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Author Topic: Coin Photography...what are the BASICs?  (Read 3083 times)

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Offline Robert T2

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Coin Photography...what are the BASICs?
« on: May 28, 2007, 06:27:29 pm »
Hi All, been reading through the various thread and piecing together some useful tidbits on coin photography (backgrounds, post-processing etc), but I get the impression I'm still lacking "the basics" required before employing more advanced techniques.

I have a Fuji Finepix pseudo-SLR which has a reasonable macro capability and occaionally I take a good shot... but no consistency. I generally rely on the Auto exposure functionality and manual focus. I guess what I'm asking is are there some good rules of thumb for coin photography in terms of F-stop settings, ISO, dpi, distance from lens, lighting types etc, that should be used for good results.

Any advice gratefully received!

regards,

Rob
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Offline slokind

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Re: Coin Photography...what are the BASICs?
« Reply #1 on: May 29, 2007, 11:34:31 pm »
I wish I could answer you, but I don't know about your camera.  I can give anyone good general advice.  First, with a camera, become capable of taking good general photos with it, anything from landscapes to parts of babies' faces, to know basically how it behaves and what you need to understand about it.  Second, go read Doug Smith's pages on photography; some of the later ones are listed in the bright yellow box at the head of his site: http://dougsmith.ancients.info/
Pat L.
Then there's the thread at the head of this category and several others in Forvm.

Offline Heliodromus

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Re: Coin Photography...what are the BASICs?
« Reply #2 on: May 30, 2007, 09:18:09 am »
Hi Rob,
The basics really come down to making sure you've got a good focused picture with decent light, and avoiding image sensor noise. One prerequisite is to use a copy stand or tripod to hold the camera rock steady - and even then you may want to use a self-timer or remote release to avoid any shake as you press the shutter button.

With these types of consumer point and shoot (I have a 2MP Canon A60 - same deal) you're really fighting the tiny image sensor to get a good picture. The small sensor size means fewer photons hitting each pixel on the sensor and therefore a lower signal-to-noise ratio than you get with the much larger (physical size, not megapixels) sensor of a DSLR. One thing to be aware of is what ISO settings mean on a digital camera - not quite the same as on a film camera. The image sensor on a digital camera inherently has a fixed sensitivity. What you are doing on a digital camera by increasing the ISO level isn't changing the sensitivity but rather amplifying the signal coming from the sensor to achieve a similar effect, but this has the downside of also amplifying the sensor noise. On a DSLR this is acceptable given the better sensor, but on a point and shoot you want to keep to the lowest end of the ISO range. Manually select ISO 50/100 or whatever is the lowest your camera will do.

For coin photography you're not really concerned about depth of field, so you really want to choose a wide aperture to let in maximum light, but stop it down a bit from the maximum to get best sharpness. Try something around F4.0 (a lower number would let in more light, but be less sharp).

For dpi/image size, there are only really two choices that make sense. Either shoot it at the image size you want, or shoot it at maximum size then reduce it later in software. If you resize it you may want to sharpen a little to compensate for sharpness lost by the resizing.

Distance from subject to lens is going to be a bit dictated by your camera and lens - you need to be far enough away for the lens to be able to focus (depends on macro capability - 3-4 inches, maybe), and to give yourself some working room and not block the light, but close enough to get the image size you want. For my setup I can get a full frame focused image at around 3-4 inches; it'd be nice to back off and have more room, but then I couldn't fill the frame.

Type of lighting source doesn't make too much difference (set custom white balance to get true colors for whatever light source you are using), although I prefer ambient light by a window. Light positioning/angle becomes important when you are moving away from the basics and trying to get the "best" picture of a particular coin. Since you'll be choosing the F-stop manually, either use aperture-priority mode to let the camera set the exposure time, or do it manually. A brighter picture will generally allow more leeway for post-processing than a darker one, and will allow for better autofocus which is all that I use.

You're really going to need to post-process to get the best result - largely to boost contrast to compensate for the poor lenses that come with these types of camera. If you're using Microsoft Windows then for free software Google's Picassa does a decent job (the auto-contrast option works wonders!), or you can use the GIMP's levels tool (Tools->Color tools->Levels). Tweaking the contrast / levels curve makes the difference between a competently taken but dull/flat picture and one that pops and looks more life-like.

Hope this helps!

Ben

Offline PeterD

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Re: Coin Photography...what are the BASICs?
« Reply #3 on: May 30, 2007, 01:07:23 pm »
I agree with most of the above, but offer the following comments.

If your macro lens doesn't get close enough you could use a close-up lens. They are available in sets quite cheaply on ebay. If you have a camera with a screw-thread in front of the lens, you need to choose the right size. Or you can do what I used to do and tape it onto the front of the lens.

Depth of field can be critical, particularly for a thick coin. That's why the aperture should be small (high stop number) and the exposure time correspondingly longer. A long exposure won't be a problem if you have your camera on a stand and use a remote or timer if necessary. And if you use bright sunlight or artificial light, you can get enough light on the subject to ensure exposure times are quite short anyway. For the same reason you shouldn't need to change the ISO setting. If you have it, 'aperture-priority' setting will achieve what you want.

Using automatic exposure is fine (providing the f-stop can be set as above), but be aware that the exposure is for the whole picture, so if you have a dark coin on a white background, the picture as a whole will be correctly exposed, but the coin will be underexposed. Some cameras, like mine, have a 'bracket' feature that takes an extra shot a stop (or whatever you want) above and below the first picture. If you don't have this feature you might have to revert to manual or vary the background of the picture. Auto focus usually works fine for me.

You can use natural light or artificial light, but artificial light is easier to control. If your camera has it, use the colour balance feature where you point at a white sheet of paper and let the camera balance automatically. Cameras with only the light bulb icon will invariably be a bit off colour-wise.

I would say keep post-processing to a minimum. If a picture is underexposed, then detail lost in the blacks can't be recovered afterwards. Better to get it right in the camera first. However, dark coins are particularly difficult to get right and sometimes altering the gamma in post-processing helps.

Lighting is a major factor in getting a good picture. I have to say that I have looked at and tried various set-ups discussed on this forum and others, but I still can't better, in most cases, a single light above the camera. However, I'm still learning.
Peter, London

Historia: A collection of coins with their historical context https://www.forumancientcoins.com/historia

Offline Heliodromus

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Re: Coin Photography...what are the BASICs?
« Reply #4 on: May 30, 2007, 01:48:10 pm »
Hi Peter,
Have you found depth of field to be a practical issue? Certainly it's going to be very shallow, but with my setup I'm definitely able to focus OK at F4.0 on my LRB. Maybe greek silver would be a different story! I also use close-up lenses (using an adaptor on the A60), and one thing to note is that increasing magnification will reduce DOF, so it's best to use as little additional magnification as possible.

The reason I suggest fixed low ISO is because that gives less noise. If you let the camera pick the ISO setting then in lower light it may choose a higher ISO setting vs a longer exposure while you'd prefer the latter since it's not an issue with the camera held steady on a stand.

Ben

Offline PeterD

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Re: Coin Photography...what are the BASICs?
« Reply #5 on: May 30, 2007, 02:25:03 pm »
Ben,
No I haven't really found depth of field to be a great practical issue, but there's no reason not to use a small stop so I would advocate it anyhow.  I'm agreeing with you on the ISO issue, but you only need to increase the ISO for low light conditions. Photographing a coin you can put as much light as you want on the subject, so certainly leave ISO low. (I've never changed it in the 6 months I've had my present camera)
Peter, London

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Offline moonmoth

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Offline Robert T2

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Re: Coin Photography...what are the BASICs?
« Reply #7 on: May 30, 2007, 04:52:29 pm »
Many thanks all and esp. Ben and Peter for you detailed replies, this is exactly the sort of information I am seeking.

I can see I'll need to dig a bit deeper into my camera's functionality to make the most of it... pretty sure I've only scratched the surface of it's capability.

The biggest limitation I have at present is the way they've set up the macro. The camera has a built in 28 to 250mm zoom lens, but the macro function only works at 28mm. This means you have to get really close to fill a frame...around 1 to 1.5cm!!! and this makes lighting near impossible. As a result I use the camera's "magnify" button which allows me to macro focus full frame LRB's at a distance of ~6-8cm... but it's still fairly crammed up for lighting and obviously this is at the cost of real resolution (6.3Mpix otherwise). Not sure there's a solution here or if I'm stuck with it on this camera.

Anyway, thanks again.

cheers,

Rob
cheers, robonrome

Offline bruce61813

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Re: Coin Photography...what are the BASICs?
« Reply #8 on: May 30, 2007, 05:03:17 pm »
There are a couple of inherent problems with digital. first you can't get to the best f-stop, which would be around f22, and the problem on resoultion. Film is still many factors more sensitve than digital sensors.  How ever, if you use a low ISO , 100 or 200 it helps give a better image, less "noise". Have you coin fill at least 2/3's for the frame, 3/4 is better, and I would use auto focus, it is probably sees the image better than you do. Lighting can be even more important, low angle side lighting will show details, but you may need additional lights or reflectors to moderate the harsh shadows. I am sure some of the others will add more to this.

Bruce
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Offline slokind

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Re: Coin Photography...what are the BASICs?
« Reply #9 on: May 30, 2007, 06:38:36 pm »
I can choose to have my Nikon digitals read exposure and focus heavily center-weighted, and this helps a lot.  In the case of tetartemoria and other gnats' guts coins, your camera may, as mine do, be set to take a string of exposures and let you choose the one you like.
Pat L.

Offline Heliodromus

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Re: Coin Photography...what are the BASICs?
« Reply #10 on: May 31, 2007, 10:05:49 am »
I just took these to test depth of field with my setup. The first picture was taken at F4.5 and the second at F4.8.  In both pictures the topmost coin is the nominal focus target. They do seem to show a reasonable depth of field, although a secondary conclusion is that my camera's auto focus isn't so great (especially in weak available light as here).

At macro distances depth of field is going to be a factor of distance to subject, aperture and magnification. Unfortunately I didn't record the other parameters (was taking LOTS of pictures), but it'd be interesting to see someone with decent manual focus do a similar test. Note that you should use minumum magnification and greatest working distance possible for best results; shooting at greater magnification than needed then resizing will give a reduced depth of field.

Ben

Offline maridvnvm

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Re: Coin Photography...what are the BASICs?
« Reply #11 on: May 31, 2007, 10:42:45 am »
Hmmm.
A PowerShotA60. The F 4.8 was taken at 1/25 of a second, manual white balance, on a 20 second self timer with Pattern metering mode, ISO 100. The F 4.5 was at 1/50th of a second with much the same settings but both at differing focal lengths.
All the information is stored in the EXIF information so you can always retrieve it later. I just picked a few bits out here as an illustration.
Regards,
Martin

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Re: Coin Photography...what are the BASICs?
« Reply #12 on: August 02, 2007, 12:28:02 am »
Many thanks to Moonmoth for your links they really helped

Offline moonmoth

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Re: Coin Photography...what are the BASICs?
« Reply #13 on: August 03, 2007, 09:43:12 am »
Thanks for the feedback - I'm glad it was helpful.
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