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07-12-2007, 11:56 PM   #1
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Does anyone have any ideas?

Hello

I think this might be the right place for a thread like this.

I just recently bought a 50mm 1.4 but I discovered it had a quite annoying fault. The focusing goes beyond infinity, does anyone with a little more insight in the construction of these lenses have any ideas on what to do? The best would be some kind of "do it your self" repair page with lots of photos on the net. It's the K version 50mm 1.4.

Does anyone have any ideas?
Thanks

07-13-2007, 12:22 AM   #2
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I wouldn't be bothered by that. If it focuses right and focus ring has no play then I don't see a problem.
07-13-2007, 10:29 AM   #3
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A long time ago I bought a used 100mmF4 macro which was the opposite. it wouldnt focus to infinity.

Pentax fixed it, I don't know how they did it, but it can be done.

I'm not sure you want to take it to bits yourself, as you don't want to get dust, grease etc between the elements
07-13-2007, 10:44 AM   #4
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A lot (if not all) of my lenses go beyond infinity - and these are all either DA,FA or DFA lenses. I think Pentax lenses are designed this way. On my copies the infinity sign is usually centered on the mark for it to be at infinity (though I dont have them with me now so I cant check right now) - but they turn all the way to where the end of the infinity sign is in line with the mark which is basically beyond ifinity.

07-13-2007, 11:05 AM   #5
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QuoteOriginally posted by Lowell Goudge Quote
I'm not sure you want to take it to bits yourself, as you don't want to get dust, grease etc between the elements
Do NOT take your lens apart by yourself! I attempted to fix an old Yashica lens whose focus collar had gotten loose. It seemed to me to just be a matter of tightening a set screw or something. I remember things going along fairly well until I removed one particular ring. That's when about a dozen tiny ball bearings fell out, hit the floor, and scattered! Luckily, I didn't do any permanent damage.
07-13-2007, 01:15 PM   #6
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Contrary to some of the alarmist opinions mentioned here, some care goes without saying though, with older pentax lenses (pre F series I believe) it is a fairly easy adjustment to make. Basically you remove the trim ring and the filter holding hood and there should be three screws which when loosened will allow you to adjust where the lens is focused in relation to the scale. This may help, it is for the Takumar 50mm 1.4 but your lens (assuming it is a K, M or A lens) should be very similar.

Edit: Just noticed that you have the K version which should be almost identical to the SMC Takumar version of the lens. I believe it is only the mount that was changed.
07-13-2007, 03:18 PM   #7
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If you have only 1 body, don't rule out it might be the camera (yes, some cameras do focus beyond infinity but considered okay as long as the viewfinder agrees with the film plane or CCD). If you must, just unscrew the retaining ring in the front, then 3 screws to remove the filter rim, then you will see 3 screws inside. Loose them slightly (not completely) and you can adjust the focus to whatever point you prefer. These 3 screws were factory threadlocked but most service centres often didn't after service.
07-13-2007, 03:52 PM   #8
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QuoteOriginally posted by wlachan Quote
If you have only 1 body, don't rule out it might be the camera (yes, some cameras do focus beyond infinity but considered okay as long as the viewfinder agrees with the film plane or CCD). If you must, just unscrew the retaining ring in the front, then 3 screws to remove the filter rim, then you will see 3 screws inside. Loose them slightly (not completely) and you can adjust the focus to whatever point you prefer. These 3 screws were factory threadlocked but most service centres often didn't after service.
if you do this be sure to watch your aperture opening as an adjustment here can also adjust the max aperture.

07-15-2007, 01:27 PM   #9
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If a lens doesn't focus at infinity, it probably means that the lens wasn't collimated correctly. If the lens was used, there is a good chance the lens was disassembled and infinity focus wasn't checked when it was reassembled. It may be easy enough to open up a lens with the right tools but not being able to get the lens to focus at the right distance is a sure sign of a botched up reassembly.
07-15-2007, 03:24 PM   #10
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QuoteOriginally posted by creampuff Quote
If a lens doesn't focus at infinity, it probably means that the lens wasn't collimated correctly. If the lens was used, there is a good chance the lens was disassembled and infinity focus wasn't checked when it was reassembled. It may be easy enough to open up a lens with the right tools but not being able to get the lens to focus at the right distance is a sure sign of a botched up reassembly.
that's not the question. their lens focuses past infinity. most of mine do too. i do know that with the super lenses like my 500mm f4.5 this is suppose to make up for any thermal changes in the lens at different tempertures.
07-15-2007, 07:32 PM   #11
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QuoteOriginally posted by roy Quote
that's not the question. their lens focuses past infinity. most of mine do too. i do know that with the super lenses like my 500mm f4.5 this is suppose to make up for any thermal changes in the lens at different tempertures.
That is exactly the point. Very long teles aside (allowing for thermal fluctuations), at the infinity stop (the point where you can't turn the focusing ring anymore) and where the infinity mark is, the lens should be able to focus at infinity. I have personally seen botched repair/cls jobs where even at the infinity mark, the focus adjustment is either already past the infinity mark (images start becoming soft) or the lens can't focus at infinity. I don't know what lenses you have or refer to but all my old and new lenses focus at infinity. If the lens is new out of the box and exhibits this problem, it is simply bad QC. If the lens is old and the helical barrel is worn, there is a chance the barrel could extend beyond the infinity mark. I would avoid such a lens because it is simply worn.
07-17-2007, 01:38 AM   #12
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Thanks for all the replies

The lens is indeed old and worn, and sending it away for repairs is not an option because that would cost me about three times the money I paid for it.

I've checked it both on a KX and MX body and compared it to my K55/1.8 and it is clearly not adjusted correctly. When my K55/1.8 tells me that the focus distance is 5 meters the 50/1.4 says 3 meters. It is not just a little bit out of focus, it is utter bokeh madness.

The lens has some pritty nasty toolmarks on the retaining ring and has probably been opened before. Looking at these toolmarks I must say it does not suprise me that they did not take the time to adjust it correctly.

Thanks to some of the replies here I now think I can open the lens and fix the problem without having to figure the lens construction out first, thanks again for all the helpfull answers!

Do I need any special tools to get the retaining ring of? I've seen some kind of tool used but cannot remeber the name, two paralel metal sticks. Where can I find this tool? Haven't seen it in any stores.

//Axel
07-17-2007, 02:37 AM   #13
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QuoteOriginally posted by Jimfear Quote

Do I need any special tools to get the retaining ring of? I've seen some kind of tool used but cannot remeber the name, two paralel metal sticks. Where can I find this tool? Haven't seen it in any stores.

//Axel
From Alan's reply, it sounds like all you need is a small screwdriver. You are referring to lens spanner wrench, which could cost you again three times what your lens is worth. Or you can make one by grinding down a pair of needle-nose pliers but it seems that you wouldn't need a spanner for this simple adjustment.
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