How to choose a projector
February 22, 2011
One option for showing off your photography, especially to the larger audience, is by using a digital projector.
Prices have often excluded all but the professional photographer from buying a digital projector, but with advances in technology and lower prices, projectors may now be an option for the consumer, too.
Families can enjoy those slideshows and camera clubs can appreciate the photos as they were meant to be, without having to huddle around a laptop or desktop monitor. With an increasing number of DSLRs offering HD video, perhaps now is the time to enjoy photographs and videos socially and on a bigger scale.
When buying a projector, there are specific features that a photographer should look out for. Accurate colour balance, high resolution and brightness are important for enjoying images, so the cheapest projector, designed primarily to show PowerPoint presentations, will not suffice.
Conversely, a £30,000 projector designed for large auditoriums is pointless if you are only going to view images in your front room. It is important to know just how much you are likely to need, so what follows are the most vital aspects that a photographer should understand before investing in a new unit.
Projector light technology
There are three main technology types used in digital projectors, with two commanding the majority of the market share.
The first technology types used in digital projectors is 3LCD technology, which is used by several brands through an affiliated organisation of the same name, although the technology was originally developed by Epson.
A 3LCD projector splits a white light source into red, green and blue (RGB colour), directing each into three separate LCD panels that let the light through. Each panel has a number of pixels, and the more pixels the greater the resolution.
The three colour images are then combined using a prism to form a full-colour image that passes through the lens. 3LCD projectors are generally accepted to display more accurate colours and skin tones than their rival technologies.
Digital Light Processing projectors
The second main type of projector is Digital Light Processing (DLP). One-chip DLP projectors reflect the white light source off a DLP chip, which is covered in individual mirrors that modulate the light.
This light then passes through a coloured spinning wheel, which filters the correct light through to the projector lens.
DLP projectors generally produce more vivid colours but can have problems producing them accurately, particularly yellows and reds.
Three-chip DLP projectors are available and are designed for professional use, commanding price tags in excess of £5,000. They operate more like a 3LCD projector by splitting the light into three, but still use a chip to reflect the light rather than panels that allow the light to pass through LCDs.
Liquid Crystal on Silicon projectors
The third projector technology is Liquid Crystal on Silicon (LCOS). These projectors use similar reflective technology to DLP projectors, but liquid crystals are used instead of mirrors to reflect the light.
Colour accuracy and saturation are considered better than with DLP, but LCOS projectors are more expensive. LCOS may also be known as Reflective LCD or, in JVC projections, ‘D-ILA’.
The light source
These three main projector types are available with either a conventional lamp or a light-emitting diode (LED) ‘lamp-free’ light source.
An LED light source has a significantly longer lifetime (typically 30,000 hours), and consumes less energy, but it is not as bright as a conventional lamp so it is less suitable for brighter conditions.
When buying a conventional lamp projector, it is worth noting the lamp lifetime, because the bulbs are expensive to replace. A typical lifespan may be in the region of 3,000 hours. By current standards, lamp projectors are better for brighter images.
As a projector uses light to display an image, the projection quality is decreased if it is used in anything but a dark room. The distance of the projector from the screen and the desired size of projection are other compromising factors. Therefore, a brighter projector has a greater capacity to display an image of a larger size, in a variety of settings, with varying levels of light.
In the real world most of us do not have access to a pitch-black room. Light can be difficult to control and its brightness varies throughout the day. A projector’s brightness is therefore a key factor to consider. It is measured in lumens and a unit with a brightness close to 2,000 lumens will be required for bright viewing. If larger projection is required for a bigger crowd (upwards of 15), then a value between 2,000 and 3,000 lumens is adequate.
A high-contrast ratio is desirable for a projector because it can produce clearer and crisper displays. The contrast ratio is measured by the ratio of luminance of the brightest white through to the darkest black. A typical contrast ratio will be displayed as, say, 10,000:1, but this only indicates the differences between the two extremes; it does not suggest the quality of the midtones and, as such, bigger is not always better.
There are two types of contrast ratio: static, which refers to the projector’s luminosity ratio in a still image; and dynamic, which refers to the ratio of luminosity over time in a moving image. The stated contrast ratio is often the dynamic kind and almost certainly for a room of near total darkness.
Be sure to check what the static contrast ratio is for viewing still images, and account for the fact that the contrast ratio will be significantly less when viewed in a ‘real’ room.
An sRGB colour space is important to accurately match the colours of an on-screen image to a projection.
Look out for manual controls because the colour accuracy can be affected by room conditions and even depend on the device connected to the projector. The same image displayed by laptop and then by a USB flash drive can show varying results.
Most projectors have manual colour temperature control, but some now offer auto controls. Recognising that an increasing number of photographers are using projectors, some manufacturers have introduced an sRGB ‘photo’ image mode to enhance colour accuracy. Canon’s XEED SX80 Mark II photo mode does this by taking into account the ambient light and brightness of the room.
Throw ratio and optical zoom
If you are likely to be viewing images on a projector in a small space, then a high throw ratio is particularly important. This refers to the ratio between the maximum projected image size and the distance of the projector from the screen.
A projector that requires two metres distance from the screen to create a maximum image size of one metre will be represented 2.00:1. An optical zoom will boost the size projection, and as most projectors have such a zoom the distance to achieve one metre projection will not be fixed. In the case above, an optical zoom of 1.2x will define a throw ratio of 1.61-2.00:1.
If you shoot video or use music with your slideshows, then audio compatibility should be considered.
Generally, phono audio inputs are standard. Most projectors will also have a built-in speaker but, at a typical one-watt output, it will barely carry over the noise levels from the fan.
Some projectors now have audio output that may be useful when using a USB flash drive to show images or video files accompanied by sound. The fan in a projector emits sound measured in decibels (dB) and a loud fan may be distracting during quiet scenes of a video, so look out for lower decibel values. Some projectors have an eco mode to reduce noise levels, but light output may be compromised.
Keystone and lens shift
Depending on the setup of the room, it may not be possible to position the projector in the vertical and horizontal centre of the screen. Most projectors have keystone correction that eliminates the distortion created by projecting an image from an angle rather than from the centre of the screen. However, in correcting the edges, compression and conversion must take place to recreate edge pixels, so quality is compromised.
More versatile than keystone is lens shift. Distortion can be corrected by physically changing the position of the lens within the projector unit, so the projector itself does not need to be moved. Lens shift makes a projector more adaptable to the room setup.
There are an increasing number of projectors now that feature auto keystone and autofocus, which reduces the setup time of fiddling with the keystone to get the projected image correct.
If a projector is going to be continually carted around from venue to venue, then size and weight become important factors. In this instance, look for a small and lightweight projector. If it is going to remain static in one location, then size and weight are less of an issue. It is also worth checking if there are compatible wall-mount options.
We can understand resolution through our knowledge of photography and video; when referring to a projector, it is the number of pixels it can display.
A higher resolution means more pixels, resulting in sharper images. While SXGA models are expensive and, at a typical 1400×1050 pixels, do not have as high a resolution as a Full HD projector at 1920×1080 pixels, the 4:3 aspect ratio and the better quality of static images makes them ideal for photographers. Full HD models have a 16:9 ratio for the primary purpose of a home cinema.
Make sure that the projector can scale to the resolution of your computer or vice versa.
SVGA: 800×600 pixels (4:3 aspect)
XGA: 1024×768 pixels (4:3 aspect)
SXGA: 1400×1050 pixels (4:3 aspect)
WXGA: 1280×720 pixels (16:9 aspect)
HD: 1920×1080 pixels (16:9 aspect)
Connections and inputs
There are many ways to connect to a projector:
HDMI (1) is important for HD video use, but is also used for DVD players and plugging a camera directly into the projector.
DVI and VGA ports (2) are commonly found on computers and laptops. Consider what your projector will be used for and ensure it has the ports to accommodate your device.
Component analogue connectivity (3) is a good option for older DVD players.
Older projectors may not have HDMI, in which case S-Video (4) is useful.
Some models also offer USB flash drive connection, so files can be viewed directly from the flash drive and a computer is not needed. If using a Wi-Fi-enabled device, then wireless connectivity is something else to look out for. By reducing the need for a computer, a projector becomes even more portable.
- Go for small and light if you plan to cart the projector around a lot
- Replacement bulbs are costly, so check the lamp’s lifetime
- 3 LCD and LCOS units are better for colour rendition
- If the projector is often static, then factor a compatible wall mount into the cost
Facts & figures
What you should look for and expect from a standard projector…
System: 3LCD or LCOS
Resolution: 1400×1050 pixels (SXGA+)
Aspect ratio: 4:3
Brightness: At least 2,000 lumens
Contrast ratio: 900:1
Throw ratio: 1.48-2.18:1
Lens zoom: At least 1.2x
Lens shift: Yes
Connectivity: DVI, HDMI, VGA, wireless
Media types: SHDC memory card and USB
Noise level: Less than 40dB
Lamp lifetime: 2,000 hours
Lamp type: 230W NSHA/LED