Here's an effective way to ruin almost all your shots for the day, before you even start: neglect to notice a big hunk of grunge on your sensor, thereby causing a big black splotch on most of your photos.

As part of the rigorous testing I do for my readership, I embarked on a thorough test of this technique, while on vacation no less, one of the first days I was at my folks' place in Ohio this summer. It was a wonderful summer day, and a walk around outside had great potential for lots of ruined shots, and I was not disappointed.

Er, I was disappointed. I mean, well, you know what I mean.

Here's the same photo, of Anthony checking out an inchworm on a stick, both in its original form, and after I made an attempt to fix it in Lightroom. By mousing over the “original” and “fixed” buttons underneath, the view switches...

original     fixed

The big black splotch on his cheek is readily apparent, but by toggling back and forth, you'll also find a couple of other grungy spots to the upper-right of his nose that I fixed. They were also caused by dust on my lens. I also “fixed” a spot directly above the big one, closer to his eye, but now that I think about it, I think that may be a freckle.

I didn't notice the spot until the evening when I first checked the images on my laptop. I was not happy. A really simple test photo while sitting in the livingroom with my laptop showed the monster gunk on my sensor...

Ignore the colors – I hadn't used my sensor-dust reference page – but it's impossible to ignore the huge splotch. Whatever is on there is huge, orders of magnitude beyond “dust”. I calculate that it's 0.49mm long. I doubt that a meadow vole crawling into the mirror box would create as big a shadow. It's huge.

And it shows up on every picture.

I normally use this popular wet method for cleaning my camera sensor, but that stuff was at home in Kyoto, so I took a chance with a can of compressed air and blew the sensor clean. (Warning: there are a lot of ways you can ruin your sensor by trying to clean it with a can of compressed air; don't try it until you understand the risks and how to mitigate them.)

I was able to get it remarkably clean in short order, but that didn't help the 100+ photos from earlier in the day.

Here's one of Anthony's cousin Josh reaching for a dandelion. Mouseover the “original” button to see the heinous splotch...

original     fixed

The splotch here looks more well defined than the one on Anthony's cheek, because this was taken at a smaller aperture (f/6.3 vs. f/5), and as I describe on my sensor-dust reference page, dust shows up more apparently with smaller apertures. (That's why the gunk-test shot shown above was taken at the very tiny f/16).

The dandelion picture was easy to fix because the splotch fell on an area of uniformity. It's more apparent (and was more difficult to fix) in the next shot of Josh...

original     fixed

Not all shots are ruined out of hand; if the splotch ends up in a cluttered part of the composition, you might not even notice it. The rest of the photos in this post have not been corrected....

I posed one other goose picture from the summer, that was better than this.

I like the cattails around the lake, and have posted about them in the past.

The big black splotch isn't very apparent in this last image both due to its location, and to its aperture (f/2.8), but the smoothness of the big leaf allows a different splotch to show up clearly. You might not have noticed it, but it's something that almost any serious digital photographer would see (and cringe at) right away. Ugh.

A good pro photographer (e.g. wedding, sports, event, etc...) has a list of things to prepare/check before heading out on a shoot, such as “format memory cards”, “ensure batteries are charged”, and “reset all camera settings”. I'm not a pro and I have no such list, but I've seen them. I've never seen “check for sensor dust” on one, but I think it should be there.

(Unless you're shooting film, of course :-)).