UV With A Drone [Part 2]

[eye4invisible]

Following on from Cadmium's earlier post (https://www.ultravio...v-with-a-drone/) I managed to squeeze in a quick test flight today, using the filter that he had put together.

 

Scattered thunderstorms were in the forecast for this weekend, so this was a rushed test at the mid-day hour, and conditions were not optimal:

* Steady breeze, not too strong, but very noticeable at higher altitudes (you can see this in the movement of the trees in the video).

* Partly cloudy

 

I had my DJI Mavic 2 Pro (M2P) drone full spectrum converted by Omni View Tech, a local DJI retailer and repair shop. I also purchased the Kolari Vision drone filter pack (6 standard) plus the M2P versions of the IRChrome and NDVI filters.

 

White balancing options are somewhat limited on the M2P. You can use a handful of presets and also set a specific temperature, but you can't CWB on a target, although it can be done in post. The M2P can shoot 4K H.265 DLOG for video and the standard DNG raw format for stills, so processing options are plentiful.

 

Initial tests for UV sensitivity yielded some promising results. I took a quick shot from my balcony, hand-holding the drone (as I had no time to fly it yesterday, when I just got my drone back from conversion).

 

Here's yesterday's shot - an SOOC resized jpeg, taken at f/2.8, ISO 320 and 1/30sec, using the "incandescent" WB setting. I think the giimbal did well to stabilise my shot:

 

Here's the test video from today's quick flight. I added a monochrome Lumetri filter in Premiere Pro, and posted this as unlisted on my semi-abandoned Youtube channel, downsizing it to 480p in the process:

 

When the drone was sat on my table, it seemed to have no problems coping with the 7.5g filter (I was able to move it up and down without an issue) but up in the air the gimbal really struggled to stabilise the video, both when stationary and on the uplift, and it seemed to have issues moving the camera up and down. When I switched out the UV filter for the KV NDVI filter (much lighter) I had no issues with stabilisation or gimbal movements. Again, this was only a quick test and in less-than-optimal conditions, so I need to revisit this when the weather permits. I may need to point the gimbal downwards for future flights.

 

The good news is that there is virtually zero vignetting using the filter in both stills and video mode.

[Andy Perrin]

White balancing options are somewhat limited on the M2P. You can use a handful of presets and also set a specific temperature, but you can't CWB on a target, although it can be done in post. The M2P can shoot 4K H.265 DLOG for video and the standard DNG raw format for stills, so processing options are plentiful.

I think you could probably just figure out the appropriate color temperature ahead of time and just set it permanently using the number? And of course you can process the RAW afterwards, but I mean if you want to approximate it in-flight.

[eye4invisible]

I think you could probably just figure out the appropriate color temperature ahead of time and just set it permanently using the number? And of course you can process the RAW afterwards, but I mean if you want to approximate it in-flight.

The lowest I can go is 2000, and that gives me the clearest FPV (first-person view) when flying the M2P. Any higher temp just gives a saturated violet cast, making FPV harder. DNGs don't give me much in the way of faux colour separation like my Sony A7 does. It's easier to just desaturate everything.

[eye4invisible]

Here's another still, shot just before take-off. Minimal processing of the raw DNG file in Lightroom - all I did was move the green-magenta tint slider (under the Basic section) all the way to the left, and the purple HSL slider all the way to the left as well.

 

Unusual that the path just in front has a patch of colour different to the rest of the periphery of the photo. I don't think it's a hotspot, though:

[Andy Perrin]

The lowest I can go is 2000, and that gives me the clearest FPV (first-person view) when flying the M2P. Any higher temp just gives a saturated violet cast, making FPV harder. DNGs don't give me much in the way of faux colour separation like my Sony A7 does. It's easier to just desaturate everything.

I tried WBing in PhotoNinja your top pic and got quite a bit of false color separation? Can I show you?

[Cadmium]

Hi Andy, Nice tests!

I am more concerned about the flight weight test. It can be make lighter without the ring, is an idea to try. I forget if the filter I used will fit the usual hole.

You stacked a monochrome Lumetri filter with the UV filter? I am confused.

I see the greener color in the foreground which I would think is some kind of UV hot spot in the lens glass perhaps, is my only idea. The filter would not have a color hot spot.

I like how the play slide is a different color.

 

I am curious about the grass 'color' gray tone in the video. The grassy area around the play slide is lighter, and the other grass and trees look darker like I would expect foliage to look in UV,

what am I seeing there? What is the difference? Am I perceiving something the wrong way?

[Cadmium]

About the green...

Ulf makes a good point here:

https://www.ultravioletphotography.com/content/index.php/topic/2928-drones/page__view__findpost__p__37462

You may have a very slight light leak where the rectangular frame twists onto the lens. Maybe try some tape around it. I don't know if any light can get into that,

but they were probably not exactly designed for UV only exposures, so any extra little bit of light could show up. Just an idea, I don't know.

[bobfriedman]

Unusual that the path just in front has a patch of colour different to the rest of the periphery of the photo. I don't think it's a hotspot, though:

 

I believe I can see a hotspot circle starting just above the playset/trees and ending on the ground perhaps? although your youtube video looks quite good.

[eye4invisible]

About the green...

Ulf makes a good point here:

https://www.ultravio...dpost__p__37462

You may have a very slight light leak where the rectangular frame twists onto the lens. Maybe try some tape around it. I don't know if any light can get into that,

but they were probably not exactly designed for UV only exposures, so any extra little bit of light could show up. Just an idea, I don't know.

That might be the case, but I can't add any more weight to the filter or the camera. I think it's struggling as it is.

[eye4invisible]

I am curious about the grass 'color' gray tone in the video. The grassy area around the play slide is lighter, and the other grass and trees look darker like I would expect foliage to look in UV,

what am I seeing there? What is the difference? Am I perceiving something the wrong way?

The play slide is located in a patch of woodchips, not grass, so we're good in that regard :)

 

And the Lumetri filter is a term for the software filters that Adobe Premiere Pro applies to videos. It's usually used for colour grading and other cinematic effects, but there are also simple B&W effects that can be added in this way. I didn't play with any contrast or tone curves in the video, so other than the monochrome, this is what I got out of the M2P's camera.

[eye4invisible]

I tried WBing in PhotoNinja your top pic and got quite a bit of false color separation? Can I show you?

Please do. I can send you the original DNG, if you like?

[Andy Perrin]

Please do. I can send you the original DNG, if you like?

Sure!

[Stefano]

Then can you please post it? I am curious to see the colors.

[eye4invisible]

Sure!

I tried to upload the DNG to here, but got an "Error You aren't permitted to upload this kind of file" message, so here's a link to the file on my Google Drive:

https://drive.google.com/file/d/1nDSHOyrBMj4RQ0KlZ8AUaY7KfkX372Fv/view?usp=sharing

[Cadmium]

I am looking forward to the results.

One thing I might mention is that Andy sent me a larger version of the first pic he posted here above,

and I was impressed with the detail, so the camera has good resolution with the UV filter.

I could show a full pixel crop from that pic if you want Andy, or let Andy Perrin?

[Andy Perrin]

Here's what I got -- there is quite a bit of vignetting but plenty of color with a WB off the street and a saturation boost.

 

[Cadmium]

The center looks like it has a hot spot to me.

[Cadmium]

Using the larger version of the top picture that Andy Broomé sent me, here is an example of a 100% crop in Photoshop (Actual Pixels) showing the native detail.

I also adjusted the levels, using "auto levels", which helped to bring out a bit more color and differentiation.

As the photo that Andy Perrin posted above, it suggests that a true white balance will bring out more color if you look close.

1/30s, f/2.8, ISO-320.

Also, I didn't sharpen this pic or anything else than what I said, just auto levels and crop, but I don't know if it was sharpened before I got it or not, looks detailed though, but kind of grainy is all.

[Andy Perrin]

Cadmium, I don’t think it is a hotspot (and also adjusted the vignette with the vignette tool in PhotoNinja). I think it is just the usual lens falloff. When I brighten the corners, the center tends to overexpose. I see that all the time with wide angle lenses.

[Cadmium]

I see, OK.

 

I added the settings for that shot above. Lens shows both 28mm and 10mm, so I am not sure which it is.

[eye4invisible]

Cadmium, I don’t think it is a hotspot (and also adjusted the vignette with the vignette tool in PhotoNinja). I think it is just the usual lens falloff. When I brighten the corners, the center tends to overexpose. I see that all the time with wide angle lenses.

Yes, at ~10mm, this lens is very wide, so it's not a huge surprise. Not sure where it's showing as 28mm focal length, but the max aperture is f/2.8.

 

Better flying weather is in the forecast for tomorrow, so hopefully I can do another test flight to check the gimbal stability.

[Cadmium]

I see now, "35mm focal length = 28mm".

[bobfriedman]

Cadmium, I don’t think it is a hotspot (and also adjusted the vignette with the vignette tool in PhotoNinja). I think it is just the usual lens falloff. When I brighten the corners, the center tends to overexpose. I see that all the time with wide angle lenses.

 

looks like a hotspot to me as well