Lots of light

Electronic light sensors are very sensitive to levels of light, to levels of amplification and the color of light. Video cameras are famous for their need for lots of light to achieve maximum quality. Digital still cameras are very similiar to video cameras for most of the same reasons, except that still cameras usually need more light but also give images with more resolution.

Lots of light provides:

  Light to Dark Scales
For Eye and for Camera 		 

The two graduated scales in the image below represent the differences in what the human eye is able to see versus what the camera is able to see. The camera's scale is on the right side. As you can see it has a smaller range from light to dark than does a human eye. In other words, it gets impossible to shoot pictures long before it gets impossible for the audience to see.

Eye Range Camera Range
Eyes are very sensitive but they don't see all the tones at once. As we change where we look our eyes are adjusting to match the lightness or darkness of the scene.

Although our eyes keep making adjustments we don't usually notice because the adjustments are so smooth and continuous.

The green double-headed arrow represents how much of the overall range the eye can see at one time - if it did not adjust itself.

The red double-headed arrow represents how much of the range the eye sees by constantly making adjustments to the iris (aperture) and color/grayscale response.

As lights are turned down our eyes adjust.

Down here the eyes can still see, even if darkly.

Cameras, like eyes, do not see the entire range of light and dark at once. They need to be adjusted on a sliding scale.

Cameras are adjusted by the photographer for the lighting condition, but the adjustments can't go as far as human eyes.

The green double-headed arrow represents how much of the overall camera range the camera can image at one time - without adjustments.

The red double-headed arrow represents how much range the camera can cover with adjustments to aperture, shutter speed and ISO.

Down here, below the lower red arrow, the camera is basically blind. It can no longer be adjusted for conditions which are this dark.

This means that to adjust stage lighting for the camera you need to use the camera to view the effect of light-level changes. Human eyes will keep adjusting into darkness, well beyond the ability of cameras to adjust. Further, the difference between bright and dark stages is very different in appearance for a camera.

To adjust any camera, use the brightest lights you can, even if it seems to your eye that the stage is looking like daylight. Set the camera to this light level - for optimal shutter speed and f/stop. Then, adjust the stage lights to the darkest level which looks right to the camera, without changing the camera settings. It will still look bright to the eye. Use the camera, not your eyes, to judge the light level. This is the range you can use to go from brightest to darkest, for the camera.

With this adjustment the photographed result will mimic the eye's response under a wider range of light levels.

     

I have several times asked lighting designers whether there is a plot out to create lighting which is deliberately difficult or impossible for a camera. It is in jest because I know no lighting designer is working hard just to make life tough for photographers. Who would even want to bother? What I really suspect is that lighting designers kind of slide ever so slowly into a rut of moodier and moodier lighting. The eye adjusts to a low-lght range, of course, but it will also adjust to bright-light range.

But to create low lighting and then to expect photographs which are of top technical quality and which match studio-strobe conditions is unrealistic, unfair and very frustrating for a photog. It isn't pleasant to look as though you don't know how to shoot because of conditions you can't control. It isn't fair to expect a stage photo, under those conditions, to look like a carefully worked studio shot.

Color Balance (white balance)

Getting the right color balance is important. It means all the colors available look their brightest and the detail is most visible. The wrong color balance not only produces murky colors but also less detail. Part of that is because most of the detail is held in the green channel (we are about twice as sensitive to green light in the spectrum as we are to red or to blue).

Color correcting in Photoshop produces brighter, livelier colors. But there is usually some lose of part of the spectrum in coverage. It is far better to get the color balance right in the camera at the start.

 

Pixel Size

The number of pixels on a CCD chip doesn't really tell you a lot about the performance of the camera or the ability of the chip to produce images.

Only if all other factors, including size, remain the same does a change in the number of pixels change the amount of usable data.

Pixel size affects the image in several specific ways:

  1. The larger the size of each pixel the more sensitive to light allowing use in lower light levels
  2. The larger the size of each pixel the cleaner the image data increasing the percent of usable data
  3. The larger the size of each pixel the wider the range of tones (gray scale) between white and black
  4. The larger the size of each pixel the richer the color overall

The larger the number of chips on the same size CCD the smaller each pixel has to be.
The larger the size of the CCD for the same number of pixels the larger the size of each pixel.

The pictures above illustrate the idea of a various pixel sizes in CCD's. Real pixels are much tinier, of course. These illustrations are only to diagram the concept. In this example each CCD creates the same picture on exposure to the image from the lens, regardless of the actual size of the CCD. Only the pixel size changes. The larger each pixel in the picture, the better the overall quality. (remember, pixel means "picture element" - in a manner of speaking this is the "atom" in any digital picture - the digital element which is closest to resolution in film and to some extent to grain in film)

Light Sensitivity Setting (ISO)

The smaller the pixel the less light is available for each section of the image. The larger the pixel the more light is brought in for each area of the same image, as in the illustration above with the three pictures. When each area of the picture can gather more light because it is physically larger that means you can operate in darker settings. The darker the scene the higher the ISO needs to be to get the picture. Setting the ISO to a higher (more sensitive) number is done by boosting gain (increasing voltage) in the camera. As the gain increases (ISO number increases) the more digital (electrical) noise. This is similar to turning up the volume very high on a very weak radio signal. The signal is amplified along with all the static (electrical noise, analogous here to digital noise).

ISO As the ISO (sensitivity) rating is set higher (better able to shoot in darker conditions) the scale becomes rougher. You still have a light and a dark but the range of tones between becomes fewer. At the same time the amplification needed to boost the signal produces artifacts in terms of added "digital noise" - much like snow on a television set. (if you remember TV "snow")
100
400
800
1600

 

The extra gain (amplification) also tends to somewhat scatter the detail in the image. That is, like film, the higher the ISO the lower the detail and the lower the ISO the higher the amount of detail. Technical reasons for the lower detail at higher speed differ for film and for digital imaging chips but the effect with either is similar.