How do I get rid of black spots on images

[michaelmorris]

I'm finally getting around to processing a large backlog of images taken with my DSLR. For most of these images I have dark and flat frames. In many of the images I have processed so far, when I get towards the end of the processing sequence and the full amount of non-linear stretching has been done I get seemingly randomly distributed black splodges in the background that are mostly between about 5 and 15 pixels across.

I can remove them using the stamp or heel tools in Photoshop, but this does take ages if there quite a few of them.

What causes them? (is this poor flats?)

Is there a way of removing them or at least making them less visible that doesn't involve dealing with each one in turn?

Thanks

[Spikey]

Sounds like dust bunnies. Post a pic up Michael so we can have a look.

[Stephen]

Flats should remove dust bunnies, how did you take them?

[steppenwolf]

Can we see a typical example, please?

[michaelmorris]

Can we see a typical example, please?

Here you are. This is the central part of an image. Also, the image has been shrunk by 67%

[michaelmorris]

Flats should remove dust bunnies, how did you take them?

Flats taken with homemade light box.

[Spikey]

Looks like crud and dust to me but rather a lot of it. Can you post one of your flats up please Michael, suitably stretched.

If it is crud then it doesn't look like your flats aren't having an effect, what is your flats workflow i.e. how are you measuring the brightness of the flat and how are you subtracting it from your images ?

[Andy_E]

I must say they look like bunnies to me

[Shibby]

Not to me - looks like some sort of sharpening artefact. I would check your RAW or cosmetic settings in DSS (if that's what you use?)

[michaelmorris]

Not to me - looks like some sort of sharpening artefact. I would check your RAW or cosmetic settings in DSS (if that's what you use?)

Replies I've had from another forum seem to strongly point to artefacts from noise reduction software (Noise Ninja). Looking at examples of similar artefacts post noise reduction certainly seem to support this hypothesis. I'll play around with the settings in Noise Ninja to see if this effect can be lessened. I've had someone post a good 'fix' that uses a median filter applied to dark areas only (using the Select>colour range to select the darkened areas only). That just leaves the splodges in the lighter areas to clean up manually.

[Spikey]

ah yes could be, but wouldn't you apply this after the image is stacked? so you would in effect see if before & after the application of noise ninja.

[michaelmorris]

ah yes could be, but wouldn't you apply this after the image is stacked? so you would in effect see if before & after the application of noise ninja.

Noise reduction is almost the last thing I am applying. Only enhancing colour saturation and sharpening follow it.