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westie4us
Mon, 28 Apr 2008 2:02:19 EDT
 Small blue dot

I need some advise. I noticed when I took this picture in PS to edit it had a small blue dot in the lower bottom of the photo.Can you tell me what caused this and how to fix it? Was this caused by the way I set my camera settings? Thanks

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Mark
Mon, 28 Apr 2008 18:08:05 EDT
 Re: Small blue dot

Looks like there is a dust particle on your sensor. At higher f-stops (smaller apertures), any dust on the sensor becomes much more noticeable and will appear as a dark spot.

Sensor dust is one drawback with DSLRs, and is quite common since each time you swap lenses dust can enter the mirror chamber and eventually end up on the sensor itself.

The manual for your camera should provide instructions for sensor cleaning, though this procedure is not for the faint of heart.

I use a "rocket blower" (a rubber bulb that puffs air) to clean my DSLR sensors about every 3-6 months, and once you learn how, it's really quite easy.

Nikon also includes a "Dust Off" feature with the D80 (and most other models) that uses a reference image to automatically map out dust if you use Capture NX to process your image files. However, if you have just one or two dust spots, you can just as easily "clone" them out manually using Photoshop.

Some digital camera makers have a dust cleaning system that vibrates the sensor to remove dust particles, but there is some debate as to whether this is of any real benefit, or just an advertising gimmick.

Dust has always been the bane of photography. I remember fighting it on my negatives when enlarging a print. Now, even with digital, dust is still a problem :-)
westie4us
Mon, 28 Apr 2008 19:43:07 EDT
 Re: Small blue dot

Thank you Mark for your reply! I just had my sensor professionally cleaned about two months ago and got a blower recently to do cleaning myself.So I'll give it a try.I was worried that the blue dot could be a hot pixel but wasn't sure.Good to know it may just be dust.
Mark
Mon, 28 Apr 2008 20:08:51 EDT
 Re: Small blue dot

westie4us wrote:
Thank you Mark for your reply! I just had my sensor professionally cleaned about two months ago and got a blower recently to do cleaning myself.So I'll give it a try.I was worried that the blue dot could be a hot pixel but wasn't sure.Good to know it may just be dust.

If it's a hot (or dead) pixel, it will usually be limited to a single pixel (with an "alias" halo around it) when viewed at 100%.

I can't tell from your resized image how big the spot actually is, so you might want to email me the original full-size image file, or a crop of the section with the spot so I can better identify it.
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