First attempt at focus stacking with a rail

[JohnRostron]

Most of my focus stacking so far has been by adjusting the focus. I did try one by edging the camera and subject closer and closer by hand. Recently I spotted a cheap rail on Ebay so I invested. The subject was a glass sculpture. One problem with photographing glass, as Mike Buckley reminds us, is controlling reflections. I avoided this by shooting into the light. The statue was placed on my window ledge, about 7-8cm in front of the window. The view down the garden behind had no obvious distractions. (I had even removed the rotary washing line from its socket.) I placed a ruler against the front of the statue to find the starting focus position on the rail, (using the lines on the ruler to focus on), then placed it behind the statue to find the finishing position on the rail.

I took about 25 shots at about 2.5mm intervals. The images were stacked using Helicon Focus.

As usual with a distant, out-of-focus background, I found that the focus stacking software gives weird results. I post-processed the DMap image by blurring the background to reduce this.

The final result was not as good as I had hoped. Here it is. Let me know what you think.



C&C welcome.

John

[chauncey]

John, your asking quite a lot of your software taking all those minute reflections into consideration.
The only obvious problem is lower right portion of the subject...would have expected more clarity
from the background that is exhibited in the glass.

[DanK]

John,

for the most part, this looks good, although it is not the ideal for testing stacking. Better to use something detailed so that you can see if any areas remain out of focus.

Most of my stacking is done with plain backgrounds, but to the extent that I have done them outdoors, I don't recall problems with backgrounds looking odd. For example, in this recent one, I blurred the bottom left in PP because it was too close and therefore distractingly in focus, but the top and right are straight out of my stacking software (Zerene):



I don't know whether Helicon has this feature, but Zerene's DMap procedure has a contrast adjustment that you can use to indicate areas that the software should not try to stack. It is quite handy for avoiding the kinds of mush that one sometimes gets in some areas of a stack.

I'll have to play around with some various stacking methods to see if I get the kinds of problems you are having. It's possible that I just haven't done enough stacking with complex backgrounds to see it.

Dan

[IzzieK]

John...I like the subject very much and the minute details in the glass itself of the background. William is good at this so I think you should follow his advice and see how you go. Overall, you did a very nice shot of what you wanted to achieve...I am still thinking about a rail but it seems that it kept getting back to forgetting to buy it. Lots of studio work it can do with one...lucky you!

[Shadowman]

Looks like a loss of detail in the base, the dolphins have a nice soft quality.

[JohnRostron]

Thanks to Will, Dan, Izzie and John for your comments and suggestions. Will, I take the point about expecting a lot from the software. I will probably try again using a translucent background and see what happens there. Most of my stacking so far has been done on flowers, so I thought I would try something different.

Dan, I have been using Zyrene and Helicon in the trial version so far with the default settings. I will look at the Zyrene Dmap contrast adjustment as you suggest. This will mean reading the manual!

John

[bnnrcn]

A little clarity might improve the image, very nice subject

[chauncey]

FWIW...during a fit of error I bought on of those automatic focusing rail. Used it once...unsuccessfully.
Fast forward...now I only do stacking while shooting tethered with software that allows computer
controlled focusing changes, then stack in PS CC.

[DanK]

John,

I just did a quick test that taught me something about the problem you mentioned. It is only a 6-shot stack because the wind kicked up and made the remainder too far off in alignment to use. Here are my conclusions, based on very little data:

1. Depth map stacking (DMap) can create the messed up backgrounds that you have encountered. In some cases, Zerene's DMap wll also.
2. Increasing the contrast percentage in Zerene can help, but depending on the image, it might not be enough.
3. Zerene PMax, which is not a depth mapping algorithm, seems to be largely free of it.

I'll post the pictures below. Here is what I would do:

1. I most often use depth mapping for flowers because it is better than PMax for maintaining colors and some textures.
2. If the result is problematic, I do a PMax stack also. DMap is more prone to halos from parallax than PMax is, which is the most common reason for me to use both.
3. Use the retouching tool in Zerene to get rid of the problems. I often paint from a PMax onto a DMap to lessen halos, and I also paint from one individual slice in some cases. I'll show you one of those.

First, today's test, rearmost image:



PMax stack, all 6 images:



DMap stack, contrast set to 50%:



Here is one where I retouched from a single image:



When the stack was done, the petals in the background were more in focus than I wanted because of the rearmost slices. So, I simply retouched from the front-most image.

BTW, someone can correct me if I am wrong, but I believe stacking in PS CC is a depth map.

Dan

[Loose Canon]

Hi John,

Difficult test subject. Hard for me to tell what’s going on so I’ll just toss out a couple of observations that haven’t been mentioned.

When zoomed in tight a lot of artifacts become quite noticeable around the edges of the glass piece. Looks like maybe some “ghosting” and maybe other things are happening.

I would have thought that the base would have retained way more detail than it has. I would definitely consider this result unacceptable but this could easily be due to the lighting coupled with artifact.

John I have only run the trial periods on Zerene and Helicon so I only have limited experience with these. My stacking needs are not as complicated and I don’t usually have to worry about backgrounds. Most of my stacking is done in the studio and PS has fulfilled the need (so far).

If I were going to have complex BG’s to worry about with multiple shots I would seriously consider compositing with just one nice base BG shot, process the stack, and composite the subject to the nice BG. In the field I would think there would be too many variables to have to worry about (wind, changing light, changing focal points, etc. Things that would mess with the stacking software trying to do its job).

One problem with photographing glass... ...is controlling reflections. I avoided this by shooting into the light.

It doesn’t matter where the light is coming from, with highly reflective subjects you can never avoid dealing with reflections of one kind or another. Glass being worse than most.

I have to wonder why you chose to stack this and then why so many shots at such a tiny interval. Of course, I have no idea what the specifics are, how far away you were, how big the subject, but f/5.6 and five feet distance @ 28mm (EXIF is saying f/5 @ 28mm) should give at least a couple of feet DoF just as an example. I find that the least amount of shots the higher chance of success.

I might also add that I find stacking with a rail far easier, quicker, and more successful.