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LENSTORATION: Tamron Adaptall 38-100mm f/3.5 (CZ-38M) No Infinity and Stuck Aperture Blades

Tamron Adaptall 38-100mm f/3.5 (CZ-38M) No Infinity and Stuck Aperture Blades
Tamron Adaptall 38-100mm f/3.5 (CZ-38M) No Infinity and Stuck Aperture Blades



05 September 2017

The Tamron Adaptall 1 38-100mm f/3.5 has 2 versions. The later version that I have has a model number of 'CZ-38M'. It's easy to derive that the model number means 'compact zoom, 38mm macro'. This RARE and beautiful constant maximum aperture zoom lens has mostly single coated amber-colored glass, but one element inside has reflection that shows cobalt blue color.


My copy was picked up from Post Office NIA yesterday. It looked fine on the outside with need for a little cleaning to make it look clean and new. Two things: it doesn't focus to infinity at 38mm, and the aperture blades are stuck wide open. There is also huge dent on the filter thread.

I took care of the dent first, which was easily fixed. A little dent still remained. However, I went to bed weeping because I couldn't get the front elements out due to the dent.

Today is the day I'm supposed to go out to take gather some sample shots with my Petri 55mm f/1.8 (TOKINA) and the new Tamron Adaptall 38-100mm f/3.5, but I stayed home to fix this instead.

So today, after many tries and failures and almost giving up, miracles seem to happen every time we arrive at a dead end where it becomes impossible to go on due to some impossibly stuck parts. So I decided to finally have the item returned, but the cheapest shipping was P2,000 through the Post Office. So fuck it, that option is out. Our only choice is to persevere and be determined to solve this problem!

A little wiggling here and there, and a little more perseverance and things were suddenly looking bright. Another problem pops up... the images look blurry and glowing! My goodness, I'm sure I mixed up the order of the elements in the third group. So I have to open up the impossibly tight mechanisms again (owgad) to correct this.

Before I put things back together, I cleaned the glass then painted the edges with black paint to help boost the contrast and reduce internal reflections (that's why you see alot of glasses painted black on the sides/edges). There is a noticeable improvement because the images don't glow anymore when I point the lens to my laptop screen.

The last thing I did made everything clear to me -- the rear group was in the wrong position and was screwed too near into the lens. To derive that the rear group was the main cause of all my troubles, I unscrewed it bit by bit so that when the lens is mounted to the camera, that rear group of glass sits closer to the sensor than before.

That trick did it. Looking back again, I laugh at myself how much trouble and tears I went through when it was just the rear group alone that's been the cause. Now I'm looking forward to go out tomorrow and do my test shots in the field.

The huge dent here is what makes it impossible for the front group of elements to be removed.

The lens does not seem to focus to infinity at 38mm.

Upon looking inside, why does the aperture blades not fully retract at the widest aperture? I loosed up those screws a bit to be able to rotate the whole plate clockwise. This will pull the aperture blades to its correct position.

The aperture blades can now close when I removed the rear group of elements. When I screwed it back, it got stuck again. So we derive that it shouldn't be sagad. So this also unwittingly solves another problem -- now we can focus to infinity at 38mm!

Most of the glass elements do not have blackened edges. So naturally, I would paint them to minimize internal reflections and improve contrast and flare control. From left to right are the front group to the rear group. Each group consists of several glass elements inside.
Group 1 (front) = 3 elements
Group 2 = 2 elements
Group 3 = 2 elements
Group 4 (rear) = 3 elements
Overall there are 10 elements in 4 groups.


Why blacken the edges of your lens element?




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