Moderators: rjlittlefield, ChrisR, Chris S., Pau
This combination raises a red flag. When you move the camera to change focus with a large subject, you introduce perspective changes that can wreak havoc with stacking. It's far better to leave the camera in one place and change focus by turning the ring on the lens. See http://zerenesystems.com/cms/stacker/do ... versusrail for a discussion of the perspective change issues.photomac wrote:-Approximate size of subject field: I was shooting an area approximately 1.5' x 2.0'
-Optics: Nikon 60mm 2.8 micro lens on a Nikon D800
-Mechanics of acquiring stack: I used a Novoflex mini focusing rack
-Relative camera/subject movement: camera moved progressively closer to the flowers on the focusing rack
Thanks for the images. I'll take a closer look at those later. On quick scan, I see a lot of defects that are typical of DMap in general but possibly are being made much worse with perspective changes. So I'm still at the "can't tell for sure" stage, but the next thing to do is definitely to switch strategies for stepping focus.photomac wrote:Per your previous request, I've attached a few detailed pics so you can see the type of blury and distorted results I am getting.
Yes. Tethering software can run your lens at the finest increments of its focus motor, which by design is more than fine enough to focus precisely at any distance even at widest aperture. Typically those finest movements are too small to see the ring turn, even though it really is.-Will the tethering software help overcome the problem of my lens' very short focus throw?
You're correct about the issues with PMax.-PMax slabs first and then try doing a DMap process on the those sub stacks. I was avoiding doing the PMax slabs because I had read that PMax introduces color variations as well as noise and contrast issues.
At very high magnification there's no substitute for using a rail or its equivalent such as a microscope focus block. At somewhat lower magnifications they're less than ideal from an optical standpoint, but still the optical problems are not too bad and the convenience is great so the rail is still a good method. As the magnification gets progressively lower, the rail gets progressively worse, and at some point it becomes unusable. The changes are smooth and continuous, so there's no brightline criterion for what's best in each situation. The matrix at the top of the Ring-versus-Rail article tries to summarize the tradeoffs.-Is there a time when focus rails are appropriate? Perhaps smaller subjects? It seems a lot of stackers enjoy using their rails so I assumed it would help produce better results.
Sorry, I should have noticed in your original post—and from your forum name—that you work on a Mac. SlabberJockey is something I knocked together for my own use. Once it was in existence, I figured that I might as well offer it to others who might find it useful. But I use Windows PCs, and know very little about MacIntosh computers. SlabberJockey is a Microsoft Access application, and can be run under the free runtime version of Access. To the best of my knowledge, Access is available only for PCs—though perhaps some Mac wizard could teach us otherwise. However, that's probably unnecessary, as Bill Eldridge wrote a very nice program called Bugslabber, which runs on both Macs and Windows computers. The need for a Mac-compatible program was one of the main reasons Bill wrote it. I briefly tried Bugslabber in a beta version, and thought it seemed pretty good. Last I heard, you just need to PM Bill if you want to try his program. As I recall, if you like Bugslabber and intend to keep using it, he asks that you make, on the honor system, a $10 donation to a charitable organization that fosters girls’ science education.And thank you for the suggestion on the slab software - do you know if any of them work with a Mac? I was under the impression that the SlabberJockey did not, but I could be wrong.
I do this frequenty, in order to get the advantages of each approach (PMax and DMap), while avoiding their disadvantages. For a 100x, 1500-image stack of a difficult subject that Zerene Stacker seems to miraculously assemble out of a cloud of blur—yes, try this, especially for a low-key image where the darker sections have increased potential to accumulate noise. But for a subject like yours—high key, capable of being shot with a shallow stack—no. Zerene Stacker can probably handle this situation in its sleep.PMax slabs first and then try doing a DMap process on the those sub stacks.
While technically true, I think too much worry exists about this PMax trait—which I hesitate to call an “issue.” I use PMax and DMap about equally, and for situations where PMax works better, correcting color and contrast takes me less than a minute in Photoshop, with a curves layer. Your D800 sensor should produce very little noise, at base ISO, so even if it accumulates, I think you’ll usually find it not to be a problem. And if it is, you can always perform noise reduction on the input images or the stacked image.I was avoiding doing the PMax slabs because I had read that PMax introduces color variations as well as noise and contrast issues.
I wouldn’t worry that two different DOF calculation tools gave different numbers, as they probably use different formulae and assumptions, and the question of "optimal increments" is very much an open one at present. The source Rik referenced in this thread (and indeed, created) is excellent, but you need not worry about such differences right now. A DOF calculation tool just gets you into reasonable territory; after that, personal experimentation is the best way to determine what focus increments work for you. And as we agree, "reasonable territory" under any calculation system involves many fewer frames than originally used here.photomac wrote:If I do a simple calculation on DOFMaster though, f8 and 20 inches distance from camera to subject gives me .8" of DOF. That would require a few more frames than you suggested. . . .
Pointing out examples in your image is difficult for me, as the whole frame--not just portions of it--says “flare” to my eye. What I see reminds me of the lack of contrast I see in my own images if light is spilling onto the front of my lens.I do wonder about the potential of light spraying into the lens given my setup. Do you mind pointing out to me any examples of veiling flare you noticed in my examples? I would just like to be able to spot it for myself in the future so I can determine whether I need to tweak my setup. I like the 'glowy' effect I get with light behind the subject, but I'm wondering if that is offset by flaring issues.
Yes indeed! And you might even try running test shots at some small aperture such as f/32. Sure, you’d get diffraction blur; but you would also get most of the subject in focus in a single exposure, which would let you test a bunch of lighting regimes. Then, once that’s nailed down, you could open up, turn your speedlights down to compensate, and run your stack.The good news in this discussion is that shooting in preparation for a stack will be much less time intensive going forward.
