Diffuse On Axis Lighting Rig: My Latest Iteration

i think I have finally figuring this out.

It looks like that coin is in some sort of a plastic holder. I've never had good results with axial lighting when coins are in a holder or slab. One possibility is to widen the light source so that the glare from the plastic is uniform across the coin, and then use Photoshop levels command to cancel out the glare.

Some possibilities:
1: the lens. I recall getting shots like that with an early version of the Olympus 135mm bellows lens. It was the lens flaring badly from light being reflected from the top surface of the glass, I also suspected that lens of suffering separation. I returned it and purchased a replacement from the last batch produced( much more modern lens coatings). If you were using the Ard 75 you asked about in the other post then perhaps you do have bad coatings(Edit This is less of a possibility now, see main edit).....but that leads me to the next possible issue.

2: You appear to have used black contact paper to line the inside of the axial rig. In your photos you can see how shiny( and therefore reflective) the surface of that material is. In my first iteration I used that same sort of self adhesive paper I ended up switching to Edmund optical black out material( also self adhesive) its not as good as their non-adhesive blackout material but it was easier to fit and it was a massive improvement over the contact paper. You can get two large sheets( should last you a very long time) for around US$30.00( including postage). Alternatively I think you would find black toweling material would even be cheaper and extremely effective( but it will be even more of a dust trap than the Edmund's black out material). As a quick test to see how much ancillary reflection is going on. Take a plastic Styrofoam cup cut it so that it fits snugly under the beam-splitter while sitting over the coins. You are making a tube that will only allow axial light hitting the coin to be reflected back to the lens. If it is light being reflected from the inside walls of the rig you should see some reduction in flaring. You won't eliminate the flaring completely as you will still be getting reflection from the sides of the rig above the beam-splitter.

3: The most functionally important part of my rig is the light absorbing shroud I place over it( see the original photos). The outside is covered in black contact paper so it is quite shiny( and reflective) and that what I wanted: to reflect light away. The inside surfaces are covered in the Edmund's black out material. (edit seems not to be as important as I thought it was)

How are you diffusing the light? I have a permanently installed diffuser between the LED lights and the "entrance" to the rig. Its white nylon cut from either a flash diffuser or a larger photographic reflector( I used both sources for different purposes). I also have ( not mentioned in my earlier posts a slight snoot light tunnel I had plans to be able to install honey comb and designed the entrance to the rig so I could place the honeycomb in the light path( it was a huge failure). As a result it left a slight rectangular tunnel that helps keep the light directed just to the beam-splitter.

In a little while I will try my rig out minus the shroud and using a lens that flares badly and I will see if I can repeat you results.

Edit. I tried my rig without the shroud and it didn't result in any degradation ( but this may be due to where I have my Macro rig ( its safe from most ambient reflections):




I could get an exaggerated version of your shots by directing a spot light (standard light with a snoot/light cone) onto the top surface of the beam-splitter so that light was reflected directly into the lens( not more Beam-splitter is supposed to have an anti-reflective coating on the top side:





I think you can ignore my comments regarding flaring and you may find placing a black towel so that it "catches" the light that passes straight through the beam-splitter will see considerable improvement. I now think your problem is predominantly light being reflected from the top surface of the beam-splitter into the lens.

You might want to look at a thinner piece of glass, but I don't think you need to get a proper 50/50 beam-splitter just something to stop light being reflected back onto the top of the glass you use. I used to use some black toweling material stretched over a wooden frame and I just placed it so the light that just shone straight through the beam-splitter hit the toweling. Its a cheap solution and its easy to try.

Your last two shots are really good so I also wonder whether you might want to try reducing the exposure a little( you may be over exposing the shots)

the first coin is a slabbed coin. the rest are in no holders.

well I thought the canadian plated penny is very tough to photograph. well axis lighting is the answer.

like your photo wizzy. I found the light you purchased. if its not the same it is very close. I will put some pictures up when. I receive the light. have a great one great photo well focused.