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Rainbow stripes in element
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PostPosted: Wed Jul 29, 2020 4:43 pm    Post subject: Rainbow stripes in element Reply with quote
I recently got Nikon 35mm f/2 non AI. The glass has haze which I think I might be able to clean.
However, there are also two to three rainbow stripes/arcs on the inner elements. This is the first time
I had these of all my lenses. Anyone know what they are? Separation between elements? Or oil on the glass?

Thanks!

Just did a quick search on the internet and found it is most likely separation. Will see how if affects the image.


PostPosted: Wed Jul 29, 2020 5:17 pm    Post subject: Reply with quote
Can we see? Smile


PostPosted: Wed Jul 29, 2020 6:00 pm    Post subject: Reply with quote
Sounds like separation, which only affects contrast by lowering it, sharpness will not be affected!


PostPosted: Thu Jul 30, 2020 12:16 am    Post subject: Reply with quote
Klaus wrote:
Quote:
Sounds like separation, which only affects contrast by lowering it, sharpness will not be affected!


Klaus, it really depends. I have a 25-15 converter for my 25/1.4 Cine Ektar. Lovely thing, but the front group has strong Newton's rings all the way across. I've shot with it, got footage with rainbow strips.

vivaldibow wrote:
Quote:
Will see how if affects the image.


That's the spirit! Don't ask us what we think the lens will do, ask the lens.

Cheers,

Dan


PostPosted: Thu Jul 30, 2020 12:33 am    Post subject: Re: Rainbow stripes in element Reply with quote
vivaldibow wrote:
I recently got Nikon 35mm f/2 non AI. The glass has haze which I think I might be able to clean.
However, there are also two to three rainbow stripes/arcs on the inner elements. This is the first time
I had these of all my lenses. Anyone know what they are? Separation between elements? Or oil on the glass?

Thanks!

Just did a quick search on the internet and found it is most likely separation. Will see how if affects the image.


Most probably generally not visible, except you may see in the defocused disks of point sources of light a slight darkening in the areas where the separation occurs. Hold the lens up and look through it at a plain light colored wall. Can you see the areas of separation as slightly darker than the rest of it. If so, those areas will show up as slightly darker in defocused circles, and more strongly the more in defocused circles caused by point sources of light.


PostPosted: Thu Jul 30, 2020 10:19 am    Post subject: Reply with quote
kds315* wrote:
Sounds like separation, which only affects contrast by lowering it, sharpness will not be affected!

There is one more possible affect: I have a lens on hand with bokeh butchered by separation.


PostPosted: Thu Jul 30, 2020 1:36 pm    Post subject: Reply with quote
kds315* wrote:
Sounds like separation, which only affects contrast by lowering it, sharpness will not be affected!



danfromm wrote:

Klaus, it really depends. I have a 25-15 converter for my 25/1.4 Cine Ektar. Lovely thing, but the front group has strong Newton's rings all the way across. I've shot with it, got footage with rainbow strips.


The only lens I have showing separation is an Zeiss Opton Sonnar 2/85mm. Interestingly, there are two different separations:

1) in the front part: rainbow reflections from when looking from the front, only a slight darkening when looking from the back side (=film / sensor side).
2) in the back part: just a slight darkening when looking from the front side, but rainbow colored reflections when looking from the back (=sensor) side.

So in principle it seems that the rainbow colored reflections from the back element might pose a problem. However, there's probably not that much light reflecting from the sensor into the back element of the lens to make it a serious problem.

S


PostPosted: Thu Jul 30, 2020 9:23 pm    Post subject: Reply with quote
I have a pentax 67 105mm 2.4 that developed separation whilst sitting in its case in my den. Discovered it when selling off most of my p67 kit. Decided that with the resale value reduced by it I would just keep it. Tested I to see what difference and I couldn't find any issues in the (small sample) of photos I took with it.


PostPosted: Fri Jul 31, 2020 10:56 am    Post subject: Reply with quote
I have a Topcor rangefinder lens which shows a green/pink alternating interference pattern across the cemented front group. The pattern is seen from reflected light whether from the front and rear. I have a Sigma with the same pattern on one of the doublets in the centre of the lens and based on the images from it, I don't think it affects the image quality at all. In both cases, the pattern goes across the entirety of the elements with equal spacing. Just, strangely, on the Sigma the pattern has corners at the edge - as in the lines are not perfectly parallel all the way across, they bend slightly towards the edge of the element.


PostPosted: Sun Aug 02, 2020 4:26 am    Post subject: Reply with quote
Thanks very much everyone for your comments. I am attaching a picture showing the rainbow pattern and
a test photo taken with the lens. It is still pretty sharp. Contrast may be degraded by haze. Other
than that, I haven't really tested it. But overall, still very very usable. This lens collects nearly all the issues
that could happen to a vintage lens: haze, fungus, separation, schneideritis, choppy focus. Coming from Florida
weather, this is not unusual. Surprisingly, the front element doesn't have a single scratch. I can tell it used to be a
heavy user, which is a good thing.


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