100-400L/70-300L Decision

[HDNitehawk]

I'll give a few more thoughts.
The 70-200mm has 4 stops of IS. The 100-400mm has 2 stops of IS. Low light this will be important.
In every other aspect except 400mm the 70-200mm will give you better IQ and better stabilization.
Comparing the IQ at 400mm for both the IQ of the 400mm is slight over the 70-200mm;

http://www.the-digital-picture.com/R...mp=7&APIComp=2

One of the improvements that you will see with the 70-200mm is the improvement made my the newer coatings used on it. Improved color is one of the benifits. The 100-400mm is an older lens and is due for replacement, it doesn't have some of the latest technology incorporated in it.

Another thought I would have in your situation is to buy both the teleconverter and the 400mm f/5.6. B&H has this lens for $1199, the 100-400mm is $1459 and the difference would go a long way to pay for the tele convertor. (you have to put the lenses in cart to see the actual sell price). The logic would be on sunny days when you have a shutter speed over 1/1000 or you are using a tripod you could use the 400mm, at other times use the 70-200mm.

The 400mm f/5.6 gives you the best IQ option.

http://www.the-digital-picture.com/R...mp=0&APIComp=0

It might be good to rent a 100-400mm if you can to see the differences.

[clemmb]

I'll give a few more thoughts.
The 70-200mm has 4 stops of IS. The 100-400mm has 2 stops of IS. Low light this will be important.
.

4 stops @ 200mm. I wonder what it is with 2x so you are @400mm.
Low light is important for hand holding but also for subject movement. IS will not help with subject movement. Using a 1.4x giving an f4 @280mm will probably be better than 300mm @ f5.6.

[HDNitehawk]

4 stops @ 200mm. I wonder what it is with 2x so you are @400mm.
Low light is important for hand holding but also for subject movement. IS will not help with subject movement. Using a 1.4x giving an f4 @280mm will probably be better than 300mm @ f5.6.

Do you think it drops progressively with length?
Actually I have never seen an article or a discussion if a tele convertor affects IS.

I didn't know we were talking IS for subject movement, just low light situations.

[clemmb]

Do you think it drops progressively with length?
Actually I have never seen an article or a discussion if a tele convertor affects IS.

I didn't know we were talking IS for subject movement, just low light situations.

While ahab1372 answered my questions in a logical manor, and he may be 100% right, I have to think the IS mechanism in the 70-200 lens is not designed to dampen out the shake at 280mm or 400mm as well. It would have to be over designed for that.
I was confusing this thread with a similar thread where the subject was going to be animals in Africa at dusk.