One of the banes of digital photographers who have to change lenses in less than ideal field conditions is the potential to collect dust on the sensor. This dust turns to dark spots on your image and if you have a lot of images shot at the same time, you have a lot of spots to deal with.
In this tip, I'm going to show you a tip using a basic Lightroom function to find and clean spots on a single image and then remove the same spots in all the images shot at that event.
In this image, made at the now closed to the public, Cheltenham Badlands, I've nearly completed my post processing. All that's left is spot removal, sharpening and noise reduction..
When I zoom in, I can see some spots in the sky as you'll see in this image.
Sometimes it's hard to see the spots so here's the tip. First activate the spot healing brush. Then go to the bottom of the image area and activate Visualize Spots. The screen goes dark and the blackest areas appear in white. The round sharp white dots are sensor dust.
Now just size your healing brush to heal the dust spot.
Heal each spot that you see. When you are done, you want to sync the correction across all images from that shoot.
Select all the images you want to correct in the Filmstrip. Click the Sync button at the bottom of the right side panels when in the Develop module. This brings up the Synchronization dialogue. Make sure you select Spot Removal and then click Synchronize. Like magic, the spots are healed across all the selected images.
The beauty of this Synchronize method, is that no other data gets changed. You could use Synchronize for a completely different sync, such as White Balance and so long as you only select the items you want synced, nothing else gets changed in the target. The only potential gotcha is that you must select the source image first, then shift or command click to select the others. You can tell because the outline colour will be brighter on the "most selected" image. This is the source for all synchronized changes. The synchronization is one time, so if you make changes, say cleaning more spots, you would have to sync the new spots removed again.
This is a fast and efficient way to deal with sensor dust. While many cameras say that they clean the sensors at shutdown, they really just give it a vibration to dislodge big particles, Those particles fall into a tray in the camera. They don't get ejected so could end up back on the sensor as the camera is jostled around. There are lots of sensor cleaning tools out there. Be careful. The sensor is delicate and you wouldn't want to damage it.
Try to always turn the camera off and wait a few seconds before changing lenses. This will help dissipate the charge that builds up on the sensor that attracts dust. Try to avoid pointing the camera body straight up when changing lenses to reduce the effect of gravity dropping dust into the camera. Keep lenses, body caps and rear lens caps clean so they don't become dust transports.
Sensor dust accumulation is a normal reality of digital photography. Good planning and control along with the right tools in post production can make dust spots an area of low concern.