Hi Nick,
Have uploaded the files, sent RAW as I thought you may do more with them.
I have noticed within the viewing window, or rear screen, (if in live view), that as you focus closer or further away, the image size, (area) in the frame grows larger or smaller, I know why this happens, so I thought maybe a focussing rail may help, but also realise that as you move further away on the rail, the subject will be marginally smaller, but if the difference is a more regular, smaller amount this might not confuse the rendering as much. I could do with a rail anyway, so it may be my next purchase.
It is interesting, and enjoyable.
Thanks Andrew. Here is what I found.
I think the first and second image were out of order. I swapped them around so the sequence went from back to front. That helped a bit but it didn't get rid of the halos. Neither did setting the Radius to a large amount with method B, even the maximum Radius of 60.
That led me to retouching. Here we see one of the problem areas. On the left is an individual image from the set of six. On the right is the stack.. We want to try to get rid of the halos indicated by the green, blue and red arrows. If I hold the left mouse button down what is in the circle on the left will be painted into the circle on the right.
Illustration 1 annotated by
gardenersassistant, on Flickr
Now I have painted from the individual image over the halos marked by the green and blue arrows. That worked well. I'm now moving down to deal with the halos indicated by the red arrow.
Illustration 2 annotated by
gardenersassistant, on Flickr
But look what happens next. In the image where the petal I'm working on is in focus, the petal on the right, which is nearer to the camera, is out of focus. And the out of focus image of that petal is larger than the in focus image of it. As the yellow arrow indicates, I am painting the out of focus petal on to the stack.
Illustration 3 annotated by
gardenersassistant, on Flickr
OK, let's use a smaller painting circle. At the point I've got to shown below, the circle has started painting from the out of focus petal, as indicated by the yellow arrow. But beneath that the remainder of the original halo that I'm trying to get rid of is still there, indicated by the brown arrow. If I paint over those remains I'll just get even more of the out of focus petal painted on to the stack.
Illustration 4 annotated by
gardenersassistant, on Flickr
There are only two and a half ways I know to (possibly) solve this problem. One is to remove from the stack the images that have the rear elements haloed. Of course this reduces the depth of field and the image may simply not work if you do that, either because it doesn't have as much depth of field as you want, or because taking out those images leaves a nasty transition between in focus and out of focus areas. Second, you can try cloning to solve the problem. This may or may not work. It may be easy, possible but difficult and/or time-consuming, or impossible (for example because there is no suitable source area to clone). The half solution is to give up. That is what I do if it starts getting complicated. (I suppose another half solution is to decide that the issues are not serious enough to stop you using the image for the purpose you have in mind for it. I do that sometimes with flaws that are small enough that I think most people won't notice. If the flaws are that small I can enjoy the image even though I'm aware that the flaws are there.)
In my experience this is an all too common problem with botanical subjects. It arises when there are two areas which overlap (or as in this case, almost overlap - there are overlapping ones elsewhere in the image) , both of which areas are required in focus, and which are separated by a large enough distance to cause enough expansion of the nearer element as it goes out of focus to be problematic. (I went into an example of this from around 22:00 in
this video.)
Why doesn't it happen so much when stacking high insects etc? Well, perhaps it does, I don't know, I don't do that sort of stacking, but I suspect that you don't get so much of this type of "overlap of distant surfaces" problem with insects. Plants do tend to have bits that are rather spread out, on different branches/stems that can be a rather long way apart relative to the scale of the scene. It depends on the scene of course, and I think I've become a bit more canny about what scenes I try and which ones I pass on by (or try but abandon quickly if they get difficult).
2019-02-17 20-24-23 (A,Radius6,Smoothing5) by Andrew Wright, on Flickr
2019-02-17 20-19-34 (A,Radius11,Smoothing5) by Andrew Wright, on Flickr
2019-02-17 20-12-22 (A,Radius11,Smoothing5) by Andrew Wright, on Flickr
2019-02-19 21-02-27 (B,Radius12,Smoothing5)
