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04-02-2021, 10:11 AM   #1
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Lens Repair for SMC Pentax Reflex Zoom 1:8~12 400~600mm

I recently purchased a mint "looking" SMC Pentax 400-600mm F8-12 from Japan. Serial number 7364609. The lens is indeed beautiful and looks to have never been used. Unfortunately it does not work. It is very sharp from about 10 to 20 feet. Resolution then degrades as distance goes to infinity making the lens useless for the wildlife and lunar photography that I purchased it for. I found great resolution in the verticle axis, poor resoultion in the horizontal. So something seems to be causing an astigmatism. A star I imaged looked at is a bit elliptical in shape. A possible collumnation problem?

I took the lens into a repair shop. They verified the problems that I found, but were unable to service the lens. They suggested that I contact Pentax.

Anyone have ideas, personal experience, service manuals, or knowledge of anyone who can help?

04-02-2021, 11:18 AM   #2
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The problem with repairing older lenses is obtaining parts so any if the authorized repair centers in the US is likely to decline servicing your lens. You might try finding an "old school" lens or telescope repair person locally that might be able to adjust it.

Otherwise you could try NSB-Tekunos in Japan, setup and run by former Pentax engineers and technicians. They seem to have parts for old cameras and lenses or may even be able to fabricate them. All things considered their prices are reasonable. The trick to contacting them is to use the email address embedded in their repair form PDF.

See the following threads for more information:
Repair report - good experience with NSB-Tekunos repair - PentaxForums.com
Focus ring jammed on a SMC Pentax A* 300 mm f/2.8 - PentaxForums.com
04-02-2021, 12:24 PM   #3
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QuoteOriginally posted by jmcsys Quote
. . . .Anyone have ideas, personal experience, service manuals, or knowledge of anyone who can help?
follow this link for possible sources for repair

QuoteQuote:
US
KEH.com (GA, Most current and vintage gear)
Eric Hendrickson (Vintage cameras, Current and vintage lenses)
Precision Camera (Authorized to perform warranty service, NC)
Advance Camera (Most current and vintage gear, Portland, OR)
General Camera Repair (LA, CA)
Garry's Camera Repair (IL, select film SLRs)
International Camera Repair (LA, CA)
Halcyon Cameras | Vintage Camera Restoration (Vintage film cameras, San Diego, CA)
Camera Repair Japan (Services Sigma lenses and more, Atlanta, GA)
Allied Camera (MN, manual film cameras)
Bill Rogers Camera (LV, NV, film-era cameras and lenses)
Phototronic (Topeka, KS, film and digital camera repair)
Lezot's Camera Center (VT, film SLRs / medium format)
Read more at: Pentax Repair Facilities (Wordwide listing) - Page 9 - PentaxForums.com

my own personal experience is with Phototronic here in Topeka KS

https://phototronic.biz/

he is very friendly and fixed a dfa 150-450mm zoom for me
04-02-2021, 12:28 PM   #4
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QuoteOriginally posted by Not a Number Quote
The problem with repairing older lenses is obtaining parts so any if the authorized repair centers in the US is likely to decline servicing your lens. You might try finding an "old school" lens or telescope repair person locally that might be able to adjust it.

Otherwise you could try NSB-Tekunos in Japan, setup and run by former Pentax engineers and technicians. They seem to have parts for old cameras and lenses or may even be able to fabricate them. All things considered their prices are reasonable. The trick to contacting them is to use the email address embedded in their repair form PDF.

See the following threads for more information:
Repair report - good experience with NSB-Tekunos repair - PentaxForums.com
Focus ring jammed on a SMC Pentax A* 300 mm f/2.8 - PentaxForums.com
Thank you. I am frustrated and worried about sinking more good $$$ after bad. I’ve tinkered with other lens and reset infinity stops. I’d be up to messing with this one if I had a clear tutorial or service manual. I will give your links a try. Again thanks.

---------- Post added 04-02-21 at 12:31 PM ----------

QuoteOriginally posted by aslyfox Quote
follow this link for possible sources for repair



Read more at: Pentax Repair Facilities (Wordwide listing) - Page 9 - PentaxForums.com

my own personal experience is with Phototronic here in Topeka KS

Camera Repair - phototronic.biz

he is very friendly and fixed a dfa 150-450mm zoom for me
Thank you for the links. This has been a frustrating and expensive trial. Your links might just be the ticket.

04-02-2021, 01:09 PM   #5
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Check the minimum focus distance too.
04-02-2021, 01:14 PM   #6
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QuoteOriginally posted by jmcsys Quote
Thank you for the links. This has been a frustrating and expensive trial. Your links might just be the ticket.
Perhaps a return to the seller might be in order?


Steve
04-02-2021, 01:22 PM   #7
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QuoteOriginally posted by stevebrot Quote
Perhaps a return to the seller might be in order?


Steve
It will cost me $150 in shipping to return the lens to Japan. To be fair the seller refunded a portion of the price. So all told, I have $180 in the lens. Enough to hurt, but if I can get a reasonable repair, or help in doing it myself, I might not fair too badly.
04-02-2021, 01:41 PM - 1 Like   #8
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QuoteOriginally posted by Not a Number Quote
You might try finding an "old school" lens or telescope repair person locally
These lenses (I had one - briefly) are akin to many small astronomical Maksutov/Cassegrain telescopes. Look for your local amateur astronomy club - there may be some knowledgeable folks there who can help you get it aligned. Your symptoms are typical of a mis-alignment between the little mirror at the front end of the lens and the big mirror at the rear. I'm not sure if these are adjustable, though.

04-02-2021, 03:00 PM   #9
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I bought one some years ago which also was in great condition except that the zoom ring was jammed. I suspect it had had little use from new and the grease had solidified. I sent it to the UK official service centre who then had to send it back to Japan to be repaired. I don't think that option is available any more though, the lens is just too old.

A web search should get you adjustment techiques for mirror lenses but how easy that would be on a zoom like this is anyone's guess.
04-02-2021, 03:32 PM   #10
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The minimum focus distance for this lens is 300cm or ~9.84ft. Usually if the infinity setting is off the minimum will be off too.
04-20-2021, 07:00 AM   #11
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I have not precisely measured the minimum focus distance but can confirm that it is very close to the 9.8 ft you mention. I have used ball bearings, stars, and any number of pin point highlights as well as a toy laser beam to check for defocused diffraction doughnuts. They all show virtually perfect concentric circles, so I think collumnation looks pretty good.

What I do see is a depth of field that is razor thin. Only a narrow band over most of its focus range. At infinity, the moon is impossible to focus. Even with my best tripod and head locked down tight, there is too much play In the system to focus precisely enough with such a shallow field.

The photos I take show a double image in the "just out of focus objects and textures" after the in focus region.

When taking pictures of an ISO_12233 target with lens set at 500mm, I get over 2000 lines_per_sensor_height vertically while getting around 1500 horizontally. When using the 80MB HiRes mode of my LUMIX g9, I do get considerably better resolution, but still see significantly better performance in the verticals axis.

Sometimes my results are pretty darn good, but mostly the images are soft with a few regions that are well focused. But those regions may have more to do with visual elements that align more vertically. It is hard to tell and my eyes could be playing tricks.

Ive attached a photo. The in focus portion looks pretty good. But study the out of focus area. Both the fence finials and the tree branch show a double image ghosting effect. Is this normal for this lens?

Any thoughts?
Attached Images
View Picture EXIF
DC-G9  Photo 

Last edited by jmcsys; 04-20-2021 at 07:51 AM. Reason: fix typos, improve clarity, and add a photo
04-27-2021, 09:40 AM   #12
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I have just looked at the reviews of the lens on this forum and notice that there is a rear filter mount. Check anything in the mount just in case it is a lens, rather than the filter that is normal.
04-27-2021, 08:26 PM   #13
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QuoteOriginally posted by pentasonic49 Quote
I have just looked at the reviews of the lens on this forum and notice that there is a rear filter mount. Check anything in the mount just in case it is a lens, rather than the filter that is normal.
Thank you for your reply. Your suggestion is clever and had it worked would have made for an easy fix. Unfortunately it did not pan out. Ive attached two photos illustrating the situation. In the 1st photo, the rear most lens element is pictured close to the filter seat where it sits when the lens is set for 400mm. Mounted flush on the seat bed looks to be some kind of leaf spring assembly. The second photo shows how the rear element retracts into the lens body when adjusted for about 500mm. At 600mm the rear element has retracted so far that it can hardly be seen.
Attached Images
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IPhone 11  Photo 
View Picture EXIF
IPhone 11  Photo 
04-28-2021, 09:49 AM   #14
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With a mirror lens it is usual to get doughnut ring shaped out of focus images, so the out of focus parts of your picture may not be wrong, just very different from what an ordinary lens would give.
The leaf spring may hold some pins in place, only slackening off the central screw would reveal its secrets. If you do slacken the screw, be alert for anything pressing and lifting the spring. The correct screwdrivers to use on these lenses are the cross point JIS type, not Phillips, Posidrive or Superdrive.
04-28-2021, 11:59 AM   #15
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The rear mounted filter is part of the optical design so there should always be one mounted.
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