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12-02-2023, 03:30 AM   #1
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SMC-M 28mm 2.8 & 35mm 2.8 Aperture Delay

It's very common for the SMC-M 28mm 2.8 & 35mm 2.8 lenses to have this kind of aperture delay, which transforms in overexposed photos if you are using a film camera, specially when using closed down apertures like f11 to f22.

I was wondering if the problem is also happening with the following lenses:

SMC-M 28mm F2
SMC-A 28mm F2.8
SMC-M 35mm F2
SMC-A 35mm F2.8

Or if you guys have suggesitions of the best 28 and 35 lenses for K mount.

Also if someone has experience repairing this issue.

Thinking on getting some 28 and 35mm new lenses without this problem since I love shooting with my MX

THANK YOU!

12-02-2023, 06:29 AM   #2
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Hello ! I had a simiral issue with a Tamron zoom lens, got it fixed years ago, not sure if it was the spring Wich got loose or the oil on the aperture blades that got sticky. In the end it should be fixable. If you can try the lens before buying it should help but not everyone have access to that kind of shop with vintage glass.
12-02-2023, 06:59 AM   #3
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QuoteOriginally posted by Juan La Torre Quote
It's very common for the SMC-M 28mm 2.8 & 35mm 2.8 lenses to have this kind of aperture delay, which transforms in overexposed photos if you are using a film camera, specially when using closed down apertures like f11 to f22.

I was wondering if the problem is also happening with the following lenses:

SMC-M 28mm F2
SMC-A 28mm F2.8
SMC-M 35mm F2
SMC-A 35mm F2.8

Or if you guys have suggesitions of the best 28 and 35 lenses for K mount.

Also if someone has experience repairing this issue.

Thinking on getting some 28 and 35mm new lenses without this problem since I love shooting with my MX

THANK YOU!
In my experience, that's a relatively common issue with many vintage lenses.

Though I have seen it less with fixed focal length lenses than zooms, I don't know if that's a good guide.

And there are some lenses that are (in)famous for doing it... some Soligors, if I remember right.

I had a M28 f2.8 that never gave me a problem. I upgraded it to an A28 f2.8 with similar good luck, as it does P-TTL flash...

If you are concerned about age, there is a current FA35mm f2.0 and there was a 28mm FA lens a few years back. Those would be newer and less likely to fail.

And last time I priced 35mm f2.8s, the manual focus ones were about the same price as used copies of the FA35mm f2.0, which makes no sense...

-Eric
12-02-2023, 07:31 AM   #4
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QuoteOriginally posted by Juan La Torre Quote
Also if someone has experience repairing this issue
The problem as I understand it is solely due to oil seeping onto the blades. The solution is to take the lens apart and clean the blades in alcohol.

It is possible for any lens of that era to develop this issue, although I think the M 35/2.8 is known for it especially.

I have an extensive collection of K and M series lenses and none of them have sticky blades. That includes the aforementioned M 35/2.8

QuoteOriginally posted by Juan La Torre Quote
Or if you guys have suggesitions of the best 28 and 35 lenses for K mount.
For 28mm the K 28/3.5 is very highly regarded, as is the M 28/2.0. If money is no object you could also look at the K 28/2.0 (Hollywood)..... but that is in a league of its own.

I own the two M series 35mm lenses but cannot say I have used them much

12-02-2023, 07:50 AM - 1 Like   #5
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SMC Pentax-M 35/2.8 and -A 35/2.8 lenses are notorious for slow diaphragm due to oil on the blades.

I have owned several copies of these lenses and all eventually required service for this problem.
After several years problem often reoccurs.

Chris
12-03-2023, 02:14 AM   #6
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I've not experienced sticky aperture problems with either my Takumar-A 28mm f/2.8 or my Pentax-M 28mm f/2.8 ... more generally, the only lenses I've had this issue with are old manual aperture lenses, I've got two Enna 35mm f/3.5 lenses awaiting attention at the moment
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28mm, 35mm, 35mm 2.8 aperture, aperture, camera, delay, f2, f2.8, lenses, smc-m, smc-m 28/2.8 aperture, smc-m 28mm, smc-m 35mm f2.8, vintage
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