Photon Xtreme loose Pentax lenses - another solution

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fizzbangwhallop
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Photon Xtreme loose Pentax lenses - another solution

Postby fizzbangwhallop » 10 Jul 2017, 14:48

Leading on from my thread on getting the Pentax, or any other, lenses serviced by Dave at the camerarepairworkshop near Milton Keynes

viewtopic.php?f=29&t=16715&p=137291#p137291

Last week I sat down and looked at a lens to see if there might be another way to prevent or reduce the chance of a wandering poi with a loose lens. Seems to me that most of the play is between the moving lens and the focus ring so if there was a way to reduce that then it can only be good......then I thought of heatshrink and an in-depth investigation of fleabay brought up this......

http://www.ebay.co.uk/itm/290816583730

Second from bottom in the description list......92mm flat, 59mm diameter, clear, wall thickness 0.1mm.....The diameter of my 105/2.8 lens is 50.94mm and I can slide strips of paper in under the focusing ring. Fully extended the lens is 18mm out from the focussing ring but focussed at 100m odd there's only 7 or 8mm showing so that gives me a bearing surface of around 10mm.

A metre of it arrived today and I've just tried it...initially cutting a piece 18mm long gave a bit of overhang but when heated too quickly this dragged it forwards so it lost its concentricity :eh:

Cutting a bit at 17mm with no overhang and just "pecking" at it with the paint stripper gun gave a much better, more controlled finish and shrink. Too much heat for too long can wrinkle the surface but can be smoothed/stretched out with care.

This single layer slid under the focus ring with no problem so I've added a second bit over the top of the first... the focus ring has more feel to it which suggests I've just about filled the gap.

The sleeve doesn't adhere to the lens so it can be slid around once in place.....and easily removed. I did try pushing it further under the focussing ring but it started connecting with the internal threads and squeezed itself back out when the lens was wound in...so there'd be nothing to gain by fitting it with the lens apart....e.g. When Dave was servicing it.

I've yet to do it to my 2 working lenses on the .17Rem and the .20Prac but I'll let you know what happens when I get to zero those with the heatshrink in place.

Encouraging either way....could be a right result!! :thumbup:

Cheers

Fizz
8-)
Last edited by fizzbangwhallop on 11 Jul 2017, 10:22, edited 1 time in total.
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A correct grip on the butt & cheekweld is imperative for accurate shooting....but, heck.....I just like posting. :crazy: :lol:

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blueeyes
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Re: Photon Xtreme Pentax lenses - another solution

Postby blueeyes » 10 Jul 2017, 17:11

Watching with interest :thumbup:

nealh
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Re: Photon Xtreme Pentax lenses - another solution

Postby nealh » 11 Jul 2017, 02:58

After viewing your screen shots I can't remember your subject. Nothing shrunk on my end. :lolno:
I love this country; it's the damn government I'm afraid of!

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fizzbangwhallop
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Re: Photon Xtreme Pentax lenses - another solution

Postby fizzbangwhallop » 11 Jul 2017, 11:02

blueeyes wrote:Watching with interest :thumbup:


Morning chap.... hope you're well! :thumbup:

I've just been having a play to work out the best way to shrink this stuff onto the lens as my bog-standard decorators heat gun only has 2 settings...hot and effing hot... :o and the fleabay details says it shrinks at 100degrees C.

So...lessons learned, without burning my delicate pinkies although it got close at times... :lol:

Luckily the minimum order is a metre so plenty of stuff to 'practise' with :lol:

a) If you heat it too much it actually curls up the edge. On a couple of attempts with 2 layers, this curled lip caught on the focussing ring and squeezed the shrink off the lens as it was wound in - easier to start again. :thumbdown:

As a result....if I was going to a second layer, I would cut the first layer piece slightly shorter so the second layer overlapped the edges... and helped prevent the lower layer curling up. :thumbup:

b) The Super Takumar I tried it on yesterday took 2 layers but the two Super-Multi-Coateds I've been having a go at this morning only needed a single layer... so there could be tighter tolerances on the this later lens :thumbup:

c) I stood the lens on its base so I could spin it whilst holding the heat gun at about 2 inches... your fingers and the reaction of the shrink will tell you whether you're about right and just flicked the gun backwards and forwards across the shrink. :thumbup:

d) The shrink comes flat which means the 2 folds are a weak point... I found that if the heat was applied to these too quickly they shrank more than the surrounding shrink :thumbdown:

So I started at the mid-points to stretch the folds into place, I did get 'dimples' around the folds but a bit more short n sharp heat smoothed these out. :thumbup:

I was going to try n get out to stick some rounds down the rifles but the rain has beaten me to it... I'm pretty encouraged by the improvement though so I'll be sticking with it and seeing how it turns out in the long run.

My lenses have all been serviced by Dave at the Camera Repair workshop and he's currently got an SMC 105/2.8 lens with play between the focussing ring and the main body... none of my others have/had wobble at the back end but I got a text from a 'keeper local to me last night saying his lens had worked loose - I'll try the shrink on that before it goes to Dave to see how much improvement it makes on its own.

cheers

Fizz
8-)
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A correct grip on the butt & cheekweld is imperative for accurate shooting....but, heck.....I just like posting. :crazy: :lol:

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blueeyes
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Re: Photon Xtreme loose Pentax lenses - another solution

Postby blueeyes » 11 Jul 2017, 14:56

Good stuff Fizz, look forward to the results what caliber is the keeper using, and what kind of usage has it had to loosen up :thumbup:

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fizzbangwhallop
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Re: Photon Xtreme loose Pentax lenses - another solution

Postby fizzbangwhallop » 11 Jul 2017, 17:31

blueeyes wrote:Good stuff Fizz, look forward to the results what caliber is the keeper using, and what kind of usage has it had to loosen up :thumbup:


First time I've seen the lens today... it's a 135mm SMC on a 17Hornet and has got movement in the rear section between the focussing ring and the body which, at the moment, I don't know if this can be fixed by Dave at TCRW. (Hopefully Dave's going to have a look at my 105/2.8 which is suffering from the same problem tomorrow and let me know)

I did fit some heatshrink on the 135 though, that certainly helped reduce the play in it and he's going to stick some rounds through that and my spare 105/2.8 Super Takumar as soon as he gets a chance..... blinking rain. :(

Cheers

Fizz
8-)
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A correct grip on the butt & cheekweld is imperative for accurate shooting....but, heck.....I just like posting. :crazy: :lol:

reejoc
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Location: Worcs

Re: Photon Xtreme loose Pentax lenses - another solution

Postby reejoc » 13 Jul 2017, 16:37

I've got exactly this problem with a Takumar SMC 55mm. POI moves by up to 2cm at 30m.

I've emailed Dave but not sure what exactly he could do to stop the play if it's inherent to the lens design.

Doesn't your heatshrink method create friction when focusing?

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fizzbangwhallop
Posts: 1735
Joined: 18 Oct 2011, 11:27
Location: north herts

Re: Photon Xtreme loose Pentax lenses - another solution

Postby fizzbangwhallop » 13 Jul 2017, 17:32

reejoc wrote:I've got exactly this problem with a Takumar SMC 55mm. POI moves by up to 2cm at 30m.

I've emailed Dave but not sure what exactly he could do to stop the play if it's inherent to the lens design.

Doesn't your heatshrink method create friction when focusing?


Dave hasn't come back to me on whether he managed to get rid of the play in the focussing ring to the body...he's not there tomorrow so I'll pop down the market tomorrow and see if Niv has brought my lens over from Dave.

There is a bit of friction but it just firms up the feel of the focus.... as it fills the gap between the lens and the focussing ring. One layer s'be fine, maybe a second....... n it's quick n easy enough to repeat if the second layer doesn't work. The heatshrink itself is slippery stuff.... same as the the stuff on the outside of batteries.

Cheers

Fizz
8-)

Edit... Friday.... popped down the market but Niv wasn't there :( so it'll be Monday at least before I can get hold of Dave.

Fizz
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A correct grip on the butt & cheekweld is imperative for accurate shooting....but, heck.....I just like posting. :crazy: :lol:

reejoc
Posts: 10
Joined: 01 Apr 2017, 14:04
Location: Worcs

Re: Photon Xtreme loose Pentax lenses - another solution

Postby reejoc » 16 Jul 2017, 18:56

Well I had a think and ended up putting 2 layers of black electrical insulating tape around the focusing ring which seems to stop the play while allowing (slightly stiffer) movement

No idea yet whether this will translate to an fixed POI or whether it will stand up to use in the field.


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