I'm trying to tell if any of the lens elements in my 50mm Sumicron Dual Range have a separation problem. How do I determine lens separation when looking through the lens?

thank you-

josiah

-- josiah (josiahmercury@hotmail.com), January 25, 2002

Answers

The separation I see in 1 of my lenses looks like shiny spots along the outer edge of the glass (when viewing the lens elements @ a slight angle, not straight on).

-- Chris Chen (Washington, DC) (furcafe@NOSPAMcris.com), January 25, 2002.

I should amend my post to clarify that the separated areas are more like irregular blobs or splotches, not little spots.

-- Chris Chen (Washington, DC) (furcafe@NOSPAMcris.com), January 25, 2002.

The separation in my 135 elmarit manifests as a "rainbow" effect around the circumference of the lens which you can see if you point the front towards the light.

-- steve (stephenjjones@btopenworld.com), January 25, 2002.

Separation can look like flakes, blobs or rainbows... Trouble is fungus can also look like flakes or blobs, and oil on the lens can look like rainbows.

:( Regards,

-- Jack Flesher (jbflesher@msn.com), January 25, 2002.

My 28mm M-lens shows very slight separation of one of the inner front elements from the mount (this element isn't cemented to another piece of glass). It's a small silvery arc about 1mm wide where the glass hits the metal, and runs about 15 degrees around the edge. Only visible from certain angles.

-- Andy Piper (apidens@denver.infi.net), January 25, 2002.

Josiah. The problem is that separation can have a number of appearances. I think most common is a white arc at the periphery of one of the lens elements (which could be a very small arc). Also can see a much more diffuse "chicken wire" type of appearance (particularly in old lenses like Summars and Xenons). It can also, as others have mentioned, be observed as an iridescent patch at the periphery of an element or a spreaging glue-like blob.

Not all lens separation needs to be repaired. There are some minor arc-type separations that remain as they are, never progress for many many years, and since they are very peripheral, do not have any noticeable effect on performance. Other forms of separation require a are very expensive repair, and some are not fixable.

To observe these, you need to look carefully, allowing a collimated beam of light (eg., pen light) to glance off the different elements as you rotate the lens. You also need to look through the lens in both directions.

But if you want to sleep peacefully, I recommend you not inspect your lenses too carefully. The first time I started studying the glass of my lenses, I was treated to a bewildering array of sights that concerned me and that I was probably better off not knowing about. Most of these are minor things that have little or no effect on image quality (only, perhaps, rsale value). The problems that do affect the image are usually not very subtle.

-- Eliot (erosen@lij.edu), January 25, 2002.

To follow Eliot's post, a lens w/separation can still perform very well--just make sure you get a discount on the price!

-- Chris Chen (Washington, DC) (furcafe@NOSPAMcris.com), January 25, 2002.

and they can easily be fixed by Leica; I used to have a 50 DR with decementing problems and Leica NJ fixed it, price wasn´t cheap.

-- r watson (al1231234@hotmail.com), January 25, 2002.

Another place to get your lens fixed, @ least if you're in the U.S., is John Van Stelten's Focal Point. He can also re-coat your lens.

-- Chris Chen (Washington, DC) (furcafe@NOSPAMcris.com), January 26, 2002.