I was sharing lenses with fellow Nikon F-Mount user Shuwen because it was just very versatile - she was using her 16-85VR, I was using my 70-300VR (or 12-24) or the other way around, and whenever one needed just the other part of the zoom range, we would swap lenses quickly without having to unmount the backpack, find the lens, fiddle around with the lens caps, etc. - what I want to say is: we swapped lenses often.
And now look at this photo (yes, its not exactly a masterpiece, but thats not the point). That day, we got up at 4am (yes - holy shit!!!) for a shower, quick breakfast and a one hour drive from Palm Springs to Joshua Tree National Park to catch the sunrise, and then this:
Dawn, Joshua Tree NP (FinePix S5Pro, 1/7s @ ISO 100; f/16, 18 mm DX)
The evening before, I checked my photos - and there was no dust. That nasty little hairy fluff must have waited patiently in the mirror chamber of my camera to strike - it first appears on the 5th photo from that session. That's the problem: you change the lens, and you might just get some fluff into the mirror chamber of the camera. No immediate effect, but the movement of the mirror keeps it in motion and eventually it will be attracted by the charged sensor enough and there you have it. See above.
(of course, stopping down to f/16 is a lot, and thats why the hair shows so clearly, but nevertheless, it would have been just as easily visible at f/8 - because the spot in the middle is there right from the 1st photo of that day)
Guess what - after I removed that fluff from the sensor with the Arctic Butterfly the exact same thing happened again to me again only two days later. I never had that happen to me so much before. So, I've learned my lesson from that, and its:
First: carry something like the Arctic Butterfly with you at all times for "emergency situations" like these (because mine was in the hotel room a one hour drive away, in other words: useless). Unfortunately, my camera has no built-in sensor dust removal feature - I can't really give any good advice what would be a good practice for cameras that have this.
Second: check your photos often for dust and fluff - you can do that even with the camera's tiny display, and here's how I do it:
- Stop down the lens as far as possible. That will be somewhere in the range of f/16 to f/32 usually and this will make the dust really sharp and visible. Camera shake is mostly irrelevant, because the dust moves with the sensor.
- Point the camera at an evenly lit surface or light source (the blue sky, a white wall, whatever).
- Set the camera to manual focus and completely de-focus it (ie. set the lens to its close focus minimum so that everything that you normal would see is completely blurred)
- overexpose by at least one stop (no matter which metering method you use) so that you get a bright enough image even when you're in direct sunlight
- release the shutter and use the image control at maximum magnification. Scroll across the entire image and inspect it carefully - when you're in bright sunlight, put the camera in your camera bag or hide it in a jacket so that you get a good look at the display.
But there's more to come. When we got back to the hotel I removed the fluff with the Arctic Butterfly. And yes, I have to correct my first evaluation: it actually is somewhat useful. It just needs a lot of swipes and spins to get small normal dust particles (but with fluff like above, one swipe should be enough).
But somehow, I managed to get some greasy dirt on my sensor while cleaning it. It might have been lurking somewhere, or I somehow contaminated the brush of the Arctic Butterfly with it, I don't know (what I do know now is why they sell a version with replacement brushes that is even more expensive! LOL). A big fat smear covered the lower right corner of the sensor - and that's the upper right corner of the frame, what an excellent spot for dirt when you're about to make photos of sea & sky...
So, the total desaster was there: I needed a wet cleaning to remove that grease. And of course, there's no camera store in Palm Springs (golf players don't need it), the next store that had sensor cleaning swabs was a half-hour drive away - and they ran out of the cleaning fluid! So, what to do?
I still had some cotton swabs (Q-Tips) with me and after a pilgrimage through three local pharmacies (well, more precisely, two - because the first one that was listed in Yelp didn't exist!) one was actually carrying high percentage alcohol and donated a small portion of it for my cleaning purposes (so: thanks to the friendly pharmacist of the medical court at East Tachevah Drive, Palm Springs:-).
Problem: my cotton swabs apparently weren't clean. Or the alcohol I got from the pharmacy wasn't pure enough. Because after it dried, I had a nice hazy residue on the sensor - which I carefully removed with a microfibre tissue. After that, I gave the sensor 20 swipes with the Arctic Butterfly, then checked again as described above: clean at last!
One problem with using cotton swabs though is that you might actually touch the mirror chamber of the camera with it, and you bet that one fluff of that cotton will come off there, going to ambush you... therefore, I think I'll carry some wet & dry sensor cleaning swabs with me from now on...