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| Accuracy of judging runout via lightsource… http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10101&t=56180 |
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| Author: | meddlingfool [ Fri Jan 05, 2024 12:39 am ] |
| Post subject: | Accuracy of judging runout via lightsource… |
Nm… |
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| Author: | J De Rocher [ Fri Jan 05, 2024 1:32 am ] |
| Post subject: | Re: Accuracy of judging runout via lightsource… |
It may be the lighting conditions the photos were taken under, or it may be my computer monitor, but I can't see the reflections well enough to have an opinion. John Arnold posted the photos below on Mandolin Cafe in 2009 that show different types of runout under a fluorescent light where they are pretty easy to see. The photos are explained in the last post in this thread: https://www.mandolincafe.com/forum/threads/109030-Runout Attachment: runoutSamples - from John Arnold on mandolincafe.jpg
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| Author: | Clay S. [ Fri Jan 05, 2024 3:24 pm ] |
| Post subject: | Re: Accuracy of judging runout via lightsource… |
After Josh French mentioned you could use a camera flash to show runout I tried it on a few soundboards. It does seem to work O.K. As John Arnold mentioned the smoother the surface the more defined the light appears to be, but I think it is still somewhat "readable" on rough surfaced boards. The smooth planed soundboard (E) showed a fairly straight line and little runout as expected. The un-joined soundboard F showed twist and runout opposite of what I would have expected - so I rechecked my measurements and found I had screwed up and marked the opposite edges from what they should have been. I marked the 1:10 edge as the 1:50 and vice versa - the light was right and I was wrong! The third soundboard (g) had runout on one edge of 1:20 and the other edge 1:36. Either edge I would find acceptable but the 1:36 would be better runout-wise, and this seems to show up under the flash also ("G" mark toward center picture) The florescent tube might give better results but a flash picture from a smart phone might be more convenient when checking out soundboards onsite. |
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| Author: | J De Rocher [ Fri Jan 05, 2024 3:53 pm ] |
| Post subject: | Re: Accuracy of judging runout via lightsource… |
That's great to know about using a phone flash. Thanks for the tip and photos. Ed - I'm curious. Did what you saw under the fluorescent light not agree with a different test for runout? |
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| Author: | Clay S. [ Fri Jan 05, 2024 4:38 pm ] |
| Post subject: | Re: Accuracy of judging runout via lightsource… |
Hi Jay, I was using a small flash on a compact camera, and assume it would be similar to what a cell phone uses, but I could be wrong, so I may have mis-spoke. I'll try to check it with my wife's phone. |
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| Author: | meddlingfool [ Fri Jan 05, 2024 8:08 pm ] |
| Post subject: | Re: Accuracy of judging runout via lightsource… |
What I saw under the flouro was fairly even patterns on tops with some pretty gnarly runout… |
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| Author: | Clay S. [ Sat Jan 06, 2024 1:44 am ] |
| Post subject: | Re: Accuracy of judging runout via lightsource… |
The cell phone camera/flash does appear to work. I had my daughter take some pictures of a soundboard with similar patterns to what the camera flash showed. |
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| Author: | J De Rocher [ Sat Jan 06, 2024 7:21 pm ] |
| Post subject: | Re: Accuracy of judging runout via lightsource… |
The flash on my iphone worked for this too. I'm really surprised at how well it works since the light is such a tiny point source rather than a long thin source like a fluorescent tube. It works better if there isn't a bright ceiling light directly overhead and best in low surrounding light. You can take photos, but it's actually easier to see the reflection using the phone light in its flashlight mode and scanning it across the top a foot or two above the surface. It works really well on redwood because of the contrast. As Clay mentioned it could be handy when checking out wood on site. Attachment: iphone flash spruce top.jpg Attachment: iphone flash redwood top.jpg
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