A ways back I made a cheapo axial lighting setup, using a tilted sheet of glass to reflect light straight down on the coin, with the camera lens looking straight through the glass. This brings out subtle colors that can usually only be seen with the coin tilted "just so" in a point source light. It also shows every surface defect with brutal clarity, so definitely not glamour shots in any way! The digital images have a sort of blue-purple cast to them, maybe from the daylight bulb I used and long exposure time, so I tried to tune that out to show what the coin looked like through the finder. Manual focus so I hope they aren't fuzzy. First up is a Peace dollar, 1921, I just bought (feel free to offer your opinion as to grade). There is a toned over scratch near the hair bun and a short shallow mark between T and Y, neither very noticeable in hand. regular lighting: axial lighting:
For some coins, axial lighting is a huge boon. For this particular coin, I think the regular lighting looks better.
Top picture is much better. Axial lighting needs to be very diffuse to work well, and for most coins it isn't the solution. The only time I'd consider using it is with a raw coins where the only thing I want to see is the toning and I don't want to see the surfaces. As such, I've never used it.
I've been wanting to try an axial setup for years, but still haven't gotten around to it. There's a good chance I never will. I learned about optics from telescope-making books, where everyone was SUPER SUPER FUSSY about optical paths. Putting an extra sheet of glass in the path was something that you wanted to avoid if at all possible, and a tilted sheet of glass was right out. It would cause ghost images and other artifacts. When you're looking at a bright star against a pitch-black background, those are harder to ignore. You can make a beam-splitter from a pair of 45-degree prisms. One large enough for a DSLR using a macro lens would be really expensive. But for a cell phone... hmm.
I used to play around with axial lighting. It was fun but not something a person really needs. It's a great way to hide surface problems but why ever do that? Not something you want to do if you are selling a coin.
I agree, it looks better with the standard lighting. Let's look at another one, a CBH with thick toning and a distinct bluish color if you can get it at the right angle in the light. this is what it looked like in the viewfinder:
here is an 1890 dime I bought a long time ago, raw, ebay, dipped white (didn't know any better at the time); wrapped in brown paper and put away in a box until it picked up some tone. In hand it has some light tone, with axial it really lights up.
I thought there was general agreement that axial lighting was pretty much the only way to accurately capture toning?
Nope. You can diffuse the heck out of other light and use enough lighting angles to fill all the and get a good picture of the toning. The coin, no, but the toning, yes. The exception is toned proof seated, Morgan, Barber, and Indian cents. You pretty much need the light coming straight down at the coin for this. Total pain through a slab.
With the light hitting perpendicular to the slab, I'm guessing that even polarization wouldn't help? (I guess it could say some interesting things about stresses in the slab, but nothing relevant to the coin...)
Yeah I could never get axial to work with slabs. I'm not sure how PCGS does their Tru Views, it looks like axial light but I have heard that is not what they use.
One area where I think axial light is helpful is with some of the old copper tokens I have. They are all dark brown and hard to photograph. They really pop under axial. here is an admission "ticket" to the Peale Museum in Philadelphia, designed by Christian Gobrecht.
Polarization would make it worse because of the artifacts that would be induced by the slab plastic. A head-on, very diffuse light might work OK through a slab with some modern DSLRs that have 14-bit ADCs, but only if the slab is totally free of defects. You'll get super low contrast in the picture, but you can recover that in post processing if you have enough bit depth to start with and those lower bits aren't all noise. I might illustrate that today, since I have time.
OK, that didn't take too long. Here's something that's close to axial lighting. It's actually a really cheap ring light, made by cutting a hole in a piece of white paper and cramming it onto my lens as a reflector, pointing the lights up at the camera. If you have a lens prone to flare, this won't work well. Here it is with the lights on. Here's what comes out of the camera. Pretty useless picture, right? Here's its histogram. Note that less than 1/4 of the full dynamic range is used. Therefore, with a camera that produces at least 11 bits per channel, I should be able to stretch this histogram out and still have a halfway decent 8-bit image. Fortunately, mine has 14. I'd like to say that simply adjusting the contrast for the entire image produced this, but doing that also revealed the unevenness of the lighting that was a result of having 2 bulbs and not more. I had to make further local adjustments to get this: And its histogram: As mentioned in my previous post, this worked because the slab is free of blemishes. A scratch, along with any shadow it cast on the coin would have been included in the detail that was brought out by enhancing the contrast, and you'd see them clear as day.
Unfortunately, I'm stuck in the Canon ecosystem. I've got great lenses, but my 6D Mark II struggles to get past 11 bits. And I spent a lot of time working in 16-bit space in a previous life (MRI and CT images), so I'm over-sensitive to the loss.
sorry, don't have a picture handy, and I put the setup away. it's pretty crude, just 2 cheap wood picture frames with glass, and the backs taken off, put together with hinges. I set this on the base of my copy stand and set up a gooseneck light so the light travels across the stand base, and when the upper frame is tilted about 45 degrees, the light will reflect straight down onto the coin, which is sitting on the glass of the bottom frame, with cloth backing under the coin. Fiddle with the angle of the glass until the coin looks bright through the view finder. I also put a small object (like an eraser) on the copy stand base between the light and the frame that is just tall enough to block direct light from the lamp hitting the coin. Obviously the results are better with optically flat glass (much more expensive) but I'm just goofing around. hope that helps.
