Recently all the photos taken with my digital SLR have obvious spots at two fixed places. Can I get rid of them by cleaning the sensor? Also, I see a lot of colored spots in my night photos but I guess that’s a different problem; how do I solve that? M.K.
Yes, it’s quite likely that the two dots are caused by specks on the sensor. You can send the camera to a service, or consider cleaning the sensor yourself with one of the products from VisibleDust such as the Zeeion Blower (from B&H Photo; from Amazon). For more stubborn spots (such as water droplets) you would need to use the special swabs (from B&H Photo; from Amazon) plus the SensorClean liquid (from B&H Photo; from Amazon).
But take maximum care not to scratch the sensor; follow the accessory manufacturer’s instructions to the letter!
If the two specks still appear in your photos after the cleaning, it is possible that the sensor has some dead pixels: photosensitive dots that can no longer function. If your DSLR includes a custom function for Pixel Mapping, activate that feature as discussed in the owner’s manual. If not, you would need to send the camera to a service centre for an inspection.
The colorful speckles (or graininess) that you see in night photos — made at very high ISO or during very long exposures — are an entirely different matter. Those are simply evidence of digital noise; that’s common with any camera. If you find the digital noise pattern to be objectionable, set the Noise Reduction feature to a higher level. Or, use the Noise Reduction utility in your RAW converter or other imaging software. For the best results — smooth photos with minimal blurring of fine detail — consider buying one of the highly-rated aftermarket programs specifically for noise reduction: Noise Ninja or Nik Dfine (from B&H Photo; from Amazon).
The colored spots (speckles due to digital noise) are particularly obvious in the original image made with in-camera Noise Reduction turned Off. Later, I applied Noise Reduction to the RAW capture in Adobe Camera Raw. Finally, I tried one of the special aftermarket Noise Reduction programs on the JPEG version of the photo and that provided an even better effect. Photos: ©2009 Peter K. Burian