Lens spots

[truls]

I sometimes see cameras at auctions having slight marks on them. Could someone explain how these spots occur and if it would affect picture quality in color or black and white?

Here is an example from Industar 26M on a Fed2 - the spots are clearly seen:

[hansz]

Hard to say, from the photograph alone.
It might be (induced) imperfections of the coating, which is generally speaking not too bad; it might be signs of fungus, which is - most of the times - BAD.

Most favourably, they are just reflections - which in the case above, I doubt.

Only in close examination you can tell, so , whwn in doubt, don't buy it, or agree on a refunding scheme...

Hans

[daveh]

Small chips/imperfections can be painted out with matt-black. The lens just becomes slightly slower than it would be.

Old (very old) lenses would sometimes have air-bubbles in the glass but they still seemed to function.

[lloydy]

I think that looking for, and expecting, perfection in an old lens is like herding cats. It ain't gonna happen.

I've got lenses with fungus, the real bad ones make a difference to the image but most don't ( and I have 2 copies of some lenses with 'average' fungus and I really can't see any difference in the final image ), lenses with bubbles in the glass. That makes no difference at all as far as I can see ( but what do I know ) and more than one lens with 'unexplained marks'. I haven't got a clue what they are, often they don't scrub off, but again I don't see degradation of the image that I can put down to the 'defect' on or in the glass.

I appreciate that it's nice to have clean glass, it's why I have 2 copies of a few slightly fungused lenses. But....guess which lenses I actually use when I'm out taking pictures. The mint lenses or the fungused ones? When I'm out in the elements, in the woods and up hills I take the cheap lens and leave the expensive ones in the display cabinet. Do I notice the difference in the final image? No.

[Berndt]

Truls, I might be blind or stupid, but I can't see any clear "spots" at your picture. You mean this purple blotches ? Maybe some defect in the coating ? Hard to tell from the picture.

I've got lenses with fungus, the real bad ones make a difference to the image but most don't

From what I noticed, much depends on the light here. Fungus infected lenses don't like backlight. Pictures can get pretty milky then and the wider the lens is open, the stronger becomes this effect. At "normal" light and medium apertures, you are right - the difference can often not be seen.

However, apart from the experiences in my thread "lens cleaning", it isn't always that nasty. I got the most ( often pretty dirty ) lenses on used cameras cleaned very easily ( especially folders and TLRs, where the lenses are pretty easy to disassemble ). More modern lenses, especially zoom- and telephoto ones often require advanced skills in taking them apart though. If those are showing signs of fungus, they are mostly just junk.

Scratches and bubbles do mostly not affect the picture quality at all.

I take the cheap lens and leave the expensive ones in the display cabinet.

I often do the same

[col]

I don't want perfection

[col]

Some weeks back I purchased a little French 127 camera, the front of the lens looks like it has been cleaned with a saucepan cleaning scourer.. After taking some snaps one thing was clear... results look fantastic really old world ..that's if you like very soft pictures.

[lloydy]

Sept 30, 2012 20:12:49 GMT -5 col said:

I don't want perfection

I think that's one of the joys of using old lenses and cameras, not looking for perfection in the final image, but instead looking for an image that is as good as it can possibly be. The slight softness of a moderately fungused or marked lens can very often be corrected in the digital post process, and possibly even in a traditional darkroom?
I've got lenses with elements that have bubbles, they got through the quality control of the day. Can they be that bad?

[Deleted]

Sept 30, 2012 16:49:20 GMT -5 lloydy said:

I think that looking for, and expecting, perfection in an old lens is like herding cats. It ain't gonna happen.

I've got lenses with fungus, the real bad ones make a difference to the image but most don't ( and I have 2 copies of some lenses with 'average' fungus and I really can't see any difference in the final image ), lenses with bubbles in the glass. That makes no difference at all as far as I can see ( but what do I know ) and more than one lens with 'unexplained marks'. I haven't got a clue what they are, often they don't scrub off, but again I don't see degradation of the image that I can put down to the 'defect' on or in the glass.

I appreciate that it's nice to have clean glass, it's why I have 2 copies of a few slightly fungused lenses. But....guess which lenses I actually use when I'm out taking pictures. The mint lenses or the fungused ones? When I'm out in the elements, in the woods and up hills I take the cheap lens and leave the expensive ones in the display cabinet. Do I notice the difference in the final image? No.

If you have lenses with fungus I hope you keep them isolated from "clean" lenses and camera bodies or you are likely to have more lenses with fungus. I have a simple rule for lenses with fungus: they go in the garbage.

[Stephen]

Most marks, bubbles, spots and fungus marks have little or no effect on the image at medium apertures, only at full open, where the softness shows more. It does not affect definition much, resolution of a test chart remains pretty constant, just losing contrast as the damage increases.

With colour, a polariser can help, the polarised light will diffuse less, and with B/W the use of yellow, orange and red really helps raise contrast, red in particular cures a lot of ills in a damaged lens, as does a generous sized hood.

After all, good money is paid for soft portrait lens, although they "bleed" the blur in the other way round to a soft lens. A true soft lens retains a sharp core with perforated plates added or other formulae alterations. Vaseline on a filter does not produce the same effect, similar but the "bleed" is different.

An intriguing lens, that simply should not work well, but it did, was the Garutso Balanced Lens, used in several big Hollywood films in the early 1950's.

It was a standard prime lens, but the front had fresnel type rings around the front element, and the formulae of the rim was different to the main lens.

This resulted in a lens that could focus on the background and the foreground at the same time, true deep focus without Gregg Toland's small aperture system Hollywood used.

The front had a spiders web of etched steel to support the fresnel and a special focus ring to get the distance view and the near both clear. It was adjusted carefully for each shot.

None of the additions to the front of the lens showed on the final film, but it had a deep flaw, it only worked in B/W, as it produced bad colour fringing, which the inventor Mr Garutso could not cure.

The later Baush and Lomb Vistavision lenes used the same ideas, but used two lenses feeding a prism and mirrors to combine the image, rather like the Fields lens that is gaining popularity these days. The Fields lens uses complex light paths to improve the depth of field from a single main element, eliminating colour fringing.

Hollywood has used some strange lenses over the years, often with dual irises, and other so called optical flaws to get special effects.

Stephen.

[truls]

OK, then I will not worry about imperfect lenses. About fungus: As I know little about this how can one stop the spreading of fungus? Can lenses be placed in a dry environment or will the fungus spread anyway?

[Stephen]

As long as dry, the fungus stops, and it can be cleaned off, but often will leave traces of etching on the coatings or the glass itself. stored dry, the fungus will not increase, but it is a risk to leave it, so best cleaned off by a repairman etc.

Most damage from etching will not cloud the lens much if caught in time, but fogging can occur if the fungus goes for the coating, or a general spread over the surface, rather than a pattern.

All out of use lenses should be stored long term with a desiccant, in sealed dry containers, not left in leather cases, the leather can harbour the spores of the fungus. With leather cases, clean and wax, and store dry, and when the lens are used with them , put a pouch of desiccant in the case with the lenses.

Stephen.

[lloydy]

Oct 1, 2012 17:12:08 GMT -5 wayne said:

Sept 30, 2012 16:49:20 GMT -5 lloydy said:

I think that looking for, and expecting, perfection in an old lens is like herding cats. It ain't gonna happen.

I've got lenses with fungus, the real bad ones make a difference to the image but most don't ( and I have 2 copies of some lenses with 'average' fungus and I really can't see any difference in the final image ), lenses with bubbles in the glass. That makes no difference at all as far as I can see ( but what do I know ) and more than one lens with 'unexplained marks'. I haven't got a clue what they are, often they don't scrub off, but again I don't see degradation of the image that I can put down to the 'defect' on or in the glass.

I appreciate that it's nice to have clean glass, it's why I have 2 copies of a few slightly fungused lenses. But....guess which lenses I actually use when I'm out taking pictures. The mint lenses or the fungused ones? When I'm out in the elements, in the woods and up hills I take the cheap lens and leave the expensive ones in the display cabinet. Do I notice the difference in the final image? No.

If you have lenses with fungus I hope you keep them isolated from "clean" lenses and camera bodies or you are likely to have more lenses with fungus. I have a simple rule for lenses with fungus: they go in the garbage.

No, I store them with my other stuff as I have done for 40 years, I've never had fungus develop in any lens except for one stored in a metal cupboard for a couple of years that I forgot about. And the condensation and darkness created the ideal conditions. I've bought fungused lenses ( and cleaned most of them ) but only one has developed it while in my custody.
Now, I store my lenses in opaque plastic storage boxes that aren't air tight, they get sunlight, are stored without caps, and I have a dehumidifier running in the storage area full time, that takes about 4 litres of water a week out of the air at the moment.
The spores that start the fungus are airborne anyway, so avoiding them is just about impossible, I think it's far safer to create an environment where it wont take hold and grow. Take away the dark, humid environment.

And I've got a big garbage bin for unwanted fungused lenses