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How much head reflection is acceptable?

thbmok

Brilliant_Rock
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Jul 30, 2010
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891
I'm still new to colored stones so I'm really curious what people with more experience think of head reflection. At what point does it break a purchase? I have seen gems with beautiful color at full arm's length (~24 inches) black out completely at closer than half arm's length (~6-12 inches) due to head reflection. Would you buy such a stone?

To be clear, I'm talking about the dark spots that appear on the gem as I look directly down the table of the gem and draw the gem closer to my face, with the main light source behind my head. This is similar to how the arrows appear darker in well cut diamonds as I draw the stone closer to my face. I hope I'm using the correct terms. Thanks in advance.
 

Pandora II

Ideal_Rock
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Maybe I don't understand, but if there is shadow caused by your head obstructing the light then that is nothing to do with the gem and everything to do with the lighting so it would have no influence on my buying a gemstone or not.
 

thbmok

Brilliant_Rock
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Thanks, but I'm pretty sure the head reflection I'm referring to is a result of how the gem is cut and draws in light. Under the same lighting, I have also seen gems that don't darken up as much as I draw the gem in from full arm's length (~24 inches) to half arm's length (~12 inches).
 

LD

Ideal_Rock
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I'm not sure whether you mean head reflection or something called extinction. Extinction can occur so that only part of the gem "blacks out" or, it can be wider spread so the gem looks very dark with only flashes of the body colour. If it's extinction you'll know because if you view the gem and rotate it slowly, the areas that were blacked out may suddenly show body colour and vice versa.

If you're talking about head reflection then good gems shouldn't completely black out in shadow and their colour wouldn't be wiped out even in lower lighting conditions - so if you're looking at a gem that only looks good in bright sunlight or strong lighting conditions then I'd pass. Good gemstones hold their colour in nearly all lighting conditions but may appear slightly less intense or vibrant in some more than others BUT you should still be able to see the body colour and not black.

Just an FYI - forget what you know about diamonds because coloured gemstones are different!

Here's an article that contains some information on extinction that may help:

http://www.ruby-sapphire.com/brilliance_windows_extinction.htm
 

Michael_E

Brilliant_Rock
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thbmok|1315591156|3013712 said:
Thanks, but I'm pretty sure the head reflection I'm referring to is a result of how the gem is cut and draws in light. Under the same lighting, I have also seen gems that don't darken up as much as I draw the gem in from full arm's length (~24 inches) to half arm's length (~12 inches).
A gem can only reflect what's in front of it. The reflections that you see can be from directly in front of the gem, (your head), or from farther off to the side of your head, (closer to the horizon from the gem's point of view). In order to get light from around your head to be reflected back to you eyes, a cutter will design the stone with a fairly shallow pavilion, a tall crown and a small table. You need to be careful where the light that you're reflecting back to the eyes is coming from though, since there is generally more light coming from higher on the horizon and that's where your head is. A well designed stone will show minimal head shadow and acceptable brightness at arm's length. Getting any stone down to 12" from your eyes and you'll always see some darkening from head reflection.

There are a few ways around this however. The best way is to cover your head with aluminum foil, (which also repels aliens). You can also only look at gems through a small hole in a white piece of paper. Lastly you can close one eye and look at the stone by positioning it off to one side of your head...this will get at least 1/2 of the stone reflecting greater brightness. Of course if you are a pin head, (small head = small head reflection), everything looks good, a fact which goes a long way in explaining why department stores can sell the stuff that they do. :lol:
 

LD

Ideal_Rock
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Michael_E|1315594359|3013779 said:
thbmok|1315591156|3013712 said:
Thanks, but I'm pretty sure the head reflection I'm referring to is a result of how the gem is cut and draws in light. Under the same lighting, I have also seen gems that don't darken up as much as I draw the gem in from full arm's length (~24 inches) to half arm's length (~12 inches).
A gem can only reflect what's in front of it. The reflections that you see can be from directly in front of the gem, (your head), or from farther off to the side of your head, (closer to the horizon from the gem's point of view). In order to get light from around your head to be reflected back to you eyes, a cutter will design the stone with a fairly shallow pavilion, a tall crown and a small table. You need to be careful where the light that you're reflecting back to the eyes is coming from though, since there is generally more light coming from higher on the horizon and that's where your head is. A well designed stone will show minimal head shadow and acceptable brightness at arm's length. Getting any stone down to 12" from your eyes and you'll always see some darkening from head reflection.

There are a few ways around this however. The best way is to cover your head with aluminum foil, (which also repels aliens). You can also only look at gems through a small hole in a white piece of paper. Lastly you can close one eye and look at the stone by positioning it off to one side of your head...this will get at least 1/2 of the stone reflecting greater brightness. Of course if you are a pin head, (small head = small head reflection), everything looks good, a fact which goes a long way in explaining why department stores can sell the stuff that they do. :lol:
:lol: :shock: :lol: :shock: :lol: :shock: :lol:

I find the aluminium foil combined with the the small hole in a white piece of paper and closing one eye particularly effective - although this does have the disadvantage of picking up local radio stations which is slightly annoying when one is trying to concentrate on the gem in hand. On occasion, I have been taken to a nice secure room - this of course is extremely helpful because it's very peaceful and quiet - although why I have to stay in there for at least 21 days I'm not sure. :confused:
 

thbmok

Brilliant_Rock
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Thanks LovingDiamonds, I certainly understand that colored stones get much more complicated, given all the variances in different materials, colors, and cuts. In terms of the head reflection I'm trying to address in this thread it's really just a function of the viewing distance of the gem as Michael_E is describing.

Hopefully the attached illustration helps describe how I view the gems and what I see as head reflection. I put the gem in a gem box and hold it in my hand, looking down at it with the main light source behind my head (sun/ceiling lights). Not wearing any funny hats or masks. :lol: The only thing I'm changing is the viewing distance of the gem, from full arm's length (~24in) to less than half arm's length (~6in). The illustration shows the worst case of what I have see as head reflection, the gem looks absolutely fine at a viewing distance of 24 inches, but has increasing amounts of head reflection as I shorten the viewing distance until it blacks out almost completely at 6 inches. For the purpose of this thread I'm just trying to understand how much head reflection is acceptable with colored stones so I can adjust my expectations accordingly.

headreflection.png
 

pregcurious

Ideal_Rock
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Mar 18, 2009
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Michael_E|1315594359|3013779 said:
There are a few ways around this however. The best way is to cover your head with aluminum foil, (which also repels aliens). You can also only look at gems through a small hole in a white piece of paper. Lastly you can close one eye and look at the stone by positioning it off to one side of your head...this will get at least 1/2 of the stone reflecting greater brightness. Of course if you are a pin head, (small head = small head reflection), everything looks good, a fact which goes a long way in explaining why department stores can sell the stuff that they do. :lol:
This is the funniest post I have ever read on PS. Thank you, Michael, for making my day.
 

LD

Ideal_Rock
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thbmok|1315596912|3013811 said:
Thanks LovingDiamonds, I certainly understand that colored stones get much more complicated, given all the variances in different materials, colors, and cuts. In terms of the head reflection I'm trying to address in this thread it's really just a function of the viewing distance of the gem as Michael_E is describing.

Hopefully the attached illustration helps describe how I view the gems and what I see as head reflection. I put the gem in a gem box and hold it in my hand, looking down at it with the main light source behind my head (sun/ceiling lights). Not wearing any funny hats or masks. :lol: The only thing I'm changing is the viewing distance of the gem, from full arm's length (~24in) to less than half arm's length (~6in). The illustration shows the worst case of what I have see as head reflection, the gem looks absolutely fine at a viewing distance of 24 inches, but has increasing amounts of head reflection as I shorten the viewing distance until it blacks out almost completely at 6 inches. For the purpose of this thread I'm just trying to understand how much head reflection is acceptable with colored stones so I can adjust my expectations accordingly.

Basically very little. As I said in my earlier post, if a gem blacks out when you view it, even close up, why would you buy it? There are no "acceptable" limits and it really is up to the buyer as to what he/she tolerates. Personally, I wouldn't buy a stone that the lighting affected the colour as dramatically as you describe. Coloured gemstones are bought first and foremost for colour.
 

JewelFreak

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Made my day, too, Michael. Wonder if you get the same radio stations as LD does.

Head reflection is a term I haven't heard before -- sounds to me like simple old shadow, and LD & Michael are right -- a good colored stone should show its color in pretty much any light or shade. I just tried what you diagrammed with a blue spinel, the darkest stone I have, and yup, still blue anywhere I moved it. Whatever this fading-to-black critter is that you have, send it back if you can!

--- Laurie
 

movie zombie

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Michael_E|1315594359|3013779 said:
[There are a few ways around this however. The best way is to cover your head with aluminum foil, (which also repels aliens). You can also only look at gems through a small hole in a white piece of paper. Lastly you can close one eye and look at the stone by positioning it off to one side of your head...this will get at least 1/2 of the stone reflecting greater brightness. Of course if you are a pin head, (small head = small head reflection), everything looks good, a fact which goes a long way in explaining why department stores can sell the stuff that they do. :lol:

did you start happy hour w/o me, Michael?! that is just too funny! :lol:
 

thbmok

Brilliant_Rock
Joined
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Messages
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JewelFreak|1315603395|3013904 said:
I just tried what you diagrammed with a blue spinel, the darkest stone I have, and yup, still blue anywhere I moved it. Whatever this fading-to-black critter is that you have, send it back if you can!
Sounds like you have a nice blue spinel!

As Michael_E suggested, the amount of head shadow/reflection depends on the cut of the gem, the lighting setup, and the viewing distance. And as I said, I have also seen stones that don't show much head shadow/reflection with a viewing distance of as close as 6 -12 inches in the same lighting setup. I think head shadow/reflection, if it is an issue, is more noticeable in lighter tone material as well.

If I buy and keep one of these stones with lots of head shadow/reflection I'll certainly take and post pictures. :geek:
 

thbmok

Brilliant_Rock
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Well, my SO likes and is keeping one of the gems with quite a bit of head shadow/reflection so here's a collage of photos of what I see in person. Nothing fancy in the lighting setup. Photos were taken at night in the kitchen. The only light source is the fluorescent ceiling lamp. Gems are sitting in their gem boxes on top of the kitchen counter. I took the photos by holding the camera in front of my face and looking down at the gems at various distances. The only thing I changed between the four shots was the distance between the camera and the gems.

The collage captures what I see in person with the gems at a viewing distance of 24/18/12/6 inches. One of the gems has quite a bit of head shadow/reflection whereas the other has a minimal amount. I think it's pretty obvious which one is which. The photos are not modified in any way other than resizing, cropping, and adding the text. The photos are pretty spot on and representative of what I see, although the top gem is slightly more pink in person.

Hopefully this clears up what I'm seeing and trying to describe. I understand there are no common limits in terms of what is acceptable or not with colored gems. I'm just trying to get a sense from the more experienced buyers/collectors here of what they view as acceptable in their eyes. I want to see more individual opinions if you will. Thanks for reading and sharing your thoughts.

head.png
 

movie zombie

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at 6 inches at the far right i can see your head shadow within the boxes themselves! your head is between the boxes and the ceiling light and i would expect to see the difference in the stones. there is absolutely no way that light can travel through whatever is blocking the light...in this case, your head. this is something that would not bother me at all because how many times will my head be that close to the stones while i'm wearing them? the far left at 24 inches shows stones worth keeping.
 

Michael_E

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JewelFreak|1315603395|3013904 said:
Head reflection is a term I haven't heard before -- sounds to me like simple old shadow
.
.

--- Laurie

There is no such thing as a simple shadow. Try reflecting a shadow...it isn't possible. If you try, you'll find that you are reflecting everything in front of the mirror and that you can see a reflection of yourself, as well as much of your surroundings, even if the entire mirror is in your shadow. A diamond is no different, it is basically a bunch of mirrors, (the pavilion), and prisms, (the crown), and all it can do is reflect what is in front of it. Regardless of the cut design, the closer you are to the stone, the greater the area that the reflection of your head takes up in your view of the stone.

One of the problems with these sorts of discussions is this diagram:


Unless the light is in a totally dark room, there are always other things in the room which will reflect that light. Since the diamond is reflecting all those other things as well as the light itself, you'll see varying intensities of reflected light, (and color), in the diamond, even if the light is blocked and your head is shadowing the diamond. To keep from boring everyone to death I'll get to the point. The point is that you need to examine each stone that you are thinking of buying under the same sort of lighting conditions that they will be worn in. For colored stones this should be in bright diffuse lighting, (a bright overcast day works well), since this type of lighting eliminates influences from an uneven lighting environment and will show you just how much "head reflection" the stone is showing at arms length.

The original question of how much of these dark reflections are acceptable is really a personal one since there are so many variables. I would say that if more than 30% of the stone is dark under good lighting conditions at arms length, that the stone may need a recut, (just make sure that the darkness is not a window, extinction or a dark area behind you(OOOOO the bogeyman is after you!) :shock: ).

headreflection copy.png
 

cellentani

Ideal_Rock
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3,820
In addition to your head obstructing light, are you sure the darkness isn't also due to camera reflection? I have a camera with a black case, and light colored gems will reflect the darkness in photos. I can somewhat get around this by making a lens-size hole in a piece of white cardstock, and shooting through the opening. However, there will still be some dark reflection if photographed straight on, due to the darkness of the lens.
 

thbmok

Brilliant_Rock
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891
The photo collage correlates with what I see in person without the camera in front of my face. The amount of head reflection is similar for both gems outdoors in sunlight.
 
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