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Zinnia, UVIVF w/ "Nemo," Noise-reduction Stacking

Fluorescence Processing UV Lighting White Balance
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#1 Andy Perrin

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Posted 12 August 2020 - 17:50

Last night I took some photos of this flower, which looks something like a coneflower. [Edit: It is a zinnia. Thanks, Andrea!] I tried a new method for processing. My previous attempts at shooting flowers in-situ have had issues with flower movement from wind, so this time I decided to try taking multiple images with high ISO and short exposures to maximize the chance of getting a sharp image, then throw away all the blurry ones and stack the rest to reduce noise.

First a visible photo. This was taken with the Sony A7S converted camera, a Hoya UV/IR cut (which transmits UV up to 380-390nm or so) and the LED on my iPhone (which probably doesn't emit much UV). I subsequently corrected the colors using a Color Checkr Passport in Photo Ninja. The lens was the EL-Nikkor 80mm/5.6 metal.

Visible reflectance photo
F/8, ISO1600, 1/100"
Attached Image: _DSC5788 visible UVP.jpg
--

Onward to the UVIVF. These used the Daylight white balance setting on the camera for white balance. This was chosen simply because other people on here have used it and I don't know what else to do. The torch was the new 15W torch from eBay (we NEED a better name for that thing!) and I forgot to remove the glowing ring, although I don't think it affected the results much because the torch was ~0.5-1 meter from the flower. The torch was unmodified.

Next, 30 photos were taken with the torch on, of which 16 were usable (sharp). I also took another 30 "dark frame" images so that the stacking software would remove any remaining visible light from the scene. (The flower was in near total darkness, so these frames appeared black.) These images were taken automatically for me using the Sony TimeLapse camera app, which they sell in their app store for $12US. It is essentially a built-in intervalometer for the camera.

The images were then stacked using the Mac program Starry Sky Stacker, intended for astrophotography purposes, but well-suited to dealing with moving blossoms also. I chose to take the arithmetic mean of the images, as opposed to median, 60th percentile, or max value, which are other options in that software. Final post processing involved a small amount of denoising with Neat Image plugin for PS, and sharpening with SmartDeblur applied to the center of the flower. Only the disc/cone in the center of the flower was sharpened, leaving the petals unsharpened.

UVIVF, whole frame (reduced size)
F/8, ISO1600, 1/10" x 16 images
Attached Image: _DSC5729-Mean UVP.jpg

1:1 crop [ETA: the color profile was messed up on this one, reupload is below with proper profile]
F/8, ISO1600, 1/10" x 16 images
Attached Image: _DSC5729-Mean crop UVP.jpg

ETA: here is a reupload using the original color profile.
Attached Image: _DSC5729-Mean crop UVP.jpg

Overall I would describe this as a very successful experiment, and definitely I recommend the stacking method for dealing with flower motion.

Edited by Andy Perrin, 14 August 2020 - 00:39.


#2 Stefano

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Posted 12 August 2020 - 18:23

[a bit off-topic] Do you use a 26650 cell for the torch? Because I find it very interesting and it would be nice to know where I can find a genuine 26650 cell, with at least decent quality (you have to be very careful, because scams are very common especially around Li-ion cells).

Edit: To the admins, if you want to remove my post, do it.

Edited by Stefano, 12 August 2020 - 18:50.


#3 Andy Perrin

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Posted 12 August 2020 - 18:30

View PostStefano, on 12 August 2020 - 18:23, said:

[a bit off-topic] Do you use a 26650 cell for the torch? Because I find it very interesting and it would be nice to know where I can find a genuine 26650 cell, with at least decent quality (you have to be very careful, because scams are very common especially around Li-ion cells).
Stefano, could you please not derail my thread before it's even started yet? You could have asked me this in PM. I actually don't know what kind of battery it has -- it came with it installed, and on top of that the battery has no markings at all. If you want to reply to this, please PM me.

#4 Bernard Foot

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Posted 12 August 2020 - 19:58

Sounds like a lot of work - but the results justify it. Great pictures.

Why is the colour balance of the two UVIVF images so diferent?
Bernard Foot

#5 Stefano

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Posted 12 August 2020 - 20:05

Also, on topic now, do you think the violet center of the flower has that color due to pollution from UV/deep violet? Did you use the same "leaky" Hoya UV/IR cut filter for the UVIVF shots? (I think yes, but you didn't specify).

#6 Andy Perrin

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Posted 12 August 2020 - 21:01

View PostBernard Foot, on 12 August 2020 - 19:58, said:

Sounds like a lot of work - but the results justify it. Great pictures.

Why is the colour balance of the two UVIVF images so diferent?
Yeah, THAT is what sRGB does to my poor images. I was having a lot of trouble getting instagram to not destroy my photos last night, and I found that including the color profile in the image file was the culprit. Leaving it out fixed the problem. When I uploaded just now I must have used the instagram version. I could go back and fix it. [And done.]

Stefano - no idea. It's possible. And yes, only one filter. But I don't really think it's likely. Would need to do more work to rule it out, and I don't own ANYTHING that can cut the visible exactly at 400.

Here is a UV reflectance image produced by the same methodology, this time starting with 60 images and ending up with 11 images. It actually was very easy - just set up camera and let it take the photos, and then you prune them afterwards in the stacker program. Describing the process is much more involved than carrying it out, Bernard! Focus error here was in fact not due to motion (mostly) but due to photographer not being able to see screen well in direct sunshine. :grin:

Attached Image: UV reflectance-Mean 2 UVP.jpg

Edited by Andy Perrin, 12 August 2020 - 21:12.


#7 Andrea B.

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Posted 12 August 2020 - 22:30

It's a garden cultivar, Zinnia.
Now I'll start at the beginning and read everything. :grin:
Andrea G. Blum
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#8 Andrea B.

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Posted 12 August 2020 - 23:11

Well....very cool experiment. And it seems to have worked out well. The details around the central disk are good in the crop-in that you show - pollen specks and textures are seen. I'm happy to know of the Mac software also.

Now imagine also stacking for depth of field in breezy situations. This would require an enormo amount of shooting !!

As for the white balance in UVIVF photos, yes, this is always tricky unless you want to indulge in an expensive gadget. As I recall in my own previous experiments with UVIVF, using a cool K setting was also useful in attempting to capture the actual colour of the visible fluorescence. But let me ask this question: did the resulting photo match what you saw with your own eyes? Even though it is *very* difficult to match colours by memory, I ask anyway. :lol:

I'm curious as to how many images you think might be necessary to reduce noise? That Sony A7S is not very noisy at ISO-1600, if I recall correctly.
Andrea G. Blum
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#9 Andy Perrin

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Posted 12 August 2020 - 23:45

Andrea, it depends on the single-image signal-to-noise ratio. If you have good SNR in each image then you don't need as many of them. Sony A7S is fine at ISO1600, but the noise also depends on available light and the other exposure settings. The UV photo above was made with 11 very noisy photos:

Single image 1:1 crop (ISO6400, F/8, 1/15" in the shade):
Attached Image: _DSC5853 1-1 single image.jpg

11 image stack:
Attached Image: UV reflectance-Mean 1-1.jpg

After Neat image:
Attached Image: UV reflectance-Mean 1-1 + neat image.jpg

#10 Stefano

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Posted 12 August 2020 - 23:49

As long as it is random noise, it is easy to just average it out. It is a bit trickier if you have "constant noise" (I get vertical stripes for example), and in that case you have to use a mask, as you did.

#11 Cadmium

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Posted 13 August 2020 - 00:23

Andy, Excellent shots! I especially like those crops, and the second crop best. :smile:
Stefano, yes, it uses 26650 size batteries.

Edited by Cadmium, 13 August 2020 - 01:31.


#12 Andy Perrin

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Posted 13 August 2020 - 02:04

Thanks, Cadmium!

#13 Andrea B.

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Posted 13 August 2020 - 18:57

Whoa! That is still way more noise than I expected from the A7S at ISO-6400 even given that this was a UV photo.

It looks kind of like conversion artifacts?
But I am certainly not knowledgeable about that topic. I'm just remembering some of the crazy artifacts I got attempting to convert raw UV files in ACR years ago.

What did you have saturation set at while shooting? A lower saturation setting would not, of course, cause the noise to go away, but it might lessen its intensity?

Whatever the cause, the stacking certainly does reduce the noise.

I'm wondering if an added subtitle might be useful for searching:

Zinnia, UVIVF with 15W "Nemo", Noise-reduction Stacking

Your call, no biggie.
Andrea G. Blum
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#14 Andy Perrin

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Posted 13 August 2020 - 19:10

This was from RAW, so saturation wasn’t set? The noise was not due to ISO, it’s from being in the shade! No sun is bad for UV. Also you have a Baader and probably not shooting at F/8 1/15”?

Remember the whole point here is to shoot intentionally underexposed photos rapidly to preserve sharpness at the expense of noise and then stack to kill the noise.

Edited by Andy Perrin, 13 August 2020 - 19:27.


#15 dabateman

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Posted 13 August 2020 - 23:28

Excellent images.
Just to add, on topic that starry sky stacker is for Mac only. Which is probably why I hadn't heard of it.
For Windows users deep sky stacker (DSS commonly called) will work the same. But its not available for Apple computers.

I wonder how Siril might work for you. Just found out about it:
https://www.siril.org/

Edited by dabateman, 13 August 2020 - 23:39.


#16 Andy Perrin

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Posted 14 August 2020 - 00:29

Try it, report back! I'm pretty sure any of those astro programs will do a decent job for this kind of thing, especially at night when you have a lit subject (which can substitute for "stars").