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Helleborus hybridus comparisons

Fluorescence
7 replies to this topic

#1 Johan

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Posted 11 May 2014 - 18:51

These are quite small (20cm height), and are green with red specks on the petals by daylight.
We have some of them in the garden! They produce some interesting shaped seeds but they
are also just nice in a cottage garden by themselves or mixed in as show flowers.

First I did a 50 image stack using the fancy and expensive new Baader UVIR cut filter:

Posted Image

It's ok as a stack, but a bit one dimensional.

So did a different 50 stack, this time retouching in a background out of focus to bring the foreground seeds to prominence.
Retouching is the Zerene Stacker equivalent of cloning, basically you retain the sharp info and paint in one of the other layers.
Blah blah here: http://extreme-macro...ene-retouching/ - I'm big on stacking but sometimes you can overstack things
and you lose all sense of depth. So I liked this next one better:

Posted Image




I also did a few single shot f/16 comparison shots to see the effect of filtration over the camera lens.
Note I've tried to equalise them in a very simple way, they were mainly to judge colour:

1) Baader UVIR cut on UV-capable el-nikkor 80:

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2) Wratten VII 2B:
I have a Wratten 2a on the way, but looking for a 2c and 2e now.

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I have a hard time seeing much of a difference!


3) Unfiltered. Unfiltered makes for the eye candy but I don't fully understand it.
I don't understand why the camera is seeing <410nm as red, I don't really get the
red/blue posterisation patching and it 'feels' blown.
Maybe someone has some insight regarding what's going on. Food for thought. Ref link for self.

Posted Image


4) Then, just for giggles, I tried a standard Hoya UV(0) filter which has been gathering dust in my filter box:


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Which I found very interesting actually, almost the best of both worlds!



Anyhow I thought the Baader-filtered stack was a little boring, lacking in colour, so did another 50 image stack this time
with full sized images using the Hoya UV. The full sized images produce much nicer detail and don't look as sharpened -
I use Topaz Detail which can be a bit brutal if the image is only 1500px across in the first place. Also I resisted the use of two
new things I've been learning recently, luminance masks and a white colour burning brush. They're both good tools but
I need to use them in more moderation, neither is especially subtle.

I do quite like this, at least it has some nice colour, but don't like the shadow much (need more torches and diffusion!)


Posted Image


One thing I'm wondering, what exactly is the benefit of shooting this with a UV-capable lens then putting a barrier up to prevent
the UV being seen by the sensor. Wouldn't it be just as effective using a non-uv capable lens? :(

Edited by Andrea B., 04 July 2014 - 03:48.

My new extreme-macro.co.uk site, macro from 1:1 to 10:1 and beyond. Your comments and input there would be gratefully appreciated.

#2 msubees

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Posted 11 May 2014 - 18:57

nice work!

#3 colinbm

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Posted 12 May 2014 - 07:55

Good presentation Johan
Col

#4 JCDowdy

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Posted 12 May 2014 - 13:36

View PostJohan, on 11 May 2014 - 18:51, said:

One thing I'm wondering, what exactly is the benefit of shooting this with a UV-capable lens then putting a barrier up to prevent
the UV being seen by the sensor. Wouldn't it be just as effective using a non-uv capable lens? :)

Yes, if you are photographing UV-induced fluorescent emissions at visible wavelengths.

For that matter you could use an unmodified camera, but even still one should use a UV blocking filter because even standard lenses and cameras might exhibit out of band response to the relativly strong UV excitation source. So for UVA-induced visible fluorescent photography why not try your UV blocking filter on your best visible light macro rig! :(

It is an unfortunate that the term "UV photography" is alternatively used to refer to UVA-induced visible fluorescent photography.

A friend of mine actually has patents in this area (http://www.google.co...tents/US7738032). Perhaps it is only a semantic argument, but nonetheless confusing to people who's initial introduction was the alternate, fluorescent, definition.

- John

Edited by JCDowdy, 12 May 2014 - 13:38.


#5 Alex H

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Posted 12 May 2014 - 16:31

Which one, colour vise, is the closest to how you have seen the fluorescence?

#6 Johan

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Posted 12 May 2014 - 19:48

View PostAlex H, on 12 May 2014 - 16:31, said:

Which one, colour vise, is the closest to how you have seen the fluorescence?

Probably the last one although that's also a bit off. As in when I look at it myself, it depends a bit on how close, the angle of and which torch I use. But through my eyes the petals are more orange than yellow or green, the petal markings are red rather than magenta and the seeds can be either pink or blue depending at the angle you shine the torch.

I think a worthwhile exercise for me might be a 'variations' type shoot, playing with all the filters, colour temperature and exposure time. That should give me a decent steer on what does what and what I can do to make things look like I think they should.

I also believe I found out through online research that the pretty one, the red one, is actually misinterpretation by the Bayer filter. This makes that image make more sense to me, and the banding on the seeds. Almost as if once the blue becomes too much it goes red.

Btw JC, this is an unmodified camera!
My new extreme-macro.co.uk site, macro from 1:1 to 10:1 and beyond. Your comments and input there would be gratefully appreciated.

#7 Shane

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Posted 14 May 2014 - 15:23

Quote

It is an unfortunate that the term "UV photography" is alternatively used to refer to UVA-induced visible fluorescent photography.
.

Quote

Perhaps it is only a semantic argument, but nonetheless confusing to people who's initial introduction was the alternate, fluorescent, definition.

It is unfortunate that these definitions have become diluted and corrupted as the damage is done and it is almost impossible to turn back the clock.

Unfortunately, through no fault of their own, it is propagated by those with no understanding of the process. The other common term "UV fluorescence" is also a misapplied and misleading description. I believe I have ranted about this more than once http://www.fotozones...kia/#entry41540.

Phosphorescence is another corrupted and grossly misused term.

#8 Andrea B.

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Posted 14 May 2014 - 21:40

Shane, that link was from back in 2007 when I was first learning to shoot UV and UVIVF (and other). Happy memories!!
You and Vivek were adamant about my learning the proper terminology. :D :( :D

That's when it was decided to use the phrase UV-Induced Visible Fluorescence for the common type of fluorescence photography.
Name the Excitation Wavelength. Then name the Emission Wavelength.

And I have faithfully used that terminology ever since. B)
Andrea G. Blum
Often found hanging out with flowers & bees.