Changing the front element on an AF 70-210, f4

[sam_marsh1]

I picked up a cheap Beercan (70-210 f4) lens recently which has a pockmarked

front element with some small chips in the glass. The rest of the lens seems

fine. Obviously, I could keep a look out for another cheap one with a clean

front element but with fungus or something else, but I started thinking about a

cheaper option.

 

Looking at http://members.aol.com/xkaes/8020045.htm I notice that the old 70-

210 MD lens has 12 elements in 9 groups, just like the AF one. Does anybody

have any idea whether I could pick one of those up cheap and just take the

front element? I may give it a try as I've not got much to lose.

 

I'd be very grateful if anyone had any comments on this.

 

Thanks, Sam.

[peterblaise]

.

 

Hi Sam,

 

Don't forget you can clean it well and fill the pits with India ink to prevent light comping through the pits from affecting the image. If you did find a lens with a good front element, KEEP THAT LENS, and move your pitted lens on to someone else! I've almost NEVER had any even supposedly badly scratched lens actually affect image qualities. About all a scratch does is cut the resale cost of a lens in half! Otherwise, show us how the images are affected - shoot a newspaper on a wall or something full frame and look for aberrations or whatever.

 

Let us know what you do.

 

-- Click! Peter Blaise, Minolta Rokkor Alpha DiMage Photographer

[georg_kern]

AF and MD are optically identical, so in theory it should work. But you never know if they took away or added 1/10 of a mm here or there. If you can find a vey cheap MD (maybe with worn-out mechanics) it is worth a try - and DIY is always fun.

 

(...but it can be difficult to remove the front ring, if you do not have the approbiate tools)

 

 

Regards

 

Georg

[sam_marsh1]

Thanks Georg and Peter.

 

The lens does still take cracking pictures although I'm guessing I'll have to be a little more careful about flare. I think I'll keep an eye out for a very cheap MD lens and give it a try. As long as I don't do something stupid the procedure should be 100% reversible. I'll let you know how I get on. It could take some time!

 

Frustratingly, I have got the 80-200mm MD lens which (by the link above) seems to be optically slightly different, although the font element looks remarkably similar. I might even give this a go first...

 

Sam.