get you too much here, "What is it worth to YOU?" is the only question you need answer. This trade-off is yours alone. Good luck and be cautious.