Guide / Tutorial [Advanced] Photographing slabbed coins using a polarising filter

[Charliemouse]

I wondered whether the use of a polarising filter could help to reduce reflections or glare from the surface of coin slabs.

Note: I do not think this article will be useful for most people.  This is definitely deeper down the photography rabbit hole than most will want to go.  I hope some find it useful, or at least theoretically interesting.

What's a polarising filter used for?

Without getting anywhere into the physics, a polarising filter attaches to the front of the camera lens, and works the same way as polarising sunglasses.  It has the following properties:

• Darkens the image by reducing the amount of light entering the camera by approximately 2/3rds (1.5 stops in camera-speak).
• Increases contrast in things like skies and water, making them appear bluer and deeper in colour.
• Reduces haze.
• Reduces reflections in glass, plastic or water surfaces.

Obviously the last property is most interesting for coin photography.

One advantage a photographic filter has over sunglasses is that it can be easily rotated on the front of the lens, to optimise the exact effect of the polarisation.

Experiment

I photographed a slabbed coin containing both silver and gold, while pointing a light directly at the surface to maximise the effect of the reflection.

I took three photographs.  Other than setting the white balance, no post-processing adjustments were made.

1. Without a polarising filter.

2. With a polarising filter, but rotated to the wrong angle.

3. With filter rotated 90° to the second picture.

Results

With the filter at the wrong angle, the image is arguably worse than with no filter, probably because of the reduction in available light robbing some contrast.

With the filter correctly adjusted (a simple thing to do with the filter in place) the best image is produced, almost eliminating the glare.  The light reflected from the coin remains the same, with colours richer and clearer.

Conclusion

If you find it difficult to photograph a slabbed coin because of reflections and glare caused by your lighting set-up, then using a polarising filter should definitely help.

Edited January 5 by Charliemouse

[stefffana]

I will not talk about photography or angles, filters and lights because my knowledge is very limited.

But this coin is absolutely stunning and you should show us both sides.

The Perth Mint Centenary Sovereign issued in 22ct gold surrounded by a pure silver ring is absolutely unique, made at the highest Perth Mint quality standards. 

I am happy you have bought it from me, because you can show everyone this coin in its real beauty.🤗

 

[Charliemouse]

10 hours ago, stefffana said:

I will not talk about photography or angles, filters and lights because my knowledge is very limited.

But this coin is absolutely stunning and you should show us both sides.

The Perth Mint Centenary Sovereign issued in 22ct gold surrounded by a pure silver ring is absolutely unique, made at the highest Perth Mint quality standards. 

I am happy you have bought it from me, because you can show everyone this coin in its real beauty.🤗

Thank you.  As you ask so nicely...

[Charliemouse]

I took a short video with my phone, capturing the screen of my camera, to try to show the effect of the polariser.

The video starts with the polariser in the wrong position, like with image #2 above.

After a few seconds, I rotate the filter to the optimal position.

Hopefully you can see the change, as the glare from the surface of the slab reduces while the light from the coin remains constant.

 

 

[stefffana]

20 minutes ago, Charliemouse said:

I took a short video with my phone, capturing the screen of my camera, to try to show the effect of the polariser.

The video starts with the polariser in the wrong position, like with image #2 above.

After a few seconds, I rotate the filter to the optimal position.

Hopefully you can see the change, as the glare from the surface of the slab reduces while the light from the coin remains constant.

 

 

Your video is not working properly! I can't hear!

Reported!

Edited January 6 by stefffana

[HonestMoneyGoldSilver]

It's amazing how you turned helping out ladies with their side hustles into a mastery of photographing coins. Well done!

[Charliemouse]

58 minutes ago, stefffana said:

Your video is not working properly! I can't hear!

Reported!

You can't hear the polarised light?  Turn the volume up, mate.

[Charliemouse]

Unforeseen benefit.  Using a polariser works great with OMP.

Here's a picture of a Rwanda Dragon, still sealed in plastic.