How much have tele-prime lenses improved over the years?

Question

Context

I'm considering the Nikon 500mm f4 AIS P lens as a way to get longer reach that's better than my current setup Nikon 300mm f4 AF with 1.4x TC to get birds and related wildlife.

I've heard good things about it. People also point that once lens got focusing motors the weight noticeably increased, especially for larger tele-primes. This can see as a 1.5kg increase when the first AF, of the same focal length and f-stop, was released. Following that trend, weight slowly dropped as, in the case of the 500mm, more exotic materials are used and VR helps a lot in getting the shot. I believe the current iteration is close to the same weight as the lens I'm considering.

Question

Is it worthwhile to invest in a lens if I can find it for around $1k or is it always better to wait and eventually buy the newest and greatest lens, as newer coatings may improve the IQ and related of a lens?

I don't see myself going pro or being able to afford a new tele-prime lens and I think many people can say that as well. I'm also use to manual focus with the Nikon 300mm/4 with the teleconverter. I know that I can rent it but I want one to keep.

A more general question, are older telephoto lenses a lot worse than their new counterparts or are the improvements not completely on image quality but more on usability (AF, VR, etc)?

My metric for worse would be the sharpness of the image when viewed at 100%, as well as how it renders the out of focus areas, if it's distracting or not.

Answer 1

In answer to the question in your title: A bit, but mostly in size and weight, and the inclusion of new(ish) features like autofocus and stabilisation, rather than with optical characteristics like 'sharpness'.

Regarding the specific lens you mention (500mm AIS P Nikkor), this lens was a high end model when it was released and will therefore likely stand up very well optically when compared with equivalent modern high end Nikkors (example), and surprisingly it's actually fractionally lighter and smaller as well. Naturally it has no AF or stabilisation.

Caveats: - I've never used a 500mm AIS P Nikkor and my answer is largely based on experience with shorter telephoto lenses and research. - I'm only referring to high end name brand tele lenses here. Conversely, cheaper consumer tele lenses have seen quite significant improvements in the past 30 years (Fresnel lens elements, hybrid lens elements, ultrasonic motors, IS, etc.).

Answer 2

A more general question, are older telephoto lenses a lot worse than their new counterparts or are the improvements not completely on image quality but more on usability (AF, VR, etc)?

It depends entirely upon the two particular lenses in question. Some are very close optically to their replacements, others are barely in the same zip code.