Focus shifting - D850

Discussion in 'Nikon' started by erik_christensen|3, Feb 28, 2020.

  1. Micro-step stacking is probably best reserved for closeups of relatively static objects, where DOF even at modest magnification is measured in fractions of an inch. Like any tool, it must be used appropriately. It is usually best to leave the background out of focus for closeups in nature, but you might want to show more of a flower in crisp detail than single-focus can accomplish.

    Landscapes can be handled more simply, IMO, with as few as two or three images. In lieu of swings and tilts, focus stacking can render key details in a landscape from foregound to infinity. I stacked two images for this shot, to capture the fence in the foreground with the round barn in the background. If you look closely, parts of the fence are OOF where they overlap the barn, as well as the grass in middle plane. Even at f/8, one or the other would be greatly OOF without stacking. Anything which moves between frames may be doubled in rendering, like grass or twigs in the wind. A minimalist approach is probably the best. However just because you have dozens of frames doesn't mean you have to use them all.

    At close range, the magnification can change significantly, due to focus breathing (internal focus changes the focal length), or simply because the lens moves further from the film plane when focused closer. Software like Helicon Focus will adjust and align key points in the images so that there is near perfect overlap.

    I prefer to use a focusing rail for macro stacking (product and table-top photography), which results in far less change in magnification, and allows focus on key areas with great precision. Manual focusing is appropriate if the depth of the subject exceeds the range of the focusing rail, and improves the odds that AF with stepping will hit on the right plane.

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    Last edited: Mar 1, 2020
  2. Sometimes it's easier to manually focus several frames at various points, then use the stacking software to put them together.
    Ed_Ingold and Andrew Garrard like this.
  3. Currently using Z6 for macro shots using focus stacking. Should the initial focus point be set using auto focus or manual focus? Or does it matter?
  4. AF, it can't adjust focus if you put it on manual!!

    Although, I guess you can set it manually, as long as you engage AF for the actual shooting.....;)
    erik_christensen|3 and Mary Doo like this.
  5. erik_christensen|3

    erik_christensen|3 Self-employed

    I tested it this morning even that it was a little haze, and I selected 9 frames 1 width and it decided to take 12 frames. Another also with 9 frames but width 7 and it took 10 frames. the attached is with the latter setting, it is a little too dark due to the haze. I will find a better location later, but I am travelling one week now.

    2020-03-03 21-40-25 (B,Radius49,Smoothing4).JPG
  6. You can get the best of both AF and Manual focusing if you disable AF with the shutter release, and focus using the AF button on the rear. You can then spot focus (single servo) on the foreground, mid ground and background for successive shots. A well lighted scene as in the previous post hardly needs stacked focusing, much less 9 or more images. If you had a row of flowers 5' from the camera against a mountain in the background, as in those glossy Swiss calendars, focus stacking would be of great value.

    I have never needed nor used more than three frames for landscapes. Closeups of 3D objects like flowers and fungus, an automatic stacking sequence would be great (on a windless day). My Sony doesn't have that feature, so I have to improvise using a focusing rail and partial turns of the knob. It's a cumbersome process which I find "exciting" only to the extent I know how do it, not as a regular activity.
  7. erik_christensen|3

    erik_christensen|3 Self-employed

    Ed Ingold – Next time I will try the manual stacking and take max 4 frames with focus of foreground, 1-2 at middle and 1 far. I have never used AF on the shutter release only on rear button. I used various settings of the above and special software for stacking of the 9 frames, and the first 3 attempts ended up with like “not everything saved”. It turned out, that my computer had not finished the operation after 10 min or so. I just image a macro fan taking 100+ he can go on holiday during the operation. I have previously used a focus rail for flowers, and even that it is good, one has to be very patient. Nearly all macro/close up of flowers are indoors, as it is always windy when it is good light, where I am living. Thank you for your comments.
    mike_halliwell likes this.
  8. You gotta be careful with things that move between frames such as waterfalls or the sea or waving trees/fields of grass.

    Sometimes the auto-blend algorithm gets messed-up (technical term) and makes some very obvious mistakes.

    It is indeed a very computer intensive task esp. with D850 files!

    The good/bad thing is that the spec. for a good gaming rig is pretty much the same as a good image stacking set up. It took me some time to explain to my then boss, that even though it was being sold as a high-end gaming rig, I really needed it for Abode Photoshop and Premiere etc etc....:D

    From what I understand (!?) the software has to have all the images open in RAM and compare them all. It only keeps clusters of sharp pixels and makes the 'soft' bits transparent with the assumption that there will be a sharp bit either above or below in the stack to keep and fill in the voids.

    That takes more processing power than most cameras currently have internally, but that could change...!

    It may work with landscapes with 3 or 4 images, but a complex macro of 100+ frames? that's not realistically happening any time soon.

    People have enough trouble waiting for the buffer to empty, nevermind processing a 60 pic stack that takes a current hi-end i7 PC with 32 GB of RAM etc, most of lunchtime to render.....:(
    erik_christensen|3 likes this.
  9. Technically, while you do need access to all of the images, you don't need all of them at once, or indeed all of any of them at once. (You can blend on parts of the image and stitch, and since you're only looking for the region of highest local contrast I believe you could do that cumulatively, only ever comparing the new frame with the accumulated "best so far".)

    But I've never actually coded it up myself, and having more data available probably helps refine things a bit.
    erik_christensen|3 likes this.
  10. That may be true for some software, but good old Photoshop puts each full image on a separate layer... and then the lights dim.

    Helicon and Zerene Stacker might well do it differently, but the're not that much quicker...;)
  11. erik_christensen|3

    erik_christensen|3 Self-employed

    I am using Helicon, but since it mainly is for landscape with a limited number of frames, then I will postpone an upgrade of RAM or what else could be required.
  12. True - but Photoshop has a fairly complex image tiling system. It ought to be able to handle images much larger than would fit in RAM. No argument that there may be faster ways that are less generalised, though.
    RCap likes this.
  13. The power of your computer will have an impact on the speed of the process. I have a Windows i7-6700 with 16 GB of RAM. My camera is a D750 which creates 24 MP raw images so the files for a D850 will be even larger, unless you create JPEG files. When I check the performance of the computer the RAM is maxed out on large stacks so more RAM might improve the speed of the process. When I stack a few macro images, 5 to 10, the stacking process takes a few minutes. I have stacked as many as 80 macro images and that process took about 30 minutes. However, it is a rather simple operation. I created a macro, or Action in Photoshop. I click on the Action button and the computer does the rest. I step away from the computer for a while and when I come back the stacked image is finished.
    I have also tried Zerene but I have found that Photoshop does a better job in my experience.
  14. erik_christensen|3

    erik_christensen|3 Self-employed

    I have i5-4690 16gb RAM only and use NEF full size which is about 55-60MP and using Helicon as plugin for LR. I was just not aware that it could take that long time, but as you say leave the computer and make a fresh cup of coffee may sweeten the process. I assume it will take some time before I am on the 80 macro images.
  15. Mary Doo likes this.

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