hi Danny
hope you got some good shots today.
Just curious about where you draw the "too slow" line for long tele primes for wildlife work.
300mm f/x, 400mm f/y, 500mm f/z etc ?
I think that the M.43 makers are self constrained by their 'smallness' philosophy and cannot bring themselves to even cocontemplate a lens larger than a certain physical diameter, around 75mm, limiting the usefulness of anything much above 300mm. so I don't think either maker will build anything longer in a prime
Peter
Howdy Pete
F/5.6 is my lowest and i wouldn't like to go below that without having to raise the ISO. Personally and only personally, don't like shooting over ISO 400-500. The Panasonic 100-400 I could still use at a push. I shoot with the sun at my back, but today there was no sun most of the day, so on goes the 300 F/2.8. When the sun was out (not long enough) the 500 f/4.5 goes on.
On a BIF or waiting for a bird to take off the lenses are always used wide open mate. The 300 at F/2.8, the 500 at F/4.5 and the 800 at F/5.6. the only time they might get stopped down is if the ISO is dropped to 200 on a perched bird, then the shutter speed drops as well. On power boat racing and jet-ski racing, they are always left wide open.
As you know already Pete, it's a compromise between ISO and shutter speed for action shots. The ISO is locked on ISO 400, the lenses stay wide open and the shutter speed is changed slightly to suit.
There is a market for sure, but it's a small one. M4/3 has the benefit of that crop factor and in some cases that's where FF loses out when they need to crop heavily and often they do. The file size has to drop too much to catch up and they end up with a tiny image while ours are still at full size and 16 - 20 mp. That's why we are here Pete as you know.
A lot depends on what people take and how they go about it. Some can use ISO's, shutter speeds and focal lengths I simply can't and vice versa of course.
All the best next door Pete and yeah, F/5.6 and it has to be sharp wide open personally.
Danny.
Awww hang on, a fresh one from today. Nasty conditions with the 300 F/2.8L and no cropping. They are darn fast at this speed and distance.

Full frame from m4/3 with the 300 F/2.8

Just caught the back tail in, so it would end up a crop like this mate.
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Worry about the image that comes out of the box rather than the box itself
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Birds and BIF's .....
https://www.flickr.com/photos/124733969@N06/sets/
The need for speed .....
https://www.flickr.com/photos/130646821@N03/