Sunflower in UV,NIR,LWIR

[Nate]

Went out this weekend to the arboretum, wanted to get some pics of the Sunflowers before they're gone. Also the wildfire smoke has gone and pleasant to be outdoors again.

Gear I used for NIR was the Canon EOS M, Canon EF 50mm f/1.8 STM Lens with an astro 850nm planted inside the EOS adapter.

For UV was Canon T7(1500D), EL Nikkor 80mm Enlarger metal version with the Antilia U in camera body with the UVR Optics NIR Block on the lens with Hood tube.

LWIR was with the Pulsar Helion XP 50

 

 

ISO800, 1/6th sec, F8

 

ISO100, 1/800th sec, F3.2 850+nm

 

another shot but closer in to see the visitors ISO100, 1/400 sec F3.2

 

 

These last were with the Pulsar in different color modes, straight out of camera,640res jpgs. The lens is so fast, it's hard to get everything in focus. Time is off as I had the battery out, Pics were taken about 9:30am

 

White Hot-  Very hard to not over expose(failed)  pretty hot center

 

Rainbow

 

Black hot

 

Thanks for checking these out.

 

 

 

[Stefano]

That Canon lens is sharp in IR even though it's a modern lens (optimized for visible light).

 

Also the look of sunflowers in LWIR could be mostly emissive as the dark center would heat up more when illuminated by sunlight and thus glow more. You can see shadows, but it's hard to tell how much they are due to a temperature difference or actual shadows. LWIR is a mix of both, and I don't have experience with it. Andy says you can see shadows quite easily.

[Nate]

If I were to guess, I think it's the difference in temp in the shadow on the back leaf. But knowing how fast the shadows move due the Earth rotation, that leaf in back would need to cool down very quickly, otherwise there'd be smudge on the top side of the shadow. I think there might be some sort of reflection too.

I think I need to cast a shadow with something at this same spot on a unrestricted Sun facing leaf.

[Andy Perrin]

I love the UV pic!

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In direct sun, you can see shadows very easily. Nate, you can just wave your shadow around and you should see it moving on the screen. It's much harder to tell after the fact then it is in person. The thing is, if something is in shadow, it cools off, which then makes it emit less too. But that heating process takes time, so when you wave your shadow around, if it changes instantly it's definitely reflected light that's making the difference.

 

BTW, Gigapixel upscales it well:

 

[colinbm]

Beautiful collection Nate.

[Nate]

Thanks Andy, That is interesting about the shadows. Learning so much about this device that I mainly bought for checking around me at night while I did astrophotography.

8 hours ago, Andy Perrin said:

Gigapixel upscales it well

It really does, The pics above minus the thermal might have some giga in them, I find the scale up, then scale down method an important part of my workflow most of the time. I love the Topaz software, I have all but sharpen and the new photo AI.   Mask, adjust, Giga pix, studio2, denoise, and my favorite Video enhance which does total magic on high iso UV videos.

Thanks @colinbm

[Doug A]

Fantastic captures. The UV is amazing. Glad you are able to go out shooting again. 

Thanks for sharing,

Doug A

[cazza132]

Excellent UV & IR shots - nicely detailed! Interesting LWIR. As discussed, it would be interesting to see how much of the LWIR is reflected rather than emitted.

[Nate]

Thanks @Doug Aand @cazza132

I'm trying to think what would be a good test for that cazza.

[Stefano]

A test could be to physically shadow something with a shadow and see if the shadow persists. If it does, it's thermal.

[Nate]

I just played around with one of my thermals, and I couldn't cast any shadow on anything. Even standing for about a minute. I don't have any plants around to test that, so I'll need to checkout where the sunflowers are this weekend.

[Stefano]

This video which I posted here in 2020 still fascinates me.

 

[Andy Perrin]

2 hours ago, Nate said:

I just played around with one of my thermals, and I couldn't cast any shadow on anything. Even standing for about a minute. I don't have any plants around to test that, so I'll need to checkout where the sunflowers are this weekend.

A minute is long enough to make a distinguishable temperature difference, not just a shadow, but a change to the emitted light also. If you couldn't do it, you must not have had direct sunlight. To make the effect more obvious you should, of course, choose a surface with a low emissivity.  I'm way too busy to make a video for you today, but if I get some time I'll do one this week maybe.

 

In the mean time you can look at Stefano's video, which is MWIR. It shows the effect nicely, but it can certainly be seen in LWIR also.

[Nate]

Great video! I was expecting the outcome of the shadow remaining on the wall, but not expecting to see the shadow in real time. I got to try this.

[Andy Perrin]

Yeah, so, the real-time shadow is due to blocking the reflected light. The lagging shadow is from less emission in the shaded area because it is cooler.

 

The percent of reflected light is equal to 1-emissivity, so a surface with an 0.75 emissivity like brick will reflect 1-0.75 = 25% of the light. That means lower emissivity surfaces will show the "real-time shadow" better.

[Nate]

Non of the surfaces I was tying today showed any block in reflection, does it need to be a certain material?

[Andy Perrin]

You need direct sunlight. I don't know what the light was like when you tried it. If you can't see your shadow in visible light, you definitely won't be able to see it in LWIR. It needs to be a lower emissivity surface, as I just finished explaining. I linked a list of emissivities above so you can pick one.

 

While the emissivity should be on the low side, you should pick something that isn't glossy like aluminum foil, or it will take quite a long time to change the temperature. Not for nothing do they use it for heat shields. I would go for something like gravel (emissivity = 0.28).

[Nate]

Thanks Andy, definitely trying this next outing

[Andy Perrin]

See above edits!

[lukaszgryglicki]

Seen trees shadows in FLIR many times on partially cloudy day.

Once sun was behind the cloud shadows were still there (colder areas).

 

[Andy Perrin]

Yeah, there are the two kinds of shadows, lukas, and trees are very large and non-moving, so they have a long time to cool the area under them even if the sun goes behind a cloud. It's not the same situation as a human waving their hands around. What he wants to see is BOTH kinds of shadows, type 1 (thermal emission differences) and type 2 (reflection differences).

[Ming]

Nate's pictures and the discussion of two kinds of shadows really opened my eyes.  Thanks.

 

[dabateman]

With thermal you can also see absorption as well. Just hold your hand on a blanket, then remove it and you will see the heat you left behind. 

So you get absorption,  reflection and emission. 

[Andy Perrin]

Transmission too! Try a garbage bag.

[Nate]

I discovered that by accident once, I had my trash ready to take out and saw everything inside the bag.