What type of light bulb is best for coin photography - 5000k? 4000k? 3000k? 2500k? And if I'm looking for a camera to photograph coins, what exactly am I looking for? I've heard references to "magnification ratios" (being of 1:1, 2:1, 3:1. etc.) and "image ratios." Are they the key?
There are many, many threads on coin photography here on CT. You will get much more information in a shorter period if you search them.
The camera and lens is the important part. If the camera lets you do a custom white balance it will adjust to the type of lighting you are using. The lens is where you get the ratio. A nice macro lens at 1:1 works well.
Turn Lock White Balance on and offYou can lock the white balance when recording videos on your iPhone to improve accurate color capture based on lighting conditions. To turn on Lock White Balance, go to Settings > Camera > Record Video, then turn on Lock White Balance. Change the camera's video recording settings on iPhone
Some quick answers, since any of the three questions you ask can become internet rabbit holes. 1. The best light source is one which can illuminate your coin evenly. If you can't get the light "on target" not much else matters. You also want a source which produces different wavelengths of light evenly across the visible spectrum rather than just producing a lot of light at some wavelengths and very little at others. Sunlight and incandescent bulbs do this naturally, but LEDs and fluorescents can only simulate that output. The quality of this simulation can be measured by a statistic called CRI -- in general, the higher the CRI the better the source is for visible light photography. With a modern digital camera, color temperature is less important as long as your camera is set appropriately. 2. Magnification ratios measure the size of the image recorded on film divided by the size of a flat cross section of the object. For a coin, that's typically the coin's diameter. So, for example, if a coin is 48mm in diameter and you use a so-called "full frame" camera like a Sony A7 to "fill the frame" vertically, the reproduction ratio would be 1:2. If both the coin and the image size is 24mm, the reproduction ratio would be 1:1. Many lens and camera combinations do not allow focusing that closely, so you may need a special purpose ("macro") lens or accessories to accomplish what you want. 3. Image ratios are also called aspect ratios and measure the shape of the recorded image. So if a camera's sensor is 36mm wide and 24mm tall, the image ratio is 3:2. If it's 17.3mm wide and 13mm tall, it's 4:3.
So magnification ratios and image ratios are two different things, and I need a magnification ratio of 1:1 or 2:1 or 3:1?
Magnification ratio refers to the size of the image on the sensor as compared to the size of the actual object. 1:1 means that they're the same size, 3:1 means that the image on the sensor is 3x life size. A full-frame sensor is 24x36 mm. With 1:1 magnification, a dime (17.9 mm) would fill 3/4 of the sensor vertically. This is plenty of magnification for full-coin pictures unless you're specializing in sceats and fanams. Most macro lenses sold focus to 1:1. Using a different size sensor doesn't change the magnification, only the amount of the object and its surroundings that is captured.
Magnification ratio refers to the size of the image on the sensor as compared to the size of the actual object. 1:1 means that they're the same size, 3:1 means that the image on the sensor is 3x life size. A full-frame sensor is 24x36 mm. With 1:1 magnification, a dime (17.9 mm) would fill 3/4 of the sensor vertically. This is plenty of magnification for full-coin pictures unless you're specializing in sceats and fanams. Most macro lenses sold focus to 1:1. Using a different size sensor doesn't change the magnification, only the amount of the object and its surroundings that is captured.
Magnification ratio refers to the size of the image on the sensor as compared to the size of the actual object. 1:1 means that they're the same size, 3:1 means that the image on the sensor is 3x life size. A full-frame sensor is 24x36 mm. With 1:1 magnification, a dime (17.9 mm) would fill 3/4 of the sensor vertically. This is plenty of magnification for full-coin pictures unless you're specializing in sceats and fanams. Most macro lenses sold focus to 1:1. Using a different size sensor doesn't change the magnification, only the amount of the object and its surroundings that is captured.
