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07-02-2019, 09:21 AM   #1
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Pentax LX with no-aperture-ring lenses

I have an LX (and a KP) and I was thinking about picking up a D-FA 100mm f/2.8 WR Macro, but it has no aperture ring. What happens if I can't adjust the aperture on the lens since it has no aperture ring? According to the manual, if I set it to A mode on the shutter speed dial it will meter and expose wide open, which is fine for my purposes. But elsewhere I've seen that it will stop down all the way to f/22, which is not what I want. Can I use this lens with the A setting on the shutter speed or am I better off getting an older 100mm with the aperture ring on it?

07-02-2019, 11:17 AM   #2
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QuoteOriginally posted by reuvens Quote
What happens if I can't adjust the aperture on the lens since it has no aperture ring?
The camera will initially meter wide open, but will stop down fully to minimum aperture for the actual exposure.* Whether the OTF metering for extended exposures kicks in depends on the initial reading, so it is almost assured to be a huge fail for most cases.

Short story...the LX requires either a fixed aperture lens or aperture ring to set the aperture.


Steve

* The actuator mechanism on the LX performs full travel at all times, hence the full stop-down.
07-02-2019, 01:59 PM   #3
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QuoteOriginally posted by reuvens Quote
I have an LX (and a KP) and I was thinking about picking up a D-FA 100mm f/2.8 WR Macro, but it has no aperture ring. What happens if I can't adjust the aperture on the lens since it has no aperture ring? According to the manual, if I set it to A mode on the shutter speed dial it will meter and expose wide open, which is fine for my purposes. But elsewhere I've seen that it will stop down all the way to f/22, which is not what I want. Can I use this lens with the A setting on the shutter speed or am I better off getting an older 100mm with the aperture ring on it?
Yeah it's a no go on the LX, you'll need a newer film body like the Z-1/Z-1P to fully control a lens with no aperture ring.

Phil.
07-02-2019, 03:35 PM   #4
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QuoteOriginally posted by reuvens Quote
... or am I better off getting an older 100mm with the aperture ring on it?
For what it's worth, the FA 100/f2.8 Macro is optically identical to the D-FA version and includes an aperture ring (although you lose the WR).

07-02-2019, 05:00 PM   #5
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QuoteOriginally posted by nickthetasmaniac Quote
For what it's worth, the FA 100/f2.8 Macro is optically identical to the D-FA version and includes an aperture ring (although you lose the WR).
My personal first choice for that design series.


Steve
07-02-2019, 05:01 PM   #6
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I was really hoping for that WR, but I suppose sacrifices must be made for my film addiction.

07-02-2019, 07:31 PM   #7
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the old M100 f/4 is a great lens, and can usually be found pretty cheap, get the A version, and it works in auto on your KP too, little bit more for an A.
no auto focus, but auto focus and macro is a mixed bag. Also, the 100 f/4s only go to 1:2 without adding extension.
07-02-2019, 08:03 PM   #8
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QuoteOriginally posted by reuvens Quote
I have an LX (and a KP) and I was thinking about picking up a D-FA 100mm f/2.8 WR Macro, but it has no aperture ring. What happens if I can't adjust the aperture on the lens since it has no aperture ring? According to the manual, if I set it to A mode on the shutter speed dial it will meter and expose wide open, which is fine for my purposes. But elsewhere I've seen that it will stop down all the way to f/22, which is not what I want. Can I use this lens with the A setting on the shutter speed or am I better off getting an older 100mm with the aperture ring on it?
As others have said, the LX requires an aperture ring on the lens. However, ANY Pentax camera with a program mode or shutter preferred automatic will work. You have to have a camera body that is able to control the lens aperture. A non aperture ringed lens is effectively an A series lens that is stuck on the A setting.
There are tons of very good Pentax K, M and A lenses out there, as well as many screw mount lenses that will also work well with the LX, but the D FA 100/2.8 macro is not the droid you are looking for.
A word to the wise, the A 100/2.8 Macro is one of the best macro lenses ever made by anyone, but it suffers from sensor reflections in some situations, so while it is an excellent choice for film, it is iffy on digital. I bought the D FA 100 macro because of random reflections I got with the A lens.


Last edited by Wheatfield; 07-02-2019 at 08:08 PM.
07-02-2019, 08:13 PM   #9
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QuoteOriginally posted by reuvens Quote
am I better off getting an older 100mm with the aperture ring on it?
yes.....
07-02-2019, 10:10 PM   #10
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The DF A has two versions. The non WR has an aperture ring. Also as someone else said the F and FA versions have the same optical format (albeit in a larger heavier design without a dedicated hood.
07-03-2019, 12:41 PM   #11
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QuoteOriginally posted by reuvens Quote
I was really hoping for that WR, but I suppose sacrifices must be made for my film addiction.
BTW, since you are considering macro lenses, you might also consider the Pentax M 50mm f4 macro - and 100mm version, as they are extremely high resolving. Example below shows that even a 36Mpixel Nikon D800 cannot attain the resolution these lenses can under ideal conditions.



You can see from the closeup of the area shows just how much real detail is not actually resolved.
Full res version -> Kodak Techpan 04-27 scan compare
07-12-2019, 02:07 AM   #12
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QuoteOriginally posted by reuvens Quote
I have an LX (and a KP) and I was thinking about picking up a D-FA 100mm f/2.8 WR Macro, but it has no aperture ring. What happens if I can't adjust the aperture on the lens since it has no aperture ring? According to the manual, if I set it to A mode on the shutter speed dial it will meter and expose wide open, which is fine for my purposes. But elsewhere I've seen that it will stop down all the way to f/22, which is not what I want. Can I use this lens with the A setting on the shutter speed or am I better off getting an older 100mm with the aperture ring on it?
I have a bit of the same problem, My first film camera was a mz-5, I could mount almost any modern lens, unfortunately the plastic mirror mechanism broke almost immediately. So I bought a Me super (no modern lenses works with that ... Luckily I had some manual lenses, for macro I have a third party 65mm f2.8 lens ( unbranded venus optics) which does not brake the (my) bank.
07-12-2019, 07:58 AM   #13
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The earliest Pentax camera that will work with a lens without an aperture ring is the Super Program, however, it doesn’t provide a way to manually set aperture, so it can only be used in program mode or shutter priority mode. After the SP, most (but not all) cameras would work, however only a few gave the ability to set the aperture manually on the body (PZ-1p being the one I’m familiar with.)
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