Which Lenses to Buy?

[JTPAIN]

Thanks for the help!

Have decided to either go for the 70-300mm L IS or the 100-400mm L IS for telephoto - which produces better images?

The general consensus seems to be that the 70-300mm is better with the more up-to-date technology and IS and generally produces better images, faster. Is this entirely true?

I am guessing that canon will announce a replacement for the 100-400mm in February? hopefully along with a new '650d' with the new processor!!

[neuroanatomist]

Have decided to either go for the 70-300mm L IS or the 100-400mm L IS for telephoto - which produces better images?

The 70-300mm L will deliver slightly better IQ than the 100-400mm. It also has better IS, has a slightly faster AF, and is more compact. But...it's 300mm, not 400mm. Depending on what you shoot, that can make a lot of difference. Personally, I started with the 300mm f/4L IS, and I found that it wasn't long enough...so, I switched to the 100-400mm. Even then, I find myself needing to crop the images quite a bit - and cropping increases noise and decreases IQ. If I had to crop an extra 30% to make up for the loss of that 100mm, I would not be pleased with the results.

If you'll be close to your subjects (at feeders, for example), then 300mm would do fine...but in the wild, I would recommend getting all the focal length you can afford (many birders use the 500/4 with a 1.4x TC). As Dr. Croubie states, the 100-400mm can use the Canon TCs, although you will not be able to autofocus even with the 1.4x, and the IQ takes a hit.

I think a 650D is very likely, but I would not count on a new 100-400mm being announced - and probably not alongside an xxxD camera even so. It's been long-rumored, and would be welcome, but I'm not sure it's coming any time soon. When Canon released the 70-300 L recently, they highlighted how great it was for APS-C cameras, and how with APS-C it was longer than the 100-400mm (on FF, of course, but that's what the 100-400mm was designed for, since it's a film-era design). So, from a marketing standpoint, the 70-300 L might be the replacement for the 100-400mm, and for the pro segment, Canon has a forthcoming 200-400mm f/4. Also, as pointed out above, if there is a new 100-400mm lens (and I for one do hope that happens), it won't be available for quite some time (many lenses are now running at a year or more between announcement and availability, shame on Canon!), and it will be much more expensive than the current version.

As for used lenses, I use Craigslist for that, not sure how active those boards are in the UK. Fredmiranda.com has a popular buy & sell board, too. I think you're far more likely to find a used 100-400mm than a used 70-300 L, because the latter is quite a new lens. I regularly see 100-400mm copies come up on my local CL for ~US$1100.

[JTPAIN]

The 70-300mm L will deliver slightly better IQ than the 100-400mm. It also has better IS, has a slightly faster AF, and is more compact.

Completely understand!

But would you say the AF is significantly faster, or the IS significantly better on the 70-300mm than the 100-400mm - I know it seems it on paper, but in the field...?