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01-18-2011, 09:37 AM   #1
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Tamron SP 19AH 70-210mm Strange behaviour

I got this lens a few months back but never liked it simply because I cant get good pictures with it. Its not really sharp. Especially at the long end.
When I use it for macros its better but something must be off Im sure.

I did open it up in the front to see if all the glass was in place and it sure looks ok. I havnt checked the back section yet but perhaps something has happened there.

If anyone here has a clue about what it could be I would love some assistance?
Even better might be a schematic over it or at least some way for me to know that all the glass is in its right place facing the raight way.

It didnt look like anyone had been inside it before but who knows. Someomne might have and maybe misplaced one of the lenses?

Please help.


Update: This link shows the 19AH cut thru.
Seems it has 4 groups and perhaps that can narrow down my problem a bit:
What Is Inside a Zoom Lens?

I can upload pictures if that would help.


Last edited by aliasant; 01-21-2011 at 06:11 AM. Reason: Fixed the lens....
01-20-2011, 09:23 AM   #2
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I gathered what guts i could find laying around and took the lens apart again.
Found 2 different elements that faced the wrong direction so that was an easy fix.
1 lens in the compensator group and the other in the variator group.
I also modified the throw on the focus ring to gain better closeup capabilities. I gained about 5 cm throw and that got me about 30% closer. Really nice espeically on the wider range.
01-20-2011, 02:00 PM   #3
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QuoteOriginally posted by aliasant Quote
I gathered what guts i could find laying around and took the lens apart again.
Found 2 different elements that faced the wrong direction so that was an easy fix.
1 lens in the compensator group and the other in the variator group.
I also modified the throw on the focus ring to gain better closeup capabilities. I gained about 5 cm throw and that got me about 30% closer. Really nice espeically on the wider range.
Wow, that must have taken some courage to do, have you recorded the steps taken to disassemble the lens? I have one which is very clean and sharp throughout but the focusing ring is abnormally stiff. Modifying the focus throw sounds very interesting, too.

Thanks,
01-21-2011, 05:17 AM - 3 Likes   #4
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Well.

I didnt take pictures this time but I did last time I opened it and I show some of them.
Its fairly simple to clean and relube the focus ring but I have no pictures of that process right now.

If you look at the third and last picture you see an aluminum ring. That is the focus throw with a black stopper screwed onto it with 3 screws.
The black part ABOVE that aluminum part is what you need to screw off.
That contains the focusing glass and if yours stiff you might need to clean it and relube it. Use very very little lube. Almost no greese is almost to much greese.

Dont remove the 2 screws (with green plastics around them) holding the glass part inside the (I dont know the real english words for the different parts so please forgive my gibberish) main focus barrel.
Just start screwing the entire focus barrel off. Its on a thin thread just above the aluminum focus throw thing.

Once its off you will have the entire focus barrel with its glass part still inside. Clean the threads while protecting the glass and then relube carefully.

I made comments for the 4 pictures that should help too.
Find them in this album:
https://www.pentaxforums.com/forums/members/aliasant-albums-lenses.html



First remove the rubber.



Then remove the plates and tape to seperate the focus barrel from the rest. You need to be able to retape the plates later so make sure they survive.


Unscrew the black focus barrel to the right of the aluminum part.
Its on a thin thread so its hard to tell if its actually coming off but it is.
Cant remeber how many turns but perhaps 8-12 or so.
Aparently I had removed the black focus stopper in this image. Thats why you see the 3 screw holes. No need to do that now.


Heres another image were you can see both focus stoppers.
1 black and 1 brass, both held by 3 screws each.
To make the focus mod you need to remove those and replace them with homemade shorter ones.
I made two small stoppers from an old aluminum ring I had. 1 screw hole in each and then I fastened the black to the hole on the right side and the brass replacement on the hole to the left. My replacement stoppers are about 0.5 cm long and that gives me an extra 5-6 cm range. Make sure the new stoppers have smooth surfaces and are not thicker then the originals. You dont want them to scrape against anything. The focusing should be as smooth as without the mod. If it isnt something is wrong.


01-21-2011, 07:29 PM   #5
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+1 aliasant,

I'll give it a try this weekend in trying to free up the focusing ring. What did you use for lubricant, will white lithium grease be alright?

Thanks,
01-22-2011, 02:09 AM   #6
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QuoteOriginally posted by excanonfd Quote
+1 aliasant,

I'll give it a try this weekend in trying to free up the focusing ring. What did you use for lubricant, will white lithium grease be alright?

Thanks,
Yes. That would work.
Sometimes if i want something lighter I have mixed lithium grease with some WD40 and some might shake their heads now but it actually works and has held together for over a year now. Maybe that blend will fall apart soon but it doesnt feel like it.

Sometimes I just want it to be fast and smooth. Not just smooth
01-22-2011, 02:38 AM   #7
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Here are some shots that shows how much I "gained" with the focus mod.

I shot my test rack at the 70mm length at f6.3 I think. Handheld under tungsten so they might not be perfectly sharp. ISO 200 and 1/25sec

Here is with the focus max zoomed in at the original focus stop.


Here is the same shot taken with the new focus stop. Quite a bit closer.


Here is a 100% crop of the original focus stop. Not perfectly sharp.


And here is a 100% crop of the new modded focus stop. Very sharp indeed.
01-22-2011, 07:27 PM   #8
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aliasant,

The mods have worked out for you, that's great! I don't need to use the zoom lenses for macro shots so I'll be happy with smooth focus action.

Thanks,

01-24-2011, 08:17 PM   #9
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QuoteOriginally posted by aliasant Quote
Update: This link shows the 19AH cut thru.
Yes, it has four groups:

(click on the image for the source).

I found it hard to discern the elements in the cut away, maybe the above helps.

How hard is it to check the orientation of the lens elements?

My copy is great at normal distances (it can PF a bit wide open but is pretty sharp otherwise). It isn't that great at close focusing though. I have to stop it down quite a bit to eliminate halos. I've seen better shots with this lens but I guess these are crops and/or shot a high f-stop with a lot of light (e.g., additional flash), but also confirmed with another forum member that his copy is also not that great while close focusing.

I don't want to break a nice copy but am wondering how difficult it is to just check the orientation of the lens elements. How complicated is the access and is it challenging to put the lens back together (including the tape and rubber)?

I've cleaned an M50/2 and that was very easy, once I figured out a good way to remove the front ring.

P.S.: Rep. added for the great post!
01-25-2011, 04:22 AM   #10
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QuoteOriginally posted by Class A Quote
Yes, it has four groups:

(click on the image for the source).

I found it hard to discern the elements in the cut away, maybe the above helps.
How hard is it to check the orientation of the lens elements?

My copy is great at normal distances (it can PF a bit wide open but is pretty sharp otherwise). It isn't that great at close focusing though. I have to stop it down quite a bit to eliminate halos. I've seen better shots with this lens but I guess these are crops and/or shot a high f-stop with a lot of light (e.g., additional flash), but also confirmed with another forum member that his copy is also not that great while close focusing.

I don't want to break a nice copy but am wondering how difficult it is to just check the orientation of the lens elements. How complicated is the access and is it challenging to put the lens back together (including the tape and rubber)?

I've cleaned an M50/2 and that was very easy, once I figured out a good way to remove the front ring.

P.S.: Rep. added for the great post!


Hey m8.

First.
If a 50/2 lens is one of the simplest designs the 19AH is much much harder but not the hardest.
But if you are really carefull and take notes + pictures at every step you should be able to do it.
You do need proper tools though. Good screwdrivers and spanners is a must. You can take it apart without proper tools but your likely to scratch the glass and screws or even break them.
Look here for tools: Micro-Tools Europe Tools | Lens Tools
Also, if you want to take out the different elements to check its direction you have a 99% chance of getting dust and what not between the elements when you assemble them again. This is the really hard part.

Seeing the direction of the elements isnt that hard. You see it clearly when turning the lens looking at it from the side.

The best way to reassemble without getting a ton of dust into it would be to use some kind of dust safe box to work in but on the other hand. A little dust in a lens wont do anything to the IQ. Spots of grease or anything else is a lot worse. Some surgical rubber gloves or similar is good when touching the actuall glass. Use a new pair as soon as you touch something else to prevent contamination



Thers a lot to this that I havnt mentioned and Im still figuring out how to make a smooth and clean assembly. Taking apart is the easy part

About your copy of 19AH.
I think it's quite odd.
I mean, your copy is perfectly sharp at the long range and mine is the perfect opposite. Mine seems very very sharp at the wide end and "macro" is perfectly sharp but its not that great at the longer end. It gets worse the longer I go.

It might have something to do with the compensator group but thats just a wild guess.
That group moves back and forth and then back again sort of. I might remember this part wrong but if you start at the 70mm end the compensator group will be closer to the Variator Group (VG) group ( this might be the opposite way) and when you move towards 135 that group will move to the other end of its range. Closer to the Master group.
Now if you continue and move further towards the 210mm pos the group will move again towards the VG.

Is there perhaps a way to calibrate this?

Once the elements in the VG and CG are in place there isnt any room for errors. They are fixed tight in their place.
I havnt really looked at the elements in the Focus group or the Master group but I will if someone suggests it.

Heres an image of the 4 groups in this lens. The image you uploaded is a bit wrong and I tried to add to that image so its clearer what group is what and were.

Last edited by aliasant; 02-19-2013 at 10:21 AM.
01-25-2011, 04:30 PM   #11
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QuoteOriginally posted by aliasant Quote
Thanks for the link. Some of these spanner sets cost more than I paid for the lens.
For my 50/2 operation, I used a tweezer that I had bent into shape.

QuoteOriginally posted by aliasant Quote
Also, if you want to take out the different elements to check its direction you have a 99% chance of getting dust and what not between the elements when you assemble them again. This is the really hard part.
I agree. I had a hard time keeping the elements clean. I finally went near a heater with a mild stream of air.

QuoteOriginally posted by aliasant Quote
Seeing the direction of the elements isnt that hard. You see it clearly when turning the lens looking at it from the side.
Isn't the lens barrel blocking the view?
Are there sufficiently many gaps to allow judging the direction of the elements?

QuoteOriginally posted by aliasant Quote
Taking apart is the easy part


QuoteOriginally posted by aliasant Quote
I think it's quite odd.
I mean, your copy is perfectly sharp at the long range and mine is the perfect opposite.
Yes, it is a bit odd. Maybe you are right and the compensator group can be calibrated.

QuoteOriginally posted by aliasant Quote
The image you uploaded is a bit wrong and I tried to add to that image so its clearer what group is what and were.
I compared the images and I don't see anything wrong with the image I linked to, except that the compensator and variator groups are touching each other.

Thanks a lot for your reply!
01-26-2011, 02:41 AM   #12
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QuoteOriginally posted by Class A Quote
Thanks for the link. Some of these spanner sets cost more than I paid for the lens.
For my 50/2 operation, I used a tweezer that I had bent into shape. :


I agree. I had a hard time keeping the elements clean. I finally went near a heater with a mild stream of air.

Isn't the lens barrel blocking the view?
Are there sufficiently many gaps to allow judging the direction of the elements?





Yes, it is a bit odd. Maybe you are right and the compensator group can be calibrated.


I compared the images and I don't see anything wrong with the image I linked to, except that the compensator and variator groups are touching each other.

Thanks a lot for your reply!


I bought this kit from micro-tools and its pretty good. You get 2 spanners for the price of the big one + 4 ok screwdrivers:
spannerkit
I used to improvise with tweezers but that is very risky and flimsy. Spanners makes it so much easier.

To view the lenses I of course had to take them all out of their respective barrel.
This is why I changed that image. It didnt represent the different groups properly.
Each group is contained in its own "barrel" but the lenses in each barrel are seperate once you take them out.

When I first looked at the original image I already knew that there was supposed to be 4 groups.
After seeing that image I thought that the variator and compensator groups were 1 group fixed in 1 barrel and that the Master Group was 2 groups. That was not the case of course but I didnt realise that until I had taken it apart. It did confuse me a bit and I dont like being confused when I have a lens spread out in front of me

Did some simple testshooting this morning and my 19Ah is clearly weaker at the 210mm range then my comparing Viv S1 70-210 Komine version. The Vivs1 is much sharper even if the Tammy is pretty ok too.

Still hoping that someone will tell me that there is a way to calibrate this

If there is I will have to take it apart again and if so I will document it proper and post images so that you all can see.
01-26-2011, 03:08 AM   #13
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QuoteOriginally posted by aliasant Quote
Did some simple testshooting this morning and my 19Ah is clearly weaker at the 210mm range then my comparing Viv S1 70-210 Komine version. The Vivs1 is much sharper even if the Tammy is pretty ok too.
I think the Tammy should beat the Viv. Maybe there is still something wrong with your copy.

QuoteOriginally posted by aliasant Quote
If there is I will have to take it apart again and if so I will document it proper and post images so that you all can see.
That would be very cool.

Thanks for the link to the toolkit. Not sure why one would need two spanners? I've got screwdrivers like the ones included.
01-26-2011, 03:11 AM   #14
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QuoteOriginally posted by Class A Quote
I think the Tammy should beat the Viv. Maybe there is still something wrong with your copy.


That would be very cool.

Thanks for the link to the toolkit. Not sure why one would need two spanners? I've got screwdrivers like the ones included.

The spanners are quite different and I found myself using both but for different tasks. They complement eachother well.
My 19AH still have problems for sure. I posted a quick and dirty test at the Tammy thread.
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