[Glenn M]

I have an M300 f4 lens which I am thinking of having restored.
The dilema is that this lens is so badly infected with fungus that it
would require a total and expensive stripdown to clean. Does its current
value warrant such expense?
I use pentax primes all the time and know what a superb lens this is.
If I had it cleaned, it would be too specialist for my needs and I would
sell it for a more versatile digital zoom, the 55-300 perhaps.
I cannot find a current value for this wonderful and rare lens, not even on fleabay.

[Lowell Goudge]

you don't see too many M300F4 lenses. Optically it is the same as the A300F4,

The older origonal K mount 300F4 is more common and runs about $300 in good condition, and is generally the best for the $ in terms of focal length and performance if you want low cost long lens.

It is a superb lens although like all lenses of it's era it suffers from lateral CA, although it is very manageable,

[8540tomg]

Hi Glen,

Tough call.

I think it depends on how much money you have invested in this lens to start with. If you don't have a lot invested it might be well worth getting it repaired if it is a focal length you use on a regular basis. The A* varient of this lens seems to sell for $500 to $700 depending on condition. In good condition the M* 300/4, lacking A contacts, should fetch $500 on a good day. In the condition described above it would be very difficult to sell at all.

If it is a focal length you don't use often it might be time to cut your losses and try and sell it as is or for parts. From a return on investment point of view the cost to have a technician tear it down and clean wouldn't make a lot of sense. It is my understanding fungus can also etch the glass in severe cases and I doubt replacement elements are easy to find for a lens as rare as this one.

Tom G

[Glenn M]

Hi guys,
Thanks for the interest, you rather confirm what I already suspected. I inherited this lens in
its current condition and it is such a shame. Perhaps I could have a go at cleaning it
myself, if anyone can point me in the right direction. Nothing ventured!

[goddo31]

Perhaps you could get a repair person to give you an estimate (as best they can) for the repair. I would estimate that this lens would be worth something like $400 in pretty good condition, with excellent being about what Tom mentioned.
Depending on the cost you might break even or make $100 on it, who knows. Of course that will depend on how bad it is, and real value will depend on whether it is repairable to a good state (eg. glass coatings not etched).

Alternatively, you might be able to clean it yourself. It will depend on which elements are infected, and how easy/hard they are to disassemble. Care to post a couple of pictures of the lens?

...Depending on how bad it is I might even be tempted to give cleaning it a go, if you wanted to sell it.