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Forum: Repairs and Warranty Service
01-12-2018, 12:21 AM
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I heard that about old zooms. But I see not fully opening diaphragm at 35mm and at 105mm. And it is not symmetrical at F3.5. Anyway I have already disassembled most of the lens and can`t identify exposure consistence by now. I could not get to the diaphragm yet but I will do it soon.
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Forum: Repairs and Warranty Service
01-11-2018, 03:07 AM
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Hi
I have a problem with pentax-a 35-105/3.5. Lens diaphragm can`t be opened at full scale. It seems it misses about 1/3 stop of light. I do not know how it happened since lens itself is in quite nice condition and noone opened it before. I have inspected the lens with detached mount and saw that diaphragm lever is stopping by some kind of adjustable fixer near the iris.
That is pretty bad since I can`t get to this fixer by the screwdriver from the tail of the lens. Another problem is that I was forced to remove aperture ring to see that fixer. And while doing this many small parts were released and it will be difficult to return all them to their places without special tools. Fortunately none of them were lost during disassembling. I have removed veneer ring and zooming ring then stuck. What to do next if I need only get to the diaphragm from tail? I have marked parts which were removed (see attached picture).
I need to get to the iris from tail. I am ready even disassemble the lens complete. But to do it right I need some service manual or instructions. May be someone have such old service manuals? I could not find anything like that. Even service manuals of similar lenses would help.
Thanks for the help!
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Forum: Pentax SLR Lens Discussion
04-03-2015, 03:04 PM
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You right. I`ve decided to postpone cleaning procedures till fungi will grow (if they will). Of course I will store a lens in a dry place. When I will disassemble it I will need your photos. Dropped email in PM. Thanks.
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Forum: Pentax SLR Lens Discussion
04-03-2015, 12:05 PM
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Aperture lever is sticking or its blades do not return to the closed position? I suppose you are using AE mode...
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Forum: Pentax SLR Lens Discussion
04-03-2015, 08:21 AM
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Yes, I know that dry storing conditions will not allow fungi grow up. But when used in a wild nature there are no guarantees that lens will be used in a dry conditions. That is the point. :)
I have some experience in repairing the lenses including cleaning the lenses from fungi. Disassembling of the lens is not a problem when you have special tools and knowing how use them. So if I would find a service manual or instructions for a lens then It would be easy to remove fungi by myself. Honestly I do not trust to a service center when repairing the old lenses.
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Forum: Pentax SLR Lens Discussion
04-03-2015, 05:03 AM
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That was the first I have done. I`ve used common household UV irradiator (for disinfecting the room space) for a 30 minutes. The light was sent directly into the rear lens. But you see there are at least 3 reflecting surfaces with multi-coatings. Do you think UV rays might kill fungi in such case?
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Forum: Pentax SLR Lens Discussion
04-03-2015, 02:57 AM
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I`ve got a Tamron SP 300/2.8 LD IF ( Adaptall-2 model 60b ) from EBay. It is quite nice lens but there is one moment of which I am worried about.
It has some specs at a rear group of lenses. Some of that specs looks like dried stains around the border of the lenses. And there is one looks like some small piece of a fungus. Fortunately that all issues are not affecting on the photo. But I would like to clean up the lens to prevent fungus growth (if it is a fungus).
A problem is that I need to get in to the lenses behind of the aperture blades. That means I will need to disassemble a lens tail including aperture mechanism. I would like not to do that untill I will definitely know that it will help. So I need to find some instructions or service manuals for any adaptall-2 SP lenses (I believe they have similar disassembling sequences). May be someone has experience of cleaning such lens and may advise where to start?
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Forum: Pentax Full Frame
01-14-2014, 09:43 PM
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I think that FF will not die because growing megapixel density has its reasonable cause. Modern sensors technology does not allow making photos without noise issue at all. Every new sensor of the same format can have increased megapixel density but its effective ISO level will be the same (or may be worse). So there is always a compromise between ISO setting and noise level while shooting in low-light conditions. And it could be easily solved if your sensor has enough megapixels to spare for image resizing (lowering resolution) in order to eliminate almost all noises received even on high ISO levels. Its all about the light... If you have FF-sensor you can increase megapixel density without decreasing pixel surface saving the light for every single pixel. That is why 16Mp APS-C sensor is good, but 32Mp FF-sensor is twice better. And It will be great if Pentax will make FF-camera with 30-40Mp sensor like Nikon D800. I think it will definitely find its popularity among Pentax users.
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