The RGB values did not alter at all at the centre of the image, but there is some kind of image shift. This could be due to a tiny magnification change when the filter was either fitted or removed, by a touch on the zoom.

When I checked the green leaves, there is a very tiny change in the RGB values.

The highlights have the most significant change, but mainly in brightness values.

I restate my position: based on the original two posts, from a practical point of view there is hardly any difference between with and without a filter.

Yes, I can see differences, but that is by enlarging to 300% or greater and using the sophisticated tools in Photoshop to show those differences.

I could not see a difference until:

I loaded both images into Photoshop and aligned them into a stack.

Toggle the visibility of the top layer on and off

The centre of the image stayed constant, but the left and right of the image showed considerable differences as in distortion between each other.

I still have no idea which one was shot with the filter, but the difference between the two is very easily seen.

Using the Difference Blending mode to check the alignment, most of the flowers from the centre out were aligned, but again left and right shows non alignment or colour differences.

Both images look good in their own right so my conclusion is that it really does not matter - the difference is not very significant on the screen. If making large prints, the distortion might show.

I readily admit to scanning at the greatest resolution which will still give me a manageable file. But, harkening back to my film days, I am reminded that (especially slide) films were measured in line pairs per millimeter (ppm) which was the number of pairs of parallel lines that could be distinguished (often under very high magnification). Resolution of 125-150 lppm was high, 250 lppm was virtually unheard of. If we take the number 150 lppm, that translates to 3810 line pairs per inch. It seems to me that scanning such an image at anything over 4000 dpi would be overkill.

Incidentally, if we adopt 200 lppm as a goal for a 35mm full frame and count the cross points as a reasonable measurement for image resolution, AND if we count each cross point as a pixel (yes, I know it's a stretch), we come up with a 38.71 mp image. Of course this is all estimation, speculation and innuendo, but if it's even close to accurate, this tells us two things:

1. Some of the tech films were incredibly high resolution, even by our standards, and

2. The megapixel wars are not over; they're still being fought.

Keep one thing in mind though. Films of more than 100 lppm were rare; 80 lppm was considered quite sharp. This lowers our target threshold to around 2000 dpi and around 6.2 mp.