Very sharp with great contrast over entire focal range

Octopuss wrote:

RDM5546 wrote:

Octopuss wrote:

Do you have any comments about the AF speed of the lens? Did you shoot anything moving by chance

I also have the EF100-400L II which is very similar in focus speed to the EF 70-300L. It is a lot longer lens though. If I were using it to shoot wild life I would strongly prefer the extra reach of the EF100-400L II but I think the focus properties of both lenses are nearly identical. The EF70-300L came out in 2010 long before the EF100-400L II.

Before the EF 100-400II which is weather sealed I had the EF 100-400 Mk I dating back to 2001. I hated the push pull zoom control and lack of weather or dust sealing of that lens https://photography-on-the.net/forum/showthread.php?t=50552

The arrival of the radically improved design of the 100-400L II mad quite a difference. I believe the 70-300L is the design predecessor of the 100-400L II. Both have lots similarities and the 70-300L was produced about four years before the 100-400L II.

The 70-300L is 2.1lbs which is heavy by comparison to the 1.6lbs of the cheaper consumer grade 70-300 II IS USM which was the first lens to have a nanomotor USM. However it is not metal construction rugged or weather sealed which be important i some travel use cases. The consumer grade model is not has sharp and good IQ although is good for lenses in it's price range of $600. The 70-300L is excellent IQ and something special as also is the 100-400L II but it is bigger and significantly more expensive.

Both are special lenses and the 100-400L II has a very attractive reach for shooting wildlife and small birds. With the EOS R, R6 and R5 bodies the 100-400L II works well with the Canon 1.4X III and 2X III TCs for even greater range while the 70-300L does not really work well with the TCs and they are not recommended to be used.

However the much smaller size of the 70-300L fits upright in camera bags and in travel bags much easier with less travel weight than the 100-400L II. If wildlife is the objective the I recommend something with more reach like the 100-400L II.

I recently splurged and got the RF 100-500 and the RF1.4X and 2X TCs. The IQ of the 100-500L is spectacular and maybe better than the EF100-400L III but not by much if any. However, the focus speed is faster and the keeper is therefore higher when shooting action with R5. Once you use the RF100-500 it hard to go back to the EF 100-400II though I love the lens. However, the cost of the RF 100-500 with the two TCs is very expensive at over $4,000 including sales tax.

All three of the L lenses are spectacular and the 70-300L is now ten years old so you can buy them used in great condition for around $800 if you want a top grade travel lens.

Uhm, thanks, but you didn't answer my question...

Sorry for the long winded response. Exact values or metrics for focus speed are not easy to quantify or make. The EF 70-300 is fast in focus IMHO but not as fast or accurate as the RF 100-500 and I do not think it is long enough in FL for wildlife shooting I like to do which requires 400mm minimum to make me happy.  It is well suited to shooting grandkids playing sports or soccer action shooting.  It well suited for hiqh quality travel shooting and not having the travel overhead of bigger better telephotos for wildlife like the RF100-500 that overlaps the FL of the EF70-300L but at the price of weight and travel sizing bag limits.

Since I have both lenses I would be a good source to say it is fast enough but it is definitely not a slow focus lens light some lenses can be. For shooting wildlife I find the 100-400II has much more needed reach especially considering how well it works with the 1.4X III and 2X III TCs. I have some of primes that are very slow in focus and 70-300 is fairly fast and is a handy good IQ travel lens for me but the lens reach limits it for wildlife and for me the capability is not near that of the 100-400II. Of course price matters as well as your usage. I also have the smaller and lighter RF 24-240 which is also fast, handy with excellent IQ for travel but it is not weather sealed or as rugged. These details of usage matter to me. I do not like the RF STM motor lenses that I own for focus speed and the EF 70-300 is much more suited for fast speed action shooting than the STM motor lenses I have tried.