Kiron 28 f2 - focusing issues

**pres589** · 01-20-2023, 11:14 AM

Something seems wrong with the focusing mechanism on my Kiron 28 f2. The focusing ring doesn't seem to be so well affixed to the helicoid mechanism. There's areas in the rotation of the ring where changing ring position doesn't change focus, and it isn't consistent. It's also way out of calibration, where an object 20 feet away is in focus at 1 or 2 feet on the ring (it changes as I rack through focus).

Is there a walk-through or manual for breaking down this lens and properly taking the focusing mechanism apart? I don't want to just charge into this if I can help it and my level of experience working on lenses is pretty low. I also doubt this lens is worth sending to a technician for working on as it can't be worth more than $100 or so in good condition. I like the lens but I don't love it enough to spend more than it is worth to buy something else and right now it's not great to use.

**marcusBMG** · 01-20-2023, 11:42 AM - **1 Like**

I have posted some info on this lens:

Kiron/Vivitar 28mm f2 (24mm f2) sticky iris fix - PentaxForums.com

My guess is IIRC that you just need to tighten the screws holding the focus/distance ring.

**pres589** · 01-20-2023, 02:12 PM

Originally posted by marcusBMG

I have posted some info on this lens:

Kiron/Vivitar 28mm f2 (24mm f2) sticky iris fix - PentaxForums.com

My guess is IIRC that you just need to tighten the screws holding the focus/distance ring.

That is a useful thread. There's the screw in the inner barrel next to where the serial number is painted onto the lens. Are you referring to that screw, which is shown in a picture in that thread? Any other screws I should check?

**marcusBMG** · 01-20-2023, 03:21 PM - **3 Likes**

That grub screw needs to be loosened to allow you to unscrew the front end. Then you will be able to see the 3 screws that hold the focus ring/distance scale ring. You will need a very small jewellers/modellers screwdriver (I have a cheap modellers screwdriver kit and filed down the smallest flathead bit) or eg a Starrett. A drop of nail varnish remover is good to soften any thread locker. It takes feel to get these small screws, carefully apply turning pressure while pressing very firmly to engage the screwdriver in the slot. You do not want to break the top end of the screw! If it's stubborn try warming it up with a hair dryer or hot air gun.

Last edited by marcusBMG; 01-20-2023 at 04:18 PM.

**pres589** · 01-20-2023, 04:19 PM

That was so helpful! The grub screw was annoying to deal with as it's so small that I found it hard to see if I was properly engaged with it. Two of the three screws that affix the focusing ring to the rest of the focusing mechanism were slightly loose, like 10 degrees of rotation to get them snug again loose, but it works. And the focusing distance on the ring seems accurate where I have it assembled so I'm good there.

Looking forward to using this lens tonight! Thanks again!

**marcusBMG** · 01-21-2023, 02:28 AM - **1 Like**

you're welcome

Not a Number · 01-21-2023, 03:26 AM

Kino lenses often are over-engineered which people love but make them difficult to work on.

01-20-2023, 11:14 AM	#1
pres589 Site Supporter Join Date: Jan 2014 Location: Wichita, KS Photos: Albums Posts: 4,529	Kiron 28 f2 - focusing issues Something seems wrong with the focusing mechanism on my Kiron 28 f2. The focusing ring doesn't seem to be so well affixed to the helicoid mechanism. There's areas in the rotation of the ring where changing ring position doesn't change focus, and it isn't consistent. It's also way out of calibration, where an object 20 feet away is in focus at 1 or 2 feet on the ring (it changes as I rack through focus). Is there a walk-through or manual for breaking down this lens and properly taking the focusing mechanism apart? I don't want to just charge into this if I can help it and my level of experience working on lenses is pretty low. I also doubt this lens is worth sending to a technician for working on as it can't be worth more than $100 or so in good condition. I like the lens but I don't love it enough to spend more than it is worth to buy something else and right now it's not great to use.

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01-20-2023, 11:42 AM - 1 Like	#2
marcusBMG Site Supporter Join Date: Nov 2012 Location: North Wales Photos: Gallery \| Albums Posts: 2,869	I have posted some info on this lens: Kiron/Vivitar 28mm f2 (24mm f2) sticky iris fix - PentaxForums.com My guess is IIRC that you just need to tighten the screws holding the focus/distance ring.

01-20-2023, 02:12 PM	#3
pres589 Site Supporter Join Date: Jan 2014 Location: Wichita, KS Photos: Albums Posts: 4,529 Original Poster	Originally posted by marcusBMG I have posted some info on this lens: Kiron/Vivitar 28mm f2 (24mm f2) sticky iris fix - PentaxForums.com My guess is IIRC that you just need to tighten the screws holding the focus/distance ring. That is a useful thread. There's the screw in the inner barrel next to where the serial number is painted onto the lens. Are you referring to that screw, which is shown in a picture in that thread? Any other screws I should check?

01-20-2023, 03:21 PM - 3 Likes	#4
marcusBMG Site Supporter Join Date: Nov 2012 Location: North Wales Photos: Gallery \| Albums Posts: 2,869	That grub screw needs to be loosened to allow you to unscrew the front end. Then you will be able to see the 3 screws that hold the focus ring/distance scale ring. You will need a very small jewellers/modellers screwdriver (I have a cheap modellers screwdriver kit and filed down the smallest flathead bit) or eg a Starrett. A drop of nail varnish remover is good to soften any thread locker. It takes feel to get these small screws, carefully apply turning pressure while pressing very firmly to engage the screwdriver in the slot. You do not want to break the top end of the screw! If it's stubborn try warming it up with a hair dryer or hot air gun. Last edited by marcusBMG; 01-20-2023 at 04:18 PM.

01-20-2023, 04:19 PM	#5
pres589 Site Supporter Join Date: Jan 2014 Location: Wichita, KS Photos: Albums Posts: 4,529 Original Poster	That was so helpful! The grub screw was annoying to deal with as it's so small that I found it hard to see if I was properly engaged with it. Two of the three screws that affix the focusing ring to the rest of the focusing mechanism were slightly loose, like 10 degrees of rotation to get them snug again loose, but it works. And the focusing distance on the ring seems accurate where I have it assembled so I'm good there. Looking forward to using this lens tonight! Thanks again!

01-21-2023, 02:28 AM - 1 Like	#6
marcusBMG Site Supporter Join Date: Nov 2012 Location: North Wales Photos: Gallery \| Albums Posts: 2,869	you're welcome

01-21-2023, 03:26 AM	#7
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	Kino lenses often are over-engineered which people love but make them difficult to work on.