Remove front coating? Rolleiflex 2.8E

[m m]

It looks like I'm about to acquire a Rolleiflex 2.8E with an 80/2.8 Xenotar. The taking lens' front element

coatings are terribly worn, and my trusty technicians say it would be best to remove them altogether, and I

completely agree. I'm wondering though, what good does the coating do on the outside of the front element

anyways? As long as the internal coatings are intact, what does it matter if a bit of light reflects

<em>away</em> from the front element? It seems to me that this should not contribute to any flare at least. Is

the external coating just "advertising", or am I missing something?

 

Thanks!

[blaise_duchemin]

<p>Hi,<br /> It looks like we have the same camera and ... the same problem.<br /> I don't know what the extent of the damage on yours. Mine is apparently not that bad but I am still going to go for it. My camera is currently at the repair shop (for other issues) and I am expecting a quote.<br /> <a href="../medium-format-photography-forum/00YArC">That is the thread I have started about recoating / polishing my lens, you will find some interesting insights there.</a><br /> The conclusion was in favour of a "simple" polishing. As you underlined the external coating of the individual parts is enough.</p>

[bob_sunley]

<p>Well you lose some light transmission, a few percent, but otherwise no real problems with flare, unless you have a filter on the front. That could increase the flare compared to a coated front side.</p>

[m m]

Bob: I did not think of that. I'm actually buying two Rollei's. Maybe the one with coating ttrouble should be my color camera (no filters), and the nice 3.5 Planar will be my B&W machine. Thanks for the insight!<br><br>

 

blaise: Thanks also for the link. btw, I spoke with Focal Point today, and they said it's $225 for a polish and re-coat. Same price for sending in the front group only, or the whole camera. So, my plan is to have the coating removed and shoot with it for a while, and then I can always have it re-coated later without any additional labor cost. Can't remember who I spoke with, but he was very helpful and knowledgeable. <br>

<br>

My front element looks just like yours. I have to say, from the front, it didn't look too terribly awful, but when I looked through the lens from the film side, and aimed it at a light source, it looked like I was looking through the surface of a frozen lake. Not so good!

[q.g._de_bakker]

<i>" I'm wondering though, what good does the coating do on the outside of the front element anyways? As long as the internal coatings are intact, what does it matter if a bit of light reflects away from the front element? It seems to me that this should not contribute to any flare at least. Is the external coating just "advertising", or am I missing something?"</i><br><br>Light is reflected from every surface it encounters that presents a change in refractive index. So when it passes through the front lens' front surface and hits the front lens' rear surface, part of it is reflected back to the first surface. When the reflected light hits that on its way out, part of it will be reflected back into the lens again. Light reflected off surfaces deeper in the lens will eventually meet the front lens' front surface too. So having a coating on that (and the rear lens' rear surface) certainly helps as much as a coating on any other surface in the lens.

[m m]

Oooooh. So, if I understand you correctly: light reflects back, sort of, off of the air as much as off of the glass. So, the transition is what really matters. That makes sense! Thanks.

[sobing_lee]

<p>I have similar experience . I have a Segull 4B TLR, viewfinder lense is 3 elements the middle one's coalting has remove by me using compound 2000 mix with toothplase.the effect is a bit reflect in viewfinder not big problem.<br>

In othe case I have a sigma zoom lens for OM system . I Have replace the real element ,since was broken .I use a no any coalting plastic lens (should be know degree frist,and find the midle point) the effect the colour tone was change.<br>

:P</p>

[dave_s]

<p>If the coating is just worn or discontinuous, and not cloudy or opaque, I would leave it alone, unless your 'trusty technicians' includes someone like Harry Fleenor. I wouldn't horse around with it unless I knew there was a significant problem. </p>

<p>It sounds like you haven't put any film through the camera yet, so test first. Shade your lens well and I bet you'll be happy with the results. </p>

[tom_cheshire]

<p>Dudes, think about it. Lens coatings are the dried vapors of metals. You want to remove the coating just get a tube of metal polish. That creamy stuff like Simichrome or Blue Magic. It has saved at least one hopeless lens on a Yashica 124G of mine.</p>

[photo5]

<p>My 1950 Rolleiflex has a coating that is missing on the left 1/4 of the front element. I have thought of removing the rest of it, but then, haven't seen any problems in my photos. I know if I were to sell it (which I don't plan to) I'd want to remove it, but I wouldn't attempt it myself for fear of damaging the lens itself in the process.</p>

[rodeo_joe1]

<p>"You want to remove the coating just get a tube of metal polish." - Tom, I sincerely hope that was meant as a joke. That sort of cavalier attitude to lenses is probably what caused the coating to disappear in the first place. Lens coatings are not metal, they're insoluble fluoride salts that have been evaporated at high temperature onto the glass surface, and the only way to remove them is by mechanical abrasion, which is exactly what metal polish does and in a very crude way. Do you have a Hepa-filtered cleanroom to prevent minute particles of grit getting into the cleaning process? Or a polishing machine that applies an even abrasion across the whole surface of the lens? Does the polish you're going to use have a known and certified particle size and hardness? Probably not.</p>

<p>Coatings don't just fade away, they're usually worn away by over zealous cleaning. And if part of the coating's gone, then the chances are that the underlying glass is covered with a myriad of tiny scratches too. Just removing the rest of the coating will do more harm than good unless the whole front element is going to be repolished and recoated. This is not a job for your average repair shop (especially one that appears to know so little about optics), but a dispensing optician might have the necessary equipment and expertise. Spectacle lens coating is fairly routine these days, even multicoating. So if you don't care about complete authenticity it may be possible to get the front element repolished and multicoated professionally for a reasonable cost. The Xenotar has a cemented pair as a front cell IIRC, so there may also be some risk of the polishing process separating the elements. Consult a proper optical workshop before doing anything - not a screwdriver and spanner merchant.</p>

[brett_rogers]

<blockquote>

<p><em>The Xenotar has a cemented pair as a front cell IIRC, so there may also be some risk of the polishing process separating the elements.</em></p>

</blockquote>

<p>There's a lot of discussion about the construction of the various Rolleiflex lenses <a href="http://www.freelists.org/post/rollei_list/How-rare-is-a-Rollei-with-a-Biometar">here</a> (you will have to wade through all the replies to find the pertinent details) including that of the rare Biometar 2.8 design. As far as I can recall, the Xenotars have an advantage if they need recoating (and it seems, they often do) because the front cell is a single piece of glass, not a cemented pair, unlike the 2.8 Planars fitted to Rolleiflex TLRs.</p>

[rodeo_joe1]

<p>Yes, my memory let me down on the construction of the Xenotar. The cemented pair is the inner cell, so that makes repolishing and coating the front element a better proposition.</p>