colinbm Posted May 10, 2021 Share Posted May 10, 2021 Trying to get some 'Black Water' with my converted Sigma fp. I wonder if it will see 'Black Water' with a 1200nm ? First with a 950nm filter. Second with a 1000nm filter. Link to comment
Andy Perrin Posted May 10, 2021 Share Posted May 10, 2021 The second peak is at 1205nm but the camera sensor is dead there. Best peak is 976 with a narrowband filter. Try this:https://www.thorlabs.com/thorproduct.cfm?partnumber=FB980-10or similar one. Narrow band is the way to go. Link to comment
colinbm Posted May 10, 2021 Author Share Posted May 10, 2021 The second peak is at 1205nm but the camera sensor is dead there. Best peak is 976 with a narrowband filter. I wasn't sure what the peak was, so I am either side of the peak.I can't check with my spectroscope as it only goes to 850nm but these two filters don't leak down to 850nm thank goodness.Do you reckon the water would be darker then this at 976nm ? Link to comment
Andy Perrin Posted May 10, 2021 Share Posted May 10, 2021 Yes, but the peak isn’t that big so only a little. To get really ink black water you need to be in SWIR at 1450nm. You can also exaggerate the effect by using deeper water. Try a bathtub. Link to comment
colinbm Posted May 10, 2021 Author Share Posted May 10, 2021 Thanks Andy, yes, bodies of water are black. Link to comment
Stefano Posted May 10, 2021 Share Posted May 10, 2021 Looks nice. As Andy suggested, you would get better results with that narrow bandpass filter, but the effect is already visible. Link to comment
dabateman Posted May 10, 2021 Share Posted May 10, 2021 Looks good.Lighting source will matter too. An Led is bad as very little in that wavelength. Look outside or with a halogen bulbs. I think it was a Halogen bulb that was better than an incandescent bulb when I was trying this. Link to comment
Stefano Posted May 10, 2021 Share Posted May 10, 2021 White LEDs have some far red up to 750 nm, maybe some more but after 800 nm there's nothing. If you want to use LEDs they are available at 970-980 nm, I have one but I didn't use it yet at full power since it requires a heatsink. Link to comment
colinbm Posted May 11, 2021 Author Share Posted May 11, 2021 The bathroom was lit with a 275w heat lamp, behind & above the camera a few metres away. Link to comment
Andy Perrin Posted May 11, 2021 Share Posted May 11, 2021 Sounds fine. If you could see significant amounts of red light with your eyes then probably there was plenty of near infrared also. Link to comment
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