40-150 PRO focus breathing?

CrisPhoto wrote:

Martin.au wrote:

CrisPhoto wrote:

...

Chuck a macro in as well. That's a good way to check the maths. Good work.

Good point.

i skipped the macro as it is a prime lens. But you are right, focus breathing is not limited to zoom lenses at all.

Therefore, the updated table:

Adde the 60mm macro, as expected, it is the new number one in our little chart

From the numbers,the macro lens seems to have 22% focus breathing.

But a quick focus test is showing me that the background is growing 30% when I focus from 30cm to 10cm. This would be -30% focus breathing in our table, isn't it? Confusing ...

If by "growing" you mean that the background is magnified more as you reduce the focus distance, it is not really confusing if you consider what I say in my reply to whumber here. As I pointed out in my earlier reply to you here, the formula I provided gives you the focal length of a thin lens having the same reproduction ratio and linear FoV as the target lens when both are shot at the minimum focus distance of the target lens. But a thin lens with a focal length of 47 mm has an effective focal length (see my reply to whumber here for the conventional definition of "effective focal length"), when shot at a focus distance of 188 mm of 47(1 + R) = 47(1 + 1) = 94 mm, and the effective focal length is what determines the angle of view. So it is not surprising that the 60/2.8 macro gets a more narrow AoV as you reduce the focus distance in spite of the fact that its focal length stays more or less constant.