Gemstone Photography - Technical Topic
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Christmas, New Year greetings Folks,
Has anyone tried using a circular polarising filter to control reflections? I have returned the couple of stones I had on loan from my neighbour so i can't try any ideas at the moment, will get back into it when he rocks in with a couple more examples.
Cheers, SinHof.
Has anyone tried using a circular polarising filter to control reflections? I have returned the couple of stones I had on loan from my neighbour so i can't try any ideas at the moment, will get back into it when he rocks in with a couple more examples.
Cheers, SinHof.
I've just picked up a polariser for the 60mm macro lens and plan to do a setup with it for everyone's benefit, going to be very interesting seeing how the gem responds and the differences it makes.... stay tuned 
layful:
layful:
Very interesting.
Mackka
Mackka
Oooo... tough one, the difference is almost negligible, I think the first one is Polarised, bottom full light and centre dimmed light, but the exposure would have compensated for the difference in lighting. Love the cut and exceptionally well executed, that's stunner
My two cents worth I thought the bottom one was the polarised one.
I concur with Dihusky that is one beautiful cut.
Mackka
I concur with Dihusky that is one beautiful cut.
Mackka
Thanks guys. That cut was a challenge I will think twice about doing a second time. 8.( :brokenh: :awful:
But
:trophy:
You are quite correct. It is the bottom one. The front and rear facets have cleaned up a bit the cross seems to be a better blue. Some reflections are worse I think because I have moved the silver reflective sheet and paper as I have fitted the filter. Looking at the images side by side there is a fair bit of difference which doesn't to be so obvious as posted here. Even went back and checked I had the right images
I had another bit of a play today and to be honest I think it could be improved on. The set up wasn't ideal for adjusting the filter and I think a bigger screen than the camera screen would have helped to see what was. In short, wished I hadn't posted so hastily and had spent more time on it......... Excuses, excuses.
It would be interesting to see what your results you get Dihusky as in the hands of a pro, I'm sure you will get a better result than I can. Mean while I'll keep trying to improve my technique.
The top exposure was 15 seconds. I tried that as I had read that some one got far better results doing long exposure in low light rather than a fast normal short. Personally I can't see any difference between that and the second 1.6 sec. The polarized one was 5 seconds.
Anyway I'm going to have another crack at it as I think it could be better.
But
Makka said:
:trophy:
You are quite correct. It is the bottom one. The front and rear facets have cleaned up a bit the cross seems to be a better blue. Some reflections are worse I think because I have moved the silver reflective sheet and paper as I have fitted the filter. Looking at the images side by side there is a fair bit of difference which doesn't to be so obvious as posted here. Even went back and checked I had the right images
I had another bit of a play today and to be honest I think it could be improved on. The set up wasn't ideal for adjusting the filter and I think a bigger screen than the camera screen would have helped to see what was. In short, wished I hadn't posted so hastily and had spent more time on it......... Excuses, excuses.
It would be interesting to see what your results you get Dihusky as in the hands of a pro, I'm sure you will get a better result than I can. Mean while I'll keep trying to improve my technique.
The top exposure was 15 seconds. I tried that as I had read that some one got far better results doing long exposure in low light rather than a fast normal short. Personally I can't see any difference between that and the second 1.6 sec. The polarized one was 5 seconds.
Anyway I'm going to have another crack at it as I think it could be better.
Thanks Magoo, you've done it again.
The bottom shot, through my eyes, just has more definition and better , deeper colour on the outer facets. I love the three of them and honestly there is not much between them.
Excellent work mate.
Mackka
The bottom shot, through my eyes, just has more definition and better , deeper colour on the outer facets. I love the three of them and honestly there is not much between them.
Excellent work mate.
Mackka
Thanks SinHof. Didn't see your post there. Probably pecking out my post at the time.
I had another play with the same stone again this arvo. This time rotating the polarizer through 30* then taking a shot and repeat to end up with 4 shots and a fifth with no filter.
On maximum polarization (?) I would have to increase the exposure time. I guess because of a lot of reflected light is cut out. The colour was a lot deeper but facets that were still showing glare/reflection (high lights?) became brighter. So the contrast between the deep colour and the high lights actually made it look worse.
This explains why a few of the facets in the bottom photo have more glare on them. It wasn't because I had moved a reflector, I guess it was because the exposure had been increased.
So SinHof there could be a big difference but I'm not sure it's better. :/
I tried that experiment above a few times, the stone in slightly different positions and varying the amount of light from above and each time the wife picked (with out knowing what was what) the image with only minimal polarization.
I don't think that image above could of taken anymore without making it to contrasty. I was being overly critical of the shot but still feel I should of explored it a bit more.
An interesting experiment. I'd love to see how you guys handle it. :Y:
I had another play with the same stone again this arvo. This time rotating the polarizer through 30* then taking a shot and repeat to end up with 4 shots and a fifth with no filter.
On maximum polarization (?) I would have to increase the exposure time. I guess because of a lot of reflected light is cut out. The colour was a lot deeper but facets that were still showing glare/reflection (high lights?) became brighter. So the contrast between the deep colour and the high lights actually made it look worse.
This explains why a few of the facets in the bottom photo have more glare on them. It wasn't because I had moved a reflector, I guess it was because the exposure had been increased.
So SinHof there could be a big difference but I'm not sure it's better. :/
I tried that experiment above a few times, the stone in slightly different positions and varying the amount of light from above and each time the wife picked (with out knowing what was what) the image with only minimal polarization.
I don't think that image above could of taken anymore without making it to contrasty. I was being overly critical of the shot but still feel I should of explored it a bit more.
An interesting experiment. I'd love to see how you guys handle it. :Y:
I have a question about taking photos while using a UV light to show fluorescence of a gem or mineral. I have some items that I want to photograph but am stumped how to have it show up like its seen to my eye. The top photos show my pain, theres a bright orange fluorescent just under the white stripe all help will be greatly appreciated
The modern cameras can't photograph UV as our eyes see it, within the structure of the imaging chip there is a UV filter which restricts the UV wavelengths. The cameras used in UV photography have had this filter excluded when they are made.
Theduke said:
I know nothing about it but there is a few ideas on https://www.mindat.org/mesg-13-262901.html
https://petapixel.com/2017/09/21/using-ultraviolet-light-make-nature-fluoresce-photos/
You may find this interesting also
https://www.naturesrainbows.com/
Dihusky said:
But isn't he trying to capture visible orange light not UV. So if the camera is insensitive to UV it will result in blackness when only UV is reflected back to the camera. But with florescence the UV light has been absorbed by the mineral then the emitted in the visible spectrum as 'orange' light (in this case) which should be visible to the chip?
Which is what happened in his other post regarding supposed Ruby identification. He captured the red glow.
Not disagreeing. Just trying to understand light. :rainbow:
The camera is trying to capture visible light, but what I believe is happening is the light source is UV, so a specific wavelength as opposed to the broad range of wavelengths of visible light.
As the UV illumination is generated by a light source of a specific wavelength, the energisation is also based on this so the camera can't see it accurately, unless of course the energisation converts the UV light into a visible wavelength.
I may be off the mark, but from here I think it'll take a scientific mind to explain it further... I do not possess one, mine is more mechanical and logical
Now I'm out of my depth and drowning..... HEELLLLLLLPP!!!!
As the UV illumination is generated by a light source of a specific wavelength, the energisation is also based on this so the camera can't see it accurately, unless of course the energisation converts the UV light into a visible wavelength.
I may be off the mark, but from here I think it'll take a scientific mind to explain it further... I do not possess one, mine is more mechanical and logical
Now I'm out of my depth and drowning..... HEELLLLLLLPP!!!!
After days of researching and racking my brain with the exact words to search to define what I want to know I found a interesting read. Its surprising easy if I read right lol
https://petapixel.com/2017/09/21/using-ultraviolet-light-make-nature-fluoresce-photos/
https://petapixel.com/2017/09/21/using-ultraviolet-light-make-nature-fluoresce-photos/
Dihusky said:
Yes. This is what I believe happens also. But I never liked physics. Absorbs then releases at another wave length.
From the readings I have read, and this is only since Theduke raised the question. You need a very pure wavelength of UV to capture the returned visible light. Any stray visible light will pollute the image as long exposures are required.
Although I'm not totally sure this is the whole story as a few mentioned the filter you spoke of and full spectrum cameras. :/
