Some of the reviews reported a similar problem:
https://www.amazon.co.uk/Fisheye-Concept%C2%AE-Pentax-Digital-Cameras/product-reviews/B015E2780I/ref=cm_cr_dp_d_hist_1?ie=UTF8&filterByStar=one_star&reviewerType=all_reviews#reviews-filter-bar
Which lens are you using it on. also K-1 or APS-C?
Do you have a Pentax 50mm prime, if so how is it with that?

Before spending vast sums, have a play in Elements:
http://www.amateurphotographer.co.uk/technique/expert_advice/graduated-nd-filter...

sure?
Well these look round and screw in to me:


I believe this type were common before the square ones! These Cromofilters or similar were not usually seen above 58mm and most commonly just 49, 52 and 55mm as most lenses at the time were primes with these smaller diameters.

Trying to fit anything like these on the 10-20mm would seem to me to be a non starter though. Might be OK with the 17-70 if anyone makes/made them in the correct size (but doubt they do.)

The solution would be to seek out some primes like the Pentax 20, 24, 28, 35, 40, 50mm which would be compatible with them.

Given the dynamic range of the sensors now, do you really feel they are necessary? Just do the grad in PP. However if you are doing slide film they can be very handy as PP isn't really on with that!

Are you using both optical and sensor shake reduction systems simultaneously?

If it has the detachable macro lens, have you removed it?

So should they be clothed before eviction?

One final one comprising the sky of my Irfanview conversion with your original edit for the landscape..



Looking at your raw photos from today they seem fine and much better than the associated jpegs! Problem solved?

Leave it with me. I managed to recreate your sonic circles with the first one!

I've tried several ways.
a) This a conversion first to black and white and then adjust brightness/contrast.



b) Similar to that but made an auto correction for levels and contrast first. Any darker and the circles start to be obvious.



c) Taking the original and using Adjust Color>Remove Color produces the obvious sonic circles so that wouldn't seem to be the way to go.



d) A conversion in Irfanview first converting to B&W and then adjusting coontrast to match yours (more or less.)


The circles have to be on the original so its strange they don't really show up in the OOC image. Then the differences observed just by changing the workflow.
Irfanview seems to have handled it better.

Do all those others suffer this too?

What did the original image look like? I'm happy to have a go with it even at 1000pix resolution.