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11-21-2018, 11:25 AM   #1
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DFA 150-450 Reporting 310 when at 150

I do not consider this issue a deal breaker at this point. I just received a used DFA 150-450 from forum member. I have only tested a a bit but there is one puzzling issue. When the zoom ring is turned completely to 150mm the lens returns a value of 310 to the exif. Same behavior on K-1ii and K-3ii. There is a slight detent feel just before the ring is turned all the way. If I stop at that point the lens registers 150mm. I have owned another copy of this lens (which I immediately regretted selling) and I do not recall having this issue.

The lens seems to focus as expected and accurately at all the focal lengths I have checked from 150-450. I suspect it is just a small adjustment error. The focus and zoom rings move smoothly and as expected. I do not want to return the lens because it seems otherwise as listed.

What I would like to know:

1. Has anyone else experienced this issue?
2. Does anyone with direct knowledge of Pentax lenses think this could be any more serious than just a slight adjustment error in the zoom ring?

11-21-2018, 11:35 AM   #2
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just curious have you contacted the seller and asked about whether this was known before the sale?

not suggesting any thing improper but rather if some thing might had happen to lens during shipping ?
11-21-2018, 11:53 AM   #3
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Of course I have contacted him. The lens was extremely well packed and the box is good shape. I really am just asking for experiences with the lens, whether anyone has seen this.
11-21-2018, 12:27 PM   #4
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QuoteOriginally posted by Mikesul Quote
I really am just asking for experiences with the lens, whether anyone has seen this.
That sort of failure is indicative of contamination, corrosion, or physical damage to the part of the lens body housing the array of focal length contacts (probably under the zoom ring). If there is an adjustment, it would require at least a partial tear-down. Sadly, the seller is your best resource here and a return is in order. Seeking a repair would be throwing good money after bad.


Steve

11-21-2018, 12:50 PM   #5
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Thank you, Steve. But it reports the correct value at other settings and when stopped at the detent. It also locks when at the detent
11-21-2018, 01:24 PM   #6
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Back in 2016 I reported an issue with my 150-450 where the exposure and image data failed to be recorded correctly. I posted the details in the K-1 problems thread (or whatever it was called) that used to be a sticky on the K-1 page but I've no idea how to find it anymore. I still have the affected images and can add that if you are interested.


The odd performance only happened in specific circumstances where I was tracking a moving subject whilst zooming in and releasing the shutter in Ch drive mode. In those circumstances it would record some images correctly, some with wrong information and some of the images were way underexposured.


I have still got the same 150-450 and it still works fine. It might recreate the same thing in the same circumstances but if I'm not doing that it doesn't matter as it works fine in every other way. It's a good tele zoom and I've no plans of getting rid of mine.

Tas
11-21-2018, 01:37 PM   #7
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QuoteOriginally posted by Tas Quote
Back in 2016 I reported an issue with my 150-450 where the exposure and image data failed to be recorded correctly. I posted the details in the K-1 problems thread (or whatever it was called) that used to be a sticky on the K-1 page but I've no idea how to find it anymore. I still have the affected images and can add that if you are interested.


The odd performance only happened in specific circumstances where I was tracking a moving subject whilst zooming in and releasing the shutter in Ch drive mode. In those circumstances it would record some images correctly, some with wrong information and some of the images were way underexposured.


I have still got the same 150-450 and it still works fine. It might recreate the same thing in the same circumstances but if I'm not doing that it doesn't matter as it works fine in every other way. It's a good tele zoom and I've no plans of getting rid of mine.

Tas
Thanks,Tas. That is interesting and encouraging. I think my issue may be different since is seems to only occur when I go past the final detent. Then it says 310mm but is 150mm. All other info is correct and it records 150 at the detend which is only a millimeter or so before the hard stop.
11-21-2018, 02:37 PM   #8
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QuoteOriginally posted by Mikesul Quote
But it reports the correct value at other settings and when stopped at the detent. It also locks when at the detent
My analysis was based on that description. I hope this works out well.


Steve

11-21-2018, 03:05 PM   #9
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QuoteOriginally posted by stevebrot Quote
My analysis was based on that description. I hope this works out well.


Steve
I take your thoughts very seriously, Steve. Over the years you have demonstrated care and solid knowledge about our equipment.
What keeps nagging me is that this really seems to be a mechanical issue. I just noticed that when the 150 is at the marker the extendable portion of the lens is still about a millimeter from the end. When I turn the zoom ring to the hard stop it come in that distance and stops. There is no play. Nothing is loose. It just seems that the hard stop for the short end of the lens is not aligned with the marker so that the lens is confused when it tries to report the focal length. I just took a couple of test pictures, one at the hard stop which reports 320 and anther at the detent which reports 150. They are both focused sharply and seems to cover the same area (handheld).

In any case I appreciate your thoughts. The seller is willing to take the lens back but I hate to do that unless I am sure there is a potentially serious problem. Right now all it is is an incorrect focal length at the hard stop.
11-21-2018, 04:18 PM   #10
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Michael,
Your experience is helpful since it shows that 310 shows up at either end if there is a maladjustment. I should probably just return it.
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