colinbm Posted October 28, 2014 Share Posted October 28, 2014 I have found a reference to a filter I have been looking for....It is similar to a BG3, but with a longer bandpass... http://droneyard.com/wp-content/uploads/2013/08/SchottBG3.gif The only clue I have is it was used for plant stress detection & they called it an NGB filter, I am guessing that means......No red, Green + Blue.I would love to have a piece of this glass :)CheersCol Link to comment
nfoto Posted October 28, 2014 Share Posted October 28, 2014 The filter curve you posted indicates there will be massive amounts of deep red passing through the filter ... Link to comment
colinbm Posted October 28, 2014 Author Share Posted October 28, 2014 Yes I appreciate that Bjorn, I'll have to deal with that, but it is the UV, Blue & Green, I want.It is between the BG3 & S8612 that I have been looking for.CheersCol Link to comment
enricosavazzi Posted October 28, 2014 Share Posted October 28, 2014 I believe NGB means Near-infrared, Green, Blue. Basically, it suppresses much of the red and transmits the rest of VIS and NIR. It also happens to transmit UVA, but this band is hopelessly swamped by the VIS and NIR transmission if daylight or a similar artificial source is used. The NGB filter is/was used in some converted cameras, to record the blue of the sky and some of the green of vegetation together with NIR. Link to comment
colinbm Posted October 28, 2014 Author Share Posted October 28, 2014 Yes, that is what I am looking for Enrico.Do you know where I can get some please.52mm will be fine or even down to 1 1/4" astro is OK.I can cut & mount any piece I can get :DCheersCol Link to comment
JCDowdy Posted October 28, 2014 Share Posted October 28, 2014 Col,You probably already saw this but JIC, here is a DIY plant stress filter kit. Link to comment
OlDoinyo Posted October 28, 2014 Share Posted October 28, 2014 The shape of the curve tells me it is a dichroic (not pigment-based) filter. Other than that, I can tell you little. Stacking on something like a 650SP would knock out the red and IR, in principle, though it were better this be something pigment-based (if that exists.) Stacking dichroics can do funny things sometimes. Link to comment
JCDowdy Posted October 28, 2014 Share Posted October 28, 2014 The transmission spectrum you posted appears to me to clearly be a dichroic type, with a considerable deep red pass band 690-770nm.However, as you say an absorptive filter has advantages. I ordered one of the Public Lab "infrablue" DIY filters. It is likely just some type of blue gel.I will post a transmittance spectrum once I have it in hand. Link to comment
colinbm Posted October 28, 2014 Author Share Posted October 28, 2014 Thanks everyoneHere is the filter in a camera conversion.http://www.event38.com/ProductDetails.asp?ProductCode=CAM-NGB260Col Link to comment
enricosavazzi Posted October 29, 2014 Share Posted October 29, 2014 For what is worth, I was not able to source any NGB glass of usable sizes for our typical purposes. It seems there is little demand for this type of filter. Link to comment
colinbm Posted October 29, 2014 Author Share Posted October 29, 2014 Thanks very much EnricoIt seems too many things I look for are dinosaurs ;)I never loose hope...maybe one day....CheersCol Link to comment
colinbm Posted October 29, 2014 Author Share Posted October 29, 2014 I'll look for a BG7 for now & see what it produces...........Col http://www.vpglass.com/filter_glass/images/bg7.gif Link to comment
Andrea B. Posted October 29, 2014 Share Posted October 29, 2014 Editor's Note: I am moving this technical topic from the photo section to a technical section. Link to comment
JCDowdy Posted October 30, 2014 Share Posted October 30, 2014 ......it is the UV, Blue & Green, I want.Col Have you considered something like this?BUG U 5 Camera Filter 52mm, UV+Blue/Green Bandpass Mix, Ultraviolet Photography Link to comment
Andrea B. Posted October 30, 2014 Share Posted October 30, 2014 I was just going to mention that!! ;)That Ebay seller uviroptics might be able to tell you more about the filter or filter stack you are looking for. He has been investigating filters for some time now. Link to comment
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