Jump to content


  • Content Count

  • Joined

  • Last visited

  • Days Won


marlin last won the day on June 4 2017

marlin had the most liked content!

Community Reputation

32 Excellent

About marlin

  • Rank
    Advanced Member

Contact Methods

  • Website URL

Profile Information

  • Location
    San Francisco, CA, USA
  1. Hi Folks! I'm a fan of Strobist (you should be too). I recently saw this blog on strobes for shooting outside. If you've ever tried to capture an RTI in full sun, then you've likely come up against some of the main concepts and topics in this strobist blog post. There's some good info on using ND filters in the CHI forums, so I'm not going to dive into that rabbit hole. Just poke around and you'll get the gist. Just so you know, the gist is that you need to over power the sun with your flash. Knowing that your speedlight doesn't have enough power for this, well, the below url might give you some insight as to what you're dealing with and what to purchase for your needs. http://strobist.blogspot.com/2016/10/choosing-big-lights.html#more happy F-stop!
  2. hi Janelle, Using a point a shoot, well, its a trade off right? If thats what you have, and thats the gear you've got for RTI, than you can make it work. It all depends on what expectations you have, and how you are going to use (or say/write about the final data). A point and shoot can work. Manual is good. Make sure that the manual settings are locked down. Yes, including the focus, Manual Mode, etc etc. It sounds like you've read the capture PDF. Good on you. You also might want to look into the Flash Synch Speed of the G16 --- and do some test. I cant recall if its a digital sync ... but just dont let the the curtain interfere with the image and start to clip (big dark areas on the image). You might be in the clear, but in general for any camera check that setting you might have to lower your shutter speed to let the light get in. There are numerous flashes that could / should work with both Nikon and Canon. I cant recommend a product, bc, honestly, I havent used many of them. Other Users? Can you guys chime in on this? A generic flash unit might be ok, but, be sure to dive into the flash setting on your camera, I'm pretty sure that there is a 'force flash' setting, which basically sends a signal to the hot shoe and fires what ever is in the hot shoe. Previously, i had the G12 --- and I needed to have that setting On to get my pocket wizard to actually trigger. I hope that this makes sense. Be sure so set up and 'faux' test capture and run thru the gear and the steps b4 you get on location and you should be able to work it all out. happy F stop Marlin.
  3. Taylor, I could not agree more with you. This area is a very high traffic zone. The kids, the bikes, hikers --- most of them do not know what they are walking on! I'm not saying that it should be fenced off, but at least somehow --- there should be a call out to make it more obvious. Its also vulnerable bc its in an area that natural snow fall, ice and elements will gather there ... somewhat sitting at the bottom of a natural V ... this godzilla El nino winter coming as well. Again, great work! bravo. marlin.
  4. Taylor! hey this is really great work. I've been to this petroglyph site on Donner Pass many times, (usually with the family), I've always wanted to document this, but it was always more important to try and keep the kids off of it! The subject has always been very difficult to view in day light conditions. What you did here is great work. You should share this data with the Tahoe Donner / Truckee city. I'm fairly confident that they would be interested to see this new imaging. I know of, and know that there are additional petroglyphs in the area. again, great work! Marlin.
  5. Taylor, Can you remind me, what camera are you using? What lens? Curious. Can you try a quick test w/ a completely different camera to see if you can reproduce the flaws? (again, just curious). Marlin
  6. Taylor! bummer that you're bumping into this issue. That must be painful. As Carla mentioned, we're not having this issue. Auto-Off images from our capture devices (canons) open w the correct orientation in ACR. And as she mentions, we don't, at this time, use LR. Maybe you might want to make sure that you're using the most recent version(s) of LR and the most recent version of your cameras firm ware. Also double check to see if LR fully supports your camera as well as its file type. I'm genuniely curious about this issue. Hope you get it resolved soon. marlin.
  7. Sounds to me like your flash might be resetting itself, maybe as its getting moved around, it is power gets dis connected>? Thus the restart defaulting everything back to the starting place? Maybe the springs in the battery compartment are not so springy, not keeping that constant connection? test the same operation (as carla mentions) w a separate flash ... marlin.
  8. marlin


    George! thank you for this update, we just installed Meshlabs yesterday on a new imac. I'll be sure to confirm that we have the new version. thanks!
  9. Dear All - Dale Kronkright (Head of Conservation at the Georgia O'keeffe Museum) and I recently had a convo / exchange about his forum post in re to 'Lead Soap' Honestly, I had zero idea of what lead soap actually was, so below is our thread: Check out the G+ Image gallery of O'Keeffe's "Pedernal", 1941, oil on canvas 19" x 30" Question (Marlin): Dale, this is interesting. Can you tell us more? Is lead soap a cleaner or a 'primer' like layer that was on the canvasses? Are u extracting that information sub surface? Or is the image a 'blank/empty' area of the canvas? Response (Dale): The precise mechanisms are elusive, although the chemistry is clear. In O'Keeffe's case, an in the case of many 20th century painters who used commercially primed canvases from Belgium, France and Germany, the manufacturers appeared to load the lead-in-oil priming with additional non-drying oils to prevent full hardening of the priming. Remembering that from manufacturer to wholesaler, exporters and shipping, retailer art supply and then to the artist, who my keep their 20 yards for a year or more before cutting, stretching and painting, the canvas would need to remain pliable and stretchable for two years. A pure linseed oil priming, even if lean, would harden in a couple of months. The free fatty acids in the non-cross-linked oils are available for alkaline hydrolysis. Each time there is a change in surrounding RH, water molecules move through the unprimed verso of the canvas, one direction or the other. These water molecules come in contact with available PbCO3 to form PbOH and CO2 and the alkali consumes a little free oil to create a soap. THe works that appear to have travelled the most, historically, have seen thousands of humidity changes and thus the alkalis have drilled tiny worm-holes toward the recto surface. Ultimately, all the oils and fats are consumed leaving a hard, thin-shelled "blister" that often erupts, leaving a tiny pit. Often, the free oils migrate around the microprotrusion creating islands of saturated shadows around the protrusion. THe Doerner Institut in Munich found the same phenomenon in the paintings of the same period by Max Beckmann. Stabilizing the humidity in the verso of the painting using micro-environmental framing technologies appears to slow the development of the micro-protrusions. We are using RTI to both identify, map and monitor the rate of change of these tiny blisters - 50 - 200 microns in diameter. (The 1/2" bearing in my Google+ set, when imaged in false color normal reflection vector visualization, is awesome,as it shows what the vectors are doing)
  10. Ah, yes, Thanks Carla, I did assume that you were using the cue ball spheres. whoops. I doubt that the restorer would work on the repair. Can you share a quick pic of the scratches? I'm curious to see the physical damage on the surface. marlin.
  11. Hello mgts24! thanks for the message. I will attempt to reply to your post with some useful information. You have experienced Lens Distortion. The 24mm-105mm L is a really nice lens, but it may not be the best lens to collect RTI data sets. As we know, Lens Distortion is in every lens -- thats just optics. Some have more, some have less, a lot less. We steer professional towards the prime lenses. Primes The 50mm Macro Prime is one of our daily drivers in our camera bag: http://www.bhphotovideo.com/c/product/12145-USA/Canon_2537A003_50mm_f_2_5_Compact_Macro.html The other worker bee is the 100mm L (or its previous) http://www.bhphotovideo.com/c/product/647011-USA/Canon_3554B002_EF_100mm_f_2_8L_Macro.html http://www.bhphotovideo.com/c/product/194451-USA/Canon_4657A006_100mm_f_2_8_USM_Macro.html Both of the above lenses have the least amount of lens distortion, or rather, the most acceptable amount of lens distortion. Lens Resource Websites like http://www.dpreview.com/ (go here and look up your lens), can offer valuable insight into the distortion(s) that are inherent of the lens in your camera bag. For example check out this interactive chart on sharpness on the 100mm Macro L. There other good stuff in there too. (note the comments about the 100mm being exceptional in the distortion category) http://www.dpreview.com/lensreviews/canon_100_2p8_is_usm_c16/4 Zooms. A word about zoom lenses (lenses which are adjustable, e.g. : 100mm-400mm). Its not bad to collect RTI data with a zoom lens, but its a lot better to use a Prime lens --- we know this. But another consideration, is that zoomable lenses, lenses that have that turnable ring to adjust your FoV, will often times *shift - especially if the camera is pointed down towards the earth. Your very first image might be tack sharp and in focus, but then the last image in the RTI data set might be soft and out of focus. I've seen this numerous times. The lens simply shifted during the capture sequence. If you have to use a lens that translates to adjust the FoV, then use 'tape' (gaffers tape) to physically 'tape' the lens in place to itself ---- preventing movement and keeping all silent. (don't forget that you also Must be on Manual Focus "MF" mode). Spheres in the corner. Spheres in the corner of the frame will appear egg like with lenses that contain a lot of lens distortion. Even the best prime lenses might have a little bit of 'wobble' to them. Moving the spheres towards the middle of the frame even just a tiny bit can help the distortion. In some setups you can control the sphere placement, if you can do this, you might as well. Other times, bc of the subject the sphere may end up in the corner. Remember that RTI Builder is pretty flexible and will most times, more than not, still offer a usable and acceptable result ---- even if the sphere is egg like. (hopefully enough to reveal that hidden text you are looking for). Lens Distortion Correction. quick word on Lens Distortion correction. If you want to correct for lens distortion, there are a few ways to do this. Its too much to disscuss in this post but, if you do correct your images, you would want to correct them at the DNG level or at the 'jpeg-exports' phase, and then continue to process your data from there. Hope that this Helps. Happy F-stop. Marlin.
  12. hi Ansley, firstly, I'm in a way, I'm glad, that you're spheres are scratched, because that means you are using them! however, bummer about the actual scratches them selves. The spheres that we sold you in the RTI Kit are billiard balls/spheres. They are made of polished resin. depending on just how bad the damage is, you might consider replacing the spheres. If the scratches are 'light weight' this product might be able to help: http://www.pooldawg.com/product/aramith-billiard-ball-restorer this product is similar to a rubbing compound for autos. let us know if you decided to test these product(s) Test the Spheres. You also might want to conduct a light test. In the RTI Builder app, there's a step where the user can inspect the location of the 'red cross hair' on the highlight. Maybe you can shoot an RTI of the damaged part of the sphere, and then go thru the processing phase and detect highlights ... to get a gauge on just how much the scratches are creating bad data --- if at all. Please do share you results if you learn anything significant or worthy. cheers.' marlin.
  13. Learn RTI ~ Get Trained at the CHI Studio in San Francisco, CA --- April 8-11, 2014. Sign Up Now! Details and Info http://culturalheritageimaging.org/What_We_Offer/Training/training/index.html Registration Form http://culturalheritageimaging.org/What_We_Offer/Training/training/4-day_class_reg.pdf This class is a combination of lecture, demonstration, and lots of hands-on work. Learn how to apply highlight Reflectance Transformation Imaging (RTI) Grasp the latest research in the multiview technique, RTI with microscopes, and using multispectral imaging with RTI Become familiar with related computational photography techniques, such as algorithmic rendering and photogrammetry Apply what you learn in small teams: instructors break the class into groups of three-to-five people for hands-on work After attending this class, you will know how to set up, capture, process, view, and disseminate RTI images on the Internet. Cheers! Happy F-stop!
  14. Love it, looks good! Nice work. Simple, cost effective, it must work well, certainly less expensive than an automated light array. Continuous Lighting. How do you like those lamps? output? color temp? consistent across all four bulbs? Are you getting a fast-er shutter speed at ISO 100? you have seen previous work at the smithsonian, the 'Manits' light rig? very much like your model but with flashes? I'll try to find the url good work Charles! thanks for the share! Marlin.
  15. hi Charles, thanks for the post. RTI Vs Photogrammetry. Interesting. Both will give your really interesting results. Dont forget that sharing a '3d' file sometimes isn't easy as pie, well, your viewer will need to know how to navigate the controls in your 3D 'viewer' or 'app', etc etc. I suppose thats the same for the RTI viewer too. Getting '3D' data from the RTI data is possible, its just not quite there yet --- there are still some variables that need to be worked out. We can get results right now, but there's a 'warping' in the mesh that needs more attention. When this gets fixed (outside of a lab environment), a kind of holy grail will be revealed. P-Scan is a killer app. There's a learning curve, but you've already started bc you're a good photographer. The input data is sharp, in focus, properly exposed images. The sequence, image overlap, and camera calibration are critically important to your final result. As Carla mentioned, the Pro version of P-Scan (or the Edu version) allows for automatic measurement / marker detection --- the results being metrics on your final file. If you Optimize your points correctly, the final out come is a very accurate documentation of your object. The "low-relief sarcophagus" is a good candidate for photogrammetry bc it doesn't look that reflective, contains no glass, and has many planar type surfaces (easy to shoot). If you get your lighting just right, the texture on the model will be delightful to view. Maybe you can document detailed areas with RTI and some of the larger parts of the sarcophagus with photogrammetry.(?) Hope this helps to asses. happy F-stop. Marlin.
  • Create New...