What is the secret to photographing iridescence in a slab?
lsica
Posts: 1,623 ✭✭✭✭
Yeah I know I this is the coin photographer's best kept secret and I might as well ask for the location of the 1964-D Peace Dollars. But how DO you photograph a coin with iridescencent toning in a plastic case? If can I use a direct reflection of the light source I can get it but I get tons of glare (and if I want the coin to appear anywhere near round in the photo the angle of reflection is so steep I can't polarize it out), and if I use a diffused light source I get the color but none of iridescencent effect. If anyone out there who knows feels generous and would like to share, I'd appreciate it 
Philately will get you nowhere....
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In general you want the highest lighting angle and a relatively point-source light. Get the camera and the lights farther from the coin even if it means that the coin is smaller in the field of view. Tilting can help, but is you do it too much you won't be able to keep the whole coin in focus. If you really want to tilt the coin and keep everything sharp, you can try focus stacking (combines the focused areas of several pictures and combines them into a sharp whole.
I was thinking it might involve multiple images. Sometimes I can get an image if the iridescence is on one side or the other and letting the opposite side take some glare, but I've had a few pieces where some really nice toning appears on opposite sides of the coin. Those are particularly tough. And for sure backing off from the coin is a good idea (as you know). Thats why the "1cm macro distance" advertised on many cameras often isn't all that important, and why an SLR with a macro lens or a point and shoot that takes a macro converter add on lens often is.
I'll "play" some and maybe post results when I'm done. I've got nicely toned 1955 Franklin (a date that often doesn't tone nicely) that has some nice copper toning with hints of rainbow. I'd love to get a good image of it.
As far as tilting goes the maximum would be slipping something as thick as a quarter or a nickel under the slab.
I think we tend to be programed to shoot coins straight on...
Don't be afraid to rotate the coin under the lighting until the color pops as you can re-rotate the coin image to straighten it out while photo editing.
I think I may play with axial lighting to see what that buys me. Thanks
Look up CombineZP (free software)
<< <i>Rotating it isn't a problem. And I've even done SLIGHT image stretching to get an image taken at an angle to be "round" again. But you have to be very careful with that, otherwise you get a "hey why is Liberty so fat?" image
I think I may play with axial lighting to see what that buys me. Thanks
IMHO if your having issues getting the image round again your angle is too steep.
I tend to just use a bingo chip or a couple of folded sheet of paper... 3-4 losing lottery tickets
And maybe I'm blue-sky-ing here, but does software exist to combine images taken from different lighting angles? I'm guessing that not only the color but the differing angle of shadows would make any automatic software pretty much not possible.
<< <i>doesn't take a lot of tilt to improve things (and not make liberty fat). The problem is that it doesn;t take much tilt to put everything out of focus. >>
Here's an example as I was using thin foam as an underlayment for raw coins which had rippled from the heat of halogen lights.
<< <i>Focusing problems are especially tough at macro distances or high zooms. And with any teeny-sensor camera (point and shoot) the difference between F4.4 and F8 isn't going to make much of a difference in depth of field. It's times like that I wish I had a real DSLR with lenses. But hey I also want a DCAM Walking Liberty Proof Half and I can't afford either
I couldn't go back to a Point-n-Shoot as upgrading to a DSLR was a huge improvement for me...
Yet nevertheless it's all the techniques you learn imaging that really matter not so much the camera itself.
If your paying some of the pro coin photographers to image your coins the results are not cause they have fancy equipment... they just have far more tricks up their sleeves via gained knowledge and experience.
<< <i>The key is to crack out the coin >>
LMAO
Please visit my website Millcitynumismatics.com
<< <i>
<< <i>The key is to crack out the coin >>
LMAO
Anyway, this will take lots of experimentation until you get the compromise you want. You will likely need more room to move the lights around than a P&S camera will permit if you're within inches of the coin. If you need a small, but bright light source, experiment with a couple Maglites. You could also try one diffused light source and one hand-held non-diffused light pointed to get just the highlights you want. Make a trip through the "small 'n' cheap lighting" department of your local Home Depot/Menards/Lowes and see what you might be able to experiment with, wary of their return policy. See how far you can back away from the camera and still get a decent picture when you crop so that you get more working distance.
Focus stacking with a P&S will be difficult, if not impossible, as most P&Ss don't give you a choice as to where the point of interest for the auto focus is. I wouldn't pursue this unless you actually have some degree of manual focus control.
Also, the amount you can tilt the coin without screwing up the perspective increases with your distance from the coin.
Keeper of the VAM Catalog • Professional Coin Imaging • Prime Number Set • World Coins in Early America • British Trade Dollars • Variety Attribution
<< <i>The key is to crack out the coin >>
A easier way is to polish the slab in many case it is a lot cheaper too. Luster does not show well when the focus point is the outside plastic and not the coin.
Both are done with an Panasonic DMC-FZ35K camera with the DMW-LC55 Macro Converter Lens at a distance of about 15". Both are done with white balance "Shade", both are done with two 18w GE Daylight Flourescents in Target gooseneck lamps for lighting
Image 1 (1943 Mercury): F:4.4 S:1/320, FL 86.4mm (full 18x zoom)
Image 2 (1955 Franklin): F8.0, S:1/25, FL 57.4mm (12x zoom)
Stopped down a bit for better focus and backed the lights away some so had to slow the shutter speed too
<< <i>
Yes and no. Raw coins are much easier to shoot, but I've never cracked one out of a slab just for the picture.
<< <i>A easier way is to polish the slab in many case it is a lot cheaper too. Luster does not show well when the focus point is the outside plastic and not the coin. >>
Apples and oranges. If you're just picking up lustre, then a slab is only a small hindrance. If you need to blast light directly onto the coin, such as for proofs, the clarity of the slab is the least of your worries.
<< <i>Both are done with an Panasonic DMC-FZ35K camera with the DMW-LC55 Macro Converter Lens at a distance of about 15". Both are done with white balance "Shade", both are done with two 18w GE Daylight Flourescents in Target gooseneck lamps for lighting >>
How do they compare to the coins in hand? I wouldn't use fluorescent light since it's so diffused, but that's just me. If the coins look like the photos, then no problem... they're nice shots.
<< <i>How do they compare to the coins in hand? I wouldn't use fluorescent light since it's so diffused, but that's just me. If the coins look like the photos, then no problem... they're nice shots. >>
Thanks. Actually the bulbs are the type that screw in to a regular incandescent socket and don't seem to be too diffuse. They actually can give fairly direct light.
And the coins are pretty close. The Franklin is actually more "brass" looking than "gold" in hand, but I'm thinking that may be more of an effect of the colors mixing together that are more seperately visible at higher magnification.
<< <i>Tough to tell as every coin is different. If the color is difficult to see without glare it can be a tough problem. Sometimes you just need to find the right angle to get the light at (i.e. position on the clock face) as the coin may be tilted a little in the slab.
In general you want the highest lighting angle and a relatively point-source light. Get the camera and the lights farther from the coin even if it means that the coin is smaller in the field of view. Tilting can help, but is you do it too much you won't be able to keep the whole coin in focus. If you really want to tilt the coin and keep everything sharp, you can try focus stacking (combines the focused areas of several pictures and combines them into a sharp whole. >>
I'm not much of a coin photographer, but I've used stacking programs for combining images from a Telescope, where the main benefit is stacking many shots of dim objects to increase their brightness and clarity. Would a stacking program written for coins be useful for combining images from different light sources and angles? Just curious.
<< <i>
<< <i>How do they compare to the coins in hand? I wouldn't use fluorescent light since it's so diffused, but that's just me. If the coins look like the photos, then no problem... they're nice shots. >>
Thanks. Actually the bulbs are the type that screw in to a regular incandescent socket and don't seem to be too diffuse. They actually can give fairly direct light.
And the coins are pretty close. The Franklin is actually more "brass" looking than "gold" in hand, but I'm thinking that may be more of an effect of the colors mixing together that are more separately visible at higher magnification. >>
I know the bulb type. I mean diffused as in soft and relatively spread out. I (and I think most of the photographers) prefer more direct, concentrated light, at least for picking up lustre. It will certainly help get more defined lustre bands, which in turn gets you better color in those areas. Here's an example:
<< <i>
<< <i>How do they compare to the coins in hand? I wouldn't use fluorescent light since it's so diffused, but that's just me. If the coins look like the photos, then no problem... they're nice shots. >>
Thanks. Actually the bulbs are the type that screw in to a regular incandescent socket and don't seem to be too diffuse. They actually can give fairly direct light.
And the coins are pretty close. The Franklin is actually more "brass" looking than "gold" in hand, but I'm thinking that may be more of an effect of the colors mixing together that are more seperately visible at higher magnification. >>
One of the reasons I like CFL bulbs is because they're diffuse. Using a "harder" light often makes lustrous coins too harsh for my taste. In a static picture of a coin, I usually like to see more coin than I can when there are strong, thin luster bands. Another reason I like them is because they're cool enough that you can take a piece of black paper, cut a 1" hole in it, and have a nice collimator for when you do want a harder light.
If your color is off (brass vs. gold) you should make sure you have a grey card to calibrate your white balance.
Keeper of the VAM Catalog • Professional Coin Imaging • Prime Number Set • World Coins in Early America • British Trade Dollars • Variety Attribution
Have you got any more $1G pieces for me?
Lance.
Equipment:
---DMC-FZ35 Camera
---DMW-LC55 Macro Converter
Settings:
---F8.0
---S 1/25
---ISO 80
---WB - 6500K
---FL 43mm (9x)
---Distance ~ 31cm
Lighting:
---3 GE 26w "Daylight" CFLs (100w equiv) in Target clip on gooseneck lamps on a $60 copy stand
And the first attempt for comparison
Settings differences:
---WB - "Shade"
---FL 58mm (12x)
Lighting:
---3 GE 13w "Daylight" CFLs (60w equiv)
Btw - my previous comments about the coin being more "brassy" in hand was really more an effect of the yellowish lighting of a typical incandescent.
If we tell you, it wouldn't be a secret any more.
Recipient of the coveted "You Suck" award, April 2009 for cherrypicking a 1833 CBHD LM-5, and April 2022 for a 1835 LM-12, and again in Aug 2012 for picking off a 1952 FS-902.