Yashica Electro 35 GSN lens/glass cleaning

Hi,

I'm fairly new to the analog world and I just purchased my first camera - Yashica Electro 35 GSN. For the price I paid, I'm very happy with the overall condition of the camera, although there's one small thing that bothers me. When I opened the film hatch, I found a fungus-like mark from the inner side of the lens behind the shutter (see photos bellow).



I've watched a few videos on cleaning this particular camera, with the most thorough one from the Japan Vintage Camera on YouTube. He mentions in the video the removal of the back lens for cleaning, but I was wondering if anyone came across a similar issue (as it seems as quite a tedious process)? Also, I know it's quite risky, but since the fungus is on the inner side of the lens, can it be cleaned through the shutter held open, with a disassembled lens (like in this article)?

Any advice on this issue, or maybe some resource/place where I can find more specific information about servicing Yashicas, would be greatly appreciated.

1st thing I would do is lock the shutter open on B, open the aperture to its widest setting, then sit in the sun so that the sun shines into the lens for 24 to 36 hours or put it under a UV lamp for 8 hours.
Ultraviolet light kills the fungus. Yours may be etched by the fungus.

shutterfinger said:

1st thing I would do is lock the shutter open on B, open the aperture to its widest setting, then sit in the sun so that the sun shines into the lens for 24 to 36 hours or put it under a UV lamp for 8 hours.
Ultraviolet light kills the fungus. Yours may be etched by the fungus.

Click to expand...

Thanks for a quick reply, I'll give it a go. Do you have any recommendations in terms of the UV lamp, will e.g. standard 20-30W UV bulb be enough for this?

h0nter said:

will e.g. standard 20-30W UV bulb be enough for this?

Click to expand...

I don't know as I have little experience with fungus on lens.

I did a bit more research on the UV approach suggested above and as I thought, a 30W bulb (approx. £20) won't do the job. UV bulbs at this price have more of a decorative/party purpose rather than killing fungus. However, if you ever face such problems on more expensive lenses, proper UV bulbs (UVB/C wavelength) will actually kill the fungus, more on this here. In my case, I'll try to expose it to sunlight for couple of days and then just clean it off through the open shutter (with the lens taken apart of course). Any more suggestions are welcome and I'll give an update when I'm done with the whole process.