Tamron SP 500mm (55BB) on Pentax k-50 focus problem

**DamienW** · 12-06-2021, 04:13 AM

I hate the Adaptall mount...so fiddly. Not a great mount to add and remove. I have the 2x converter, which must be placed between the lens and the adaptall mount - real hassle to get on and off. Maybe it needs some sort of lube.

That said...never had an issue with it not focussing to infinity. It overshoots a little as has been mentioned. I need to use live view magnified when trying to get focus on stars, and very little touch is needed on the focus ring to move it out of focus.

kypfer · 12-06-2021, 04:38 AM

Originally posted by DamienW

I hate the Adaptall mount...so fiddly. Not a great mount to add and remove. I have the 2x converter, which must be placed between the lens and the adaptall mount - real hassle to get on and off. Maybe it needs some sort of lube.

If you're using a Tamron original mount, they certainly can benefit from a clean and re-lube' … they do get stiff over the years.
For the 500mm mirror, I use one of the after-market Adaptall-PK adaptors. No aperture linkage to get stiff, so no problem on the 500mm

The original concept, of course, was to fit a separate mount to every Tamron lens … only needing to remove the mount if you changed camera system

Obviously the 2x was always going to be a problem, but at least if you bought one you didn't need to buy another if you changed system

Some of my Tamrons are on their fourth mount! M42 to Fuji-screw to Fuji-bayonet to PKA

lotech · 12-06-2021, 05:29 AM

Originally posted by kypfer

If you're using a Tamron original mount, they certainly can benefit from a clean and re-lube' … they do get stiff over the years.
For the 500mm mirror, I use one of the after-market Adaptall-PK adaptors. No aperture linkage to get stiff, so no problem on the 500mm

The original concept, of course, was to fit a separate mount to every Tamron lens … only needing to remove the mount if you changed camera system

Obviously the 2x was always going to be a problem, but at least if you bought one you didn't need to buy another if you changed system

Some of my Tamrons are on their fourth mount! M42 to Fuji-screw to Fuji-bayonet to PKA

I had a bad experience buying the lens on ebay, the seller said it was fitted with a PK mount, but I received the OM version instead, so I paid extra for the mount and kept the OM one for no use, some people simply don't know what they are selling, or mis post the info. !

kypfer · 12-06-2021, 11:28 AM

Originally posted by lotech

I had a bad experience buying the lens on ebay, the seller said it was fitted with a PK mount, but I received the OM version instead, so I paid extra for the mount and kept the OM one for no use, some people simply don't know what they are selling, or mis post the info. !

On the occasion I've had this sort of thing happen I've always raised the issue with the seller … mostly they're only too happy to rectify the situation one way or another … discount, refund or replacement, whichever is appropriate, even leaving me with the faulty goods 'cos they don't want to pay the return postage!
For the odd one or two who don't play ball, I raise the issue with eBay, eBay provide a full refund and the seller gets a black mark and presumably have to refund eBay anyway.
All I've ever lost is the time taken to raise the issue and maybe queue in the Post Office to return the item.

**DamienW** · 12-06-2021, 05:38 PM

Originally posted by kypfer

For the 500mm mirror, I use one of the after-market Adaptall-PK adaptors. No aperture linkage to get stiff, so no problem on the 500mm

Why didn't I know this!! This is great...I'm going straight to eBay (maybe after I make another five posts ;-)

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12-06-2021, 04:13 AM	#16
DamienW Site Supporter Join Date: Feb 2019 Location: Canberra, Australia Posts: 847	I hate the Adaptall mount...so fiddly. Not a great mount to add and remove. I have the 2x converter, which must be placed between the lens and the adaptall mount - real hassle to get on and off. Maybe it needs some sort of lube. That said...never had an issue with it not focussing to infinity. It overshoots a little as has been mentioned. I need to use live view magnified when trying to get focus on stars, and very little touch is needed on the focus ring to move it out of focus.

12-06-2021, 04:38 AM	#17
kypfer Pentaxian Join Date: Jan 2018 Location: Jersey C.I. Posts: 3,594	Originally posted by DamienW I hate the Adaptall mount...so fiddly. Not a great mount to add and remove. I have the 2x converter, which must be placed between the lens and the adaptall mount - real hassle to get on and off. Maybe it needs some sort of lube. If you're using a Tamron original mount, they certainly can benefit from a clean and re-lube' … they do get stiff over the years. For the 500mm mirror, I use one of the after-market Adaptall-PK adaptors. No aperture linkage to get stiff, so no problem on the 500mm The original concept, of course, was to fit a separate mount to every Tamron lens … only needing to remove the mount if you changed camera system Obviously the 2x was always going to be a problem, but at least if you bought one you didn't need to buy another if you changed system Some of my Tamrons are on their fourth mount! M42 to Fuji-screw to Fuji-bayonet to PKA

12-06-2021, 05:29 AM	#18
lotech Pentaxian Join Date: Apr 2012 Posts: 1,312	Originally posted by kypfer If you're using a Tamron original mount, they certainly can benefit from a clean and re-lube' … they do get stiff over the years. For the 500mm mirror, I use one of the after-market Adaptall-PK adaptors. No aperture linkage to get stiff, so no problem on the 500mm The original concept, of course, was to fit a separate mount to every Tamron lens … only needing to remove the mount if you changed camera system Obviously the 2x was always going to be a problem, but at least if you bought one you didn't need to buy another if you changed system Some of my Tamrons are on their fourth mount! M42 to Fuji-screw to Fuji-bayonet to PKA I had a bad experience buying the lens on ebay, the seller said it was fitted with a PK mount, but I received the OM version instead, so I paid extra for the mount and kept the OM one for no use, some people simply don't know what they are selling, or mis post the info. !

12-06-2021, 11:28 AM	#19
kypfer Pentaxian Join Date: Jan 2018 Location: Jersey C.I. Posts: 3,594	Originally posted by lotech I had a bad experience buying the lens on ebay, the seller said it was fitted with a PK mount, but I received the OM version instead, so I paid extra for the mount and kept the OM one for no use, some people simply don't know what they are selling, or mis post the info. ! On the occasion I've had this sort of thing happen I've always raised the issue with the seller … mostly they're only too happy to rectify the situation one way or another … discount, refund or replacement, whichever is appropriate, even leaving me with the faulty goods 'cos they don't want to pay the return postage! For the odd one or two who don't play ball, I raise the issue with eBay, eBay provide a full refund and the seller gets a black mark and presumably have to refund eBay anyway. All I've ever lost is the time taken to raise the issue and maybe queue in the Post Office to return the item.

12-06-2021, 05:38 PM	#20
DamienW Site Supporter Join Date: Feb 2019 Location: Canberra, Australia Posts: 847	Originally posted by kypfer For the 500mm mirror, I use one of the after-market Adaptall-PK adaptors. No aperture linkage to get stiff, so no problem on the 500mm Why didn't I know this!! This is great...I'm going straight to eBay (maybe after I make another five posts ;-)