[rollei_list] Re: Zeiss Tessar 15cm F4,5 Compur

  • From: "Peter K." <peterk727@xxxxxxxxx>
  • To: rollei_list@xxxxxxxxxxxxx
  • Date: Sun, 28 Feb 2010 11:41:11 -0800

Bingo. I saw the knurled ring and was able to easily separate them and clean
it. The lens is very clean.

Hey if anyone is interested, make an offer. I have pics I can email
privately if you like.

On Sat, Feb 27, 2010 at 8:10 PM, Richard Knoppow <dickburk@xxxxxxxxxxxxx>wrote:

>
> ----- Original Message ----- From: "Gene Johnson" <genej2ster@xxxxxxxxx>
>
> To: <rollei_list@xxxxxxxxxxxxx>
> Sent: Saturday, February 27, 2010 4:59 PM
>
> Subject: [rollei_list] Re: Zeiss Tessar 15cm F4,5 Compur
>
>
>  Just like Richard says,and it really does make a world of difference.
>> Something really cool about some of these old uncoated lenses. I have a
>> few
>> I just love. But they do tend to get a fog of some sort, and cleaning it
>> off
>> is easy and gets them back to original performance, which in some cases is
>> pretty darn good.
>>
>> Gene
>>
>
>   I've found haze on many lenses not just very old ones. some were coated.
> I don't know what causes it. Its not from lubricant because its on surfaces
> that are isolated and sealed. I think it may be from the paint used to coat
> the insides of the cells to make them antii-reflective. Its possible that
> something remains volitile even though the mounts are proably baked. It
> could be from the glass itself but I think being coated would affect that.
> Not all lenses have it.
>   I've found the best way to detect it is simply to shine a flashlight
> through the lens and look from the other side. Even slight haze will become
> apparent this way. I've found that even slight haze has a profound effect on
> lens contrast. I suspect one reason that older, uncoated, lenses are
> supposed to be high flare is actually due to this haze, although, as I said,
> its also to be found inside coated lenses.
>    The flashlight trick will also show up faults in cemented surfaces.
> While we are all familiar with the yellowing ring of oxidized Canada Balsam
> on old lenses there can also be problems wtih synthetic cements. They can
> separate into what looks like large bubbles between the elements but also
> can become hazy. I've found the latter on a couple of Kodak lenses. Under
> the flashlight test the cement can be seen to have a textured look something
> like an orange peel. Shining the light obliquely onto the lens surface will
> also show this up. You may need to use a magnifier to see it. The results,
> as one would expect, is a serious destruction of lens contrast, even more
> than caused by the haze. Unfortunately, the only cure for cement problems is
> to recement the elements.
>
>
> --
> Richard Knoppow
> Los Angeles, CA, USA
> dickburk@xxxxxxxxxxxxx
> ---
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-- 
Peter K
Ó¿Õ¬

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