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09-16-2009, 12:40 PM   #136
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I'm still not exactly sure how destructive it was... I need to have another look at the F-mount attachment vs. a Pentax K/M42 T-mount adapter once I get the lens back in my hands.

09-16-2009, 01:01 PM   #137
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QuoteOriginally posted by deadwolfbones Quote
I'm still not exactly sure how destructive it was... I need to have another look at the F-mount attachment vs. a Pentax K/M42 T-mount adapter once I get the lens back in my hands.
Originally this lens was only available with either M42 or K-mount. If it is a T2-version, it has been fabricated from a third party. In that case, I think, MattGunn is quite right: get the 2mm removed and you are fine.

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09-18-2009, 03:18 PM   #138
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Ok, so... looking at a T->K-mount adapter on eBay and comparing it to the Nikon mount at the end of my lens, I'm noticing the following:

The eBay adapter has the Pentax mount on one side and the T-mount screws on the interior of the other side (i.e., the outer screw threads on the T-mount lens would screw into the inner threads of the adapter).

The Nikon adapter that's on my lens has the Nikon bayonet on one side and what appears to be the outer screw threads for a T-mount on the other side. So where the Pentax adapter is totally flat on the T-mount side (with internal threads), the Nikon one extends with external threads.

So my question is, does anyone know of an adapter that has the Pentax bayonet (or M42 threads) on one end and the external T-mount threads on the other?
09-18-2009, 03:21 PM   #139
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QuoteOriginally posted by glasbak Quote
@deadwolfbones : read my advice about removing the F mount T2 piece, you are 3 scews and a K mount T2 adapter away from a working solution.
Actually, suddenly this reply makes a lot more sense.

Thanks, glasbak.

09-18-2009, 03:24 PM   #140
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QuoteOriginally posted by deadwolfbones Quote
Ok, so... looking at a T->K-mount adapter on eBay and comparing it to the Nikon mount at the end of my lens, I'm noticing the following:

The eBay adapter has the Pentax mount on one side and the T-mount screws on the interior of the other side (i.e., the outer screw threads on the T-mount lens would screw into the inner threads of the adapter).

The Nikon adapter that's on my lens has the Nikon bayonet on one side and what appears to be the outer screw threads for a T-mount on the other side. So where the Pentax adapter is totally flat on the T-mount side (with internal threads), the Nikon one extends with external threads.

So my question is, does anyone know of an adapter that has the Pentax bayonet (or M42 threads) on one end and the external T-mount threads on the other?

I have a t-mount adapter in my office. Unfortunately I'm at home at the moment. However, I have a t-mount for K and one for the latest Nikon that I use on a phase-contrast Olympus microscope. They are both the same on the t-side.
09-18-2009, 03:34 PM   #141
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QuoteOriginally posted by gofour3 Quote
I canít believe the seller of the K500/4.5 I bought on eBay, which was missing the mount, has it listed again!

SMC Pentax 500mm F4.5 4.5/500 Telephoto Zoom Lens NR on eBay.ca (item 250495404574 end time 18-Sep-09 11:10:59 EDT)
The auction concluded today at $615.
09-18-2009, 04:38 PM   #142
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QuoteOriginally posted by Blue Quote
The auction concluded today at $615.
29 bids, with multiple raises by several bidders. Blown out at the close by a sniper.
09-18-2009, 05:29 PM   #143
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QuoteOriginally posted by monochrome Quote
29 bids, with multiple raises by several bidders. Blown out at the close by a sniper.
That is going to be one frustrated sniper!

09-18-2009, 10:47 PM   #144
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QuoteOriginally posted by Blue Quote
That is going to be one frustrated sniper!
So much for eBay acting on Peter’s and my complaints about this item. It went for almost $100.00 more than what I paid for it! Yes the buyer is in for a shock when they try to mount it.

Phil.

PS We should keep an eye out for the eBay feedback the seller gets for this item!!
I’m betting on a big red “negative”.
09-18-2009, 11:06 PM   #145
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QuoteOriginally posted by gofour3 Quote
So much for eBay acting on Peter’s and my complaints about this item. It went for almost $100.00 more than what I paid for it! Yes the buyer is in for a shock when they try to mount it.

Phil.

PS We should keep an eye out for the eBay feedback the seller gets for this item!!
I’m betting on a big red “negative”.
I filed a complaint as well which was obviously ignored with yours and Peter's.
09-19-2009, 04:25 AM   #146
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QuoteOriginally posted by deadwolfbones Quote
Actually, suddenly this reply makes a lot more sense.

Thanks, glasbak.
Looking at the pictures you have posted and comparing them with other pictures of smc pentax and takumar 500 and 1000mm lenses on the web, your adapter looks quite a bit different from those pictures elsewhere and it is not clear where the original adapter stops and the modification begins. However as glasbak has said it would be well worth removing the outer part of the T mount to see what lies beneath.

T mounts are made in 2 parts, the insert with the M42 X 0.75 thread which screws onto the lens and the bayonet which is held onto the insert with 3 grub screws. The two parts are shown in the first picture bellow. If you loosen the 3 recessed grub screws in the rear most part of your adapter a couple of turns the bayonet should come off leaving the insert on the back of the adapter.

Having studied the pictures you have posted I have a basic theory of how the modification may have been made.

Although the T mount thread and is M42 X 0.75, it is possible to force them onto an M42 X 1 screw mount (I have seen this done) . If this has been done to this lens then that would explain why it can't be unscrewed (at least without tools and aditional leverage). This would also explain how the T-F mount adapter has been fitted.

If this has been done then the lens flange focal distance would have been increased by the thickness of the T mount adapter (8-10mm). This would have prevented the lens from being focussed to anywhere near infinity. In order to counteract this problem, material (6-8mm of it, hence why it still won't focus to infinity) may have been removed frome somewhere else on the mount. In the second photo bellow, the screw indicated by the arrow does not look original and is probably part of the modification. In the third picture where you have lossened the three non original screws and unscrewed the back of the lens there are 3 recesses. I presume that these are where the screws prevent the rear part from being unscrewed. Do these look like thety have been cut with a file / saw? Does the end of the screw thread look like it has been modified?
If so then this is probably where material has been removed to shorten the adapter.

If this theory is correct then there may be several ways of converting the lens back to M42 / Pentax K:
If you can unscreww the whole T mount assembly there may still be a (slightly damaged and worn) M42 thread underneath. This could be used directly on the camera but due to the modification the lens will focus beyond infinity and so won't focus as close as it should. A short extension ring may fix this.

If you can't unscrew the whole T mount assembly but can remove the bayonet from the insert then you may be able to find K-T mount and use the bayonet from this on the fitted insert (not all insert / bayonet pars are compatible but it should be possible to find one that is). This will probably not allow you to focus to infinity and either part of the adapter of the T mount will have to be shortened.

The final solution is to discard the whole back section that you have unscrewed and get someone with a screwcutting lathe to make a bit to go between the back of the adapter and a new T mount.

If you can get the bayonet off the T mount adapter and take another picture then it may be possible to make a better assessment of how to fix the adapter.
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Last edited by MattGunn; 01-23-2010 at 09:10 AM.
09-19-2009, 05:56 AM   #147
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Thanks, Matt. I'll see what I can do.
09-19-2009, 06:36 AM   #148
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This thread is awsome (especially to someone like me whose light-bulb changing success rate is in the lower 80s)!

I'd only observe that, at 30m, the minimum focusing distance of this lens is one of its major limitations imho and anything that increases it would be seriously problematic.
09-19-2009, 11:38 AM   #149
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QuoteOriginally posted by dadipentak Quote
This thread is awsome (especially to someone like me whose light-bulb changing success rate is in the lower 80s)!

I'd only observe that, at 30m, the minimum focusing distance of this lens is one of its major limitations imho and anything that increases it would be seriously problematic.
The minimum focusing distance is always a problem with such long fl lenses of "ye olde days", as focusing is completely reliant on the increase of the drawtube length. Just imagine how long the lens would get, if you could focus down to 3 meters...
This is probably the reason, why Pentax fitted the equally ancient 135-600mm zoom lens with a dedicated macro lens for the front filter thread.

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09-19-2009, 11:59 AM   #150
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QuoteOriginally posted by Ben_Edict Quote
The minimum focusing distance is always a problem with such long fl lenses of "ye olde days", as focusing is completely reliant on the increase of the drawtube length. Just imagine how long the lens would get, if you could focus down to 3 meters...
Ben
The 1000mm lens would have to extend on the focus travel by 500mm to focus at 3M. This is probably about 10 sets of macro extension tubes screwed end to end to get a rather unweildy 1.5m long 1:2 macro. I might be usefull for filling the frame with a particularly shy butterfly though
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