How to get better background blur when stacking

[austrokiwi1]

I am currently using Helicon. A week or so ago while experimenting with 10X magnification I saw a potential image that I wanted to produce. I was using an American Silver eagle and I wanted to produced a high resolution stacked image where only the face of liberty is in focus and the rest of the frame blurred( With Bokeh if you like).

This is the result of a large stack and using Helicon. Its not quite there. Although the coins field is in focus Helicon is just trying to sharpen it too much. Is there any way I can adjust the settings in Helicon to ensure the blur remains attractive


Here is the first try and I am sure the blurred area could be much better( less focused)



I was going to crop the vignetting out but I decided I like it.

[rjlittlefield]

Seeing just this one image, I can't answer your question for sure.

As a general principle, if you want a blurred background (the coin's field, in your case), then you need to use the widest available aperture and stop the stack far enough in front of the background to get the amount of blur that you want there. If parts of the subject and the background are too close together in depth, then you won't be able to get the whole subject in focus while retaining lots of blur in the background. This will be a particular problem with coins because the edge of the portrait and the edge of the field have exactly the same depth.

Can you show us how you want the blur to appear, and show us a single source frame in which it appears that way?

--Rik

[Troels]

I would either try tilting the coin a bit to make greater differences in the focus or mask off the face and add som gaussian blurr to the background.

Troels

[elf]

Using the retouch feature in Zerene Stacker would be my choice for doing this. Just choose the frame with the desired softness and do the retouching. I have no idea if Helicon Focus can do this.

[austrokiwi1]

Thanks people. I should have been clearer: With focus peaking I was able to set the start of the stack (I always start at the lowest point) at the bottom of the face while maintaining the coins field out of focus. The individual shots in the stack show a much nicer bokeh than the final stacked image. Its as if Helicon is trying to find sharp points in the blurred background. To ask my question more intelligently is there some way I can tell the stacking program not to process part of the image?

The only alternative would be to cut out the face and post it on tow a single image that has the burr I want.

Edit I tried another stack. I took a single photo with the sort of blurr I wanted and cut and merged the stacked face. Its getting close to what I want but I need to do a lot more work particularly lighting. I sorted the vignetting by changing the optical set up slightly



optical set up from front element to camera: SK 40/2.8 reversed coupled with SK210/5.6 mounted on a Minolta MD 2X convertor on a Bellows with correct extension for the SK 210 to be at infinity focus

[Charles Krebs]

My solution would be like elf's. Use the source frame that has the background "blur" you like and then, after the stacking is completed, re-touch it in as the background. This is easy to do in both Helicon and Zerene. Since this is such a flat subject you might not have a file that is blurred to your satisfaction. When taking the image stack you could be sure to include a frame or two de-focused to the degree you want. have one in the stack. It should not have any effect on the "sharp" regions, but then it gives you a source file frame to use in retouching for the desired background.