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11-30-2019, 04:32 PM   #1
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Makinon 28mm F2.8 Auto Optical formula

Dear friends

I need your help to repaire a K lens Makinon 28mm F2.8 Auto, I found it completely blurred, and I think that the lenses are wrongly assembled.
can you provide me optical formula in order to reassemble it correctely.
Many thanks in advance


Last edited by Bouchama; 11-30-2019 at 04:43 PM.
11-30-2019, 09:50 PM   #2
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QuoteOriginally posted by Bouchama Quote
Dear friends

I need your help to repaire a K lens Makinon 28mm F2.8 Auto, I found it completely blurred, and I think that the lenses are wrongly assembled.
can you provide me optical formula in order to reassemble it correctely.
Many thanks in advance
I have one of these lenses I obtained in 1983. It has always functioned fine. I cannot tell you how to repair it.

These lenses are so inexpensive. They were commonly marketed in the U.S. at K-Mart under the brand name Focal. An eBay search under Focal 28mm Pentax will produce a lot of results with low pricing.
12-01-2019, 08:36 AM   #3
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QuoteOriginally posted by Bouchama Quote
Dear friends

I need your help to repaire a K lens Makinon 28mm F2.8 Auto, I found it completely blurred, and I think that the lenses are wrongly assembled.
can you provide me optical formula in order to reassemble it correctely.
Many thanks in advance
For a number of the simpler lenses Iíve taken apart, where each element went was fairly clear. Which side of the element pointed where, however, was often a tricky question, and not always one easy to answer, even with a lens diagram.

If you can easily take it apart, there may be some obvious candidates for flipping over...

-Eric
12-01-2019, 10:21 AM   #4
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QuoteOriginally posted by TwoUptons Quote
For a number of the simpler lenses I’ve taken apart, where each element went was fairly clear. Which side of the element pointed where, however, was often a tricky question, and not always one easy to answer, even with a lens diagram.

If you can easily take it apart, there may be some obvious candidates for flipping over...
^This is more or less what I was going to say.

It is highly unlikely any of the lenses are out of order, but the possibility of a lens being reversed in its position in not unrealistic.
Heck, I've done it myself when reassembling a lens.

Bonus points: You can create your own 'effects' lenses by reversing elements, removing elements and/or swapping elements.

12-01-2019, 12:38 PM   #5
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QuoteOriginally posted by tvdtvdtvd Quote
Bonus points: You can create your own 'effects' lenses by reversing elements, removing elements and/or swapping elements.
Thatís, uh, exactly what I was doing... sure...

-Eric
12-02-2019, 01:38 AM   #6
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Hi Friends
Many Thanks for your feed-back, I understood that i have to swap elements one by one and test, but what is helpfull is to have something like the below attachement

https://pentaxklub.com/test-expresstakumar-a-28mm-f-2-8/

Thank you in advance
12-02-2019, 10:40 AM   #7
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QuoteOriginally posted by Bouchama Quote
Hi Friends
Many Thanks for your feed-back . . .

Does your lens look like this one in the P.F. lens review database, Bouchama?
Makinon 28mm F2.8 Auto Lens Reviews - Miscellaneous Lenses - Pentax Lens Review Database

I have a M42 mount version of that lens shown in the database, but I don't have an optical diagram for it. If you have a specific question about orientation of an element, I might be able to help.

Occasionally, some manufacturers used to print optical diagrams on the outside of the lens box. If you're (really!) lucky, there may be an ebay sale for your lens which includes a box and good photos.
12-02-2019, 05:05 PM   #8
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QuoteOriginally posted by .a.t. Quote
Does your lens look like this one in the P.F. lens review database, Bouchama?
Makinon 28mm F2.8 Auto Lens Reviews - Miscellaneous Lenses - Pentax Lens Review Database

I have a M42 mount version of that lens shown in the database, but I don't have an optical diagram for it. If you have a specific question about orientation of an element, I might be able to help.

Occasionally, some manufacturers used to print optical diagrams on the outside of the lens box. If you're (really!) lucky, there may be an ebay sale for your lens which includes a box and good photos.
Thanks .a.t.

yes this is the lens that i have, i have K mount version. can you draw me or send me photo of un orientation of the optical elements, i think that some of thems are swap specianly the cental ones

Thank yu in advance

12-02-2019, 09:59 PM   #9
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QuoteOriginally posted by Bouchama Quote
Thanks .a.t.
. . .

My apologies, Bouchama! I'm sorry to disappoint you, but I can't help you after all.

I tried my best to get the elements free, but they were solidly cemented into assemblies which I couldn't get apart.
And I don't want to risk trying any harder.

Good luck and I hope you'll have success in finding your answer.
12-03-2019, 01:19 AM   #10
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QuoteOriginally posted by .a.t. Quote
My apologies, Bouchama! I'm sorry to disappoint you, but I can't help you after all.

I tried my best to get the elements free, but they were solidly cemented into assemblies which I couldn't get apart.
And I don't want to risk trying any harder.

Good luck and I hope you'll have success in finding your answer.
.a.t. I understand, many Thanks for your effort
I think found the correct position of optical elements yesterday. let test today the infinity focus. however i discovred another problem, the aperature is not working fine, it open and close from min to max only even i select any aperature. my question is how disasamble the aperature system ?

Thank you.
12-03-2019, 09:49 PM   #11
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QuoteOriginally posted by Bouchama Quote
. . .my question is how disasamble the aperature system ?

Thank you.

Do you have the elements removed from the barrel, Bouchama? If so, does moving the internal aperture lever show you what might be wrong? Do the aperture blades look wet? If they have oil on them, that can slow the blades or make them erratic. Oily blades can often be cleaned without disassembly.

I really hope you won't need to disassemble the aperture. It appears to me it would be difficult to get all the pieces and springs back in properly. Your PK lens will have some differences from my M42, but I've included two pictures of my lens in case they might be helpful. (Click the photos to see a larger size.)




12-04-2019, 02:07 AM   #12
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QuoteOriginally posted by .a.t. Quote
Do you have the elements removed from the barrel, Bouchama? If so, does moving the internal aperture lever show you what might be wrong? Do the aperture blades look wet? If they have oil on them, that can slow the blades or make them erratic. Oily blades can often be cleaned without disassembly.

I really hope you won't need to disassemble the aperture. It appears to me it would be difficult to get all the pieces and springs back in properly. Your PK lens will have some differences from my M42, but I've included two pictures of my lens in case they might be helpful. (Click the photos to see a larger size.)



Many Thanks .ŗ
Will Try and let you know
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