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Focus Stacking

I love digital! My last “gear review” Blog covered high dynamic range imaging software (HDRI) . I reviewed and illustrated the concept of HDR using Photomatix. The ability to illustrate in print and on screen, something the eye has always been capable of seeing, but traditional photographic techniques and equipment simply unable to duplicate, is fascinating. I am not talking about the unrealistic and often surreal effects (though they may well have their place in an artistic media) you see, but simply the ability to present a wider dynamic range of an image–closer to what that magnificent optical instrument of nature–our eye–can see. Digital imagery has brought that to us, as well, the capability, I am certain, not too far in the future of HDR capture in camera sensors.

Just when I thought I’d seen the most significant recent development in this area, I stumbled on the similar and equally amazing (in my view) digital technology, known as “focus stacking.” This technology takes advantage of digital images by combining a series of images with different focal points, using the in-focus portions of each image, to give greater depth of field (DOF) from front to back than is possible with a single image on any lens.

One of the “selling” points of wide angle lenses is their ability to resolve great depth of field from front to back. Those “wow” landscape photos you often see with the sharply focused foreground elements (often flowers or rocks) and sharply focused distance background elements are often taken with a wide angle lens (28mm or wider) focused a very close distance to the foreground element. However, I often find that my preferred focal length is usually something significantly longer. The focus stacking technology will now allow me to get that wide angle look with a lens that has less inherent DOF.

The illustrative photographs were taken with an 18-200 zoom lens, with the focal length set at 80 mm, at f16. I took a series of 4 exposures, all at the same shutter speed and all in essentially the same light. Using the multi-area AF sensors on my Nikon D200, I had 4 focus points in the viewfinder in portrait orientation. I shot the first using the sensor closest to the foreground, and each succeeding photograph, focused further into the photograph, with the final exposure focusing on the shed. In the illustrations, here, the first photo (top) is the result of combining all 4 exposures with focus stacking.


The second photograph is focused on a point about 1/3 into the photo (the traditional “wisdom” of focusing for the greatest DOF in a landscape photo), and the third is focused on the shed in the background.


You can see that there is much greater DOF from foreground to background on the first image. In the second, the shed is, perhaps, “acceptably” sharp. On closer inspection, it is clearly not as sharp as it is in the final image. In the final image, the foreground wheat is not in sharp focus. This may not be the best image to illustrate the technique, as the foreground wheat is a rather “busy” subject, which, in my view, makes it more difficult to assess sharpness. I have just begun to experiment with this, and can see some real promise. I have had photos, in the past, which would have been, in my view, stunning, but were missing that critically sharp focus throughout, particularly in foreground elements. I am excited to try this with some of the rocks and streams images I like to make when I next get a chance to photograph the subject.

So, how did I do that? There is (of course–why else would it be posted under the “gear review” category?) software that does all the math and technology. I couldn’t begin to tell you what is happening “under the hood.” Thank God though, that there are folks out there who can and have made this possible. There are two programs I am aware of. Perhaps the most well known is a program called Helicon Focus. It is very slick and professional, with a very user-friendly interface. However, it comes at a cost — approximately $200. You can download a watermarked trial version at (SITE). Given its potential, it is a relatively inexpensive software.

Recently I found a “shareware” software called CombineZP, which is free. It is not particularly intuitive nor “user-friendly” to use, but with some experimentation, work very well. The author has a website and is very receptive to questions, comments and suggestions. The illustration here was made using CombineZP. I did find that using the “all methods” combination, took an extremely long time to process. However, I converted 3 RAW images to TIFF and they were fairly large. I might be inclined to size to my final use size before using it next time. However, I did find that it caused some artifacting around the outside of the frame, so you will need to plan for cropping.

I think this is a really cool technology and will be adding it to my “arsenal” along with HDRI for my next serious photo trip to Acadia NP in October.
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10 Responses

  1. Hmmm, let me get this straight: to use both HDR AND this technique together, means we need to do 3-5 exposures at each of these multiple focus points? Dang.. I'll be needing some more memory cards! (Just kidding, couldn't resist:)Seriously though, this is another good technique from the digital bag of tricks that is relatively easy to do if you realize in advance that you need it. I have personally never used more than two points and rarely think to do even that, just because of the focal length/apertures that I typically like, but no harm to keep in mind that this could be a solution in some cases. Nothing more frustrating than an otherwise great shot where the DOF didn't work as expected! The more you know, the more likely to get what you need in any situation.Fall at Acadia sounds like a good time..Another great article.. thanks Andy.

  2. Mark. You are right. We are going to have to start carrying laptops with spreadsheets to keep track of the number of different exposures we need to get the DOF and HDR!I don't contemplate using this technique on every exposure — nor do I envision using both techniques together very often — but it obviously could happen. One of the "bugaboos" of digital is file management and this stuff isn't making than any easier a chore.Thanks for your comment

  3. Andy, great article. I downloaded both CombineZP and Helicon and tried them both. They worked pretty well but Helicon will handle RAW files while CombineZP will only handle jpg files. I shot some macros of my wife's orchid but I would really like to try some other kinds of shots before I pass judgment. Helicon lets you use their program for 30 days, no watermarks, no impediments of any kind. The lite version is $115. I don't think the features of the PRO version are worth the extra cost to me. Keep the articles coming. This is the kind of stuff I want to know about. Thanks

  4. Mark: As an addendum to our discussion, to highlight what could perhaps become ridiculous, I was reading this morning, about the possibilities with "stitching" images — something I had forgotten about when writing the Blog. Think about the workflow to stitch together, e.g., a 5 image panorama, with full front to back DOF through focus stacking, and using HDRI to get the max out of a high contrast sunrise or sunset!!

  5. Al: Thanks for the comment. I have tried the Helicon software, too. It seems to have a slightly better developed user interface. I had forgotten that it was capable of doing RAW images — a definite workflow selling point. The price point was problematic for me. Not that I think it isn't appropriate — I just didn't have the funds — I was also disappointed that the very short trial period began from the time of download. Had I known that I would have waited. Maybe I'll contact them and see if they will give me another trial for comparison purposes.

  6. Another photographer whose blog I follow, Patrick at french-landscapes.blogspot.com/, often uses PTGui to stitch together hi resolution scenes.. and almost always uses PhotoMatix HDR (and he has a beautiful, subtle touch with it, which is rare).. can't recall if he has tried to combine them, I'll have to ask. I was being a bit facetious in my original comment, but the more I think about it, it is the new reality. I have to believe the dynamic range issue is going to be handled in-camera, either by improved sensors or built in processing, in the near future.

  7. I've not upgraded to Photoshop CS4 but I understand that it has some photo stacking capability. While I've not found much on the subject anywhere, what I did see indicated that PS capability was limited. Maybe CS5 or the next generation of cameras. We certainly don't need more megapixels. Hopefully Canon and Nikon have their experts working on improving dynamic range and focus. Of course, we want to be able to turn off so the sharpness. I don't want to lose those nice blurred backgrounds. Wouldn't it be awful if the next generation of cameras gave us only what the eye sees? I want to control focus sensitivity. I can set my camera to Depth of Field and it will choose the aperture for making everything covered by the focus points, in focus. I want to choose the what I want in focus and what I want out of focus. I'm sure the experts as Canon and Nikon can figure that out.

  8. Al: I wholeheartedly agree. The main attraction to me of the SLR-style body is the ability to make choices and control how things look. While it might be nice to have the capability in the camera, ONLY if we can turn it off.I see PS eventually incorporating all these things as part of the program. The history seems to be that they will often purchase one of these programs to integrate it into PS. I too, am still using CS3.I am "old school." I still pretty much do my controlling manually. But obviously, capabilities light "depth of field" are timesavers, if you use them correctly.

  9. Here's an interesting new thought about how the Digital World is making it more feasible to create a unique photo. This is unique in a way I hadn't contemplated in my article or any of the comments so far.A good friend, who prefers to remain anonymous, wrote me privately with this comment:"One photo . . . . was taken from the summit of Sandia Peak at dusk, looking down at the city's lights. A streak of red sunset light washed over the rocks on the mountain's summit foreground. And the sun was just sinking, brilliantly, into the western horizon. All in all, the image was stunning.But it wasn't a single photograph.Turns out the photographer composited six different photos with six different exposures taken over a period of an hour or more from a locked down tripod. This is sort of taking the notion of extended dynamic range beyond the routine "2 stops over, normal, 2 stops under" exposure. His continuum wasn't just light, it was also time. I'm not sure which was more amazing: His patience at a computer to bring it together? (Even with advanced software it wasn't easy). Or the vision, long before the first exposure was made, to see an end result that simply couldn't have been done in a single exposure. In that regard, he created a truly unique photograph from a place where tens of thousands of photographers with varying skills tramped before."I cannot say this couldn't have been done in the darkroom by a very talented person, but digital, especially with programs like Photomatix, certainly makes this also within the contemplation of us mere mortals.

  10. Andy, I found this website http://ronbigelow.com/videos/videos.htm through Photo Camel. It offers a tutorial on how to do extended depth of field in Photoshop CS4. I really like this method because it allows some additional editing after everything has been put together. This may be enough to make me consider upgrading to CS4.

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