Stitching as opposed to shooting larger format

Discussion in 'Digital Darkroom' started by jason_keen|1, Nov 1, 2010.

  1. Hi,
    I am a student photographer who is interested in stitching images with some sort of nodal point head, whether it be electronic and manual. I am working on a series that I have been shooting 4X5 with and have been intending to make 30x40 prints. However, the cost of film, processing, is something that has become an issue. I also am much less comfortable with film than digital, and I just like the digital workflow. I am not interested in creating crazy high resolution images. I'd likely stitch maybe 9-12 images, 3 or 4 horizontally and vertically, to achieve a much cleaner, nicer 30X40 print. My question is, what kind of head is best for this? What kind of software is usually best? Especially for removing distortion. I prefer things to be straight and rectilinear for the most part. I am not opposed to correcting distortion digitally and downsampling (is Photoshop the easiest for this or is there something that will automate it?).
    Hope this isn't too vague. Just looking for general information.
    Best,
    Jason
     
  2. I prefer a manual head. I like to cobble my own together out of available pan units and geared macro rails, but that's because I use this stuff for a mix of stitching, 3D (stereo) and macro. If I wanted a nice, neat off-the-shelf solution, I'd probably go with a Nodal Ninja 3 or 5, they're very competent, well made and usable.
    The best software for this sort of work is still something derived from Dertsch's Panorama Tools, either PTassembler or PTGui. Photoshop is only "easiest" as in the sense of having the least to learn, it's not "easy" to get the best results out of it.
     
  3. I've been experimenting with the Manfrotto 303SPH for several years, and am starting to take this 'art' seriously now; it (the Manfrotto) works great. Personally, I want the 'stitching' to be as painless as possible in software (the more automatic, the better, so I can start working on the image, not fixing stitches) and so far I'm having GREAT luck with PSCS5 and letting it do it's thing - you need to really screw up to have to adjust the individual images (but of course the final big shot will need some work much like many photographs...just not the individual stitches, which PSCS5 is doing, as I say, a great job on).
    If you're using a smaller camera, I've heard the Nodal Ninja is great and plan on getting one myself soon:)
     
  4. Accidental repost [IGNORE]
     
  5. Accidental repost [IGNORE]
     
  6. A logistical question... If I want to create an image that is rectilinear and not too obnoxiously distorted, is it going to best for me to move farther back from the subject and use a longer focal length?
    Jason
     
  7. Depends on how many stiches you want to use.
    The short answer is, if you think in terms of a 35mm camera, a 35mm lens is about the limit for 'no distortion' but that is based on human perception. I think the actual number is 43mm lens for 35mm format="human eye" and anything less than that (ie 42mm) will on some level be distorted - if someone sees that way. And the amount of distortion is a very rapid thing, ie 24mm looks WAY more distorted than 28mm
     
  8. Said another way, for stitching purposes - perspective is perspective; a stitch doesnt change that. That's why Giotto was so cool:)
     
  9. stp

    stp

    Jason, regarding your logistical question, I would answer "yes." Regarding your first question, the kind of photograph, or more specifically the composition within the photograph, will guide the kind of equipment that is needed. If all of the elements in the photo are relatively far away (e.g., a mountain scene with no nearby foreground objects), then the nodal point is inconsequential and no special equipment is needed. However, if there are nearby objects that appear to change their position relative to background objects as the camera is rotated, then the nodal point is important and a photographer has to have the equipment that will allow the camera to swivel on the nodal axis.
    My stitching has been relatively simple: distant landscapes shot with a moderate telephoto lens (often about 70mm), and stitching using PS4 is entirely adequate.
     
  10. You will need a two-axis pivot, centered, with a nodal slide. Novoflex and RRS make suitable, high quality devices, but they're not cheap. You could use Photoshop, but a dedicated stitching program like PTGui ($120) will save you a lot of time and trouble aligning and blending the images.
    In order to duplicate the area of a 4x5 film image, you will need to stitch a 6x6 array with an FX DSLR, because you also need a 25% overlap between frames for good matching and blending. This will produce a field of view four or five times as great as a single frame. While the perspective of the composition is determined only by distance from the subject, you would need to use a 200-250 mm lens to emulate the field of view of a "normal" 180mm lens on a 4x5 camera. (Did someone suggest using a 35mm lens to maintain perspective?) I stitch panoramas mainly to get a wider field of view, but you're proposing something different.
    The entire array will take about two minutes to shoot, compared to 1/100 of a second with a 4x5 camera. Hopefully nothing will move in this time. Unfortunately, even clouds on a calm day move enough to confuse blending in a stitched panorama, especially if you use an appropriate focal length for this emulation. Consider changing costumes and appearing twice in the same picture, just for kicks ;-)
    Distortion is removed by converting each image to a spherical projection, blending, then reverting the assembled results to a rectilinear image. That's pretty straightforward in PTGui, especially if you determine the nodal point accurately.
    Frankly, if you want 4x5 results, use a 4x5 camera. If you want a 180 degree panorama (or just a 3:1 aspect ratio), use a stitching program.
     
  11. I think that it should be fairly easy to fabricate a plate that positions the nodal point of the lens over the tripod mounting screw which should correspond with the horizontal pivot axis of the tripod. Drill and tap one 1/4" X 20 threads-per-inch in a wooden or aluminum block for the tripod mounting screw and one to mount the camera at the appropriate distance. (There are actually two nodal points for a complex lens, light rays appear to converge on the front nodal point and diverge from the rear nodal point. The front nodal point is the important one here.). Many or most lens manufacturers list nodal point locations on their web sites. Keep in mind that the front nodal point will shift with zooming and even with focus distance. A fixed focal length lens should be easier to deal with than a zoom lens for stitched images and should also typically provide less distortion. As Stephen says, don't worry about a nodal point pivot if the subject is distant. If the subject includes some moderately near objects, then a home-made plate should work. And if objects are close, then a commercial device that is adjustable and permits positioning the nodal point more exactly may be necessary.
    Another approach to creating a stitched image is to use a tilt-shift lens and translate the lens from side to side without moving the camera and then stitch together images taken at different translation positions. Jack Dykinga wrote about this method in an issue of Outdoor Photographer a few months ago. I have never tried it since I do not own a tilt-shift lens.
     
  12. In regard to your logistical question, there are two issues.
    One, foreshortening is not strictly speaking a function of focal length, but of camera-to-subject distance. If you're panning over a building that is foursquare to your camera and its ends are significantly further from your camera than its center, yes, the ends are going to be smaller than the center, and yes, you're going to get foreshortening or "wideangle distortion," and no, it's not actually distortion but normal perspective, and yes, you may find it objectionable.
    Two, many lenses exhibit barrel or pincushion distortion at extreme wide angle which is much reduced at normal or tele focal lengths. You want to pick a focal length for your lens that gives rectilinear images in order to avoid lumpy bumpy panoramas.
    In regard to your original question about nodal point heads, I am unable to help you. If the subject were either noodle heads or pointy heads, I would be able to hold forth with some authority. I am glad to note that you have got reliable advice from sources expert on a combination of the two.
     
  13. Jason, a Nodal Ninja pano head and Photoshop (CS3 on in my experience - don't know about earlier versions) will work well to do what you want.
     
  14. Nodal plates need to be adjustable, for all the reasons cited above. The simplest approach is based on Arca-Swiss type QR. The V-block plate and clamp system is very rigid and secure. The camera can't rotate on its mount because the plates are fitted to the contour of its base.
    You don't need micrometer adjustments, so a long (6-8") plate with an Arca clamp at one end for the camera will suffice. The camera is clamped to the long plate and the plate to the panning head. Slide the long plate backwards and forward while panning the camera until objects in the foreground don't shift against things further away. RRS plates have ruler markings, making it easy to restore settings.
    For some reason, the nodal point of the lens I use most often for panoramas, a Nikkor 28-70/2.8 AFS, changes very little when zoomed or focused. It all depends on the lens design. It's almost always necessary to set the nodal point. If you can sense depth with your eyes (about 75' or less), you will get parallax in a panorama.
     
  15. Although I have only used a home-made fixed nodal point pivot device with a 50mm lens, I notice that focusing rails can be purchased quite inexpensively on e-bay (less than $20, including shipping). One of these should work as an adjustable nodal point plate if it is sufficiently sturdy and long enough. I think that I will order one and try it.
     
  16. Thanks everyone. You've been a great deal of help. I have been running some tests with the equipment I have (DSLR, tripod w/ a normal 3-way head, 50mm 1.4 prime lens) and Autopano Pro. I like Autopano Pro because it seems to be the best it making things appear rectilinear and how a human eye might perceive the object, but it's having trouble blending things together at certain seams. I'm wondering if this can be attributed to not using a a head that can rotate around the nodal point? Photoshop seems great at blending things at the seams and matching things up, but it awful quite awful at automatically making things rectinlinear (as far as I can tell) and lacks an interactive layout (CS5, if this is untrue please let me know...) I've attached an image at the bottom of the post... What do you guys think? Is this just because of bad processing or is it the cause of parallax? All suggestions are incredibly helpful. Thanks all.
    http://img189.imageshack.us/img189/9335/stitche.jpg
    3 images shot horizontally and stitched.
     
  17. It seems based on your sample image you may be over complicating things. I use a Canon 5D Mark II and when needed for architecture use a 17 or 24mm Tilt Shift lens and I am able get 30 x 40 prints no problem. However, I use RAW and HDR techniques to get really high res large prints. If I cheap out and don't rent a tilt shift lens I use my 17-40 and Adobe Light room lens correction to straighten lines. Panoramas and stitching do not give you what you would get with a 4x5 film camera. When I want to get a 4X5 film camera look I use HDR and a program by Alien Skin called Exposure to give me the film grain and saturated colors of the type of film I want it to look like.
     
  18. MP, as I understand Jason's original post, he is not looking to replicate the look of 4x5 film, but to be able to create images that can be printed at 30x40 - am I correct Jason?
    These look like parallax errors to me - and I would expect there to be some with the lens so close to the subject. Auto-blend in Photoshop can often correct something like this, but not always. Have you tried the lens correction tool in Photoshop to correct perspective issues? Or the crop tool with the Perspective box ticked? Maybe there is a trade off in Photoshop between rectilinear results and accurate stitches - if you look at this example image you can see that the software will have to shift a lot of pixels to get both those areas stitched accurately, and that must have an effect on the look of the result.
    In my experience, the more effort I put into getting my lens accurately rotating on its nodal point, and less foreground objects there are in the image, the better, 'normal' looking result I get with a Photoshop stitch. Not tried other stitching software.
    If it is size, not panoramas, you are after, have you tried upsizing software or tools, or even just re-sizing in Photoshop with appropriate output sharpening?
     
  19. Actually, the correct point to rotate the camera about to eliminate parallax effects is the entrance pupil of the lens, not the front nodal point. This is not an academic point; the two points can be separated by tens of cm in some lenses. In practice, the usual setup procedures recommended for finding the "nodal point" or no-parallax point (NPP) actually find the entance pupil. See http://www.janrik.net/PanoPostings/NoParallaxPoint/TheoryOfTheNoParallaxPoint.pdf .
    I have used PTGui for ten years and have not found anything better, being able to stitch images from extreme wide angle fisheye lenses to ordinary rectilinear lenses. There are many other stitching programs that can produce excellent results too, of course, but often with more limited control and flexibility. Examples of stitching done with PTGui can be seen on my web pages at http://www.johnhpanos.com .
     
  20. You could use Photoshop, but a dedicated stitching program like PTGui ($120) will save you a lot of time and trouble aligning and blending the images.
    ...or you can use a dedicated freeware such as Hugin, which you can download from the SourceForge.net site. You'll find some tips on operating this software on some flickr groups such as Hugin and Hugin Users Group; also Perfect Panoramas and Extremely Large Panoramas might offer some useful info.

    If you're not afraid of command line apps, check out PanoTools and ImageMagic.

    If you're on Windows, have a look at PTAssembler by Max Lyons of TawbaWare (NB: I'm on Mac, so haven't had a chance to try it, but it's a shareware, so not free but dirt cheap.)

    Finally, either in addition to or instead of stitching, you may also want to improve the quality of individual shots, or rather of whatever you can capture without moving your camera, i.e., you can achieve substantial gains in both detail resolution and noise reduction by shooting exactly the same scene multiple times (even without changing the exposure if the tonality doesn't exceed camera's dynamic range), thus allowing you to print larger at high quality without the hassle of stitching. Apart from reducing noise in PS with stacks, these two aps may be worth trialing:
    • Zero Noise virtual RAW looks very promising (again, I'm saying it "looks promising" because, unfortunately, it's available on Win/PC only; here's a one-page/picture user manual for it ;)
    • commercial PhotoAcute (have just downloaded the trial version, so no first-hand experience with it either, but have heard good user feedback on it)
    Good luck and have fun!
     

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