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12-27-2012, 02:16 PM   #1
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Tamron 400 mm

I'm not sure if this is the correct forum for this post - if not please tell me where.

I found a Tamron 400 mm lens in the garage the other day. It was my father's lens and I had forgotten all about it. I wonder if anyone has any experience with it? It's a screw mount with a 40 mm outer thread. My dad used mostly Pentax cameras and I'm wondering how he used this one. Is there an adaptor available? Looking through the lens though, I can see that the blades are either damaged or have lost their linkage with the aperture ring. Can a lens be repaired? Or probably more to the point, would it just be cheaper to buy a new equivalent?



12-27-2012, 02:25 PM   #2
Ash
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Others will have more experience than me with this lens, but an image of its mount would greatly help with working out how it can fit onto a Pentax camera.
Also show us how the aperture blades are defective. It may well be repairable, but it depends how much you value the lens and what it could do for you. 400/6.8 is not very fast and I wonder how sharp this lens would be in its prime. Probably not worth as much as how much it would cost to repair it.
12-27-2012, 03:01 PM   #3
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QuoteOriginally posted by Ash Quote
Others will have more experience than me with this lens, but an image of its mount would greatly help with working out how it can fit onto a Pentax camera.
Also show us how the aperture blades are defective. It may well be repairable, but it depends how much you value the lens and what it could do for you. 400/6.8 is not very fast and I wonder how sharp this lens would be in its prime. Probably not worth as much as how much it would cost to repair it.

Ash, thanks for replying. Here are some images you requested:

The screw mount. It's a male mount with 40 mm outer diameter.


Blades. Notice how the opening is not circular.


Another shot of the blades after rotating the aperture ring a little. There are two distorted openings.


You're probably right in that it wouldn't be worth the repair bill, but I'd be curious to learn something about this lens.
12-27-2012, 05:23 PM   #4
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40mm sounds odd. Pentax screwmount should be 42mm. They also had an earlier 37mm mount but I don't think that lens is old enough.

If it is m42 then all you need is an m42 to K mount adapter and you are good to go. Read here on how to use it with k-mount: https://www.pentaxforums.com/forums/pentax-beginners-corner-q/110658-using-ma...x-dslrs-f.html

When you turn the aperture ring do the blades open and close? The image is hard to tell but it looks like you have at least one blade that is not attached to the mechanism. I doubt it would cost much to repair, assuming all the parts are there. However, beyond sentimental value I do not think it will be worth much.

One other possibility is that it is missing the mount adapter portion of the lens. Many lenses of that era were built so that the camera mount threaded onto the back of the lens, they could stock one lens and multiple mount adapters. If it is indeed 40mm then that is a strong possibility, but I think it more likely that it was m42 especially if your dad used Pentax.

12-27-2012, 05:40 PM   #5
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There is also m39 mount, but it is usually on Soviet lenses.
What exactly are the markings on the lens? Just "Tamron 400mm"? You can try finding it on ebay, see what its mount/adapter looks like and how much it is worth.
I lens like that might not produce great IQ, but I'd keep it, just for fun if nothing else. Repair costs will depend a lot on who is doing the repairing (and what exactly is wrong, of course). And 400mm is an interesting focal length to have
12-27-2012, 05:43 PM   #6
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QuoteOriginally posted by jatrax Quote
40mm sounds odd. Pentax screwmount should be 42mm. They also had an earlier 37mm mount but I don't think that lens is old enough.

If it is m42 then all you need is an m42 to K mount adapter and you are good to go. Read here on how to use it with k-mount: https://www.pentaxforums.com/forums/pentax-beginners-corner-q/110658-using-ma...x-dslrs-f.html

When you turn the aperture ring do the blades open and close? The image is hard to tell but it looks like you have at least one blade that is not attached to the mechanism. I doubt it would cost much to repair, assuming all the parts are there. However, beyond sentimental value I do not think it will be worth much.

One other possibility is that it is missing the mount adapter portion of the lens. Many lenses of that era were built so that the camera mount threaded onto the back of the lens, they could stock one lens and multiple mount adapters. If it is indeed 40mm then that is a strong possibility, but I think it more likely that it was m42 especially if your dad used Pentax.
jatrax, it's probably 42 mm if that's a known Pentax mount. I measured the cap and I could see how it could be 42 instead of 40.

When I turn the ring (0r rings, see below), the blades do attempt to open and close but there is some sort of control problem, with the aperture ring on the lens not providing much control over the blades. There are two rings at the "aperture location" for want of a better term. In the original photo above you can see a knurled ring below the DOF indicator line with aperture values on the ring (this ring is smooth where the numbers are etched). Then there is another thinner ring below that. Both move separately, and the thinner ring seems to have more control over the blades. I don't know why there should be two decoupled rings controlling the lens aperture and I suspect that this decoupling is part of the problem.

As ash pointed out, a 400 mm/6.9 is pretty slow and not likely to be a top quality lens.
12-27-2012, 05:46 PM   #7
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QuoteOriginally posted by Na Horuk Quote
There is also m39 mount, but it is usually on Soviet lenses.
What exactly are the markings on the lens? Just "Tamron 400mm"? You can try finding it on ebay, see what its mount/adapter looks like and how much it is worth.
I lens like that might not produce great IQ, but I'd keep it, just for fun if nothing else. Repair costs will depend a lot on who is doing the repairing (and what exactly is wrong, of course). And 400mm is an interesting focal length to have
Na Horuk,

The lens markings say
TAMRON f = 400 mm 1:6.9 No. 45768
Other than that, just the aperture and focus/DOF inscriptions.
I might take it into a shop and see what they say, but I'll probably just hang onto it in case someday old lenses become a trendy thing among the idle rich to collect.
12-27-2012, 06:14 PM   #8
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QuoteOriginally posted by GeoJerry Quote
Both move separately, and the thinner ring seems to have more control over the blades. I don't know why there should be two decoupled rings controlling the lens aperture and I suspect that this decoupling is part of the problem.
Two aperture rings is fairly common during that time period. You set the desired aperture with one ring and then use the other ring to open and close the aperture to the limit set by the other ring. This was before automatic aperture so stopped down the viewfinder would be very dark. The dual ring (or preset lens) option allowed you set say f/11 but focus as if the lens was wide open, then stop down to the shooting aperture. This was replaced in later m42 lenses with an auto-aperture system that only worked with some cameras and by the time k-mount came along the norm was auto-aperture.

12-27-2012, 06:58 PM   #9
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Be careful of what you try to screw it into...

It is most likely a T-Mount lens. The T-Mount has a thread diameter of 42mm, just like M42, but a thread pitch of 0.75mm instead of 1mm for M42.

You should be able to acquire a K-mount T-ring for a few dollars. Like this:

T2 T Mount T Ring Adapter for Pentax K PK K 7 K x K20D | eBay

Two aperture rings is perfectly normal for a preset lens, which all T-Mount lenses are.
12-27-2012, 07:01 PM   #10
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jatrax, boriscleto,

Thanks for the info on the technical details. I learn something new on this blog everyday it seems. I hadn't ever heard of the dual aperture ring system.
12-28-2012, 02:56 AM   #11
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I have an old Tamron 400m f/5.6 and definitely M42 ... so they made them ... and then later on Spiratone made copies as well.,

This looks older than mine though looking at the lens.
12-28-2012, 04:29 AM   #12
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I have a manual preset Tamron 400/6.3 that looks about the same, altough not identical to tis one.
It has a T-mount with a PK-adapter. Mine is light to carry and in good condition, and takes OK pictures wide open.

Seb.
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