Replace cracked front element/lens

[goinggreynow]

Morning all.
Bit of a long shot this, but there might just be someone on the forum who can point me in the right direction.
I have a Petri 28mm F2. The front element/lens is cracked, rendering the lens useless (won't go into the how!). Other than that, it has the makings of an excellent lens - fully serviced, etc.
My chances of getting hold of replacement Petri glass are somewhere between not very high and non-existent.
However, I understand that Cosina made the Petri and it was also branded Cosinon-W.
Couple of questions and would appreciate any help;
1) If I get hold of a Cosinon 28mm F2 (cheaply), I'm thinking that I may well be able to swap the glass. Does this seem logical?
2) Is it likely that the F2.8 version of these lenses would have the same size/shape front element as the F2 versions? I know this is something i should be able to answer. but am struggling.
I would really like to bring this lens back into use, even if it is only to pass it on for someone else to enjoy.
Thanks.

 

[the black fox]

its worth a go IF you can get one at the right price ,and IF the outer lens has screw in lugs . I have a full repair kit here and one old lens I have that needs cleaning is totally sealed tight from the outside I simply cant access it without damaging it . luckily it doesn't stand me a penny .

 

[droj]

1) If I get hold of a Cosinon 28mm F2 (cheaply), I'm thinking that I may well be able to swap the glass. Does this seem logical?

Only if indeed they are the same lens configuration.

2) Is it likely that the F2.8 version of these lenses would have the same size/shape front element as the F2 versions?

The f/2 front element will be bigger, so no.

The front element of such a lens is easy to swop - using something rubbery as a grip you should be able to unscrew the plastic trim ring just inboard of the filter thread, and you're on the road ...

Element retaining rings commonly have 2 opposing slots and I've successfully used the inside measurement points on a vernier caliper (which are somewhat hardened) as a spanner.

 

[Retune]

1) If I get hold of a Cosinon 28mm F2 (cheaply), I'm thinking that I may well be able to swap the glass. Does this seem logical?

Wouldn't it be more logical just to use the Cosinon, unless you happen to find one with a cracked rear element?

 

[goinggreynow]

Only if indeed they are the same lens configuration.

The f/2 front element will be bigger, so no.

The front element of such a lens is easy to swop - using something rubbery as a grip you should be able to unscrew the plastic trim ring just inboard of the filter thread, and you're on the road ...

Element retaining rings commonly have 2 opposing slots and I've successfully used the inside measurement points on a vernier caliper (which are somewhat hardened) as a spanner.

Thanks. So, it's an F2 lens or nothing. I appreciate your clarification which has saved me wasting money on something which won't fit.
I have a lens spanner and have taken apart the odd lens, so if I can source a replacement, I should be OK with fitment.

Wouldn't it be more logical just to use the Cosinon, unless you happen to find one with a cracked rear element?

Yes, probably. It's just that having just had the Petri serviced, cleaned and re-lubricated it seems a real shame to leave it sitting unused. From limited research, I think that an excellent condition Petri F2 would be worth a little more (than the donor lens) if I ever came to sell it on - very possible as I have far too many old lenses.
Thanks again.

 

[Retune]

The other thing I would wonder is whether the lens would need collimation after replacing the front element - depending on the design, its position may or may not be adjustable.