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Poinsettia


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  • 2 weeks later...

Back in post #70 when Damon was asking how auto white balance worked I should have also mentioned that (some) newer digicams set auto white balance by reading the ambient light temperature (a "Kelvin" measurement) via a sensor. I do not know if sensor detected wb also makes use of some of the software wb methods - perhaps in combination or as a double-check.

 

Auto WB has certainly improved over the years.

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A quick shot with the improved MTE 365nm LED, with the reflector & lens section removed, so I can get the lamp closer to the subject.

The exposure time has come down from 25 seconds to 10 seconds & the colours look better to me.

Col

 

post-31-0-59964800-1420808963.jpg

 

Poinsettia Flower, in UVIVF

Lamp, MTE 365nm LED without reflector or lens.

Sigma DP2 compact, IRC + GG420 filters on camera. ISO 100, F8, 10 seconds.

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Back in post #70 when Damon was asking how auto white balance worked I should have also mentioned that (some) newer digicams set auto white balance by reading the ambient light temperature (a "Kelvin" measurement) via a sensor. I do not know if sensor detected wb also makes use of some of the software wb methods - perhaps in combination or as a double-check.

 

Auto WB has certainly improved over the years.

 

I would have thought Auto WB would be the least likely choice for a standard WB for UVIVF. One would be assured to get a different WB for every subject with different emission. Surely Daylight WB is a better match for the Daylight films used as the standard in color film UVIVF photography in days gone by.

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Col--so cool. Nice work! That does look much better. Now I am encouraged to take some more pics! Kinda got lazy the past week or so.

 

John, I will try Daylight WB and compare it to what I am seeing and auto on the 30D (which are similar). I have been trying to get the UVIVFL pics to look like what they do with my eyes under the Blak-Rays. Is that not the right way? No sarcasm there, it's a genuine question.

 

First, I am a self confessed amateur here.

Second, with regular UV photos, anyone can make the false colors anything they want and nobody can empirically say with 100% assurance that they are the right/wrong colors right? At least that was what I gathered.

 

But with UVIVFL, it is visible light we are recording. We can see visible light. So is there a way to know that what I am seeing is really what is being emitted? Or does it depend on who is seeing? (ie. a moth flying at night during a full moon)

I am confused again as usual. :)

 

-D

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John, I will try Daylight WB and compare it to what I am seeing and auto on the 30D (which are similar). I have been trying to get the UVIVFL pics to look like what they do with my eyes under the Blak-Rays. Is that not the right way? No sarcasm there, it's a genuine question.

 

First, I am a self confessed amateur here.

Second, with regular UV photos, anyone can make the false colors anything they want and nobody can empirically say with 100% assurance that they are the right/wrong colors right? At least that was what I gathered.

 

But with UVIVFL, it is visible light we are recording. We can see visible light. So is there a way to know that what I am seeing is really what is being emitted? Or does it depend on who is seeing?

 

Damon,

 

Sorry, I did not intend to pontificate. There is absolutely nothing wrong with you artistically adjusting your photos to look the way you want them to look. That is the nature of art and your Blak-Ray images are great. With regard to Andrea's comment on standardization for scientific documentary purposes such artistic adjustment may be unwanted. It depends on the purpose of the photo and intent of the photographer.

 

UV false colors are, as you say, more arbitrary. The UVP standard UV color scheme, if I may call it that, is both an aesthetically pleasing and reproducible way for us to better discern the subtleties of the UV image. That does not preclude other renditions for scientific use, such as the various UV/Blue/Green interpretations of insect vision, as long as they are properly described.

 

Since UVIVF is visible, the basis for color balancing may be less flexible, at least for scientific / technical documentary purposes. Human color perception is dependent on the color content of the light that is illuminating the scene. Certainly when our eyes are dark adapted, as they would be while undertaking UVIVF photos, we are not seeing colors the same way we would in bright sunlight. We are in a sense physiologically "auto white balanced" so your choice of AWB for your images yielding a better match to what you perceive at the time is very interesting.

 

In as much as a camera's AWB function replicates the color rendition of human visual accommodation in the image produced AWB may be a better choice. That said, I fear one may be stretching the limits of the camera AWB function with such low light and limited color content of a UVIVF emission.

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Thanks for that info John. I appreciate you thinking about it some. And your thoughts are interesting as usual.

 

Curiously enough, I have been trying not to artistically adjust any of my Fluorescence photos. Aside from sharpening, de-noise and their common ilk, I don't change the colors or tones. Nada. What I have been doing is trying to duplicate what I am seeing and Auto WB has been the closest so far.

 

If we were to try and color balance UVIVFL, should we try and balance it off of what we see with our eyes or some other measurement?

 

Thanks for helping me get my head around this!

 

-D

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I think the best most of us can do with UVIVF currently for those fotos which we want to present as colour accurate (as nearly as possible) is to make use of Auto-WB - or whatever WB works best with your camera - and to follow that with editor adjustments as needed.

 

I might suggest that we take some care with labeling. I've already urged everyone to be sure to mention what filters were used in any posted work here or to label "no filters" if none were used.

 

For the attempts at accurate colour in UVIVF, I would think that simply mentioning something like "auto-WB in camera and visual adjustment in editor" would suffice, or some similar phrasing.

 

We have no objection to anyone posting "artistic", less colour accurate versions of fluorescence because it certainly does lends itself to that treatment in a lovely way. But again, the labeling would need to say something like "not colour accurate" or something similar.

 

I've brought up the problems with accurate colour in UVIVF work over the years and so far have never seen a good solution.

 

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All that said --- I suppose we could obtain instruments which read the Kelvin temperature of the light and perhaps use that as a guide to the proper white balance in the camera and in the editor both?

John, any comments on that? I never used film so I have no idea what is used for such things. Light meters? There is some handicap to never having used film and its various tools, but I cannot go backwards in time.

 

In digital cameras, as mentioned above somewhere, some newer ones do try to measure the Kelvin temp to obtain accurate auto-WB, but older ones did not work that way. So for some cameras Auto-WB might work better, but for others Daylight WB might work better. Only experimentation will tell that tale.

 

I guess that some of the old rules don't always work when software and firmware is layered on top of the camera innards to make a digicam. :)

 

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Damon, most eyes see mostly the same. Don't worry about it too much.

Older eyes tend not to see the violets & blues as well as they used to. And the whites begin to look yellow. However, the brain compensates to some extent for all that. It happens because the lens of the eye yellows with age and exposure to sunlight.

 

My left eye sees colours accurately in a "young" way because I had the cataract surgery which removes the eye lens and replaces it with a clear artificial lens. My right eye sees colours inaccurately because it still has an old yellow lens. (ugh.) When I shined the violet leaking 385nm UV-Nichia flashlight on the wall my left eye saw a larger circle of visible violet than did my right eye. BTW, the artificial lens blocks UV. That's a good thing.

 

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Col, your most recent UVIVF does look better indeed. Good work on the torch mod!!

 

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I'm going to spend the evening labeling my UVIVF fotos properly. :D

 

*******

 

Good discussion everyone !!

 

 

I can't go backwards in time.....yet.

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A long time ago, in grad school, I took a course in Light Microscopy and Image Processing. Unfortunately, it was a special topics course taught from the literature so I have no textbook to dust off and plagiarize. Consequently I enjoyed spending part of this frigid afternoon reviewing some online sources to refresh my memory.

 

I keep coming across the same general recommendation to use Daylight WB for fluorescence microscopy. In fact one highly credible source recommends against automatic white balance adjustment "especially in fluorescence" for essentially the same reasons I mentioned earlier in post #79. I think the same fundamentals must surely apply to fluorescence photography and macrophotography.

 

added

 

Another point I ran across somewhere, sorry I forgot to bookmark, was the use of point rather than area metering to avoid overexposure with so much dark background. On my Panasonics this point can be moved around on the screen as I expect it can on nicer cameras.

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I suppose I should have said that I one clicked the WB in software on some of my recent pics because the resulting image was very near what I saw with my eye and didn't change much from the original.

 

Thanks Andrea, those are all sensible suggestions.

 

John, what I don't see in that article (which was a good read and fascinating BTW) is any mention of UV Fluorescence. Is it a given that that is what they are talking about when they state fluorescence? Or does that not matter as the principles discussed stand on their own.

 

The whole UV Fluorescence at night has bothered me for some time in that there is normally very little UV at night. So why have a property that manifest itself visually at night only when a light source hits it that is not naturally around at that time? But there is at most times an appreciable amount of UV during the day.

Perhaps the fluorescence is emitting something else in addition to light. Can light be detected by any other sense besides the eyes? Skin gets warm I suppose.

 

So if Daylight WB is being found to be more accurate then maybe this UV fluorescence is being detected during the day. You can see why I am not a scientist... :D

 

Tomorrow I will do a series of shots with different WB on a common fluorescing item.

 

-D

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Thanks Andrea

"Col, your most recent UVIVF does look better indeed. Good work on the torch mod!!"

What it means is that I will be able to use two MTE 365nm LEDs with the shortened lamp, that now have the same output as three lamps before.

Col

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Yes, that's a long interesting article. Thank you for the reference !!

 

Small quibbles:

 

The author mentions that finding a neutral area in the subject against which to white balance is good practice.

However, we don't always get that neutral area in subjects under black light.

 

I see no mention of what to use as a white/grey card under black light.

It would need to be something that is guaranteed to fluoresce white under black light???

I keep forgetting to go check my little fluor rock collection for that.

 

The author discusses white balancing by the camera as being an "averaging" algorithm.

However, that is not always true for all cameras as I've been gabbling about earlier.

 

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John, spot metering on a brightly fluorescing area in the darkness will control the highlights, but can also bring about an underexposure of the midtones or darkly coloured areas. Subsequently pushing those dark areas areas in the editor will bring out noise. It might be better to use center-weighted metering or average-metering if your camera has that? Experiment, experiment.

 

Also set whatever shadow booster your camera has regardless of what metering you choose. The eye will see more range in the blacklit subject than the camera can so we always have to edit for that by opening shadows or pulling back highlights. It's usually preferable to overexpose a bit and pull back the highlights if possible. Not all cameras provide that capability. For example, newer Nikons give between 1 to 3 stops of headroom. But my old D200 probably had only about 1/2 a stop's worth of highlight headroom.

 

*****

 

Damon, maybe other creatures detect or see that UV induced fluorescence during the daylight?

The pigment (which fluoresces) is, of course, evolutionarily beneficial to the plant - but perhaps the fluorescence, per se, may not be??

Someone may know the answer to this, but its not me. I wish I had more time to research this stuff.

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  • 3 weeks later...

Pollen Close up:

 

One final nod to my poinsettias, which are still alive but don't have any new structures growing. Although they are still loaded with aging pollen. I tried to manually cross fertilize them but nada. Perhaps these store bought ones are designed for a non-reproductive life or/and I didn't do it correctly. Didn't seem to much of a mystery to do though. I have nothing in for scale but trust me these things are darn small!

 

UVIVFL: Canon 30D Unmodified, MP-E 65mm f/2.8 1-5x Macro @5X, 6 Blak-Rays B-100AP, 6 s @ f/5.6 ISO 400, No Filters. Auto WB. In complete darkness

post-51-0-95239400-1422848951.jpg

 

-D

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