[Constant aperture?]

8 minutes ago, Herco said:

In fact it does. Whether it is mechanically or electronically I can’t tell, but yeah the ‘pupil’ widens.

Thank you Herco! That is what I think also. I just wonder how it works when you use a manual lens, like Nikkor 80-200 f 4.5.

The aperture (“pupil”) obviously is constant when you zoom. I have to check that!

[Constant aperture?]

Well... f 8 at 18 mm means that the aperture is 18/8=2.25 mm. At 55 mm f8 is 55/8=6.87 mm!

So..how is this done? Does the aperture change when you zoom? 
Does it actually open (mechanically) from 2.25 mm to 6.87 mm?

 

[Constant aperture?]

3 hours ago, Greybeard said:

Not quite sure what you mean.

The maximum shutter changes based on the focal length so if you set a manual aperture of f/2.8 at 18mm, say - then aperture would change as you zoom out.

Any manual aperture smaller than f4 will remain the same through the zoom range unless you change it.

Exactly....isn’t it strange that the aperture (the opening of the lens) remains the same when you zoom in.? Shouldn’t the aperture change the same way it does at f 2.8 at 18 mm  when you zoom?

[Constant aperture?]

I have a Fuji xt30 with the xf 18-55 kit lens. The lens has a variable aperture, but if you choose f-stop smaller than 4.5, the aperture is constant throughout all focal lengths! How come? Does the aperture change while zooming even if it shows the same f-stop?