How to tell the difference between dust and fungi under lens surface?

[antitrust]

i'm meeting a seller tomorrow for a lens, he said that there are some "light spots" underneath the lens surface. that's all he described it as. he told me that he kept the lens in a dry cabinet all along.

so i suspect that they might be fungi, but the fact that he kept the lens in a dry cabinet all along might mean something else? so i'm suspecting now that it might just be dust under the lens surface.

but being a complete noob and amateur to lenses, (just making my switch from consumer digicam to film slr) i have completely no idea how to tell the difference between these two.

i've seen some pictures online of fungi and they all seem to start growing from the edges of the lens. do they grow out from the middle? and how do spores look like? just white, bright dots?

please enlighten! better still, if got pictures then lagi best.

;p

 

[Pretender]

Hi, I'm no expert on fungi but the reson I post this reply is - I too just shifted from Digicam to DSLR and got a bad deal on the lens. The lens has no fungi and looks very fresh. I had read about DSLR pictures not looking as sharp as highend digicam pictures before proccessing, so I didn't bother that much that the pictures I took were not that sharp. Later on I proccessed but still felt the sharpness was not as it should be. I still wasn't sure so I took the lens to Camera Workshop. I was told the lens has a foggy build-up and they can't do anything about it. So now I have to get a new lens. So what I would advice is take some pictures and see how they come out before you buy.

 

[antitrust]

thanks for the advice. and sorry for the lens

btw, i'm purchasing a film SLR system from him too and i have no DSLR to test it out with. I'd see how it is tomorrow. maybe i'd ask personal warranty from him or something

 

[user111]

fungus will look like curly squiggles

dust will not look curly. it will look like small whitish dashes.

fog..looks like an area of cloudiness

 

[holeinone]

Most lenses should not have fogged unless they are very old and have been stored in undesirable conditions.

Dust should not really worry you, as they come with normal use of any lens. Unless of course it's exceptionally dirty, which in most cases, should not happen. Dust will appear as little specks or think fine lines, depending on the type. Not likely to affect picture quality in most cases.

Fungus is quite obvious. They will look like spiders in some cases, with legs growing from a centre.

Fogging can be caused by the lubricant in the lens that evaporate and condense on the elements over time. If serious, the elements will have to be replaced, which may not be worth it in most cases.

 

[antitrust]

fungus will look like curly squiggles

dust will not look curly. it will look like small whitish dashes.

fog..looks like an area of cloudiness

so having said, it is rather difficult to mistake dust for fungus and vice versa?

 

[Astin]

If u deal in day time, point the lens towards a cloudy sky and see throught the lens, from front to back, then from back to front.
If u deal in night time, find a white florucent light and do the same check.
Dust look like small dots on the inside of the lens, no (or very little) effect on image quality.
Fungus look like mini spider web, normally around the edge of the lens, will affect the image quality.

 

[user111]

so having said, it is rather difficult to mistake dust for fungus and vice versa?

yeap

they are easy to differentiate

 

[antitrust]

yeap

they are easy to differentiate

i have noticed some circular stuff under my lens (not the one i'm going to buy) they look a little like marks caused by water. they should be able to be wiped away right? but what if its under the surface? will it affect image quality much?

 

[Danntbt]

i have noticed some circular stuff under my lens (not the one i'm going to buy) they look a little like marks caused by water. they should be able to be wiped away right? but what if its under the surface? will it affect image quality much?

These could be bubbles, and cannot be removed, apparently if they are tiny, should not be an issue, in any case, I think the QC for reputable lens would not pass those with bubbles large enough to affect the images taken with the lens.

I learnt this at fee of 90 bucks when I sent mine in to TCW for cleaning what I thought was fungus, only to still see it on the lens after the cleaning, and was only told then, that it was a bubble....anyway....should have gotten a second opinion before blindly sending it in.

 

[user111]

circular stuff..definitely not dust or fungus
agree that it could be bubbles
usually minor and can be left aside as it is
unless they expand over some time (long time) which in that case then just send for servicing
normally

 

[user111]

circular stuff..definitely not dust or fungus
agree that it could be bubbles
usually minor and can be left aside as it is
unless they expand over some time (long time) which in that case then just send for servicing
normally slight imperfections in glass is acceptable, no worries


keyboard error..posted twice. lolz =)

 

[sriram]

Fungus looks like spider webs spreading usually from the edges of the lens, in a haphazard pattern. Very easy to make out.

 

[Firefox]

Aside from looking like spider webs, fungi that's starting out usually have a Y-shape to it. That's before it multiplies and grows into a web.
Dust usually looks more like a single strand...