Yes, this combined with software trying to align images in the stack is definitely the cause of each cluster. The giveaway is that many clusters have the same basic pattern with clusters that are closest looking the most similar.

Steve

And by way of illustration, here's a crop from one of my stacks. The dark, thicker streaks on the left are due to dust on the sensor (they are sometimes much bigger... ). The lines of coloured dots are pixels that are stuck on for whatever reason.




Steve

I see your problem - can't miss it with those examples!

It's hard to tell whether they are due to dust or a pixel problem. My dust tends to be bigger blobs! Strange that dust alert is greyed out, particularly as the earlier K20D has it. Perhaps it's the lens. The K20D manual doesn't say what type of lens to use apart from setting to A position when the lens has an aperture ring. The K3 manual explicitly says that the lens must be a "DA, DA L, FA J lens or a D FA, FA or F lens that has an A position, and set the aperture ring to the A position". So the dust alert function won't be available if one of your pre-A lenses is attached.

However, it's possible that some might be due to dead pixels. Pixel mapping (in the spanner menu) claims to correct an image for defective pixels - permanently dead or permantly stuck on - presumably by interpolating from adjacent pixels. It won't deal with hot pixels, though, which are pixels that become temporarily stuck on due to long exposure or lots of shorter exposures in quick succession (stacking!). They revert to normal when the sensor is no longer in use. Hot pixels appear as coloured spots (the RBG colour of the pixel).

All this reminds me that I always intend to check for dust and do pixel mapping before starting a stack but always forget to do it. Note to self - do it, you know it makes sense!

Steve

Just remembered. Both my K20D and K3 have a 'dust alert' function which involves pointing the camera (with lens) at a bright, white wall or similar then pressing the shutter button. The result is an image on the rear screen showing the position of each speck of dust as it appears when you look at the sensor. You can't print it or save it permanently, but I've occasionally found it useful for tracking down a recalcitrant speck of dust. Have you tried with your camera (whatever it is)?

Steve

A really nice picture, as well as being technically excellent.

Another slime mould?

Steve

Are you seeing dust spots or hot pixels in your stack worms?

Steve

An amazing rescue job on the lens. You're a genius!

The photos are really good. It might be the lens, it might be the light, it might be your processing, but they seem to me to have the feel of photos from the days of film. Why do we bother with big, heavy and expensive modern lenses??

Steve
PS: Having cleaned the lens with hair shampoo, does it now have more shine, long-lasting smoothness and no sign of dandruff?

Just to clarify the Parkrun situation, I checked with my Parkrunning visitors who say that Parkruns are organised entirely by volunteers (which is why the official photographer is a volunteer), there is no charge for running, necessary costs are met from sponsors and donations (it's all on the website, too). The voluntary nature of it might be why they are sensititive to people trying to make money from taking photographs, however well intentioned.

Steve

As it happens, I have visitors this weekend who regularly take part in Parkruns and will be doing so while they are here (not with me, I hasten to add!). So I looked up the Parkrun policy on photography at link. It includes "We do not support photographers charging individuals for event photography at parkrun events.". It's worth reading the policy. They are trying to walk a tightrope between on the one hand photographs and social media being good publicity and in any case part of life, on the other hand the need for effective safeguarding, on the third hand the requirements of GDPR, and on the final hand the right to photograph people in a public place.

Steve

Oh yes! I can see why you've become interested in them. Strange and wonderful things. Aren't some of them huge single cells which behave in a way that seems almost intelligent?

And a wonderful photograph, too. Looking forward to seeing more .

Steve