f-Stop is Actual Focal Length divided by Diameter of the Opening.
Crop factor is a short hand referring to sensor area compared to a stand 35mm film frame. It has nothing to do with actual optics. A 5.6 is a 5.6 is a 5.6, no matter the sensor size and hence the crop factor.
A 200mm lens is still a 200mm lens on a 2/3 crop factor despite our treating it as ...
The AV (Aperture Value) is an expression that tells how many stops away from f/1 an aperture is.
Since f/1 is zero distance from f/1, it has an AV of zero (0)
Since f/1.4 is one stop slower than f/1, it has an AV of one (1)
Since f/2 is two stops away from f/1, it has an AV of two (2)
Since f/2.8 is three stops from f/1, its AV is three (3)
... and so on.
The Exif standard says that:
which is also:
There is even a nice conversion table:
However, looking at my own photos (EOS 70D), I find that the exposure value and the FNumber are close to each other but not always equal, so this doesn't follow the table below for apertures => f/8. So I ...
I find 'mikeno62' has a lot of useful videos on lens repair on Youtube.
In the following video he does a repair on loose aperture blades of the AF-s VR Micro-Nikkor 105mm 1:2.8 G ED:
It seems to be an extremely complicated repair, and you probably will not be able to find replacement parts easilly.
The biggest problem with repairing Nikon lenses yourself is that Nikon no longer sells replacement parts to anyone outsides Nikon's authorized service network, including third party repair shops. To make matters worse, as of March 31, 2020, Nikon is not renewing agreements with any current Nikon authorized outside repair shops that are not owned by Nikon. ...