Disassembling the Tamron Adaptall-2 SP (13A) 24-48mm ?

Herbert · Joined: 07 Sep 2023 Posts: 26

Dear Friends,
I am forced to use 82mm filters on my Panasonic S5 DSLR which was modified to full spectrum.
Using filters, I can film and photograph in visible light as well as in infrared.
I use 82mm because the filters are expensive and I use Canon FD lenses only.
With step up rings I can use one filter on my canon FD lens collection.

But the Tamron 13A 24-48 is special.
Only 77mm filters can be used with the lenshood attached.
I have none and even if I had, there would be no room in the hood for stepping up to 82mm.

There are engravings inside the lens barrel one could misinterpret as a thread for 57mm Filters.
In fact, the inner diameter is 57,2mm, and the thread-like recess of the the profile
inside the hood might widen the diameter to 58mm.
The outer thread of a 57mm step up ring has a diameter of 57.75mm.
So maybe, with a lot of force, a step up ring could be pressed into the tulip.

Obviously, no one wants to put his zoom lens into a vice.
Therefor I would need advice or a service manual to find out whether the 24-48 can be safely disassembled.
It looks like the the tulip and barrel / tube are one part - does anyone know whether the barrel
already guides the front elements or is it "only" the enclosure withot crucial mechanical function?

Many thanks to all, all the best,
Herbert

RokkorDoctor · Expire: 2025-05-01

I wouldn't "force" anything TBH.

Having seen on-line images of the lens with the original bayonet fit hood, my first thought is that if you (somehow) mount a step-up ring on the integral fixed vestigial tulip "hood", you'll get significant vignetting in the corners on a full-frame camera like the S5. There is a reason those small cut-outs are there.

Herbert · Joined: 07 Sep 2023 Posts: 26

Many thanks, I thought about „forcing“ because of this post:
http://forum.mflenses.com/tamron-sp-24-48-13a-t76512.html
No description of vignetting there. I also do my work in 16/9 and 16/10, so chances of vignetting are lower, but I‘ll check next week.
Again, any advice and service manual are welcome.
All the best, Herbert

RokkorDoctor · Expire: 2025-05-01

Well, those vestigial tulip hoods as found on extreme wide-angles and fish-eye lenses usually don't have a proper thread; it is a shallower thread (if a helical thread at all) and with a finer pitch than a filter thread.

If I were you, I would try and find a 72-82 or 77-82mm step-up ring, whichever works best , and fit some DIY bayonet mount on that so that it clips onto the lens similar to the original hood.

A bit of plasticard surgery and some adhesive maybe.

Herbert · Joined: 07 Sep 2023 Posts: 26

Many thanks,
but I knew about the thread before starting this thread Smile

. The tulip also recesses too much into the focus barrel for plastic card surgery on the outside. Using/modifying the original lens cap might work. But too flimsy.
This is why I want to press in a step up ring-if the tube can be safely dismantled.
Another way could also be to grind
down the thread of the 57mm part
until there is a 0.1mm or less difference in the diameters. So that the step-up ring “clicks” in. So less force needed. But I will need to check for vignetting in 16:9 on Tuesday. Service manual still appreciated. All the best, Herbert

Herbert · Joined: 07 Sep 2023 Posts: 26

The starter of this thread

http://forum.mflenses.com/tamron-sp-24-48-13a-t76512.html

answered my PM, how the step up ring was attached back then:
„I still have the lens and the filter ring is still hanging on!
I guess its just jammed in place.“
What I want, it can stay there.
So, it somehow can „work“, though the profile inside the tulip is not a thread. Tamron claimed the profile diffuses reflections.

Herbert · Joined: 07 Sep 2023 Posts: 26

I held a 58-82 mm step up ring in front of the lens,
no vignetting at 24mm at 3:2 and 16:9.
So, it could be permanently "jammed on".
Question is whether to invest into a more expensive brass ring
as those are said lo be smoother for changing filters and more durable...?
Again, I am looking a service manual for 24-48 / 13A.
Any advice?
All the best,
Herbert