Blurring around complex shapes

[Marc_R]

oh f*** .... admittingly it took me some minutes to "adjust" my brain and finally - now I got it.
Thanks Catherine!

I was heavily focused on the distance between the sharp area and the lens which stays the same during the stacking.
And the point i missed (or ignored) was that indeed the whole object moves towards the lens - hence the object will 'increase its size' and accordingly the sharp area!

Finally I tested the more than obvious physics with Helicon by setting the "autoadjustment" to 0% - at least with 3x to 10x magnification the difference is not that obvious but it can be seen.

But now the qestion comes into my mind how the software determines the amount of adjustment??

And lastly - would it be true that the image quality changes from first to last image in a stack??
If I understand the necessary auto-adjustment correctly it will resize each picture in the stack by a certain percentage so that every image after the first one will be a somewhat compressed!?

[Catherine]

You could say that, although the effect is negligibly small, and if by "compressed" you mean that the images are reduced in size - that's not necessarily the case, they can be enlarged, depending on the direction in which the stack is being processed. You can also switch to the higher quality Lanczos interpolation function in the preferences.

[Jaxjqa]

I'm just joining the discussion, but it's of great interest since I occasionally Have the same blurring problem. For Catherine - what are the negatives of switching to the Lanczos interpolation function? I assume there's a tradeoff involved. Is it a switch that should be made for certain types of stacks and not for others?

[Catherine]

I assume there's a tradeoff involved. Is it a switch that should be made for certain types of stacks and not for others?

The tradeoff is mentioned in the drop-down selector: it's slow. Lanczos performs image interpolation (resizing) with a slightly better quality at the cost of taking longer to do it. It's unlikely that you'll actually notice a difference in the final rendered image, but it's also probably not that much slower (depends on your hardware).