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08-12-2009, 02:16 PM   #1
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500mm f4.5 SMC Tak not focusing to infinity?

I finally have enough tripod and head to successfully use my M42 500mm SMC Tak. I tried doing a moon shot a few weeks back and couldn't get a sharp photo out of it. I had no problem focusing on things within the adjustment range.

The lens did suffer from the focusing mechanism wobble that seems common to these lenses, so I fixed that, thinking that it may have lead to enough misalignment to cause problems.

I took it out again this weekend after making the repairs and got the same results. Looks great in the focus range, but infinity is not there. I was focusing on some far off geese and when I had my split prism on one goose, I'd watch the front and rear of the goose coming together but not make it all the way there before I ran out of adjustment. I'm using a genuine Pentax adapter, not the flanged style.

Anyone have any experience with this lens/issue? I thought maybe I didn't get the helical screwed back together properly, but it seems I've only found two spots it screws together when reassembling and the other spot looked WAY off from being correct.

Is there something wrong/out of adjustment or are my expectations too high? The moon shot a bit fuzzy as well. Fuzzy enough to know something wasn't what I had hoped for even from the camera LCD.

Lets see if I can get some example photos to come up. The geese in the photo are about 2000 feet away. The sign is 150-200 feet away to show what this lens does on closer objects. Both photos at iso 100 and stopped down to f8 or so. Third is what I believe to be a 100% crop. I was focusing on one of the two right birds.

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08-12-2009, 02:29 PM   #2
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I have a 600mm F5 lens that I tested with my K-7 and it has no problem reaching infinity focus. For close up work I use a 3.5" focuser extention to the standard focuser.
YouTube - Pentax K-7 test Orion 120ST (600mm F5) refractor in 1536x1024 *** mode

08-12-2009, 02:38 PM   #3
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There are generally 3 smalls set screws on the focus collar. These can be loosened to adjust the collar's stop point. I had this problem with a 400 lens.
08-12-2009, 02:47 PM   #4
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I'll bet the lens I can make it work on my camera, without any modifications

But then again, my Sigma has a shorter registration distance, so it'll still more than likely focus past infinity on my camera.

wildlifephotog is right, it's usually those small set screws on the focus collar you'll want o loosen off for the adjustment. However if it doesn't work feel free to send the lens my way

08-12-2009, 03:48 PM   #5
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Little Laker, I'll keep your offer in mind, but don't hold your breath waiting for me to act on it. haha

Anyways, are you guys talking about three set screws on the ring you'd turn for focusing the lens? I loosened those and all those appear to hold in place is the scale ring that shows what focus distance you're currently at. Or are you talking about something internal?

I'll take it apart again and examine a little closer and see if I can find anything else. I notice the "wobble" is back again, so I must not have tightened those set screws enough. Hopefully I won't need to add more set screws as others have to get a more permanent wobble solution.

Edit:
Believe I found how to change the infinity focus stop. The focus stop is a ring that is held in place by friction, clamped between the focus ring and focusing mechanics by the three screws that attach the ring to rest of the assembly. I made some adjustments and was able to focus beyond furthest object I can see from my house. Couldn't get out to the state park before sundown for a proper test.

Last edited by tvfd911; 08-12-2009 at 08:42 PM.
08-14-2009, 01:59 PM   #6
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I had the same focusing problems you describe with the same lens. I nearly gave up on the 500/4.5, then. I disassembled the helicoid and when assembling it, changed the infinity focus. (By the way, you cannot change it by changing the infinity stop,...) Now I can focus clearly beyond infinity, which gives me peace of mind. That afforded to drill a couple of holes and tap some new threads, to get all the markings and scales back into their right position on top of the lens.

Nevertheless, the whole work proofed to be quite pointless. I finally was able to focus at infinity and found my images just as unsharp as before.

I exchanged these experiences with another photog who had exaclty the same problems. Our common conclusion is, that apart from possible focusing errors on the user.-side the main problems are steadiness/vibrations whatever of the lens on the tripod. A really good tripod is not enough. It must be really, really good tripod and head... I get the best results now from a gimbal mount.

AND - probably even more important ar the atmospheric turbulences, which warp and distort any object beyond perhaps 100m distance. Especially on those nice sunny summer days, when the light is good enough to step down the lens the air is also very turbulent and one will simply not get a sharp image over a longer distance, not with the 500/4.5 not with a Zeiss megamonster-lens.

Ben
08-16-2009, 09:42 AM   #7
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Ben, from what I experienced, the focus stop could be adjusted. There was a flat ring with three lobes sticking out and being clamped in place by the focusing ring. that ring had a knob or screw that stuck inwards and would hit the focus stop. By moving this ring, and adjusting the helicoid, I have plenty of adjustment now.

Here are the results of a few test shots. One of the shots is focused on the rail of the service cage on a 70ft farm silo. I'm about 70ft from the base as well. The shot of the road signs are about 1000 ft away.

I believe I'm now set with supporting this lens after my first undersized attempt. Picked up a used Gitzo pretty reasonably, honestly not sure which model, but it handles it well. I also picked up the India CineCity gimbal mount which is plenty strong. Tightens down pretty well. There is a small amount of stickyness in it when first starting to move, so I might take some lapping compound and hone the bore/shaft fit a little. I'm generally happy with the support now.
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08-16-2009, 09:48 AM   #8
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The last test shot of a tree was from 3-4000 feet away looking at a GIS map.

Ben, how would you say these compare to yours? These were taken f8-11. I have a split prism screen, but it has a blemish that makes focusing fussy and I know it isn't shimmed absolutely perfectly either. Still waiting for the replacement screen to get here...

You guys think I can get more out of it with further tweaking? Considering there being a significant breeze and atmospheric turbulances, etc. I'd be suprised with any better performance, though it would be welcomed

They aren't razer sharp by any means but it suits my needs and is an improvement over the Sigma 600mm mirror I tried.

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08-17-2009, 02:06 AM   #9
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QuoteOriginally posted by tvfd911 Quote
The last test shot of a tree was from 3-4000 feet away looking at a GIS map.

Ben, how would you say these compare to yours? These were taken f8-11. I have a split prism screen, but it has a blemish that makes focusing fussy and I know it isn't shimmed absolutely perfectly either. Still waiting for the replacement screen to get here...

You guys think I can get more out of it with further tweaking? Considering there being a significant breeze and atmospheric turbulances, etc. I'd be suprised with any better performance, though it would be welcomed

They aren't razer sharp by any means but it suits my needs and is an improvement over the Sigma 600mm mirror I tried.


Over this distance these images are really great. Lots of detail. I would not expect to see significantly more detail over such a distance, even with a more modern lens.

Your move to a Gitzo, by the way, was very wise. I bought a secondhand STudex some time ago, too and find it much more solid, than any other tripod in its weight class. I don't know, how Gitzo does this, but they really produce excellent quality. And the aluminium modells are not too expensive, either.

Ben
08-17-2009, 02:09 AM   #10
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QuoteOriginally posted by tvfd911 Quote
Ben, from what I experienced, the focus stop could be adjusted. There was a flat ring with three lobes sticking out and being clamped in place by the focusing ring. that ring had a knob or screw that stuck inwards and would hit the focus stop. By moving this ring, and adjusting the helicoid, I have plenty of adjustment now.

Have you made some photos of the adjustment. I don't quite understand, which ring you refer to, so a photograph would be helpful. We had a lot of in-depth discussions about this lens in the manualfocus forum and some guys posted a lot of phtographs about their complete disassembly/re-assembly of that lens, but nobody mentioned this easy way to adjust focus - and I myself did not find it, too. Maybe the tinkerers amongst us always think too complicated!

Ben
08-17-2009, 09:01 AM   #11
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QuoteOriginally posted by Ben_Edict Quote
Have you made some photos of the adjustment. I don't quite understand, which ring you refer to, so a photograph would be helpful. We had a lot of in-depth discussions about this lens in the manualfocus forum and some guys posted a lot of phtographs about their complete disassembly/re-assembly of that lens, but nobody mentioned this easy way to adjust focus - and I myself did not find it, too. Maybe the tinkerers amongst us always think too complicated!

Ben
Ben,

Flipped through my photos and realized I got so concentrated on figuring out the setup that I quit taking photos before I got to the solution. Took the lens back apart this morning to capture some images quickly. I'll give a quick description of the steps to get there first:

1. Remove the lens mount and ribbed retaining at the ring closest to the focussing group. (third ribbed ring from the camera mount)
2. Remove the scale ring (unsure of proper term) as shown in the first photo.
3. Looking from the camera mount end, look between the focussing ring and focussing assembly. There are three screws there as shown in photo 2. Remove these.
4. Now you will see the focus stop ring. photo 3. Most of it is parallel to the lens assembly, but has three tabs that are held in place by clamping force/friction when the lens is together. Someone etched the correct placement of those tabs on my lens. I'm guessing this was done by the original assembler. If yours has the same, it would likely confirm that idea.

To get proper infinity focus: I had to ignore the etch marks.

5. By grasping the ridge of the focus assembly the focus ring was screwed to, one can adjust the focus assembly. I turned it in completely so the helicoids were bottomed out (focus assembly is collapsed)
6. Then I extended it approximately 1/16th of a turn and placed the stop ring at this location and reassembled.

Note: to make sure your focus scales end up at the top of the lens again, have the lens set against the infinity stop during reassembly. The distance scale may not read correctly, but can be turned match again.

This adjustment gave me infinity and I don't think I lost much, if anything at the minimum focus distance. I didn't purchase this lens for photos of close stuff, so I wasn't overly concerned about that anyways.

I am assuming you've had the lens apart for taking care of the wobble, or at least have heard of taking out those little L-brackets and unscrewing the helicoid. I counted 6 or so thread leads, so I suspect that if someone took that helicoid apart and back together enough, they would be able to get it matched up the same way the assembler did during manufacturing. Adjusting this ring appears to simply compensate for catching a different helicoid than the assembler did.
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08-17-2009, 09:16 AM   #12
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QuoteOriginally posted by Ben_Edict Quote
Over this distance these images are really great. Lots of detail. I would not expect to see significantly more detail over such a distance, even with a more modern lens.

Your move to a Gitzo, by the way, was very wise. I bought a secondhand STudex some time ago, too and find it much more solid, than any other tripod in its weight class. I don't know, how Gitzo does this, but they really produce excellent quality. And the aluminium modells are not too expensive, either.

Ben
Glad to hear that this investment is finally performing as it is capable of. The only thing I would like to do yet is build a cable release I can trigger by stepping on it. Someone on the forum here, Wildman? maybe, posted that in a long lens suggestions posting. I've been using the wireless remote with the 3 sec timer so far to reduce vibration, but the foot release seems more convienent for critters.

Too bad all the corn is too tall now to see anything. About the only place I can utilize the lens at the moment is for eagles over the marsh where the tree test photo was taken.
08-17-2009, 01:35 PM   #13
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QuoteOriginally posted by tvfd911 Quote
The only thing I would like to do yet is build a cable release I can trigger by stepping on it. Someone on the forum here, Wildman? maybe, posted that in a long lens suggestions posting.
go to a goodwill/second hand store and get a foot pedal for a sewing machine, I'm sure it can easily be modified.
02-20-2017, 04:40 PM   #14
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Thanks for the only focus adjustment information I can find for this lense.
I bought a cheap takumar smc 400 67 and tried to dissassemble to find someone has broken off a mount screw in the sleeve. What I would like to know is how the mount screws enter the sleeve to secure the mount. They are very long and must enter the lense body under the sleeve. Do you have any images under the mount block screw holes where the sleeve is slid off.?


Regards
Ray



QuoteOriginally posted by tvfd911 Quote
Ben,

Flipped through my photos and realized I got so concentrated on figuring out the setup that I quit taking photos before I got to the solution. Took the lens back apart this morning to capture some images quickly. I'll give a quick description of the steps to get there first:

1. Remove the lens mount and ribbed retaining at the ring closest to the focussing group. (third ribbed ring from the camera mount)
2. Remove the scale ring (unsure of proper term) as shown in the first photo.
3. Looking from the camera mount end, look between the focussing ring and focussing assembly. There are three screws there as shown in photo 2. Remove these.
4. Now you will see the focus stop ring. photo 3. Most of it is parallel to the lens assembly, but has three tabs that are held in place by clamping force/friction when the lens is together. Someone etched the correct placement of those tabs on my lens. I'm guessing this was done by the original assembler. If yours has the same, it would likely confirm that idea.

To get proper infinity focus: I had to ignore the etch marks.

5. By grasping the ridge of the focus assembly the focus ring was screwed to, one can adjust the focus assembly. I turned it in completely so the helicoids were bottomed out (focus assembly is collapsed)
6. Then I extended it approximately 1/16th of a turn and placed the stop ring at this location and reassembled.

Note: to make sure your focus scales end up at the top of the lens again, have the lens set against the infinity stop during reassembly. The distance scale may not read correctly, but can be turned match again.

This adjustment gave me infinity and I don't think I lost much, if anything at the minimum focus distance. I didn't purchase this lens for photos of close stuff, so I wasn't overly concerned about that anyways.

I am assuming you've had the lens apart for taking care of the wobble, or at least have heard of taking out those little L-brackets and unscrewing the helicoid. I counted 6 or so thread leads, so I suspect that if someone took that helicoid apart and back together enough, they would be able to get it matched up the same way the assembler did during manufacturing. Adjusting this ring appears to simply compensate for catching a different helicoid than the assembler did.


---------- Post added 02-20-17 at 04:52 PM ----------

Thanks for the only focus adjustment information I can find for this lense.
I bought a cheap takumar smc 400 67 and tried to dissassemble to find someone has broken off a mount screw in the sleeve. What I would like to know is how the mount screws enter the sleeve to secure the mount. They are very long and must enter the lense body under the sleeve. Do you have any images under the mount block screw holes where the sleeve is slid off.?


Regards
Ray



QuoteOriginally posted by tvfd911 Quote
Ben,

Flipped through my photos and realized I got so concentrated on figuring out the setup that I quit taking photos before I got to the solution. Took the lens back apart this morning to capture some images quickly. I'll give a quick description of the steps to get there first:

1. Remove the lens mount and ribbed retaining at the ring closest to the focussing group. (third ribbed ring from the camera mount)
2. Remove the scale ring (unsure of proper term) as shown in the first photo.
3. Looking from the camera mount end, look between the focussing ring and focussing assembly. There are three screws there as shown in photo 2. Remove these.
4. Now you will see the focus stop ring. photo 3. Most of it is parallel to the lens assembly, but has three tabs that are held in place by clamping force/friction when the lens is together. Someone etched the correct placement of those tabs on my lens. I'm guessing this was done by the original assembler. If yours has the same, it would likely confirm that idea.

To get proper infinity focus: I had to ignore the etch marks.

5. By grasping the ridge of the focus assembly the focus ring was screwed to, one can adjust the focus assembly. I turned it in completely so the helicoids were bottomed out (focus assembly is collapsed)
6. Then I extended it approximately 1/16th of a turn and placed the stop ring at this location and reassembled.

Note: to make sure your focus scales end up at the top of the lens again, have the lens set against the infinity stop during reassembly. The distance scale may not read correctly, but can be turned match again.

This adjustment gave me infinity and I don't think I lost much, if anything at the minimum focus distance. I didn't purchase this lens for photos of close stuff, so I wasn't overly concerned about that anyways.

I am assuming you've had the lens apart for taking care of the wobble, or at least have heard of taking out those little L-brackets and unscrewing the helicoid. I counted 6 or so thread leads, so I suspect that if someone took that helicoid apart and back together enough, they would be able to get it matched up the same way the assembler did during manufacturing. Adjusting this ring appears to simply compensate for catching a different helicoid than the assembler did.
02-22-2017, 12:05 AM   #15
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Edit that last.
I found the takamur 400 f4 67 does not need the mounting block removed to dissassemble.
After several iterations of assembly I have finally got infinity focus with the stop to match.
The trick as suggested is to bottom out the whole helecoid and ignor the stop set makers mark to ensure infinity focus.

Some one must have dismantled in the past to attempt to get closer focus, lost one screw and broke another. Luckily the optics are sealed from the mechanicals.


Now if someone can tell me which grease to use and how to remove a broken mount screw....

Ray


QuoteOriginally posted by Sunfish Quote
Thanks for the only focus adjustment information I can find for this lense.
I bought a cheap takumar smc 400 67 and tried to dissassemble to find someone has broken off a mount screw in the sleeve. What I would like to know is how the mount screws enter the sleeve to secure the mount. They are very long and must enter the lense body under the sleeve. Do you have any images under the mount block screw holes where the sleeve is slid off.?


Regards
Ray





---------- Post added 02-20-17 at 04:52 PM ----------

Thanks for the only focus adjustment information I can find for this lense.
I bought a cheap takumar smc 400 67 and tried to dissassemble to find someone has broken off a mount screw in the sleeve. What I would like to know is how the mount screws enter the sleeve to secure the mount. They are very long and must enter the lense body under the sleeve. Do you have any images under the mount block screw holes where the sleeve is slid off.?


Regards
Ray
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