Any field that involves visual images such as photography or movies uses aspect ratios to define the proportions of the images. Aspect ratios are commonly used to describe the relationship between the width and the height of TV’s and computer monitors.
An aspect ratio is basically same as reducing a fraction. For example, 4/8 is the same as 1/2. So when a canvas measures 9×12, you can reduce it to 3:4.
In photography, cameras produce images with different aspect ratios. Compact cameras normally have aspect rations of 4:3 and DSLR have an aspect ratio of 3:2.
You have to pay attention to the aspect ratios or else you’ll have to change the image to make it fit. For example, if a TV has a different aspect ratio than the movie, then it would have to be cropped, stretched to fit, or displayed with black stripes along two of the edges.
The same problem exists in painting. If you’re working from a photo, then you want to choose a canvas that has the same proportions as the photo. Otherwise you’ll have to crop the image or stretch it to fit the canvas. An 8″x10″ photo has an aspect ratio of 4:5. It would fit onto the following canvas sizes; 8×10, 16×20, 24×30 and so on.
It’s more efficient to work within standard aspect ratios so that you can use standard sized canvases and picture frames.
Framing becomes a lot simpler if you make images that have the same proportions the standard frames that you can buy in a store. If you work at non standard aspect ratio, then you’ll have to resort to custom framing.
Every color model has a range of colors that it can produce. This is the gamut, or the range of colors that are available within a color system. A computer monitor is capable of displaying brighter colors than a magazine, or even a painting.
If you take a picture of a tall building and it appears to be leaning backwards because of the perspective, this is “keystoning.” The name comes from the keystone found in stone arches that have a trapezoid shape.
The Color Rendition Index is a rating that represents the color accuracy of the colors a light source. Light bulb manufacturers use a standard test to come up with the CRI rating for their lights.
The accuracy is rated from 1 to 100 with 100 being the most accurate. Tungsten light bulbs and sunlight rate 100. Most compact fluorescent bulbs start in the low 80’s. Follow this link to read more about how to achieve more accurate colors when photographing your art.
SLR & DSLR
A Single Lens Reflex camera uses a mirror so that you can see through the lens as you look through the viewfinder. When you take a picture the mirror in the SLR flips up to allow the light to pass through the sensor. A DSLR is a Digital Single Lens Reflex camera.
Being able to see through the lens give you an advantage because you have an accurate preview of what’s going to be recorded on the film or sensor. Less expensive point and shoot cameras often have a viewfinder that’s basically a hole in the camera body. It allows you to frame the image, but it doesn’t give you an accurate preview so that you can check the depth of field or to see if it’s in focus.
Another advantage of SLRs is they have interchangeable lenses. You can change to a wide angle lens or a telephoto lens, depending on what’s best for the situation. The disadvantage of SLRs is that they’re generally more expensive than compact cameras. They’re also bulkier and heavier. You can’t fit an SLR in your pocket like a point and shoot or phone.
JPEG or JPG
JPEG is an acronym for Joint Photographic Experts Group. It’s the default file format for digital cameras. It uses compression to reduce the file size so that you can fit more pictures on a card.
When you take a picture, the camera processes it before saving it to the memory card. For example, it adjusts the white balance, and sharpens the image.
The raw file format saves the unprocessed file to the memory card. You can then process the raw file on your computer. The benefit is that you can change the white balance and other settings when you process it on your computer. The raw file format will allow you to make more adjustments in post processing than a JPEG.
The disadvantages are that the file size is much larger, and there’s no standard file format. Each camera manufacturer has it’s own proprietary file format. The Adobe Camera Raw plugin for Photoshop will allow you to open and process the most common raw file formats
ISO is an acronym that stands for International Organization Of Standards. The ISO setting on a camera controls how sensitive the sensor is to light.
The typical ISO settings on cameras range from 100 to 1600. Some cameras go much higher than this. The lower the number is, the less sensitive the sensor is to light.
A higher ISO means the sensor is more sensitive to light and will allow you to shoot in darker situations. The downside is that it will introduce more noise into the pictures. The amount of noise varies by the make and model of the camera.
Shutter / Shutter Speed
The shutter is the mechanism that controls how long the light is exposed to the sensor. How long the shutter remains open is the shutter speed.
The shutter speed controls motion blur, it can be used to freeze a fast moving object or make it appear blurry.
A shutter speed of 1/1000 of a second will freeze fast moving objects and motion blur begins somewhere at or below 1/30th of a second.
Aperture / F-Stop / Iris
The adjustable opening inside the lens that allows the light into the camera is the aperture or iris. It controls how much light enters through the lens.
The aperture setting controls the depth of field (see below).
F-stop is the measurement of the size of the aperture, but more accurately it is the ratio of the size of the opening to the focal length of the lens. It typically ranges from f2 to f22.
One confusing concept regarding f-stops is the larger number represents the smaller opening. On the lens above, F22 is the smallest aperture while F2 is the largest. Although the actual range F-stops vary by the
Depth of Field (DOF)
How much of the subject is in focus is the depth of field. A wide opening such as F2 produces a shallow depth of field, less of the subject ise in focus. A smaller opening produces a larger depth of field, much more of the subject is in focus.
Shallow Depth of Field
A photograph where a short distance of space is in focus, while the rest of the image is out of focus. Photographers use a shallow depth of field as a creative effect. You can use it to blur out the unimportant details in a background. Think of a photograph of food where the subject is in focus but everything in the background is blurry.
Extended Depth of Field
A photograph where the majority of the photograph is in focus. This is popular in landscape photography where the foreground trees and the mountains in the background are all sharp. Smaller f-stops, such as f22 produce an extended depth of field.
Bokeh is pronounced bouquet. It’s the area of a picture that is out of focus. Photographers use bokeh to intentionally leave the distracting areas of a photo out of focus. The soft out of focus areas can draw more attention to the subject matter.
Overexposure / Underexposure
A picture that’s too bright is an overexposure. An overexposure happens when the sensor inside of the camera receives too much light.
You can fix an overexposure by lowering the ISO, using a smaller f-stop, or a faster shutter speed. A smaller f-stop has a larger number, f22 has a smaller opening than f2.
A picture that’s too dark is an underexposure which is when the sensor receives too little light. To lighten the image you can increase the ISO, use a larger fstop, or a slower shutter speed.
The auto white balance function on digital camera attempts to adjust the white balance image automatically. It’s often accurate in normal conditions but it’s not the best setting for photographing artwork because paintings that have a predominant color can fool it.
Another issue is that the color can vary slightly between each shot, because the changing subject matter has a small influence on how it processes it.
White Balance / Color Balance
Color Balance and white balance are the same. They both refer to adjusting the colors in a photo so that they appear neutral.
Ideally, this happens when the picture is taken, although corrections can be made in photo editing software.
The white balance setting on a camera adjusts for the differences in the colors of various lighting situations. When you match the proper white balance setting with the lighting, it will remove any color cast and the colors will appear natural.
Using the indoor white balance settings outdoors will produce pictures with an overall strong, blue color cast.
These settings have icons to represent the different lighting situations. For example, an icon of the sun represents the daylight white balance setting.
The color of the light that a light source produces is measured in Kelvins. All light sources have a color to them, even the lighting that your eye perceives as white light. Daylight has a color temperature of 5500K and incandescent light bulbs have a color temperature of about 3400K.
The white balance settings correspond to the color temperature of the light source. The color temperature of common light sources are listed in the graphic above.
When you shoot in automatic mode the exposure is set for you. Most of the time it produces acceptable results. Although, there are times when the exposure needs adjusting. The exposure compensation is the function on your camera that you use to lighten or darken the exposure when shooting in automatic. Most cameras have a +/- icon for the exposure compensation feature.
If the image appears too dark, move the exposure compensation towards the + side, and vice versa if it’s too light.
The gauge on the camera that measure the exposure is the exposure meter. Cameras have them built in but there are also hand held exposure meters.
It’s normally represented by a series of lines with with a center mark and a zero that represents a proper exposure. One side will have a minus sign to indicate underexposure and the other side will have a plus sign to indicate overexposure. I have seen them represented vertically and horizontally.
Wide angle lenses offer a wider field of view. You can use them to fit more of scene into the picture. This will allow you to fit more into a scene, especially in situation where you can’t step further back from the subject.
The disadvantage is they distort the image. Straight lines will appear to curve, especially at the edges of the photo. It’s called barrel distortion because the image bows outward like a barrel.
A lens that is fixed at one focal length is a prime lens. A 50mm lens is an example of a prime lens.
Many photographers claim that a prime lens will create sharper images because the optics are optimized for on specific focal length.
A lens that allows you to change the focal length is a zoom lens. A 18-55mm lens will allow you take pictures with a focal length anywhere from 18mm all the way up to 55mm.
The advantage of a zoom lens is you can change focal lengths to suit individual circumstance without having to change the lens.
The word “pixel” comes from Picture Element. If you use a photo editing program to zoom into a picture you will notice the image is made up of individual squares of colors.
Digital photos are made up a grid of color. A pixel is an individual square.
AEL Auto Exposure Lock
The auto exposure lock will allow you to meter a small portion of a scene and lock the exposure and use those settings to take a picture of a different scene.
This function is useful in situations where the scene will fool the exposure meter. For instance, if you photograph a person outdoors against a white wall, the brightness of the wall will cause the camera to underexpose the image.
You can point the camera at something that has a middle value, such as green grass, and lock in the exposure. Then when you point it at the person in front of the wall, it will use the reading from the grass.
AEB Auto Exposure Bracketing
When photographing artwork, it’s a common practice to take multiple pictures of the same painting with different exposures.
The typical approach is to take three photos with different exposures: normal exposure, overexposure, and underexposure.
AEB is a function that’s available on some cameras that will take all three exposures for you automatically. It may fire all three shots at once, or you may have to press the button three times in a row.
This function will also allow you to determine by how much you want to overexpose and underexpose by.
High Key Image / Low Key Image
A scene that consists mostly of bright highlights is a high key image. An example of a high key image would be a snowy landscape on a sunny afternoon.
High key images can be difficult to paint because you have to work within a limited value range.
A predominately dark image, such as a painting of a night scene, is a low key image. While the painting may have some highlights in it, the overall scene is made up of dark values.
Both high key and low key images are difficult to paint because the limited range of values allows less room for error in your color matching. They’re also more difficult to photograph because they fool the exposure meter. I have written extensively about why this is and how to fix it in my post about how to photograph art.
Red, Green, and Blue are the three primary colors of the additive color system. RGB is in use by any system that uses light to display colors: TV’s, computer monitors, cameras, and theatre lighting.
Cyan, Magenta, and Yellow are the secondary colors in the RGB color model. For example, mixing red and green creates yellow. Mixing green and blue creates cyan.
The RGB color mode is capable of producing a larger range of color than RYB, or CMYK.
RYB is an acronym for Red, Yellow, and Blue. Painters often use these as the primary colors. These colors work as primaries although some colors are unachievable with this limited color range.
The red, yellow, and blue system is missing magenta and cyan.The pinks, greens, and purples that it produces lack intensity. The purples are especially dull.
The true subtractive primaries are cyan, yellow, and magenta.
Cyan, Magenta, Yellow, and Black are the three primary colors for printing. Also known as “four color process printing” or simply “process printing.”
Phthalo Blue, Quinacridone Magenta, and Hansa Yellow Medium are what I believe are the closest artists colors to the printing primaries.
Red, dark blue, and green are the secondary colors in this color system.
These are the most common art terms that I think are the most popular. I hope that they inspire you to learn more about art, and give you some new concepts to research.