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5 Days Ago   #1
Pentaxian




Join Date: Oct 2015
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Pentax F 17-28 Fish Eye Focus Ring / Distance Scale

Hi,

a question regarding the Focus Ring / Distance Scale of Pentax F 17-28 Fish Eye. I got a good copy today and AF works fine, it is no sharpness wonder but ok for the effect.

however, is it possible that the distance scale on the ring is pure ornament? At close focus it seems to be ok, but targeting at infinity the ring indicates something between 1.5 and 5 meters. Pictures are sharp, though. Same in LV. When I manually focus on or close to infinity, pictures are un-sharp. In the OVF they seem to be sharp, also in LV.

Is the distance ring misaligned or just worthless?

Cheers,

5 Days Ago   #2
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Join Date: Apr 2016
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The lens has a pretty fragile mechanism for infinity focus adjustment. I've had two that have had the same issue. All it takes is for one screw to fail and that throws the focus scale off.
5 Days Ago   #3
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Original Poster
QuoteOriginally posted by HarisF1 Quote
The lens has a pretty fragile mechanism for infinity focus adjustment. I've had two that have had the same issue. All it takes is for one screw to fail and that throws the focus scale off.
Thanks, can this be repaired? Is it even necessary? AF seems to focus fine.
5 Days Ago   #4
dms
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I also have the same problem w/ this lens. Infinity at 17mm is at about 1.55 ft, while at 28mm it is 3.1 ft. Since I can focus at infinity at all FL's and the DOF is large, I am leaving it this way.

I purchased it as UG from KEH and it was perfect except for this fault. I would think they would have fixed it if it was a simple procedure.

BTW the AF is accurate as far as I can tell, just the indicated distance is wrong, and it cannot focus very close--especially near the wide end.


Last edited by dms; 5 Days Ago at 03:35 PM.
5 Days Ago   #5
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@dms Yeah, the same like mine, except the scale is off to the other side. Close focus is only 45 cm this is working here, but thats really not very close. If it would be an easy fix, I'd try but sending it off for a service is probably to expensive.
5 Days Ago - 1 Like   #6
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Either the focusing scale becomes degraded as these lenses age or they are simply not accurate from the day they are sold? Mine was also off, just did not worry about. On the other hand, as I mentioned in another post, my used one from a private seller came with a bent aperture lever and I had to disassemble it. Worked for a while and now it is stuck again at certain focal lengths. May need to buy another one. As far as sharpness...I just stopped it down and had no problem with the sharpness and depth of field. Unique lens and excellent sharpness if used at the right settings IMHO. For example:
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4 Days Ago   #7
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Original Poster
Ok, but just in case: does anyone know if this can be repaired?
3 Days Ago   #8
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Yes I believe it can be repaired. The repairer may have to be a little bit creative when it comes to fixing the loose bit.

Essentially there is an (upside down) L shaped piece that has the job of holding the position of the front elements with respect to lens body. I've done a rough sketch to show what it looks like - from memory so it may be wrong. I think there's a third layer to help alignment too, can't really remember it.

In mine, the screw was loose and the L piece moved out of place which meant the front elements didn't sit in one spot.

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Last edited by HarisF1; 3 Days Ago at 01:17 PM.
3 Days Ago   #9
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Original Poster
QuoteOriginally posted by HarisF1 Quote
Yes I believe it can be repaired. The repairer may have to be a little bit creative when it comes to fixing the loose bit.

Essentially there is an (upside down) L shaped piece that has the job of holding the position of the front elements with respect to lens body. I've done a rough sketch to show what it looks like.

In mine, the screw was loose and the L piece moved out of place which meant the front elements didn't sit in one spot.
Thank you, I may give it a try and send it to a service.
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