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06-22-2013, 03:27 AM   #1
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How to adjust infinity focus on Takumar 35MM 3.5

Hello,
Could someone please describe clearly to me how to adjust infinity focus?

My takumar 35mm 3.5 only has a depth of about 5 feet or so and thats it. I have taken off the front name plate ring, then the three little screws that hold the thread ring for the filter. Then you reach the 3 adjustment screws, when you loosen those, you can now rotate the focus ring and lock it place, say, instead of "infinity to .45m" you set it on ".05-45m" (estimate numbers dont have the lens in front of me) but what all that does is limit how much the lens can go up and down now! I don't understand how that adjusts anything???....
So... I tried to get the rear little lens to unscrew and come off the body a bit deeper into the body of the camera when mounted to see the effect (as I have fixed infinity focus on a 50mm 1.4 lens like that). When I did that what happend is that I increased the distance between the small rear lens and the large front lens, the effect it gave me was WORSE infinity focus, so I understand that the lenses have to be closer together to get to infinity focus, I now see that the front bigger lens can be screwed out, I try it and and it starts to screw out, I screw it in deeper instead to bring it closer, and it goes a bit deeper then it was originally. The depth of focus becomes about twice as good at that point but the lenses still need to be closer.. and thats where I am stumped...

Could somebody please explain to me in lay mans term on how the infinity adjustments works because I am feeling real slow right now, read a couple of breezy explained blogs on how to adjust a takumark 50mm i believe, and everyone seems to be able to adjust the 35mm accordingly except for me!
Help!!!!

06-22-2013, 03:35 AM   #2
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Additional information:

I am using a cheaper adapter off of ebay (Quality made actually) but it does introduce that tiny, idk 1/32" gap between the camera and the lens vs an original pentax adapter that fits inside the body, but please note that all my other manual lenses focus fine on it, and beside that point, even when I hold the takumar 35mm lens against the body without anything in place, so there is NO GAP between the body and the lens (Just holding it close by hand) It still does not reach inifinity focus.. thank you (to whoever helps me ) thx all
06-22-2013, 04:36 AM   #3
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This is the correct kind of third party adapter to use (for m42 - K-mount)
http://www.ebay.co.uk/itm/M42-42mm-PK-K-Lens-Mount-Adapter-Ring-Infinity-Foc...item51adc5996c

If you're using this kind and still have problems there's something wrong with your lens.
06-22-2013, 04:51 AM   #4
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Your Takumar or other M42 lenses will only focus correctly with the adapter that is flush with the mount when inserted. This is the one you should use ASAHI PENTAX M42 SCREW TO PENTAX P/K BAYONET FITTING ADAPTER. | eBay, it doesn't matter if it a genuine or cheaper version, I have both and they work...The moment you use an adapter that protrudes beyond the camera mount, you increase the flange depth and lose infinity...

06-22-2013, 06:22 AM   #5
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QuoteOriginally posted by bornamachine Quote
So... I tried to get the rear little lens to unscrew and come off the body a bit deeper into the body of the camera when mounted to see the effect (as I have fixed infinity focus on a 50mm 1.4 lens like that).
I have no idea where have you read that you can do that to adjust infinity focus.
Please take some time and read this instructional. It seems like you're misunderstanding step #12. You want to take the focusing ring off, visually adjust the focus until you achieve infinity, then remount the focusing ring with the infinity hard stop right next to the stopping screw and tighten its 3 screws. That's how you adjust focus for your particular camera.
However, I believe that the offset created by the adapter is too much for the lens to be able to compensate for.
06-22-2013, 05:58 PM   #6
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QuoteOriginally posted by altopiet Quote
Your Takumar or other M42 lenses will only focus correctly with the adapter that is flush with the mount when inserted. This is the one you should use ASAHI PENTAX M42 SCREW TO PENTAX P/K BAYONET FITTING ADAPTER. | eBay, it doesn't matter if it a genuine or cheaper version, I have both and they work...The moment you use an adapter that protrudes beyond the camera mount, you increase the flange depth and lose infinity...
Thanks for all the replies, and yes I do understand that the adapter introduces a gap between the camera body and the lens, BUT even when I hold the lens with my hand FLUSH to the body without an adapter, the depth of focus is about 25 feet, and everything beyond that does not focus, so it tells me that even if I was to get a flush type of adapter, I would still not attain infinity focus. This is my 2nd 35mm lens i am trying on the k5 body.
06-22-2013, 05:59 PM   #7
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QuoteOriginally posted by siamthai Quote
This is the correct kind of third party adapter to use (for m42 - K-mount)
M42 42mm to PK K Lens Mount Adapter Ring Infinity Focus for Pentax | eBay

If you're using this kind and still have problems there's something wrong with your lens.
The lenses are adjustable, I am trying to figure out how to adjust it. Thank you
06-22-2013, 06:27 PM   #8
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Not many lenses have enough adjustment range to work with the extra distance added by that flanged adapter. It doesn't seem like the flange is very thick but then again, the lens designers didn't expect to be that far off. When you have loosened the three screws, moved the focus ring off infinity, then tightened the screws, you reach a point where that adjustment won't do any more. The focus helix is fully engaged and there are no more threads. That is a direct result of the adapter flange thickness. It may be that your lens has other problems and you are making them worse.

06-22-2013, 07:38 PM   #9
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On a 35 mm the shift from sensor plane to N2 is very small, if we use them we know the difference between inf and 25 foot is very small.
Let me do it
1/u + 1/v = 1/35
BorneAmachine says 25 foot which is 7620 mm
And , U = 35.00mm because 1/infinity = 0
BorneAmachine's measurement
1/u +1/7620 = 1/35
..
..
u = 35.16 mm ( correct my math if wrong)
So BorneAmachine is "hand holding" a lens against a k5- with NO mount and can hold it "FLUSH" to within 0.16 mm ( 6.3 thou inch) ?? and therefore can condemn the lens adjustment ??
And I see ( without calc) the hyperfocal of the f/3.5 35 mm is around 9 metre ( 30 foot) so how can BorneAmachine determine 25 foot to infinity anyway?
What- taking shots with a lens hand held against a K-5 and check the sharpness ?

Last edited by wombat2go; 06-22-2013 at 07:50 PM.
06-24-2013, 12:09 AM   #10
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QuoteOriginally posted by Just1MoreDave Quote
Not many lenses have enough adjustment range to work with the extra distance added by that flanged adapter. It doesn't seem like the flange is very thick but then again, the lens designers didn't expect to be that far off. When you have loosened the three screws, moved the focus ring off infinity, then tightened the screws, you reach a point where that adjustment won't do any more. The focus helix is fully engaged and there are no more threads. That is a direct result of the adapter flange thickness. It may be that your lens has other problems and you are making them worse.
Thank you! You may be one of the few people that actually read through what I am writing, yes, the threads bottom out and the focus is at MAXIMUM infinity focus that a barrel can provide, and, yes, I do understand that the flange adds a thickness thus moving the lens further from the body and worsening the infinity focus, but as I have mentioned, I held it FLUSH against the body and it still won't focus on far objects. Thank you! I am still trying to figure out what is wrong.... I have also noticed that the infinity focus is as well as I would like on my K mount lenses.... maybe something is wrong with the camera...
06-24-2013, 12:12 AM   #11
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QuoteOriginally posted by wombat2go Quote
On a 35 mm the shift from sensor plane to N2 is very small, if we use them we know the difference between inf and 25 foot is very small.
Let me do it
1/u + 1/v = 1/35
BorneAmachine says 25 foot which is 7620 mm
And , U = 35.00mm because 1/infinity = 0
BorneAmachine's measurement
1/u +1/7620 = 1/35
..
..
u = 35.16 mm ( correct my math if wrong)
So BorneAmachine is "hand holding" a lens against a k5- with NO mount and can hold it "FLUSH" to within 0.16 mm ( 6.3 thou inch) ?? and therefore can condemn the lens adjustment ??
And I see ( without calc) the hyperfocal of the f/3.5 35 mm is around 9 metre ( 30 foot) so how can BorneAmachine determine 25 foot to infinity anyway?
What- taking shots with a lens hand held against a K-5 and check the sharpness ?
Ok, am I the only one who got lost with this reply? Thanks for the reply but the 25foot range was just a guesstimate, also, I will try to post some pics, but i have already gotten rid of the first 35mm takumar and purchased a different one, yet I am experiencing the same problem!!... Could this be a camera problem?...
06-24-2013, 07:35 AM   #12
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I'd still say the adapter is the problem. The shorter the focal length of a lens, the less movement is required to change focus. If there is a flange on the adapter that spaces the lens forward even 1/32 inch, that is significant on a 35mm lens, while a longer lens would show less effect. Get the correct Pentax adapter without a flange.
06-24-2013, 08:26 AM   #13
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I think all of us read what you wrote but as for myself I find it very hard to believe someone could have the bad luck of buying two takumar lenses and both need to be adjusted. i have owned more than 20 takumars including the 35mm and none of them have been adjusted. I really don't see why you don't buy the correct kind of adapter and see if that fix your problem. Buying from eBay will only take 2-3 weeks to get delivered and they are cheap. But my advice is to buy a original Pentax adapter since they are better.

I guess you have other lenses so that you can test if something is wrong with your camera. If they work then the Takumar will work on your camera.
06-24-2013, 11:26 PM   #14
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I've got the second lens to focus correctly (using the ebay adapter).. now the lens can focus on a far object, then a little past it, so i have achieved infinity focus.
It now takes crystal clear pictures!

I've attached photos how to disassemble the lens.
Basically the rear lens is stationary and is placed at a set distance inside the camera body and does not move, the upper lens moves up and down, the closer the top lens moves to the rear fixed lens the more infinity focus you achieve.
You open the lens up (I used a socket with tape for friction),
undo the 3 screws,
take off the filter ring
, loosen the 3 focus ring screws,
rotate the focus ring to the 0.45 mark,
tighten one screw,
rotate the focus ring towards the infinity mark,
the lens will sink as deep as it can go
once the lens moves as far as it can go in, stop,
loosen the screw again,
set the focus ring on the infinity mark,
and tighten the 3 screws.
Your lens is now sunk in the barrel as deep as it can possibly go, and that is the most infinity focus your lens can achieve. One other thing you can do is try and screw the lens deeper in, unless it is already maxed out. You can also take out the main lens and clean behind it.
Hold the lens
Use 2 flat blade screw drivers in little tiny cut outs in the ring
screw counterclockwise to unscrew (For cleaning)
screw clockwise to screw in (for checking its as deep as it will go, or reassembly)

You have now cleaned the lens and set maximum infinity possible on your lens.
Reassemble in the opposite order.

Why this lens managed to focus and not the last one???

My theory: Takumar made 3 versions of this lens, first being able to reach f22, latter 2 reaching f16, the previous lens I had was a f22 lens and its rear lens protruded beyond the body further then this f16 version, and if you have read in my earlier post that when I unscrewed the rear lens by grasping it with pliers, and it brought the rear lens DEEPER into the body, the infinity focus worsened (Meaning it had to sit LESS DEEP to achieve infinity focus but unable to do due to lens design). You can see from the last picture that the rear lens of this f16 is sitting more flush with the body) Anyyway, that is my logical conclusion why the f16 is able to infinity focus on my K5 and the f22 was not.

Thanks to all for the input.
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06-25-2013, 03:00 PM   #15
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Allow me not to agree with your methods.

Firstly, although this method of focusing is possible and certainly employed in some modern lens designs, clearly the Takumars were not thought to be able to do this, and I would not buy such a hacked lens.

Secondly, there is no such thing as
QuoteQuote:
MAXIMUM infinity focus
because it is a pleonasm.

Thirdly, your method does not guarantee that you achieve the furthest focusing. That's what the other entrances in the helicoid are for.

Also, the other comment with the focal length makes perfect sense, if it doesn't to you, maybe try and read it again later.
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