Geez somewhere I missed this thread, glad I found it. Tony very informative.
As Tony has said 400mm is a good starting lens for bird photoging, that is not to say you cant use a 300 or even if you want a 200mm lens, just means more work. Getting to know your birds habits etc.
I have use a 300mm for quite a bit, a kit lens. I found that using this has helped me to get to know how to stalk my quarry. It would be nice to have a 800mm lens, but I would not have learned what I have by using it straight of the bat.
I have a habit that more than likely will stay with me, I see a bird I want to photograph and it is a bit far for the lens, I still take a shot, then move a bit closer take another shot. Hopeing I can get close enough for nearly a full frame shot. Does not happen too often, but I still got some real good images, as far as a kit lens goes.
Now I have a Sigma 150-500mm lens, same thing applies, just because you have that bit more reach, does not mean you are going to get the image you want straight away. You still have to work at it.
I have posted 2 images I have taken with the 70-300mm lens. 1st image is exact size out of the camera. If you know your species enough, you know what they are more like to react like, waiting long enough they do come closer to you.
The second image is cropped to show that you can still get good images with a shorter lens. If you are close enough, you do not need to crop as hard. If I was further away from the bird, and I tried to crop this amount it would not look as good, pixel pinching. If you can afford go for a 400mm minimum
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Enough of my babble.
Handing back to Tony
Peter