Excessive heat, sharp heating/de-heating, and uneven heating may affect lens' internal to shrink and warp in highly unnatural manner. Considering that cameras and lenses has their own high/low temperature limits, I think the 40W lamp is way too hot for your lenses, your camera, and their AF chips. Besides, I learned the hard way that such measures just don't adequate to protect the lens against fungus, because heat does not reduce humidity (which causes fungus) to the ideal level for lens storage. The best defense against humidity (which causes fungus) I have found so far is this: 1. Put your each of your lenses in an airtight plastic bag, alongside with couple silica gel packs. The silica gel packs should be inserted INSIDE the plastic bag, not outside the plastic bag. 2. Check out the silica gel packs every 3-6 months, and replace them if its color has changed considerably. The color shift indicates that the silica gels has absorbed moisture to its limit, and it cannot absorbed moisture much longer. You should also check the plastic bags for tiny scratches that may allow humidity to slip in. If the plastic bag is scratched, replace with a good one. 3. If you go traveling, do not leave the plastic bags at home. Bring it along with the lenses in your camera bag. Take your lenses out from its airtight plastic bags only when you need it. 4. If the lenses is to be stored for a long time, it's better if you have an airtight box, such as an unused mini freezer. You still need to put the lens & silica gel packs in airtight plastic bags, because the airtight box is only meant to be the second protection against room humidity. In my home town, I can found the unused mini freezer with perfect airtight seals at a low price. Of course, do not repair and turn the freezer on when storing your lenses in it :) Warmest Regards, Januar Rahadi. Bandung, Indonesia. >I put a 40W light bulb in the bottom of the cupboard where my gear >is. I also drilled a few holes in the shelves to let the air >circulate upwards in a kind of "S" pattern. I don't store anything in >the bottom part where the bulb is, only on the shelves above. This >seems to keep things dry and warmish. I will probably turn the bulb >off in the drier winters that we have. > >If anyone has had bad experience or recommends against this, >please let me know !! > >Craig
