stacking ?

When you stack multiple images, particularly at macro magnifications, my limited experience says that because each image is at a different magnification (and FOV) they won't align perfectly. Thus, all but one image in the stack will need to be expanded/compressed. When I've tried stacks, I end up with a fuzzy area near the edge that must be cropped. Is there software or manual methods to avoid this problem? Would it be better in a macro stack to leave the focus fixed and move the camera (on a rail) rather than adjust the focus? Do you alway plan for the crop and set up accordingly? Thanks for any suggestions.

Hello Mark,
I got interested in and started investigating image stacking about a year ago. Their is a lot to learn and I don't claim to be an expert but even just beginning with stacking anyone can achieve good results. In my opinion Pat Sampson is "The" resident professional on stacking and he may be able to help with your questions as well.
Of course the very basics require a steady tripod and I would suggest a cable release to avoid accidental minor camera movement. I think it may be best to begin with subjects that are small in depth (front to rear) and so will require fewer exposures to be stacked and married into one image.
I had some success with this and started searching the internet for articles on stacking and technique. One really good website that I found helpful is Laurie Knights Photo website... http://www.laurieknight.net/article
After searching several sites for info on stacking it became clear that I was interested in stacking enough to purchase a rail and stacking software to take my learning to the next level.
I think using a rail is the logical next step and their are several on the market so do your homework. I believe a basic manually operated rail can be purchased for under $100, in fact you could even make one if your handy and inclined. I looked at several and purchased a higher end automated rail with lots of features from Cognisys Inc., their rail is called the "Stack Shot" and you can find info on it here... http://www.cognisys-inc.com/stackshot/stackshot.php
The next step in the process is software to merge the stacked images into one. I am sure this can be done in PS but personally have not tried it. I looked at 2 software companies that were mentioned most often by others, Zerene Stacker and HeliconSoft. I purchased the HeliconSoft, http://www.heliconsoft.com/
As mentioned, I am not an expert and still have lots to learn. The product choices I mention here I like but they are not the only ones available. Also I believe if you want to make your own rail, I saw directions for that on the Laurie Knight Photography website mentioned above.

I hope this has been helpful, happy shooting and stacking! Craig

PS Here is one of my stacks that I really like a lot, http://www.naturephotographers.net/imagecritique/ic.cgi?a=vp&pr=161872&CGISESSID=42f9ca6a438bbb6d57edef240a8b6403&u=2227

Would it be better in a macro stack to leave the focus fixed and move the camera (on a rail) rather than adjust the focus?

Mark, No matter what you do, magnification changes. Use a rail or don't use it. There are really very few shots that I have seen that I'd call superb stacks on NPN - it shows if you look properly, that is. Most of the great stacks I have seen are outside NPN. I agree, Pat Sampson is one of the few who get it clean and nice most often, Ian Wolfenden is another (pardon me, if I missed some obvious good choices) - on Flora where I participate usually.

I have not been happy with a single stack I have dome myself even though, for small web versions fooling people (so I think, not to under estimate anyone's observation) is much easier than on a big print.

Most stacks look very very artificial (I'd like to lump them together with the famous "HDR" photos from the Ghostlands) - with "perfect" front to back depth of field and after that totally Zero.

Sometimes I get the halo, and sometimes I don't, and since my technique is always the same, I'm not sure what's going on. I stack photos often and feel it has greatly improved my macro work. I use a simple Kirk rail with my 105mm AF macro lens, but I prefer to use the focus ring on my old 200mm Ai-S macro. Cable release is mandatory. I bought Helicon Focus after doing it the slow way in Photoshop and have never looked back. Most of the macro shots on this blog post (http://jwallphoto.blogspot.com/2011/08/urban-getaway.html) are stacked, and IMO only the cattail leaves show it (the leaves were moving, so I did a "short stack" of just 4 frames and missed the edge of one of the leaves). I think getting everything you want in focus while keeping the background looking like you shot wide open (or nearly so) looks excellent.

Mark : I'm not well up on the technical aspects of stacking and am not quite sure what you are referring to when you mention the ` fuzzy area near the edge '. Do you mean all round the image or just in the fg or bg ? Using Helicon, so long as I am careful, I don't seem to have this problem, though I do often allow for a blurred fg and/or bg depending on the effect I want with a particular flower, so I may be circumventing any such problem. Incidentally, I only work by shifting the focus, not with a rail.

Maybe if you could post an image here which you feel is problematic it would make the issue clearer ?

Mark,

Sorry, I'm getting to this late. With regard to the fuzzy area, I think Ian and I don't see it because Helicon doesn't process it. My understanding from more than a couple of years ago is that Helicon Focus, uses only the image information that is in registration in every image in the stack. I still have no idea how the algorithm determines registration. So I think Helicon is cropping out the boundary of the image that's not carried throughout the stack, if that's the blurred area you're referring too.

Just by the way, I think Ram is absolutely right about changing the magnification whether you use a rail or the focus ring. It's less noticeable of course, the farther you're away from the subject. At most of my shooting distances, it isn't a problem. At true macro distances stacking in my experience becomes a lot more questionable. (smile) Again, just my experience.

With regards to John's comment above, I agree wholeheartedly. Both that I prefer Helicon and that regardless of technique sometimes I get artifacts and sometimes I don't. I think that's just the nature of the algorithm. I do always look for them though and am prepared with my cloning brush. (smile)

I'll be glad to continue the discussion in this thread and will try and research any questions you have to the extent that I think I can.

pat

I greatly appreciate the suggestions and comments from all of you. I had earlier tried the trial versions of Helicon Focus and Zerene Stacker (I'm on a Mac.), which is where I saw the "blurred rim" but don't remember what program produced it. Since I wanted to process the raw files directly, I purchased Helicon Focus and have been working with it for a few days. I can already see that this is going to be a major challenge since I like to work at high (1:2 or higher) magnifications outdoors...someday maybe I'll get a stack that's good enough to post.

Mark, I'm curious as to why you chose Helicon over Zerene. If anyone else can compare these two programs, I'd appreciate it as well as I am considering which way to go.

Scott, for me the issues was Helicon's ability to use RAW images. I want to go directly from LR to stacker on my Mac and Zerene made me create and save TIF images before working on the stack. With Helicon, I could work directly from the RAW files without saving TIF intermediates, which were discarded after a successful stack. There was a problem in that Helicon didn't include any rotation or processing adjustments made in LR. I've since discovered that Helicon can work from a LR processed file on a Mac using the File/Plug-in Extras menu. It seems like it still creates a TIF file, but doesn't save it, so there's no extra clean up after a stacking attempt.

Thanks, Mark.