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Fogged rear elements (Soligor 105mm/2.8)
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PostPosted: Mon May 20, 2019 3:10 pm    Post subject: Fogged rear elements (Soligor 105mm/2.8) Reply with quote

I recently picked up a Soligor 105/2.8 (a small T2 mount telephoto) despite the rear group being so badly fogged you could hardly see through the lens. I thought the issue was balsam separation, but on attempting to clean it I found the group was actually an air spaced doublet.

Quick efforts cleaning it with the usual solvents (iso-propanol, iso-octane & acetone) have improved matters, to the point where it can be used, but it's still badly fogged. Can anyone suggest other approaches to cleaning these elements?

In the meantime I've tried the lens without the rear group and found with some extension it works pretty well! It appears to be roughly 200mm with the rear group missing, and the only problem on a quick check was increased CA, noticeable after zooming in on the cameras display. My helicoidal MFT-M42 adapter has just enough extension to bring infinity focus to the right region so with it mounted on this I can use it at 105mm (with the rear group) or 200mm (without the group). As the lens itself is considerably smaller than any of my 135mm or longer lenses it could become the missing telephoto for my smallest camera bag Smile

The serial number of mine is H346xx which doesn't seem to fit any of the formats on the soligar serial numbers list, any guesses on the manufacturer?

It has an orange rhombus (& green numbers) on the preset ring, just an orange triangle on the aperture ring.
White metric distances & orange imperial ones on the focus ring, white DOF makings with a thin red line at the centre.
The name ring has 'Soligor' in italics, followed by '1:2.8 F=105mm MADE IN JAPAN'...


Last edited by DConvert on Wed May 22, 2019 7:59 pm; edited 1 time in total


PostPosted: Wed May 22, 2019 7:58 pm    Post subject: Reply with quote

Here's a shot with the rear group:
#1


And this is with the group removed & a little extension added to allow focus:
#2


PostPosted: Thu May 23, 2019 3:33 pm    Post subject: Re: Fogged rear elements (Soligor 105mm/2.8) Reply with quote

DConvert wrote:
In the meantime I've tried the lens without the rear group and found with some extension it works pretty well! It appears to be roughly 200mm with the rear group missing, and the only problem on a quick check was increased CA


Before WWII that was quite normal, many lenses were made for that usage. You could screw out half of it and use that half as a telephoto lens. CA were no problem because there was B&W photography only.

But the Soligor probably was not made for being used in that way ...