Axial Lights

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mjkzz
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Axial Lights

Post by mjkzz »

I was in process of getting an axial light setup, then something shined into my eyes, large bright disk, it was a 77mm UV filter reflecting lights from my softboxes for video. Then it hit me, why not use that UV filter to build an co-axial setup? So I did and cancelled my order.

I am sure a lot of people here have done similar things, but I did this one so fast, having all parts used on hands, so I figure maybe it is a fun experiments to share, it is so simple.
pm_coax_coin_setup.jpg
some images shot with this configuration
q21024.jpg
q1024.jpg

mjkzz
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Re: Axial Lights

Post by mjkzz »

actually the two US quarter coins did not have that tube around them. This one did where I replaced the UV filter with a piece of K9 grade 1.1mm thick glass. The UV filter was casting some color tint, however slight.
axialsetup.jpg
HK10.jpg

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Scarodactyl
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Re: Axial Lights

Post by Scarodactyl »

Very nice results! You sometimes see this kind of solution on stereo microscopes (particularly older high end greenoughs) and on somw of the system zoom lenses like the Navitars (in addition to normal coaxial illuminators). I can see why, it seems like you can get great results with a much less involved setup. Thought about adding a polarizer and analyzer to finetune reflections?

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Re: Axial Lights

Post by mjkzz »

@Scarodactyl, good idea to add polarizer. Thanks.

ray_parkhurst
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Re: Axial Lights

Post by ray_parkhurst »

Axial lighting is a very popular topic among coin photographers since it gives a very even illumination, but is also very revealing of flaws. This is great for folks wanting to document surface details, but not so great for folks wanting "glamor" shots of their coins.

One interesting thing is that coins (or whatever) with "toning", caused by a layer of oxides or sulfides with varying thickness, are revealed well with this technique. Coins that may look dark and dull will exhibit a myriad of beautiful colors under axial lighting.

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Scarodactyl
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Re: Axial Lights

Post by Scarodactyl »

Do people ever use epi dic on coins? That might be interesting.

lothman
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Re: Axial Lights

Post by lothman »

it is not really 100% coaxial, you have some shadow throw on left side edges, the right side are illuminated. But I think this is what gives the coin a 3D shape.

Thanks for sharing this trick. Does a coated filter bring better or worse results?

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Re: Axial Lights

Post by mjkzz »

Thanks Ray for those knowledge.

Everything was accidental, I want to make a video to illustrate what I "found" (co-axial light), I needed something to block out video lights to make the effect clearer, at same time, something shiny. A coin was the perfect choice. Yet it turns out it actually is better to block out ambient lights. Other than being shiny, coins have more features, all kind of dents and scratches (my intended purpose - catching scratches on surface). This experiment also shows this type of light can reach places that is hard to illuminate, like the bottom of a pipe like structure.

Searching more on the net, yeah, this type of light is widely used in coin photography :-) cool.

@Scarodactyl, not sure what epi is, I have zero knowledge about optics, all these stuff are new (yet fascinating) to me.

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Re: Axial Lights

Post by mjkzz »

lothman wrote:
Sun Dec 05, 2021 3:38 am
it is not really 100% coaxial, you have some shadow throw on left side edges, the right side are illuminated. But I think this is what gives the coin a 3D shape.

Thanks for sharing this trick. Does a coated filter bring better or worse results?
I am pretty sure it is not 100% coaxial, but which image are you referring to? The first two coins had ambient light mixed in. The Hong Kong dollar coin was complete dark when the glass was removed -- the final exposure is completely due to reflected lights.

Coated filter? You mean the 2nd setup with glass (vs UV filter)? The UV filter is causing some kind of color cast, messing up my WB, so I bought a piece of glass with "K9 optical grade" on it and it is thin as I can get, only 1.1mm thick. Yes, the color cast is gone but I can not tell the difference other than that.

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Re: Axial Lights

Post by mjkzz »

"glamor" shots edit: using the "dome light", less contrasty and visually appealing (to me), all details seem to be there, just less pronounced.
hkdome.jpg
Setup
domelight.jpg

lothman
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Re: Axial Lights

Post by lothman »

mjkzz wrote:
Sun Dec 05, 2021 3:52 am


I am pretty sure it is not 100% coaxial, but which image are you referring to? The first two coins had ambient light mixed in. The Hong Kong dollar coin was complete dark when the glass was removed -- the final exposure is completely due to reflected lights.
I meant this:
q21024.jpg

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Re: Axial Lights

Post by mjkzz »

lothman wrote:
Sun Dec 05, 2021 4:17 am
mjkzz wrote:
Sun Dec 05, 2021 3:52 am


I am pretty sure it is not 100% coaxial, but which image are you referring to? The first two coins had ambient light mixed in. The Hong Kong dollar coin was complete dark when the glass was removed -- the final exposure is completely due to reflected lights.
I meant this:
q21024.jpg
Good eyes and yes, exactly. But that is also the exact reason I posted the Hong Kong dollar coin image and its setup :D

The first two US quarter coin images had ambient light mixed in, that is why I posted the 2nd setup with Hong Kong dollar coin. The HK coin was "blackness" checked -- take a picture with no illumination and then put the light sources on, in that HK coin case, the coin was in a deep tube blocking any lights EXCEPT from top. So the HK coin illustrates "coaxial" effect much better.

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Re: Axial Lights

Post by mjkzz »

From what lothman observed and my experiments, I think sometimes maybe it is NOT a good idea to limit ourselves to single type of lights, maybe mix them a little. For example, with a tube around the coin in a dome light setup, I can get coaxial effect, too, but with reduced "darkness" around the edge . . . varying the height of the tube . . . varying the diameter of the tube . . . things will get very, very interesting. :D

ray_parkhurst
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Re: Axial Lights

Post by ray_parkhurst »

Almost all external "axial" systems introduce some amount of off-axis light. Personally, I find this mix very appealing. "Pure" axial systems create very dark edges around the features of the coin, with bright fields and feature surfaces, so the contrast is too high. Your first images are really nice, with overall good dynamic range and shadow detail, along with virtually no blown-out highlights. Even with the extra side-lighting, the US Quarter image is still nice as the overall "axial" contrast is still dominant However, I find your last image of the HK coin less appealing as it has too low contrast, and poor shadow details on the edges. Notice that the image goes from mid-tone on the field, to highlights on the edges, then back to mid-tones on the top surfaces of the features. This is due to the light dome giving lighting from generally a low angle vs the coin surface.

There is a lot of this is documented in various threads over on Coin Community Forum. Take a look at these if you're interested: (note I am "rmpsrpms" on that forum)

https://www.coincommunity.com/forum/top ... _ID=172628
https://www.coincommunity.com/forum/top ... _ID=241822
https://www.coincommunity.com/forum/top ... _ID=178690
https://www.coincommunity.com/forum/top ... _ID=274860
https://www.coincommunity.com/forum/top ... _ID=134056
https://www.coincommunity.com/forum/top ... _ID=411871
https://www.coincommunity.com/forum/top ... _ID=197120
https://www.coincommunity.com/forum/top ... _ID=106762
https://www.coincommunity.com/forum/top ... _ID=254675
https://www.coincommunity.com/forum/top ... _ID=169009

mjkzz
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Re: Axial Lights

Post by mjkzz »

oh WOW!, THANKS Ray. And thanks for those links, very impressed. I think I am a member of that site, too, just have not checked it for a long time.

You are absolutely right, I like the first two US quarter images, therefore I posted them even though they are not "pure" co-axial. They were results of all kind of mistakes while in excitement of "discovering" it -- ie, the idea of using simple UV filter, worked and worked well. Now, it is time to fine tune it, maybe find a way to mix co-axial and diffused ambient lights. For example, by using different tube (blocking ambient) of different height, I see different effects and furthermore, for different sized coins, rather interesting.

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