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10-14-2017, 06:36 PM   #1
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Which diopter to get 1:1 ratio with a 180mm 1:2?

Can't find the right formula.
I have an old Sigma Apo Macro 5.6/180mm (manual focus). It can reach only 1:2 reproduction ratio.
At the time Sigma sold a 52mm achromatic diopter lens that allowed to reach 1:1.

I have two questions:
1) how many diopters I need?
2) any suggestion about a coated achromatic diopter of good quality that can be found second hand? Kenko and Marumi make such doublets these days. The Marumi should be multicoated, but it's way too expensive for my taste, I'd prefer a more economical solution.

This Sigma is one of the very few lenses I ever bought new.
I'm glad I did. On the K-1 is one of my preferred objectives, and probably (second hand price is unclear) it's the the lens with the best price/performance ratio I'm currently using.
I'm fine focusing with such a slow max aperture, I don't complain about the lack of AF, but I find the 1:2 reproduction ratio a bit limiting.
If I could ever find a a good, cheap achromatic diopter, I hope it would match well the Sigma and allow for more flexibility.
Every now and then I see on Ebay a Sigma diopter, or those originally sold with Soligor/Promaster 90mm macro lenses. Though I'm not sure they would be strong enough to give 1:1 on a 180mm.

Cheers

Paolo


Last edited by cyberjunkie; 10-14-2017 at 06:53 PM.
10-14-2017, 08:22 PM   #2
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According to this calculator a +2 diopter should give you close to 1× magnification.

Macro Extension Tubes & Close-up Lenses
10-14-2017, 10:00 PM   #3
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Original Poster
Thanks a lot.
Does anybody remember how +2 diopters (500mm FL) achromatic close-up lenses made by Nikon or Pentax were called?
I remember some had rather obscure identifications

Cheers

Paolo

10-15-2017, 02:23 AM   #4
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QuoteOriginally posted by cyberjunkie Quote
Can't find the right formula.
I have an old Sigma Apo Macro 5.6/180mm (manual focus). It can reach only 1:2 reproduction ratio.
At the time Sigma sold a 52mm achromatic diopter lens that allowed to reach 1:1.

I have two questions:
1) how many diopters I need?
2) any suggestion about a coated achromatic diopter of good quality that can be found second hand? Kenko and Marumi make such doublets these days. The Marumi should be multicoated, but it's way too expensive for my taste, I'd prefer a more economical solution.

This Sigma is one of the very few lenses I ever bought new.
I'm glad I did. On the K-1 is one of my preferred objectives, and probably (second hand price is unclear) it's the the lens with the best price/performance ratio I'm currently using.
I'm fine focusing with such a slow max aperture, I don't complain about the lack of AF, but I find the 1:2 reproduction ratio a bit limiting.
If I could ever find a a good, cheap achromatic diopter, I hope it would match well the Sigma and allow for more flexibility.
Every now and then I see on Ebay a Sigma diopter, or those originally sold with Soligor/Promaster 90mm macro lenses. Though I'm not sure they would be strong enough to give 1:1 on a 180mm.

Cheers

Paolo

I would imagine you could stack the dioptres to get the macro you need.
I have a dioptre that came with a Sigma 75-250mm lens (52mm filter thread) but it has no indication of what strength it is.
I also have a Nikon close up no 3T which apparently is a 1.5 or 1.6 dioptre and a Nikon close up 0. 0.7dioptre. Also in 52mm thread.
One day I might stack them.


Last edited by Skodadriver; 10-15-2017 at 02:30 AM. Reason: Added some text.
10-15-2017, 04:00 AM   #5
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QuoteOriginally posted by cyberjunkie Quote
Can't find the right formula.
I have an old Sigma Apo Macro 5.6/180mm (manual focus). It can reach only 1:2 reproduction ratio.
At the time Sigma sold a 52mm achromatic diopter lens that allowed to reach 1:1.

I have two questions:
1) how many diopters I need?
2) any suggestion about a coated achromatic diopter of good quality that can be found second hand? Kenko and Marumi make such doublets these days. The Marumi should be multicoated, but it's way too expensive for my taste, I'd prefer a more economical solution.

This Sigma is one of the very few lenses I ever bought new.
I'm glad I did. On the K-1 is one of my preferred objectives, and probably (second hand price is unclear) it's the the lens with the best price/performance ratio I'm currently using.
I'm fine focusing with such a slow max aperture, I don't complain about the lack of AF, but I find the 1:2 reproduction ratio a bit limiting.
If I could ever find a a good, cheap achromatic diopter, I hope it would match well the Sigma and allow for more flexibility.
Every now and then I see on Ebay a Sigma diopter, or those originally sold with Soligor/Promaster 90mm macro lenses. Though I'm not sure they would be strong enough to give 1:1 on a 180mm.

Cheers

Paolo
A list of achromatic close-up lenses here.
10-15-2017, 11:10 AM   #6
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See this thread on Pentax closeup lenses
Pentax close-up lenses - PentaxForums.com
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