Photographing bronze coins

Photographing bronze coins 2015-02-02T21:22:42+00:00

Home Forums Flying Eagle and Indian Head Cents Forum Photographing bronze coins

Viewing 8 posts - 1 through 8 (of 10 total)
  • Author
    Posts
  • DVCollectorDVCollector
    Moderator
    Post count: 103

    I’ve started this thread as a place to post my photographic experiments and techniques on bronze coins. I will add more examples as continue my experiments.

    Bronze coins can be tricky to photograph because our eyes see colors differently than cameras. The diagram below compares the human eye’s response to color and luminosity to a CMOS sensor. As you can see, the green cone cells are more sensitive than red or blue. It’s probably an adaptation to spot greenery (and food sources) over greater distances. In terms of bronze coins, our eyes will see greens (patina) stressed over other redder tones. A camera’s CMOS sensor on the other hand, captures a much larger color gamut than our eyes, so we must compensate for that in post-processing.

    Eye sensitivity to color vs. CMOS

    A second factor to consider: even the best prosumer dSLR cameras apply a curve that punches up certain colors, such as skin tones, to produce a more ‘pleasing’ photograph. But this “feature” also works against capturing accurate color in bronze coins: they often appear over-saturated, especially in the reds. Take a look at this graded, “red” IHC, shot by an auction house, and analyzed by ACR software. As you can see on the histogram, the reds are pushed hard against the upper tonal range (red arrow), a sure sign the tones (and colors) are improperly balanced.

    Histogram of over-exposed MS coin

    Are many MS bronze coins truly this saturated and bright? Probably not, but the photographer has chosen to emphasize the “red” and MS grade of the coin by pushing the color and brightness. By my thinking, the best qualities of MS coins are not in their reflectivity, but in their details–especially when studying varieties. Therefore, you shoot the coin to emphasize those details and to also capture an accurate sense of color.

    The same mistakes made when shooting MS bronze coins often apply to toned “brown” bronze coins. When a toned coin is put under the camera, it will apply color curves that punch up the reds and lighten the coin. So we must compensate for that, by applying our own curves to put the coin back at a realistic tonal range. Using ACR, it is easy to apply curve presets to correct the color and tonal range for one or even a batch of coins. Even before it even gets to Photoshop, the resulting tone and color can be close to the actual coin:

    Bronze coin in ACR

    A few quick adjustments produce this result, which is very close to the actual coin seen in normal viewing light.

    Final result after post-processing

    What if people think the above coin is “too dark”? It’s been my experience that most coin photos are too bright, which makes proper color rendition very difficult, as more subtle color variations will be emphasized. While lightening the photo may bring out more detail, at what point does the coin look “washed-out” or even cleaned?

    Compare the coin photo above to this one, which has been brightened substantially in Photoshop. It may be more dramatic, but it almost looks “cleaned” to me, when the actual coin has an original mid-brown tone.

    Lighter version


    • This topic was modified 3 years, 3 months ago by DVCollector DVCollector.
    RussRuss
    Keymaster
    Post count: 124

    Wow, very awesome. Yeah, I agree that the 1882 looks cleaned in comparison. As if it were rubbed between the fingers, or something. May want to experiment with lighting angles from the North – her nose, eyebrow and earlobe are bright. I think light from the north livens up the headdress, too, because light from the west tends to cast shadows on the other side of the LIBERTY headband and feather tips, kind of making the headdress dark. Generally in my experience, RPDs tend to be easier to see with the light from the north or the south – although some can’t be seen unless the light comes from the east or west… no golden rules here, for sure!

    I didn’t know that about the visible spectrum and the CMOS sensor, so thanks for posting that stuff!


    Collecting Flying Eagle and Indian Head pennies never made more cents!

    • This reply was modified 3 years, 3 months ago by Russ Russ.
    DVCollectorDVCollector
    Moderator
    Post count: 103

    Yep–there are some bright points on the portrait. I find that’s common no matter the lighting angle…it’s especially problematic when shooting a coin that probably had some cleaning, as is the case below. The metal is reflective, but not from luster–so you end up with hot points. These can be minimized in post-processing sometimes.

    1902 cleaned

    On the other hand, when a coin is mid-AU and better, the highlights are easily controlled–using a lighting method I’ve developed. 🙂 The AU-MS coin reflects light off luster rather than polish, so there are few specular highlights. This method also maximizes the details captured on the coin, such as breaks, clash marks, and doubling.

    1864 no L with die lines

    Since this technique literally picks out ever detail, it’s great for MS coins. But, for the same reason, the results are really lousy on circulated coins. As a demo, here’s the 1907 RPD-043 shot with low-angle directional light. This is the best method for worn coins, as it minimizes all the hits, scratches and dents:

    1907 RPD-043

    Compare the same area on this coin shot with my method for high grade coins. As you can see, the RPD is nearly impossible to see, because every scratch and mark obscures the 0/0. The result looks like a war zone!

    This just doesn't work


    • This reply was modified 3 years, 3 months ago by DVCollector DVCollector.
    DVCollectorDVCollector
    Moderator
    Post count: 103

    So what happens when you shoot a XF to low AU coin? The results are mixed, because enough luster has been compromised by wear as well as enough surface chatter to be distracting. Here’s the same coin shot with two methods.

    First, my method using stacking. While not nearly as bad as the coin above, it still amplifies surface chatter and discoloration to the point it looks cleaned:

    Then shot with diffuse, directional light. The result has far more accurate color and tone:


    • This reply was modified 3 years, 3 months ago by DVCollector DVCollector.
    DVCollectorDVCollector
    Moderator
    Post count: 103

    Here’s another example of my focus-stacking/lighting technique. Where the last picture of the 1864 was a toned-down, more ‘natural’ lighting technique, here I have pushed the technique as far as it will go. It probably doesn’t get much more detailed than this! 😀 Notice how this shot picks out more of the die clash, as well as many minute details, including some scratches not visible in the last shot. The color looks less natural; it’s due to lighting angle and what colors are reflected off the surfaces.

    Technical details: I shot this at ISO 64 for maximum detail/minimum noise, f9 1/100, saved as RAW, no sharpening in-camera–only a small amount in post-processing. Shot with my sharper 60mm. The final output is stacked from 75 individual pictures–not something you can do except for coins that really merit this level of detail. Imagine a high-grade DDO or a bold RPD like the 1894/1894 shot with this technique! I put the coin on a black background because I think it’s less distracting when viewing fine detail. With a photo of this quality, you could lock your best varieties away for safety and study the photograph alone.

    You can see the 100% resolution picture here–it’s something to see! 😀
    https://farm8.staticflickr.com/7419/16266635120_172ae936e1_o.jpg


    • This reply was modified 3 years, 3 months ago by DVCollector DVCollector.
    RussRuss
    Keymaster
    Post count: 124

    Wow, what a great shot. It brought out some scratches I never saw, lol. The crack forming the length of the neck is interesting. Also there is ‘spider webbing’ in the center of the coin, west of the ear, from die deterioration. My memory tells me that I’ve seen that type of die deterioration most often in 1863 with CN coinage. The die lines under the ear are also most often seen in 1863. A LOT of things lead me to believe that this die was hubbed in 1863 and remained undated. I think it could have received another hubbing after being in storage, given the boldness of the devices, die rust and die damage. Although the die is deteriorated and clashed at least twice, you can still see the string in the pearls very boldly. Very often, the string can’t be seen at all on MS coins. On this example, you can see them between each pearl. Nice.

    There does appear to be a very minor MPD between the 8 and 6, and a minor RPD on the western tip of the 4’s base (could be a digit punch defect). Too minor to list, however.


    Collecting Flying Eagle and Indian Head pennies never made more cents!

    DVCollectorDVCollector
    Moderator
    Post count: 103

    Although the die is deteriorated and clashed at least twice, you can still see the string in the pearls very boldly. Very often, the string can’t be seen at all on MS coins. On this example, you can see them between each pearl. Nice.

    Thanks–It may just be my technique that brings these details out. On my more “natural” shot, they are hard to see–full-size link below. I also see some lines in the fields between the date and bust. The rim cuds are more interesting too. Wish I had an MS 1887 DDO or any major MPD to shoot! 😀 Note: this level of detail just isn’t possible on slabbed coins. The plastic window degrades the optics (even when totally clear)–there is no real workaround.

    https://farm8.staticflickr.com/7314/16252152908_a4334b8ee9_o.jpg


    • This reply was modified 3 years, 3 months ago by DVCollector DVCollector.
    DVCollectorDVCollector
    Moderator
    Post count: 103

    Here’s the obverse/reverse of your 1864, shot with the same process: 🙂

    full sized pic here:
    https://farm8.staticflickr.com/7357/16458176751_4e8b2704ba_o.jpg


Viewing 8 posts - 1 through 8 (of 10 total)

You must be logged in to reply to this topic.