Hi Folks
Some time ago when I bought my first "dust resistant" lens, the PENTAX 60-250, and stuck it on my weather sealed K-7 I immediately started to worry. As someone who was always good at physics (as well as blowing my own trumpet), I immediately realised the problem a pumping zoom action would mean to the the camera and the question of dust.
On the one hand tight seals are provided to keep dust out but on the other is it possibly to making the problem worse ? The pumping action of zooms, and in particular long zooms like my 60-250, shifts around a lot of volume of air inside the camera and it has to go somewhere. Is it possible that the few gaps through which negative/positive air pressure can now vent is making sucking in dust worse? Because air pressure will increase around those few small gaps it can find. (And thereby increasing the power to suck in more dust).
I took out the little microphone rubber stopper and moved the zoom in and out with the opening close to my ear. Good lord, the amount of air coming through this little hole I reckon would be enough to pump up a bicycle tube and the camera sounded like it suffered a bad asthma attack. I also figured all this compressed rush of air can't be good for some of the more delicate parts inside the camera.
So then I got thinking, wouldn't it be good if I kept this microphone hole open all the time, this way at least I have control over where the air flow takes place. (And I have never made use of a microphone, so I don't really need it). And as I am not only good at physics but am also a good thinker (that trumpet again) I thought wouldn't it be good if I could provide a small air filter for this mice hole to allow air to move freely and also keep out dust. And here is what I came up with.
Parts you need:
Small piece of masking tape
Three hole punches, inner Ų 10mm, 8mm and 3mm
A piece of release paper (say from a band aid or sticky label)
A small piece of filter paper from a dust mask
A steady hand, its going to be fiddly
Stick a piece of masking tape on the release paper, put it on a piece of timber masking tape up, take the 10mmŲ punch and knock out a disk, put the disk you just punched out on the timber and punch a hole in the middle with the 3mmŲ punch.
Now take the 8mmŲ punch and knock out a small disk from the filter paper. Peel off the masking paper disk from the release paper and stick this little filter paper disk over the punched out hole of the masking paper. You may need a pair of tweezers for this.
Next stick this over the microphone hole. The pictures provided are pretty well self explanatory.
To test the filter hold the camera with the mice hole close to your lips and pump away (the zoom that is) and if you can feel the air flowing you have succeeded. This means most, if not all, air will now pass through this hole as long as the little filter paper disk is not too thick in which case it will restrict air flow.
I don't really know if all this is working as far as dust filtering is concerned but I feel I have at least done something.
Greetings from sunny Melbourne
Last edited by Schraubstock; 07-24-2011 at 03:10 AM.