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Help me reassemble this 2/4.5mm C-mount lens
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PostPosted: Tue Nov 01, 2016 1:42 pm    Post subject: Help me reassemble this 2/4.5mm C-mount lens Reply with quote
Rear system in question. Lens gave bad results thus i assumed wrong position of rear elements. Front system is not in question. Two elements there that cannot be misplaced. There is very small light entrance to rear system. All rear elements can be put in reverse position. Many tries did not produce usable quality on Pentax Q with smallest sensor. Either sharp only in middle or plain weak. Can you give me few logical order assembly suggestions. Glued element = 2 elements. Last elements are quite big, nearly matching the size of C-mount.



PostPosted: Wed Nov 02, 2016 5:20 am    Post subject: Reply with quote
Add the location of the aperture.
Is the trapezoid shape the rear element?
The spacers are not need in the diagram. but the relative spacing is important and may help.
The glued elements are called a Dublet, or Triplet if 3 elements are glued together.

From what you've drawn, it looks like the first 4 elements(3 groups) are in front of the aperture, and one element(1 group) behind, is that correct? because you talk about the last elements as being more than 2...

A diagram like this is easier to figure out


A picture of the elements removed may also help.


PostPosted: Wed Nov 02, 2016 9:54 am    Post subject: Reply with quote
What you see on photo is complete rear system. Lens has no aperture. 3rd and 4th element form Doublet. Nr.5 is trapezoid yes.



PostPosted: Wed Nov 02, 2016 2:53 pm    Post subject: Reply with quote
You said:
Quote:
sharp only in middle

I wonder if it was intended to be used at macro distances...


PostPosted: Wed Nov 02, 2016 3:36 pm    Post subject: Reply with quote
Might be true, close to medium distances are not that bad but infinity is terrible. It is quality Tamron lens and it should perform. I will try to find best combination and put custom aperture inside.
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