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Garden Knapweed (visible, UV, SWIR)

Infrared Multispectral SWIR
5 replies to this topic

#1 Andy Perrin

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Posted 01 July 2019 - 23:08

The visible and UV are both F/16, ISO100 and 0.8" and 5" respectively. Filters were BG38 2mm + Hoya UVIR cut for visible, and S8612 1.75mm + UG11 2mm for UV. Camera was the Sony A7S.

SWIR (1500-1600nm) is F/4-ish but focal stacked, 2/15", gain=0.5 using the Wollansak 25mm lens (which apparently works nicely from UV to SWIR) and the 1500nm long pass filter from Thorlabs. Camera was the NoblePeak TriWave.

Visible
Attached Image: _DSC2353 vis UVP.jpg

UV
Attached Image: _DSC2352 UV UVP.jpg

SWIR (1500-1600nm)
This is a focal stack of 12 images.
Attached Image: purple flower SWIR focal stack UVP.jpg

Edited by Andy Perrin, 01 July 2019 - 23:10.


#2 dabateman

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Posted 02 July 2019 - 07:25

Nice images.
Now with the Wollensak 25mm you can capture UVA, visible and SWIR all with out moving the camera. However, I would expect some serious focus shift over that range. With that lens and the triwave.
Have you compared the triwave UV response to your A7S yet?

#3 Andy Perrin

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Posted 02 July 2019 - 07:27

No, I haven’t done any UV with the TriWave yet. The trouble is that it’s a huge pain to change filters since none of them have screws. Even with the wollensak I could not attach a 25mm filter without taping it on. What I want is a filter wheel, but I’m having a hard time matching threads for one of those too. The Kowa lens is M35.5x0.5 threaded and the Wollensak is god knows.

Edited by Andy Perrin, 02 July 2019 - 07:29.


#4 dabateman

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Posted 02 July 2019 - 07:36

My Wollensak came mint in box with original filter. I think its 25mm 0.7 but I might be wrong. I will measure the original filter latter today.

A Chinese 25mm to 58mm and 25mm to 37mm adapters work fine on my lens.

Edited by dabateman, 02 July 2019 - 07:38.


#5 Andy Perrin

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Posted 02 July 2019 - 07:43

Filters below 35 mm usually are 0.5 pitch so I bet it’s that if your Chinese one works.

#6 dabateman

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Posted 02 July 2019 - 13:32

The original Wollensak filter is 25mm 0.5 pitch. I don't think its 0.6, looks like 0.5.

I am surprised its not 0.75. So I have been cross threading in my adapter rings and filters this whole time. Makes sense as I only get a couple turns with 0.75 ring or filter. But they do hold.

All my 25mm filters are in 0.75 pitch filters or with adapters. Only the original Wollensak filter is 0.5 pitch.
The raf camera 52mm to 25mm adapter is also 0.75 pitch as originally to be used with microscope lenses. The Nikon M25 lenses are all 25mm by 0.75 pitch.

Edited by dabateman, 02 July 2019 - 13:36.