previous page in this Simple Lens Check article


Fungus - I just had to use this pik found off the net to show this fine example of lens fungus.
Lens fungus occurs when the lens has been stored in a moist environment for extended periods of time.
When purchasing a lens from a tropical country EXPECT fungus...

A fungal attack can be seen as a few different ways.
When looking in through the lens , again backwards is best , focus your eye on the various lens element surfaces.
Sometimes looking up at a fluorescent ceiling light can show fungus better than a normal globe light.
At the start fungus may look like a dot with a round ring 1 or so millimetres away from the centre of the dot.
Another type of fungus will look like dark spider webs as shown below .. sometimes forming from an edge growing inward to the centre.
Again another sort of fungus will have a very white appearance and be quite thick and clumped in one area.

All types are bad !

A small amount of dark fungus wont affect pictures all that much , but none is better.

Repairs are possible but I wont go into it that now , but simply , replacement of the entire lens is recommended.
An example of lens funghi
http://www.chem.helsinki.fi/~toomas/photo/fungus/


If you lens looks all spiderweby like the one below don't even bother sending it away to be cleaned.
The chance of this one being repairable is very low , which is very sad , as the Zeiss Flektogon 50 is such a nice lens :-(
Carl Zeiss 50 fungus


Other general lens things to look for are ...

Making sure the focus and aperture rings rotate smoothly.
Checking the filter ring and body mount is not dented or otherwise damaged.
No unusual looseness or movement in the front lens elements compared to the rest of the lense body.
In the case of a zoom lens , with the lens pointing down the zoom control should not fall forward under its own weight.

More rarely are very serious faults , such as bubbles in the coating , glass flaws , yellowing of the glass and separation.

Always remember !! .. whatever fault you find , it ALWAYS will have less of an impact on your pictures if the fault is at the front of the lens.
For example , a 10mm scratch on the front element will not be as bad to your pictures as a 5mm scratch on the very back element.


next page in this Simple Lens Check article

Hosted by www.Geocities.ws

1