Jump to content

All Activity

This stream auto-updates     

  1. Today
  2. Last week
  3. Eleni Koutoula and colleagues at the Archaeological Computing Research Group at U. of Southampton did some work on transmitted RTI using visible light and infrared radiation some years ago, for example, this demonstration at the CAA conference in 2013: https://uk.caa-international.org/2013/02/19/reflectance-transformation-imaging/ As you mentioned, among the challenges of this method would be that the setup doesn't follow a basic assumption on which RTI is based, which is that the reflected light can be modeled using a biquadratic function in the case of PTMs or hemispherical harmonics in the case of RTIs. That doesn't mean you couldn't find a way to process transmitted "RTI" microscopy and get an interesting result (once you supply a set of light positions) or that the information gained using transmitted "RTI" microscopy wouldn't be useful. With more transmitted light positions, you should get more information than is possible using a single light position. There are examples of reflected RTI microscopy using a light array dome, for example, see Paul Messier's "monkey brain": http://www.paulmessier.com/single-post/2014/10/01/The-first-batch-of-studios-Monkey-Brain-light-arrays-for-RTI-microscopy-have-shipped-to-museum-conservation-departments Also, there are some interesting results using an LED array microscope with phase contrast, bright-field, and dark-field illumination to achieve extremely high resolution and 3D imaging: http://www.laurawaller.com/research/
  4. Earlier
  5. cdschroer

    Problems with Flat Runs on Pottery

    Jack - It would help to see some screen shots of what is happening. Things with narrow edges are difficult to get alignment of the 2 sides. I can't tell from your post, whether you are shooting circuits with the pieces upright, or shooting each side and turning over. That would affect the approach to solving this. Also since you say that images of the "bottom" don't align - I'm wondering if they would align to themselves in a separate chunk - then you might be able to bring the chunks together. That is not the optimum way to do it, but it could be a interesting test. I think you know that the biggest issue with relatively flat subjects, is having enough data across the thin edges to get the sides to be in the right relationship to each other. Also, if you shoot each side, you can put each side on a different background, so that the software doesn't match the backgrounds - this can create errors in alignment. That kind of problem could be solved by masking - but it's easier to just use different backgrounds. Carla
  6. KLW

    flat run question

    Thank you for the advice! I'll try it.
  7. ozbigben

    flat run question

    There are a couple of variations on this. My preference is to mask all images as it simplifies supporting the object and reduces alignment issues. Photographing the flat surfaces is the easy bit. Connecting the 2 surfaces as one object requires images that can connect around the thin profile of the object, preferably at each end of the object. To achieve this you'll need to be able to shoot horizontally to the object, or even better, from slightly below the object. This in turn means supporting the object a little higher above the table. Alternatively if you can support the object on its side it's easier as you're shooting from above and can easily move across the edge. For the thicker end you may be able to get enough surface detail in each image as you move from front to back but for the tapered end I'd add a small round'ish object just beyond the tip to provide a continuous connection of images. I use a different object for the left/right sides if you need to move the object in between shooting each side. Focus is critical when shooting near the edge because you have very little area of detail for alignment. A slight focus shift can break the alignment.
  8. KLW

    flat run question

    Hello, I have a few small objects I've been working on and have run into an issue with alignment. Sometimes only one of the two camera groups will align and other times they both align, but top and bottom are not recognized and I end up getting a mess. The objects in question are flat bone tools and I thought they would work better shot as flat runs rather than as circuits on a turntable as they are too fragile to stand on end. They're about 7 inches long and 1/2 inch wide at the widest and tapers down to a point. I suspect my issues lie with the set up. My question is, do I need to change the background (what the object is lying on) when shooting each side (top and bottom)? And since I'm moving around the object, I would not need to mask it right? Thank you
  9. Niki

    RTI Builder Unknown error

    dear dave, thank you very much!!! It works with smaller and less images, but not with the original size. We find out the next problem: Our PTM file: We are using Canon EOS 5D SR with Canon 24-70mm zoomlense. This inscription paper (about 30x50 cm) has this distortion and "slipping edges" on all corners. Center of the image is fine. But just in the PTM file, the captured images are completely sharp all over the image. Thank you dear Dave! yours, niki
  10. Dave Martin

    RTI Builder Unknown error

    Niki, If it is a resource issue due to the size of the images, one way to identify if it is absolute image size that is causing a problem, or just the total demand on the system, might be to try processing a reduced number of your hi-res images. I don't know how many you have in your full set - I have 50-100 typically - but if you maybe tried with maybe just ten images? - the RTI obviously wouldn't be as good but it might help to diagnose the problem? I'm sorry that, as just another user, I can only use my RTI and computer troubleshooting experience, I haven't any access to the innards of the programs! Dave
  11. Dave Martin

    RTI Builder Unknown error

    Nikki, another tiny thought in case it helps shed light on the problem. You might just see something if you have memory monitoring displayed when it crashes on your big images? and there might also be something written into the Windows logs? Dave
  12. Niki

    RTI Builder Unknown error

    dear dave, thank you so much!!! we keep in touch. all the best yours niki
  13. Dave Martin

    RTI Builder Unknown error

    Thanks Nikki, sounds as if moving (slowly!) towards possible indicators. I'm glad it works for at least sample images so software setup looks OK. I don't know about any absolute image size limits, I just did a quick search here and found this thread which does describe processing large images 10328x7760px, albeit I think on a Mac. I'm sorry that I can't help much more at present - I'm not in front of my (PC based) RTI workstation, I think it may be a case of waiting until Carla and team at CHI are on-air (San Francisco time). mfG Dave
  14. Niki

    RTI Builder Unknown error

    dear dave, it works with the sample files... is it possible that our images are to big? 8688x5792pix thank you!!! niki
  15. Niki

    RTI Builder Unknown error

    dear dave, i will try now. best niki
  16. Dave Martin

    RTI Builder Unknown error

    Also Nikki, another thought - if you download one of the sample image sets from the CHI website, which are known to work OK, do they work on this PC? Dave
  17. Dave Martin

    RTI Builder Unknown error

    Nikki, Firstly, now that error message is visible, there is a thread here on this forum about exactly that message which might give you some clues Secondly, have you tried on another PC? Dave
  18. Niki

    RTI Builder Unknown error

    dear dave, new error with HSH... see below. THANK YOU VERY MUCH!!! best niki
  19. Niki

    RTI Builder Unknown error

    dear dave, 1) yes - same error message (Processing row: 3714) ??? 2) we already did twice 3) yes we tried, but no change Do you have more ideas?? Thank you very much!! yours niki
  20. Dave Martin

    RTI Builder Unknown error

    Nikki, path looks OK as far as I can tell. Couple of questions: 1) you mention it fails after cropping, does it fail if you don't crop? 2) you mention you're trying PTM, you have downloaded and installed the PTM Fitter, haven't you? (page 10 of the processing manual) 3) if you try HSH rather than PTM, any change? Dave
  21. Niki

    RTI Builder Unknown error

    dear dave, GREAT!!! one is giving a note... here the path. C:\RTI\tulpe THANX IN ADVANCE yours niki here the screenshot...
  22. Dave Martin

    RTI Builder Unknown error

    Niki - can you post a screenshot showing the file path?
  23. Dear all, we are completely destroyed.. having an unbelievable automatic RTI Dome but cannot create any PTM file.. We checked the path if there are any spaces and we know that we should use lower case jpg. Already uninstall and reinstall RTI Builder and also Java. We still get all the time at the end after cropping: Unknown error detected. the created xml file contains at the end: Fitter returned an error ! Error : -1</xc:event> Please help us! Please please please.. all the best from Vienna, niki photographer austrian archaeological institute
  24. Dave Martin

    3D File Formats to Archive and Display

    Jack, I think this is an important question to consider, and the answer may depend on the purpose and the longevity expected. You mention Archive and Display, and I think there are useful parallels in terms of images, especially as we may have one format for long-term assured storage and another for speedier manipulation and display. You mention DNG, and DNG can contain TIFFs. Top-level archives which accept images will often specify they must be un-compressed TIFFs. This seems counter-intuitive in that they are taking on storage obligations which could be significantly reduced, but they are protecting against future licensing changes. The TIFF standard has no proprietary issues, but some of the algorithms behind compression standards, whilst open to read and implement at present, are private property, and there is the danger that permission may be revoked. Whilst not implying any concerns over or criticism of Khronos, it states at the top of https://www.khronos.org/gltf/ “glTF™ (GL Transmission Format) is a royalty-free specification” – in other words, it looks to be remaining Khronos’s property. There are precedents to be a little concerned, especially for the long-term. The Graphics Interchange Format (‘GIF’) is now thought of by most as a container for handy little images or animations etc. The GIF was developed by the Compuserve BBS team, and internally the data is losslessly compressed using LZW. LZW is proprietary, and from what I recall, there were attempts by those who owned them to assert their rights the LZW algorithm, and this led to the development of the open PNG standard. I don’t have an answer in the ‘model archiving’ space but will be interested to learn. Dave
  25. Jack Hubler-Dayton

    3D File Formats to Archive and Display

    Hello All, DNGs are the standard for archiving photos for posterity, my question is what is the best 3D file format? OBJ? I have noticed that STL and OBJ seem the most common to export from photoscan especially for CRM professionals however I find that those formats are not the easiest to share/display, especially loading online. I have used three.js in the past to display models and those developers recommend using gLTF format because of its quick load time and efficiency, hence the nickname "jpeg of 3d". Any thoughts here? PDF's are easy to share but I know they are a horribly lossy file format... P.S. On this form I found a OBJ/Collada>gLTF converter https://groups.google.com/forum/#!topic/cesium-dev/0tzql9s-e6M .
  26. I've been looking into oblique transmitted light microscopy as an inexpensive way of generating both optical contrast and resolution closer to the Abbe limit. A recent review and evaluation of the technique can be found here: https://www.sciencedirect.com/science/article/pii/S0968432817303888 Oblique illumination is a technique where the specimen is illuminated via axial light from the condenser via a patch stop with an open slit or crescent, placed on the bottom of the condenser. Oblique illumination is unusual in that it shifts the placement of the zero order and higher orders of light on the rear focal plane off-center, allowing higher orders of light to enter into image formation on one side of the zero order, but losing orders of light on the other side of the zero order. This actually enhances resolution, but only in part of the image, and oblique illumination has the unusual effect of having better resolution on the illuminated side of the image than on the shaded one. It is also possible to set up a movable slit on the condenser such that one can illuminate the specimen from several directions. My thought is that this in combination with some version of RTI might be able to generate a composite image which can recreate illumination from multiple directions, and perhaps even a composite image that could give a single image with optimal resolution throughout the image. Obviously, this is a novel technique using a directional form of transmitted light rather than reflected light and may require some modification of the RTI algorithm. I'll note that my background is in biological microscopy and that I am far from an specialist in optics or imaging algorithms, however, this is an idea I'd like to bounce off of others and see if it could be developed.
  27. Jack Hubler-Dayton

    Vertical stand for turntable photogrammetry?

    B Crane, You and me both buddy, have you had any luck since this posting? Jack
  28. Jack Hubler-Dayton

    Problems with Flat Runs on Pottery

    Ozbigben, I am aware of the issue getting good tie points on the edges of more 2d subjects. Do you have any tips for getting more good look angles on the edges, or getting more of the whole sherd in focus? I know that the recommended f stop should be no higher than f11 from CHI. I have exceeded that limit occasionally after talking with Charles Walbridge from the MIA who is active on this forum. I have been shooting on a clean background and then flipping the object and getting a few circuits on either side, I'll post some screen caps in a bit.
  1. Load more activity
×