| Author |
Message |
    
Dan
Tinkerer
Username: Dan
Post Number: 1
Registered: 08-2013
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, August 15, 2013 - 11:20 am: | 
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I have a Retina IIIc with a cracked lens. I have read numerous times that the front element and mount should have the same serial numbers but no clear explanation of why or what happens if a non matching serial number is mounted. I have the proper lens element, but with a different serial no. that I would like to use. Can anyone explain what will happen? |
Chris_sherlock
Tinkerer
Username: Chris_sherlock
Post Number: 84
Registered: 08-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, August 15, 2013 - 03:40 pm: |
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G'day Dan,
The lens components were matched in the factory.
You can swap the front group, but there might be a slight focus shift, which you'd need to correct afterwards.
As a bonus, you can swap the name rings over too, and no one will know what you've done....
Regards, Chris |
Dan
Tinkerer
Username: Dan
Post Number: 2
Registered: 08-2013
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, August 22, 2013 - 12:15 pm: |
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Thank you Chris. I will shoot a roll with the replacement front element and see want I get. |
Nparsons13
Tinkerer
Username: Nparsons13
Post Number: 38
Registered: 09-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, August 22, 2013 - 01:38 pm: |
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I've read in a several places that the front and rear lens elements may need to be adjusted if the front element is replaced, and I've always wondered: When the Curtar and Longar front elements are used, why don't they need the same adjustment? Or do they? |
Chris_sherlock
Tinkerer
Username: Chris_sherlock
Post Number: 85
Registered: 08-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, August 23, 2013 - 03:19 pm: |
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There is no provision to 'adjust' the front or rear groups in these lenses, there is only the provision to adjust the position of the whole lens/shutter assembly relative to the film plane. This can be done by adjusting the position of the focus scale ring on the helical, or by the addition or subtraction of shims.
The complete lenses must always have been fairly close to each other in terms of focal length or the accessory lenses wouldn't have been a great match.
There is unlikely to ever be any problem with the wide-angle since it had an effective maximum aperture or f/4 or f/5.6 depending on the model, and so the much wider depth-of-field compared to the standard lens would mask any focus problems.
The 80mm lens would have slightly narrower depth-of-field than the standard lens, so if there was going to be a problem with focus because the standard front/rear set were ill-matched in some fashion, then it would be with this lens.
Regards, Chris |
