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Old 12-07-2005, 04:09 AM
rasiel rasiel is offline
Join Date: Sep 2005
Posts: 276
Default FAQ 1 of 2

Thanks for the plug Sevencee :-)

It would take me all night to even scratch the surface unfortunately. It's just not the easiest thing to do. But for starters let's make an FAQ of sorts:

What camera should I buy?

The answer to this most common of questions has no easy answer but if you're buying a camera which you intend to use to photograph coins then it is absolutely essential that it has a MACRO feature. This allows focusing objects close to the lens and (good thing) most cameras today should have this capability.

A second feature that is desirable is SPOT METERING. This allows the camera to measure a small section in the center of the frame for it to decide how long to leave the shutter open and, therefore, how much light to let in so that the image is properly exposed. Many coin images on the internet look too dark because the image is underexposed and that is because it was left up to the camera to determine the appropriate light levels. In this case most cameras will expose the background correctly because that is the largest part of the frame but it does so at the expense of the coin in the middle.

My photos are all blurry

This is usually because the coin was photographed while the camera was being held in the hand. No matter how steady your hand is it will never be steady enough to make the coin appear totally in focus. The basic setup to photograph coins so that they appear sharp is to have the camera placed on a tripod or similar fixture and, if possible, not even manually press the shutter button but rather have the camera's timer do it automatically to minimize vibrations.

The rest of the setup concerns the placement of the coin. This is easiest done on a table that is positioned far enough below that you can view the coin through the camera's viewfinder from a comfortable height. While many people will at this point photograph the coin on the bare table a more upscale look can be obtained by choosing a solid color as the background. This has the added benefit of eliminating distracting textures not related to the coin as well as smaller file sizes. To eliminate the background completely you will need software that can select the non-coin portions of the image and then simply delete the selection leaving only the coin behind. Whatever software came with your digital camera should be capable of this.

My images have the wrong color

The preliminary answer as to the why is because your camera was unable to properly compensate the WHITE BALANCE values. Although we don't notice it (much) with our naked eyes, the light coming from a fluorescent light, that from an ordinary bulb and that from daylight all look very differently from one another to the camera. The reason for this is technical but suffice it to say that the wavelength of a light source has what they call a COLOR TEMPERATURE. A camera with the appropriate white balance setting will be able to compensate the right amount of this color temperature so that the image always appears as if it came from "white" daylight. To this end it's often easiest for you to simply try each of your camera's white balance settings in sequence and then, after making note of which picture goes with which setting, simply choose the one that comes closest.

So what kind of light should I use?

Lighting is easily the most technically demanding aspect of macro photography. The only way to get great results is through a lot of trial and error. There are many factors to consider and hopefully we can start to "home in" on some methods bound to give god results quickly.

- The light itself should ideally be one with a high color temperature. In your typical office supply store you will likely find lamps that are rated as being like daylight or may actually state the color temperature. If so, ask for a lamp with 5000k (kelvin) bulbs or just daylight or something along those lines. Don't get a lamp that is too small - the light filament or area should be at least a few square inches. Let's say the bigger the better without going overboard! They are fairly popular and not very expensive.

- The position of the light is critical to success. Before you know where to set your lamp though you need to determine how close or far you must position your camera relative to the coin in order to maintain sharp focus. This is the most important step and precedes light positioning. After you can get a very sharp image only then worry about finetuning the light position. With this in place put the lamp directly in front of the coin about six to eight inches away and look again through the viewfinder. Is the coin taking up most of the center of the frame? Good. Is the top half of the coin too bright and the bottom (that closest to you) too dark? You will find that tilting the coin slightly towards the lamp by placing a pinhead-size wad of paper on the bottom will help maximize contrast. Do make sure that the coin is as evenly lit as possible and that it is neither too dark overall nor too harshly lit. Sometimes (actually quite often) placing a translucent sheet of paper between the lamp and coin diffuses, that is breaks up, the light from the lamp so that rather than a single beam the light is now coming from many angles. This is a desirable state to eliminate shadows on the surface.

- Turn off all lights in the room except for your light source. The ideal is a pitch black room if you were to turn that one off as well as it cuts down on glare, low contrast haze and white balancing issues.

- To get rid of the coin casting its shadow onto the background place it above a sheet of frosted glass.

So are two or more light sources better than one?

No. It looks weird in all but a handful of 'problem' coins. Even in cases where a coin can't be effectively lit by one light it's preferable to use reflectors from the needed angle rather than a direct light source.

How do I get both sides of the coin in one image?

This is fairly easy to do in concept but I can't give exact steps because it all depends on the brand of software you're using. What you need to do is take one of the two sides and expand its canvas or work area to roughly twice the original size. Then simply go to the other image and copy and paste it into the one whose canvas you expanded. Crop out as much of the background, save image and you're done.

My coin image is too small/big

When working with your image in software you will need to check its size. Depending on your camera's settings it will make images of any of a number of format and sizes so you will need to adjust them afterwards to fit. In your software look for the image size of the image and change the dpi (dots per inch) to 72 from whatever it was (typically 300) and then the horizontal pixels to anywhere from 500 to about 800. In almost every case the camera's image format will have been set to jpeg but if it was something different then save as jpeg at this point and if given a quality slider scale for the photo choose somewhere in the middle. It is unnecessary to use the maximum quality setting unless you intend to print the image in which case you should have left the dpi at 300. For showing the coin photos on the web a typical image of 72dpi at 600 pixels width (both sides together) saved at a quality setting of 5 will be a very reasonable 75k or so in size.

My coin image is sharp on one side but out of focus on the other

If you're certain that it's not a simple case of focus, ie. each side of your coin has the same areas out of focus, then it's probably due to the optical characteristic of DEPTH OF FIELD. Look for a moment at your finger a few inches from your face and without taking your eye off notice objects off in the distance and in your peripheral vision are blurry. This is because your eye can't focus on everything all at once. This effect is more pronounced on camera lenses and progressively more so when using magnification. The solution to the problem lies in using a larger focal length which is a number on your camer expressed as F/# where # is any number from 1 to 16 or more (sometimes up to 32). While you might be tempted to simply use the highest F number available this is not a good idea. There's no free lunch in optics unfortunately and with each click closer to that 32 two negative things begin to happen. First and foremost you begin to close your lense's internal diaphragm which is a circular curtain that lets in light. The tigher this hole the higher the number but also the longer time the camera's shutter will need to remain open in order to gather enough light to properly expose the image. That means more chances for vibrations either on the coin or the light or both to begin ruining the image. Secondarily, the quality itself of the image begins to degrade due to an effect called diffraction. Notice how even if you are very nearsighted you can make a pinhole sized opening by curling your finger and when seeing through it suddenly everything is in focus... but not a very effective way to look at the world!

If your camera therefore has the capability to do so you should choose a setting somewhere between f/8 and f/16, a happy medium where quality remains good on any lens and exposure times are small enough to avoid those dreaded vibrations blurring your photos.

[continued on the next post]
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