Sylvanite
Member
Photography is an odd blend of art and science. Its concepts are deeply rooted in the physics of light and also in the psychology of perception. Consequently, some aspects can be easily measured, but are rather loosely defined.
One such term is "field-of-view". You may never have heard the phrase, and might never really care, but it is the foundation of several basic photography concepts - and several fundamental misconceptions.
What is "field-of-view"?
Roughly speaking, field-of-view is the amount of a scene that a camera will capture (with a particular focal length lens). It is expressed in degrees. Field-of-view can be measured different ways (horizontally, diagonally, or conically). Common film/sensor formats have various aspect ratios (1:1, 3:2, 4:3, and 16:9, just to name a few), and each of the ways of measuring will yield a different result. Therefore, everything I have to say about field-of-view is approximate.
What is "crop-factor"?
Holding everything else constant, a camera with a larger sensor will capture a wider field-of-view than one with a smaller sensor. It may seem pretty obvious, but that's all "crop-factor" really means. A digital camera with a "35mm" or "full-frame" sensor has a 1.5-1.6 times larger field-of-view than a camera with an APS-C size sensor. Put the same lens on both cameras, take a picture from the same spot, and the APS sensor will yield an image that is identical except that the edges are "cropped off". A 35mm sensor is roughly twice the size (and has twice the field-of-view) of a "micro four thirds" format sensor. Compact point-and-shoot cameras typically have sensors that are even smaller.
That's all "crop-factor" means. It's a measure of the field-of-view compared to the 35mm film format. Don't read anything else into it (which is a very common mistake).
What is "focal-length"?
Focal-length is a term that defines a lens' optical length, not it's physical length. It is the distance between the optical center of the lens and the sensor (technically, the "focal plane"), when the lens is focused at infinity. It's a standard way of describing several optical properties of a lens. Don't worry about the physics - focal length is useful mainly for comparing lenses.
Standard vs. wide-angle vs. telephoto
Sometime in the distant past, someone decided that the human eye has an effective field-of-view of about 50 degrees. Anything beyond that angle is out of focus (part of one's "peripheral vision"). Therefore, a sensor size / focal length combination that yields a field-of-view of approximately 50 degrees is considered "standard". A combination with a wider field-of-view is considered "wide-angle", and one that is narrower is called "telephoto". Again, don't read more into it than that (another common mistake). For 35mm format cameras, a 50mm lens is considered "standard". Shorter focal lengths are considered wide-angle; longer ones are telephoto. For APS-C format cameras, a 35mm lens is standard; shorter is wide-angle; longer is telephoto. For micro four thirds format cameras, 25mm is standard. These are simply comparative terms. Don't worry too much about them.
About "35mm-equivalent focal-length"
I often wish this phrase had never been coined. It's a greater source of confusion than any sort of useful information. "35mm equivalent" is just a marketing term and represents little more than advertising hyperbole.
Several camera manufacturers make lenses that will fit on both 35mm format and APS-C format camera bodies. Now, the lens doesn't change when attached to the APS-C body, but the end photo will have a narrower field-of-view than one taken with the full-frame body. All "35mm-equivalent focal-length" means is that a longer focal-length lens would yield a similar field-of-view on a 35mm format camera. For example, a 135mm lens on an APS-C camera body gives close to the same field-of-view as a 200mm lens on a 35mm format camera body. That's all.
Manufacturers try to make it sound like more, and try to make it sound important, but that's just hype. The different sensor size is not necessarily an advantage nor disadvantage - it's just different.
Unfortunately, the term has caught on (it is even being used on cameras without interchangeable lenses). I've run across people who are so enthralled by the marketing myth that they actually insist that the lens somehow changes when moved to a different camera body - and that's just wrong.
In conclusion
So, does that help you with your pen photos? If you already own one DSLR camera and lens, then probably not. If you have a choice of equipment, then realize that most pen photos are taken in the short to moderate telephoto range. If you're using a 35mm format camera, that means you'll likely select a lens somewhere in the 50mm to 135mm focal-length range. If you have an APS-C format camera body, you will most likely want a lens somewhere from 40mm to 85mm. For years, my preferred lens for pen photography has been a 28-135mm zoom. If you are shooting with a compact camera, don't worry about the numbers. Just compose the photo for the perspective you want and then zoom in to fill the frame.
One such term is "field-of-view". You may never have heard the phrase, and might never really care, but it is the foundation of several basic photography concepts - and several fundamental misconceptions.
What is "field-of-view"?
Roughly speaking, field-of-view is the amount of a scene that a camera will capture (with a particular focal length lens). It is expressed in degrees. Field-of-view can be measured different ways (horizontally, diagonally, or conically). Common film/sensor formats have various aspect ratios (1:1, 3:2, 4:3, and 16:9, just to name a few), and each of the ways of measuring will yield a different result. Therefore, everything I have to say about field-of-view is approximate.
What is "crop-factor"?
Holding everything else constant, a camera with a larger sensor will capture a wider field-of-view than one with a smaller sensor. It may seem pretty obvious, but that's all "crop-factor" really means. A digital camera with a "35mm" or "full-frame" sensor has a 1.5-1.6 times larger field-of-view than a camera with an APS-C size sensor. Put the same lens on both cameras, take a picture from the same spot, and the APS sensor will yield an image that is identical except that the edges are "cropped off". A 35mm sensor is roughly twice the size (and has twice the field-of-view) of a "micro four thirds" format sensor. Compact point-and-shoot cameras typically have sensors that are even smaller.
That's all "crop-factor" means. It's a measure of the field-of-view compared to the 35mm film format. Don't read anything else into it (which is a very common mistake).
What is "focal-length"?
Focal-length is a term that defines a lens' optical length, not it's physical length. It is the distance between the optical center of the lens and the sensor (technically, the "focal plane"), when the lens is focused at infinity. It's a standard way of describing several optical properties of a lens. Don't worry about the physics - focal length is useful mainly for comparing lenses.
Standard vs. wide-angle vs. telephoto
Sometime in the distant past, someone decided that the human eye has an effective field-of-view of about 50 degrees. Anything beyond that angle is out of focus (part of one's "peripheral vision"). Therefore, a sensor size / focal length combination that yields a field-of-view of approximately 50 degrees is considered "standard". A combination with a wider field-of-view is considered "wide-angle", and one that is narrower is called "telephoto". Again, don't read more into it than that (another common mistake). For 35mm format cameras, a 50mm lens is considered "standard". Shorter focal lengths are considered wide-angle; longer ones are telephoto. For APS-C format cameras, a 35mm lens is standard; shorter is wide-angle; longer is telephoto. For micro four thirds format cameras, 25mm is standard. These are simply comparative terms. Don't worry too much about them.
About "35mm-equivalent focal-length"
I often wish this phrase had never been coined. It's a greater source of confusion than any sort of useful information. "35mm equivalent" is just a marketing term and represents little more than advertising hyperbole.
Several camera manufacturers make lenses that will fit on both 35mm format and APS-C format camera bodies. Now, the lens doesn't change when attached to the APS-C body, but the end photo will have a narrower field-of-view than one taken with the full-frame body. All "35mm-equivalent focal-length" means is that a longer focal-length lens would yield a similar field-of-view on a 35mm format camera. For example, a 135mm lens on an APS-C camera body gives close to the same field-of-view as a 200mm lens on a 35mm format camera body. That's all.
Manufacturers try to make it sound like more, and try to make it sound important, but that's just hype. The different sensor size is not necessarily an advantage nor disadvantage - it's just different.
Unfortunately, the term has caught on (it is even being used on cameras without interchangeable lenses). I've run across people who are so enthralled by the marketing myth that they actually insist that the lens somehow changes when moved to a different camera body - and that's just wrong.
In conclusion
So, does that help you with your pen photos? If you already own one DSLR camera and lens, then probably not. If you have a choice of equipment, then realize that most pen photos are taken in the short to moderate telephoto range. If you're using a 35mm format camera, that means you'll likely select a lens somewhere in the 50mm to 135mm focal-length range. If you have an APS-C format camera body, you will most likely want a lens somewhere from 40mm to 85mm. For years, my preferred lens for pen photography has been a 28-135mm zoom. If you are shooting with a compact camera, don't worry about the numbers. Just compose the photo for the perspective you want and then zoom in to fill the frame.
