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What is a power diaphragm of a 24-70 lens?

  
 
Ming-Tzu
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p.1 #1 · What is a power diaphragm of a 24-70 lens?


I sent my 24-70 f/2.8 II to Canon for routine maintenance and they responded by indicating that the power diaphragm needs to be replaced. And it would cost about $325.

Anyone know what exactly this piece is and the purpose? Wonder if it's worth it since it's a hefty repair.

Thanks!



Sep 02, 2025 at 02:17 PM
jcolwell
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p.1 #2 · What is a power diaphragm of a 24-70 lens?


The diaphragm is the mechanical part of the aperture (i.e. the collective of the blades). The aperture is the hole part of the diaphragm.


Sep 02, 2025 at 02:32 PM
EB-1
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p.1 #3 · What is a power diaphragm of a 24-70 lens?


You need it to stop down.
Since EF in 1987 Canon has used the diaphragm with electric actuator.

EBH



Sep 02, 2025 at 02:39 PM
Ming-Tzu
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p.1 #4 · What is a power diaphragm of a 24-70 lens?


Wow, so I guess I've been using this lens without being able to stop down lol. Never noticed it before interesting enough.


Sep 02, 2025 at 02:41 PM
 


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rscheffler
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p.1 #5 · What is a power diaphragm of a 24-70 lens?


It doesn't mean it's not working. It might not be working up to specs or consistently. Have you noticed any odd exposure fluctuations in your images made with this lens? Do you use it stopped down much?

Canon Japan's page listing end of support for current and recently discontinued products indicates this lens is still current and doesn't have an end of support date, yet. Therefore you probably still have 5 years or so to decide what to do.



Sep 02, 2025 at 02:53 PM
Ming-Tzu
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p.1 #6 · What is a power diaphragm of a 24-70 lens?


I've never noticed any issues but, then again, I haven't really been checking . Since it's my go-to event photography lens, I always use it stopped down for people photos and such.

I went ahead and paid for repair, because I'm not even sure if I'll be a CPS member after this initial year.

rscheffler wrote:
It doesn't mean it's not working. It might not be working up to specs or consistently. Have you noticed any odd exposure fluctuations in your images made with this lens? Do you use it stopped down much?

Canon Japan's page listing end of support for current and recently discontinued products indicates this lens is still current and doesn't have an end of support date, yet. Therefore you probably still have 5 years or so to decide what to do.




Sep 02, 2025 at 03:12 PM
Ming-Tzu
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p.1 #7 · What is a power diaphragm of a 24-70 lens?


Interestingly enough, this $325 quote is all for labor and sales tax. No charge for parts, which I'm grateful for at least.


Sep 02, 2025 at 03:13 PM







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