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Reflected UV with RTI


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#1 Ayman Yaghi

Ayman Yaghi

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Posted 18 July 2017 - 10:11 PM

Dear all 

I've tried to combinate UV Reflection with RTI  , i used a converted camera for UV reflection with monochrome setting and UV Flash , the idea was to have more phenomenons on the surfaces by using both of them  . after processing the UV Reflected photos in RTI builder and executing them , the final shape in RTI viewer is totally unsharp although the UV Reflected photos are sharp and good. something wrong with it , i just want to ask if someone has done such a try before ? any recommends pls 

best regards 

  Ayman 



#2 Taylor Bennett

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Posted 22 July 2017 - 12:17 AM

There's no inherent reason why an RTI generated from your UV reflectance images should be blurry, as long as they're as sharp as you say.  The first thing I'd check is whether the images are registered (aligned), and one way to do this is to check that the spheres are all in the same position in the images you captured to construct the RTI.  After you detect the spheres (pp. 15-17 of the RTI Guide to Highlight Image Processing), the circle and the center of each sphere should be in the same position in all the images.  If any of the spheres is out of position, then something has moved (e.g., the camera, object, or possibly just a sphere).  If the camera or object moved, you could remove the images captured from that point on from the RTI, resulting in a limited range of light positions in the final RTI.  Also, make sure you're set up on a stable surface.

 

If only the sphere you chose to detect spheres has moved (I've seen it happen), you could try detecting and aligning the images on the alternate sphere instead.  If the camera or object moved, you could either re-do the capture sequence or try aligning the images using a tool such as ImAlign (available from CHI), PTGUI, or Photoshop. 

 

If all the images are sharp and aligned properly, I'd check if anything else could have changed during the capture sequence, such as aperture or focus, zoom, or other exposure settings.  Check also to make sure you have image stabilization turned off.  Normally, these settings shouldn't change if you follow the steps in the guide, but it's easy to forget and leave something on "auto," for example, or gravity could have moved the zoom lens if you're using one.  You can get elastic bands to hold the zoom and focus rings, or just use a piece of gaffer's tape to hold them in place. 






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