New telephoto lens for full-frame

Hello,

I've been shooting with a 1.6 crop for a long time, and my 70-200 F4L IS was all what I need, but recently I have switched to the FF world with a 5d3, and now the 70-200 is somewhat short for my needs. I also have a 100 F2.8 macro that I could use for portraits (in the 70- range), and a 1.4x kenko TC. I am thinking of entering the wildlife and birds world, and the 100-400L seems the standard, but I have tested both the 70-300L and the 100-400L with the Kenko 1.4x and it seems that the sharpness of the 70-300 let me reach the 560mm cropping a 420mm. Maybe I was just not getting the most of the 100-400 as I only could test it in the shop, at F8 with a not too distant target. So the question is, could the F2.8 100 be enough for low light and do I replace the 70-200 for the 70-300 or keep it and add more weight to my already large bag?

In fact the options seem to be:

- Sell the 70-200 F4L IS and replace it with a 70-300 F4-5.6L, it would be the best match for the previous 1.6x 70-200 although it is bigger and slower.

- Keep the 70-200 F4L IS and get a 100-400, although I would increase a lot the weight and the 100-400 is quite old.

- Keep the 70-200 F4L IS and get a 400 5.6L, also an old lens with no IS.

Regards,

As you have the kenko 1.4 which works nicely with the 70-300L think that would be my choice, although I have never tried the 100-400 as I have the 400 5.6, which since getting my 70-300L has seen very little use. I just like the versatility of the zoom and the IS.

Its a hard choice - good luck with it.

I find the 100-400 to be a very sharp lens that takes full advantage of my full frame cameras. The 100-400 will now auto focus with a 1.4xt on the 5d III. Not very quickly, but usable. The 100-400 will give you the reach you need with birds and wildlife. I don't think you will find the 70-300 to be as useful on a full frame camera.

you could upgrade the 70-200 for a 2.8 version and get a 1.4 TC

or

get a Sigma 120-300 f2.8 as well as a 1.4 TC

I have tried to like the 100-400 and even after loaning one from a friend for a long weekend found it clumsy, slow and soft. I was comparing it to my 70-200/2.8IS II and 1.4 & 2xTC.

There's another option - look for a used Canon EF 70-300mm f/4.5-5.6 DO IS USM. It is an odd lens and folks either love them or hate them. I love mine. It is a perfect match for a 6D . . . small camera/small lens. They make great travel companions.

I too recently switched to FF from a digital Rebel. I have the same 70-200 lens that you do. You do understand that a 200 is a 200 whether on a crop body or a Full Frame body? You only see a Cropped image of what a 320mm lens would show in the viewfinder, but it's still a 200mm lens. If you want to get higher than 200mm I would suggest getting either the 1.4II extender or the 300mm F4L IS. There is so much misinformation concerning cropped cameras. You loose field of view, you don't gain magnification. Good luck with whatever you decide.

Ditto re 70-300L with 6D.

If you are serious about bird and wildlife photography, you should consider lenses at least 400mm long. With Canon, it leaves you either with the ancient 100-400 and 400/5.6 or requires paying much more for the super teles.

One option that may be tempting is getting the 70-200/2.8 II and a teleconverter. The teleconverter significantly impacts focusing speed though and I would not recommend it if you expect to use the 400mm regularly. It's a great combo if you are in the 70-200mm range 95% of the time and need the reach only occasionally.

At the end I decided to replace the 70-200 with the 70-300, if 70-200 was enough on a crop body, 70-300 should be enough on a full frame one. I know the crop factor does not increase magnification, just crop the field of view, but given the pixel density of a 7d is much greater than of a 5d3, you effectively get an almost 1.6x magnification.

I got the 70-300L from Amazon for 1375€, and I'm selling the 70-200 F4L IS for 800€, I am going to start saving for a 500mm if finally I really like birding and wildlife and, nobody knows how, I improve enough my skills to really take advantage of a real super tele.

Regards, and thanks for all the answers.

100-400L seems like best choice if you want to get back to the old length like on the APS-C. I use it quite a bit and you do need to get used to the push pull zoom. No problems in China, India, Malaysia, all over the world. If you can wait there is a rumored upgrade but that has been going around for a while too.