Zerene Stacking Halos Using DMax

[Round Tuit]

I stacked 9 frames of these morning glories buds using the PMax and DMax algorithms of Zerene Stacker. The resulting pictures looked identical in the Zerene windows but the DMax one showed several obvious halos when I imported it into Lightroom. My wide spectrum monitor is calibrated and I used the prophoto as my editing gamut. I did manage to get rid of most of the halos except for the very tip of the right side bud which I will have to go back and fix. Does anyone have an explanation for this phenomena or better yet, a way to make the halos show in Zerene?

[DanK]

The cause of this is usually parallax--the images farther back are smaller--and it most often arises when there is a substantial distance front to back between an edge on the forward image and whatever is behind it. Given that there is nothing behind the right-hand flower, my guess (I would want to see a larger image) is that this is not a stacking halo. Rather, my guess would be that your rear-most image wasn't far enough back. Have you checked your stack to make sure that you have one that has that tip in sharp focus? (My solution to this is to start at the front and keep going for a while after I think I have reached the back. It is trivial to delete unnecessary photos but not to add more after the shoot.)

The algorithm used in DMax is more prone to creating halos than PMax. Overall, I prefer DMax to PMax for images like this because it does a better job preserving colors. A simple although sometimes incomplete solution to stacking halos is to create two composites, one with each method. Then use the retouching tool with the DMax image as the target and the PMax composite as the source. Just paint over the halos. I find that this eliminates many of the halos entirely and reduces many others. Sometimes you can do better retouching from individual images. I sometimes do a final cleanup in photoshop, but often I don't need to.

Calibration and color gamut aren't relevant to this problem. It is purely a problem of the position of elements in the stack.

[Round Tuit]

Dan,
I guess my question was not as clear as I had thought. My problem is not that the DMax picture has halos but rather that the halos did not show up in Zerene. They only showed up after I saved the tiff file and looked at it in Lightroom. I wondered if this is a result of the fact that Zerene does not colour manage its working file but I really don't know.

[DanK]

Ah, now I think I understand.

Color management has nothing to do with this. My guess is that the issue is simply size. The Zerene workspace is crowded--the list of files on the left, and the remaining space broken into two sections, one for an original image (or a source for retouching) and a second for the composite image. That makes the image small on the screen, and the small size hides all manner of sins, including small halos. To find small halos, I always enlarge the images. There is a drop-down menu at the bottom for this. How much to enlarge depends on your monitor, but with my 27", 2560 x 1440 monitor, I find that 50% works well. I then scan the selected area, moving systematically across and down the image.

[Round Tuit]

Size can hide a lot of defects. In this case though it isn't the culprit. My monitor is only 22" (1920x1200) but I examined both pictures at 100%. The halos are visible in the tiff file but not in the Zerene window.

[DanK]

This is a real puzzle. I have used Zerene for years, with two or three monitors of different sizes, and I have never encountered this issue. Or at least I have never noticed it. First, if I am understanding where the issue is (it's hard to see at this size), I don't understand why there would be a halo at all, if what you had behind the flower was really black. Second, I can't figure out what in the process would cause whatever this is to be visible in LR and not in Zerene, if you are viewing at the same size. The only thing I can think of, which is just a guess, is that there is something in the conversion of the working scratch file to the stored file you imported back into lightroom. What parameters do you use in saving from Zerene? I use 16 bit TIFF with LZW compression and 'retain extended dynamic range.' Do you use something different?

I will be away from computer much of the next 4 days, so I may not reply quickly.

[Round Tuit]

A full size jpeg copy of the DMax file with the location of the halos circled in red is located here.
http://web.ncf.ca/andre.lagace/CiC/Buds%20-%20DMap.jpg
I now believe that the halos are not visible in the Zerene image is because it may be displayed marginally darker than the image in the file. It takes very little darkening of the file to make the halos disappear.
I saved the Dmax file as a 16 bit TIFF, uncompressed and without checking the "retain extended dynamic range" box. The background in the picture is my turned off monitor which is flat black or very close to it. There was no direct light hitting the monitor and the room was quite dark. The individual shots were taken at 20 sec, f/10, ISO 100, FL 100mm using a 31mm extension tube.

[DanK]

I looked up the retain extended dynamic range option because I had forgotten the details. It turns out that it affects only PMax composites. See http://www.zerenesystems.com/cms/sta...es/imagesaving. (You probably have discovered this, but Rik has put very through explanations and tutorials on his website.)

I don't have Zerene on the laptop I have with me, so I can't look at anything, but your hypothesis about brightness sounds plausible to me.

You could probably easily clone this out in photoshop, and probably with the adjustment brush in LR if you set it to no feathering and auto mask.

What I often do with images like this is run them into photoshop from LR. I then select the background by color and turn it fully black with a levels adjustment. If the selection is good--you can control it with the poorly named "fuzziness" adjustment--this will often get rid of areas that are not quite black. This might take care of the remaining halo.

[Round Tuit]

What I often do with images like this is run them into photoshop from LR. I then select the background by color and turn it fully black with a levels adjustment. If the selection is good--you can control it with the poorly named "fuzziness" adjustment--this will often get rid of areas that are not quite black. This might take care of the remaining halo.

That is my goto method when I have a dark background

[IMW]

Sorry to be that person but it's DMap not DMax. For the majority of my own stacks (mainly of insects), I find that the PMax option provides the more pleasing results but a retouched blend of the two methods can work quite well.

[DanK]

Sorry to be that person but it's DMap not DMax. For the majority of my own stacks (mainly of insects), I find that the PMax option provides the more pleasing results but a retouched blend of the two methods can work quite well.

I use retouching from one composite to the other often, but always to touch up a DMap composite from a PMax composite. The reason is that PMax is less prone to halos and tends to have smaller ones when they do arise, so retouching in that direction is a quick way to address halos created by the DMap algorithm.

I searched in vain for an email interchange I had with Rik years ago about the two methods. However, my recollection, for what it's worth, is that DMap does a better job of preserving colors, while PMax does a better job of preserving fine detail. I may be remembering incorrectly. Given that most of my stacking is flowers, I generally start with DMap and clean up as needed.