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Bedrock of the Community
United States
10045 Posts |
I have been using this technique for shooting coins for a while, but now that I have focus-stacking software, I can get both a good lighting angle and a very sharp final photo!  To make this work, you'll need focus-stacking software and image-editing software that can correct distortion. The basic concept is simple: a coin is set on a flat surface that is inclined towards a light source such as the sun or a light. Try it: hold a coin so that its surface is facing towards a light source and see how the design elements become both evenly-lit and well-defined. That's basically the setup pictured below, to which I've added an inclined platform with regular grid lines--these are very important for truing up the image in post-processing. The basic setup-- the tape and blob of sticky rubber are to ensure that neither the platform nor the coin slide while shooting:  After focus-stacking, the result is sharp from rim-to-rim. However, there is some distortion along both the x- and y-axes that must be corrected:  In Photoshop, the lens correction filter can be used to correct distortion along the horizontal or vertical axis:  Although the grid lines are now parallel, the image is still compressed along the axis which was tilted away from the lens axis. The amount can be determined by using the marquee tool and the shift key to select a square and compare to the grid in the photo. The small yellow arrow shows the distance the image must be stretched here to render proper perspective:  The result: once the 4 x 4 grid is in correct proportion, the enclosed coin, will also be circular.  Now adjusted, cropped, and output--here is the final result. I should add this was shot in overcast daylight, which lends the coin a "natural" appearance. These Peru 1/2 Dinero coins are rather small (15.5mm), but the camera/lens still picks out a lot of detail. Shot with a Nikkor 105mm micro @ f11, Mirror up and EFSC enabled.  Now here is a shot taken with the same method, but using just one Jansjo light (but with a lot of diffusion). The advantage of artificial lighting for this method is that you can adjust the lighting angle easier to get the effect and tonal range you desire--this coin needed very little tonal edits. As you can also see, this lighting method picks out every surface defect, particularly in the fields:  Edited by DVCollector
08/30/2014 02:04 am
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Moderator
 United States
14463 Posts |
Nice write-up  |
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Pillar of the Community
United States
4809 Posts |
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Pillar of the Community
United States
4037 Posts |
Very nice.
You can correct the perspective distortion optically using the "tilt / shift" technique. This can also mitigate the need for focus stacking if you match the angles of coin and tilt. However, you'll still need to stretch the coin to round.
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Bedrock of the Community
 United States
10045 Posts |
Thanks for that idea--although my lenses don't permit tilt/shift. But that's OK--I think I have a method figured out. Here's one last example, shot in natural light and compiled from 36 images. The detail rendered is pretty amazing! You can see faint die cracks, re-engraving, die polish lines, and even evidence of rust on the die. Nikon D810 w/105mm micro @f11 1/15s. Thanks all for your comments!   Edited by DVCollector
08/30/2014 3:56 pm
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Pillar of the Community
2087 Posts |
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Valued Member
440 Posts |
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Pillar of the Community
United States
5825 Posts |
Your technique is different than mine but I can't find fault with your results. Except IMO you are going through a lot of extra steps to get those results. What s/w are you using to correct the image distortion caused by the angle? What hardware do you use to hold your camera? Do you use a remote shutter release? You've got good hardware, particularly the 105mm macro lens. I use similar hardware but only have a Nikkor 60mm macro lens. You never showed the other side of the coins so I can't be sure but it looks like there are remnants of a die clash. Here's my setup:  |
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Pillar of the Community
United States
4037 Posts |
That last shot is certainly showing off the capabilities of the D810. However, it is also showing that you are varying your lighting technique quite a bit. Initially your diagram made me think you were attempting "pseudo axial" lighting, ie direct reflection from light to coin. This was what you showed with the ancient coin in the other thread, indicated by the bright fields and flat surfaces of the coin. The example above of the 1916 Shilling also shows this characteristic, but the 1/2 Dino tutorial example shows light coming from a significant angle, and this last 2 Cents example has light coming from even more of an angle. I can completely understand the use of an elaborate technique if pseudo-axial lighting is the goal since getting light around a large lens like the 105VR is difficult to impossible, but for oblique lighting you can get the same result with less work (no stacking, no distortion adjustments) without tilting the coin. Perhaps a statement of the purpose of your technique would be useful. Is your goal to allow use of natural daylight?
Contact me for photographic equipment or visit my home page at: http://macrocoins.com |
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Bedrock of the Community
United States
10045 Posts |
Except IMO you are going through a lot of extra steps to get those results. Currently, the most tedious step is manually adjusting the focus increment for stacking. When I get D810-compatible tethering software this tiresome step will become automated. What s/w are you using to correct the image distortion caused by the angle?Adobe Photoshop CS6--and the steps described above where I remove perspective-based distortion are very easy and fast. What hardware do you use to hold your camera? It looks like you use a good setup! I use an Albinar copy stand--very sturdy and easily adjustable for small distances to the subject. Naturally--you wouldn't get these results without a remote shutter release. I also shoot mirror up and electronic front curtain shutter enabled. Quote:
However, it is also showing that you are varying your lighting technique quite a bit. Initially your diagram made me think you were attempting "pseudo axial" lighting, ie direct reflection from light to coin. Yes, of course--that Aussie Shilling could be called "pseudo axial". And as I said, I like to experiment, vary shots and of course I reserve the right to use artistic license--even on my coin shots. I bore pretty easily otherwise. Quote:
...but for oblique lighting you can get the same result with less work (no stacking, no distortion adjustments) without tilting the coin. Perhaps a statement of the purpose of your technique would be useful. Is your goal to allow use of natural daylight? I'll just preface by saying that previously I've been taking coin macros for several years--handheld and achieving "OK" results. One thing I took away from that experience is that tilting the coin markedly improves how evenly light falls on the coin, allows natural lighting angle adjustment while getting the camera out of the way. This also reduces the amount of editing needed to the tonal range (it keeps shadows/highlights in check). Agreeably, those two shots above are nowhere near 'quasi-axial', yet angling the coin is an integral part of the final effect, which I simply cannot achieve with a flat shot. You won't get light coverage/detail definition as you see here otherwise. I've tried so many angles before I developed this technique that I'll simply say it works--try it yourself if you like! Finally, the desired effect is a "natural look", and I think both results are very pleasing and high-quality--my ultimate goal. I don't normally go into such detail over each coin shot; my goal here was to explain a technique I find very useful. Thanks everyone!
Edited by DVCollector
08/30/2014 3:58 pm
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Valued Member
United States
234 Posts |
The focus stacking is a necessity here, right, since the coin is angled? Otherwise you wouldn't be able to get the whole coin in focus?
I'm still very much learning about coin photog, so pardon my ignorance if it's a dumb question.
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Bedrock of the Community
United States
10045 Posts |
Quote:
The focus stacking is a necessity here, right, since the coin is angled? Otherwise you wouldn't be able to get the whole coin in focus? Yes--that's an integral part of this method, otherwise you would be hard-pressed to get the coin in sharp focus, even using a very small aperture--and a much longer exposure, which also complicates getting a tack-sharp result. Edited by DVCollector
08/30/2014 4:26 pm
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Pillar of the Community
United States
2480 Posts |
This is very interesting. A few days ago I was rereading Doug Smith's information on focus stacking and wondering if I should try it.
Your results are wonderful.
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Pillar of the Community
United States
5825 Posts |
Quote:
I also shoot mirror up and electronic front curtain shutter enabled.
I considered using the "mirror up" technique to help eliminate vibration but decided not to. I use a wireless remote shutter release AND time delayed exposure. For full coins that works well for me. And I shoot at high resolution so that I can scale down the image. I've never tried saving the original as a .tiff (I think that's the hi res raw format but you end up with huge file sizes) but it's recommended if you want the best results. If I tried a REAL closeup of something like a mint mark then I'd consider the "mirror up" option. Edited by kanga
08/31/2014 08:30 am
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Pillar of the Community
2087 Posts |
Thinking about this technique I realised there is one lens, albeit expensive, that should perform brilliantly with such a set up:
The PC Micro nikkor 85 mm 2.8 D Tilt shift
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Pillar of the Community
United States
4037 Posts |
The 85PCM is indeed a great lens for this. Only caveat is it can only go 1:2, so would need an additional adapter like a PN-11 to go 1:1.
Adapters are available to allow tilt and/or shift with any MF-capable lens. These adapters are not as robust as the mechanisms built into a high quality lens like the 85PCM, but they can work well in a vertical studio setup.
Also available are bellows with tilt/shift capability, like the Nikon PB-4 or Minolta Auto Bellows III. These are pretty expensive on their own, and I find I prefer the adapters mounted to a normal bellows or lens. This is because the tilt/shift bellows move the LENS end of the bellows, while the adapters can be put on CAMERA end. Having the tilt/shift at the camera puts less emphasis on the lens quality, specifically the size of the image circle coverage.
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Replies: 20 / Views: 5,036 |
Posted 08/30/2014 12:40 am
