Author Topic: Cameras for coin photos  (Read 22864 times)

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Online fwang2450

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Re: Cameras for coin photos
« Reply #30 on: October 22, 2015, 04:25:19 PM »
According to Ray, owner of this site: http://www.macrocoins.com/, f5.6 is optimal for pennies and dimes, and f6 is best for dollar sized coins. I have been using large apertures on my Nikon 105 mm micro, which yielded not-so-sharp pictures. I was advised by the professional photographer that large apertures result in less sharpness. I have yet to test other aperture settings on this lens. But f5.6 did give excellent sharpness on the f/1.8 lens, known for its clarity.

This is where people discuss coin photography: http://www.coincommunity.com/forum/forum.asp?FORUM_ID=81
Made a mistake: should be  "f8 is best for dollar sized coins".

Offline Gilmore

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Re: Cameras for coin photos
« Reply #31 on: October 23, 2015, 10:09:17 AM »
According to Ray, owner of this site: http://www.macrocoins.com/, f5.6 is optimal for pennies and dimes, and f6 is best for dollar sized coins. I have been using large apertures on my Nikon 105 mm micro, which yielded not-so-sharp pictures. I was advised by the professional photographer that large apertures result in less sharpness. I have yet to test other aperture settings on this lens. But f5.6 did give excellent sharpness on the f/1.8 lens, known for its clarity.

This is where people discuss coin photography: http://www.coincommunity.com/forum/forum.asp?FORUM_ID=81

Yes, Ray provides tons of useful information in this forum. Here are 2 threads I learned most from.

'Coin Photo Setup' is excellent, showing and testing different setups. Best of the best, IMO.
http://www.coincommunity.com/forum/topic.asp?TOPIC_ID=87392&whichpage=1

In the '75mm Lens Shootout' thread compares different lenses.
http://www.coincommunity.com/forum/topic.asp?TOPIC_ID=98494


Here is another nice lens testing page - http://coinimaging.com/Lens_tests.html

Offline SANDAC

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Re: Cameras for coin photos
« Reply #32 on: October 23, 2015, 09:22:57 PM »
Thank you all for many interesting links to coin photography.

If focus stacking technique is not used then I agree smaller aperture like f/5.6 will be needed to keep both relief and background in focus.  However, I'll be reluctant to use aperture smaller than f/8, so for high relief coins focus stacking may be necessary. 

Anyone knows the depth of the relief (distance from the mirrored field to the highest raised device) of typical MCC?  I'm guessing it is something like 0.3mm.  Given the required depth of field, a table can be generated to show the maximum aperature wrt distance of the object (for a given camera and lens).  I wouldn't be surprise such tables already existed somewhere on the Web

Offline SANDAC

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Re: Cameras for coin photos
« Reply #33 on: November 01, 2015, 11:54:07 AM »
I'm doing a depth of focus and sharpness test using a Karl Marx medal.  The medal is 60mm in diameter, the longest string of Chinese characters at the bottom is 35mm long.  The medal is prop up by 0.7" on one side, so the difference in depth of the character string (end-to-end) is 0.4", or roughly 0.25" between each character.  The lens is Nikon 40mm macro and the camera is Nikon D5300.  The coin is 11.5" from camera's sensor.  I took 7 pictures at f3, f4, f5.6, f8, f11, f16, and f22 and stack them together to produce an animated GIF at 5 seconds per picture.  Each picture is annotated with f-stop number in white.

At f22, the long character string is in focus, but picture is obviously blurry due to diffraction blur.
At f11, lesser than half of the character string is in focus, but the picture is quite sharp.
At f8, the picture is sharpest while about 4 characters are in focus, a DOF about 0.75"
At larger aperture, the picture becomes blurry again, and fewer characters are in focus.

So the observation that f8 is the optimal aperture is on the mark.

I'd had 2 semesters of Fourier Optics almost 40 years ago.  In theory, larger aperture should produce correspondingly sharper image.  I'm puzzled by the lost of image quality at the larger apertures.  Nevertheless it goes to show that theory needs to be confirm with experimentation.

Offline dynamike51

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Re: Cameras for coin photos
« Reply #34 on: November 01, 2015, 12:51:53 PM »
SANDAC,

My point earlier is to step up the aperture to capture the sharpness at the edges of your photo. This photo you provided illustrates my point exactly - the first with F-22 has clear edges, and as you stepped down the F-stops the edges became more and more "out of focus". With portrait type of photos, that's a desired effect called "bokeh", where the photographer wants the model to be the only subject in focus but the background blurred to accentuate the subject.

The second of your "1969 first lunar landing" photos also slightly showed the same effect - the right and left edges became slightly blurred. I was thinking it's because you had the F-stop set too low.

One other thing you can try to minimize "diffraction" is to move the lens farther away from the coin.

JMHO ....  N39

Offline SANDAC

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Re: Cameras for coin photos
« Reply #35 on: November 01, 2015, 09:01:31 PM »
Don't forget both the "1969 first lunar landing" and Karl Marx are tilted with respect to the camera.  Ordinarily coins are photographed perpendicular to the camera so the entire coins will be in focus.  The DOF for f22 is such that even with a 60mm coin tilting 15 degree, it is able to get most of the coin in focus.  Whereas f8 can only get about 1/3 of the coin in focus.  However, it is not about getting the coin in focus, it is about getting the most detailed picture possible.  The focal point of both f22 and f8 are at the same spot; for f22 it is in focus everywhere but blurry everywhere whereas f8 is sharp in the 1/3 area where it is in focus.  Due to limitation of file size (the working file is 232 megabytes), I can only show small slice in a GIF.  Please take another look at the GIF image below alternating between f22 and f8 only.  The face in the wall is the focus point for both f22 and f8.  f8 shows more details than f22 in the focused area. 

While I still don't understand why apertures from f3 to f5.6 are not as sharp as f8 in my particular setup, the fact that f8 is the sweet spot makes it easy to photograph coins.  I certainly don't need to worry about the complicated focus stacking process and small tilt in some of the slabbed coins should not matter.

Offline dynamike51

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Re: Cameras for coin photos
« Reply #36 on: November 01, 2015, 09:16:23 PM »
Whether f8 is the sweet spot is a matter of opinion. With the photo you presented, one can see it (in f-8) already starts to lose the sharpness around the edges. Again, that could be due to the camera being to close to the coin.

Offline KeepOnTrying!

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Re: Cameras for coin photos
« Reply #37 on: November 28, 2015, 12:51:01 AM »
Trying out my Nikon Coolpix S9900 camera using the digital macro function. It is wifi enabled so I can upload the photos to my iPad effortlessly and post. Can also be uploaded to the PC and Mac with downloaded software.

The Four Beauties of Ancient China medal.
Front side.

I used the IKEA Jangso LED lamps here. They have a warm glow and seem to be well suited for copper, bronze and brass coin/medal photography (at least that's what I think for now!).
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Offline KeepOnTrying!

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Re: Cameras for coin photos
« Reply #38 on: November 28, 2015, 12:54:00 AM »
The other side of the Four Beauties of Ancient China medal. Will have to find a way to eliminate the coin shadows on the paper platform.
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Online fwang2450

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Re: Cameras for coin photos
« Reply #39 on: November 28, 2015, 12:57:48 AM »
Trying out my Nikon Coolpix S9900 camera using the digital macro function. It is wifi enabled so I can upload the photos to my iPad effortlessly and post. Can also be uploaded to the PC and Mac with downloaded software.

The Four Beauties of Ancient China medal.
Front side.
Looks like the white balance is not set correctly. Also, the light on the face needs to be diffused more.

Online fwang2450

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Re: Cameras for coin photos
« Reply #40 on: November 28, 2015, 01:01:28 AM »
Here is the photo I took today of the lines on the reverse of the brass Songyue, using a Canon 35mm macro lens. The magnification is 2x.

Online fwang2450

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Re: Cameras for coin photos
« Reply #41 on: November 28, 2015, 01:03:59 AM »
Here is that little pagoda on top.

Offline KeepOnTrying!

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Re: Cameras for coin photos
« Reply #42 on: November 28, 2015, 01:04:32 AM »
Looks like the white balance is not set correctly. Also, the light on the face needs to be diffused more.

I will have to look into diffusers. How do you set the white balance, on the Coolpix?
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Online fwang2450

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Re: Cameras for coin photos
« Reply #43 on: November 28, 2015, 01:07:24 AM »
Your camera should have a white balance setting.

Offline KeepOnTrying!

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Re: Cameras for coin photos
« Reply #44 on: November 28, 2015, 01:11:21 AM »
I used the "daylight" fluorescent bulb lamps for this study: The 10th Anniversary Panda Coin.

Panda Side.
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