Axial Lighting on Old Proofs

Discussion in 'Coin Chat' started by Publius2, Dec 3, 2020.

  1. Publius2

    Publius2 Well-Known Member

    One of the my recurring failures photographing coins is that of satisfactorily depicting old proofs such as the 1939 WL half depicted below. This is a PCGS PF67 coin in a pristine slab. After reading much here about axial techniques and having failed horrendously with direct light, I built an axial arrangement around an $2 picture frame, shown in this photo. The black vertical block at the lower front edge of the glass sets the glass at 45 degrees and also prevents the light from the lamps from washing across the surface of the slab.

    20201203_123359.jpg


    This first photo is my original direct-lighting effort and you can see it is a miserable failure. All photos use the same lights and camera (75W LED floods, 5500K, Nikon DSLR, ASA100, f-11, camera white-balanced to lights).
    DSC_1031.jpg

    This next photo is the raw JPEG hi-res using axial lighting. You can see that detail is somewhat washed out but what surprised me was the blue-green tint. I can only suspect that the picture frame glass has a tint that eluded me. It also has a bit of soft focus despite using manual focus to get it looking right on the computer screen before shooting. Maybe the glass pane is not really optically clear?
    DSC_1099-Original.jpg


    Finally, this is the axially-lighted coin that I have post-processed liberally to try to make it appear as close to the original coin-in-hand as possible. Better, but no cigar. The quest will continue. Your thoughts and critiques are welcome.
    DSC_1099-Adjusted.jpg
     
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  3. expat

    expat Remember you are unique, just like everyone else

    Are you shooting in a totally dark environment, because the glass can direct ambient light and reflected colors. Also, I prefer one large light source directed at the glass and I shoot the coin 4 times with a quarter turn each time to see which is more realistic. These were taken through the plastic of the original packaging after much re-positioning of the subject under the glass
    Bahamas 1973.jpg Bahamas 1975.jpg
     
    Pickin and Grinin and Chris B like this.
  4. -jeffB

    -jeffB Greshams LEO Supporter

    I'd expect picture-frame glass to be optically flawed -- the surfaces may not be especially smooth, and there may be small internal defects. This isn't an issue when there's an item right behind the glass and you're looking at it straight on, but as angle and distance to the subject increase, those defects will affect image quality.

    I've got Canon DSLRs with some high-end autofocus lenses, and they often fail when I'm trying to shoot through windows or doors at an angle. Now, that's double-paned glass, so the effect is exaggerated, but even a single pane can produce many of the same issues. It's not necessarily something you'd pick up with your naked eye, but it can become very pronounced when you're doing photography.
     
  5. messydesk

    messydesk Well-Known Member

    Looking at the first picture, without axial lighting, it looks like all you have is a single light positioned at a fairly low angle around 6:00. You should be able to get your lights closer to the camera and light the coin better. It is tricky, but can be done. Use a piece of paper for a fill reflector. Axial lighting through a slab is nearly useless, as you're going to get a direct reflection of the light source off the surface of the slab. Also, check to make sure that there is no reflection off the top of the glass. Use a black drape opposite the light to prevent that.
     
  6. -jeffB

    -jeffB Greshams LEO Supporter

    That was what I was thinking, too. I wondered about using polarizing filters to cut glare, but that only works when the light's hitting at an angle, not when it's coming in perpendicularly.

    The best I could imagine was a light source that's uniform across the entire width of the coin. You'd still get glare from the slab, but it would be more or less a constant level, and easy enough to subtract out in post-processing (if your camera has enough dynamic range).
     
  7. Publius2

    Publius2 Well-Known Member

    I took about 20 shots with direct lighting: one, two and three lights, ambient daylight only, tilted slab, various light angles, homemade diffusers, etc. and could. not get a satisfactory result. I was looking to catch the reflective fields without blowing out the glare from the devices.

    I was absolutely getting a reflection off the top of the glass from the light. The light itself was reflecting as an orb directly back into the lens (105 Sigma Macro) until I moved the light farther away from the glass pane. At 6" I got the reflection, at 8" no reflection. The photo you see employed a black piece of cardboard held at the rear top of the glass pane and manipulated until the result was the best possible. It was amazing how much difference very small adjustments to the cardboard's vertical placement and angle made in the image.
     
  8. Publius2

    Publius2 Well-Known Member

    No, there is some daylight ambient light in the room but I normally use a black drape over the entire setup (stand, camera, lights, etc). In this case, I didn't use the drape but the ambient light was very low. Without lights, at F11, and with just the ambient light the shutter speed went to about 20 seconds. But next time I will be more careful and do this at night.
     
  9. Pickin and Grinin

    Pickin and Grinin Well-Known Member

    Passing time I have used a magnifying glass to diffract the lights.
    I believe that this is the same concept being used with axial lighting but the magnification and the angle of light, along with the angle magnifier can be troublesome.
    Here is a photo, 3 lights
    upload_2020-12-3_17-12-35.png upload_2020-12-3_17-13-27.png
    I wanted to show the die state The below photos is when I put a piece of glass between the coin and lens. Only cropped with adjustments to the settings before capturing what I saw. This representation is much closer to the in hand look.
    upload_2020-12-3_17-18-43.png upload_2020-12-3_17-19-19.png
    Looking closely you can see that the obverse die was at the end of it's life, more than 1 rim to rim die crack.
    Axial lighting is a tough cookie.
     
  10. ksparrow

    ksparrow Coin Hoarder

    I have had no luck using axial lighting on slabbed coins. In my limited experience photographing proofs, I have placed a milky white plastic juice bottle with the top and bottom cut out, over the slab, as a diffuser, and used my usual 2 lights, one on each side.
     

    Attached Files:

  11. ksparrow

    ksparrow Coin Hoarder

    and a proof walker:
    Walker 1939 proof obv.jpg Walker 1939 proof rev.jpg
     
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