Problems with image stacking

[waynehicks1]

I have recently been experimenting with image stacking, with varying results. I'm finding a good percentage of the processed images are either pixelated, contain strange lines or have other discrepancies.

Could it be something I am doing wrong or is it the program, in this case Photoshop, that is creating the errors? I try to keep the camera settings the same for each shot so as to limit the chance of any errors in the final image.

I'm sure with a little tweaking I can master this technique, but maybe I just need a little nudge in the right direction.

By the way, my subject matter is fungi.

Regards

Wayne

[Bruce Williams]

Hi Wayne,

I use CS5 to process about 40% of my focus stacks (insects). However these are typically quite shallow stacks of generally no more than 10 slices (I use Zerene Stacker with deeper stacks).

Generally I find that CS5 handles the stacks well - the main problem being occasionally CS5 selecting the wrong slice in small areas of low contrast that lie immediately adjacent to areas of high contrast.

I'm somewhat puzzled by your experience of pixelation as CS5 stacks by the simple process of level masking - and so does not actually change the selected area of the source image. If the strange lines are at the border then this is probably due to the fact that there is a larger area of background in the near slices than in the far slices - this is always going to be the case.

My workflow in CS5 is as follows:

(a) File/Scripts/Load Files into Stack to load my source images into CS5. Note: I do not attempt to Automatically Align Source Images at this stage.

(b) Check that level order is correct (I prefer to stack far to near).

(c) Edit/Auto-Align Layers to allign the levels (Vignette Removal and Geometric Distortion OFF).

(d) I do a quick check on alignment by switching off the levels in turn.

(e) Edit/Purge All.

(f) Edit/Auto-Blend Layers. Select Stack Images with Seamless Tones and Colors ON.

I check the resulting stack for problems and (if necessary) correct by cloning from the best original slice(s).

Bruce

[Bruce Williams]

...CS5 does of course change the source images when aligning (resize and rotate) and will also modify colours and levels when performing the actual stack. None of these changes should result in noticable degradation of the image.

If you want to recover colour and tone to (almost) match one of the source images this can be done with Image/Adjustments/Match Color (and match stack to selected source file). You will of course need to have previously loaded the selected source file into CS5.

Bruce

[waynehicks1]

Thank you Bruce for taking the time to answer my question so thoroughly.

I, too, use CS5 so I'll use your 'workflow' next time I stack a sequence of images. I'll be out and about today so hopefully I'll have plenty of shots to play around with this evening.

Regards

Wayne

[Bruce Williams]

You're welcome Wayne.

If you still experience disappointing results you might find it worth tinkering with the level order prior to aligning - particularly if you shoot your source images hand-held.

CS5 appears to align all levels to the level at the top of the stack. So it's been suggested that placing the middle image at the top of the stack may reduce the amount of resize and rotation required in any one level. It's easy to check - just look at the level thumbnails after aligning.

If you try this don't forget to resequence the levels after alignment and before stacking (use the level name to do this).

Good luck.
Bruce

[waynehicks1]

Bruce, I just thought I'd upload this image to show you my latest attempt at stacking after following your instructions. It's a two image stack and I'm extremely pleased with the result. Constructive criticism is very welcome



Thanks again

Wayne

[Bruce Williams]

Looks to be a clean and accurate stack to me .

I look forward to seeing more of your stacked images in the Gallery.

Bruce

[FungiJohn]

I've always been a little sceptical regarding stacking software in the past, but recent improvements have changed my views.

I have used a workflow in CS5 similar to the one Bruce used and agree it is OK ..ish for small numbers of images and where the difference in focus is small.

Helicon Focus, albeit quite expensive is well worth considering if you plan to do a lot of stacking. It is also very quick in comparison to other 'free' types.

Here is a stack of 19 JPegs out of the camera with no post cleaning.



John

[Jim Ford]

Can anyone comment of the free stacking programs available?

I'm getting near the time when I'll have a 'lash-up'/'proof of concept' of an automatic focus stacking rail working, and will want to process the results.

Jim

[Lancashire Lad]

I use CombineZM Jim.

Can be freely downloaded from the hadleyweb website:-
CombineZM News

It certainly works without any fuss, (with XP & Vista - don't know about Windows7), and the results are very good.

Maximum stacks done to date are around 30 images, but I've seen stacks of 100+ images done with ZM

Haven't tried the newer version CombineZP as never felt the need to change from ZM.

Regards,
Mike.