Knowledge Centre

This Knowledge Centre provides information contributed by Federation members that may be of general interest. If you would like to pass on your experience in any of the areas below, or any additional areas please contact Steve Wilbur. I would also be interested to hear from you if you find any of the information to be incorrect or unclear.

Digital Image Projection

Many clubs are now keen to show digital images as part of presentations or for competitions. In this section we discuss some of the issues that you may face and include experience from some clubs that have already taken the plunge.

You will need a data projector and a laptop computer for holding the images.


Data projectors cost from well under £1000 to £1700 for those of a suitable quality. Spare lamps cost £300 to £400, although they normally last 1000 to 2000 hours depending on make. Most laptop computers are adequate for this purpose so a budget of about £900 should be adequate. Finally, software costs can range from next to nothing up to several hundred pounds depending on what you wish to do.

A number of clubs have made bids to the Lottery Fund Awards for All. They provide funding from £500 to £5000 for small projects. In the London area (including Bromley and Croydon) they are looking for projects that: benefit those with economic hardship, ethnic minorities, the disabled or help communities explore and share their heritage and London's diverse culture and traditions. Elsewhere in the South East the focus is broader including support for arts, heritage and other community activity. In some cases your local Council may provide support in applying for such awards.



Resolution: You should choose a projector having a native resolution of at least 1024 x 768 pixels (so-called XGA). Lower resolution projectors can sometimes convert from 800 x 600 pixels (so-call SVGA) to a higher figure, but such interpolation is not suitable for good quality image projection. There are now a number of SXGA+ format projectors available with a native resolution of about 1400 x 1024 pixels. Both DLP and LCOS versions exist (seeTechnology below) but their price is currently about £2700. There are also an increasing number of widescreen projectors intended for home cinema purposes. These normally are a maximum of 720 or 768 pixels high so offer no real advantage over XGA format projectors for most photographic work.

Dead pixels: Most projectors do not have dead pixels (ones that are permanently white, black or a primary colour), but manufacturers usually state that they consider a few dead pixels to be acceptable. One club managed to persuade their supplier to replace a projector that had a couple of dead pixels on delivery - they are not obliged to, but it might work.

Technology: There are two competing technologies for affordable digital projectors: LCD (Liquid Crystal Display) and DLP (Digital Light Processing). With LCD light is shone through three panels for R, G and B, and pixels are turned on and off to form the image. DLP is Texas Instruments technology and essentially consists of tiny mirrors where R, G and B light is alternately shone on to these and reflected on to the screen. DLP devices tend to have higher light output, but a few people can see "rainbow" effects with them due to the alternating R, G, B light. This is rare and is more of a problem with moving images when they are used for home cinema.

LCD image quality can degrade after 1500 or more hours of use particularly in the blue panel (at least three years at 10 hours use per week). Competition between the rival technologies probably means that there is not much to choose between them, although DLP is generally lighter(weight) and possibly cheaper.

Canon have their own LCoS (Liquid Crystal on Silicon) technology that has virtually no 'barn door' effect (black around pixels) so produces a very smooth clean image. Prices start at about £2000 for the Canon SX600 (1024 x 768), compared to a very good DLP projector (Optoma DX733) costing about £700 - April 2007 prices.

See Evan Powell's article for an excellent review of the issues.

Light Output: A couple of years ago the light output of projectors was typically about 1000 lumens. Now, many current models produce 2000 lumens or even more. Anything greater than about 1100 lumens will do a good job in normal club surroundings on a 6 foot screen. Some DLP projectors can produce 3000 lumens or more and these can sometimes be too bright for viewing in darkened conditions.

Contrast Ratio: Current projectors claim 450:1 contrast ratio or higher. Higher values produce the best shadow:highlight differentiation. However, even though these projectors are bright, to see good photographic detail it is always necessary to use a dark room. DLP and LCOS projectors give the best ratios - up to 2000:1 in some cases, but this is only achieved in full blackout conditions.


Lens: Data projectors generally have non-interchangeable zoom lenses. To fill a 2 metre screen the projector will typically only need to be about 3.5 m away, perhaps about half the distance of a 35mm slide projector. Data projectors usually have keystone correction facilities built in.

Aspect Ratio: The standard aspect ratio is 4:3 horizontal:vertical. Some wide screen projectors are now appearing but they seem to be targeted at the home cinema market.

Lamp Life: In most cases this will be for about 2000 hours. The projector keeps track of use and some prevent use beyond the stated life. Since lamps cost about £300 its worth checking the lamp life figure. Hitachi has been including 3 year lamp warranty with its projectors. With some of the brighter projectors there is often an economy mode that produces plenty of light for photographic images in darkened rooms and extends the nominal life of the lamp from perhaps 3000 hours to 5000 in some cases.

Connection: Data projectors are usually connected to the laptop using a 15 way analogue VGA cable (blue connector). The one provided is usually about a metre long. A 7.5 m Extension cable costs less than £20. If you need a longer distance than that between laptop and projector you should consider a wireless link. Selsdon CC have a wireless connection that works well, although there is a slight delay when images are changed.

Newer projectors usually come with a DVI connector (white connector). This is the preferred connection method if your computer has one of these too.

Screen: In most cases existing screens for slide projection are fine, but some beaded screens can produce Moire patterns with a data projector.

Cable Management: Rubber cable covers to prevent people tripping over them can be obtained in 1 metre or 3 metre lengths. Staples (on-line ordering look under "cable covers") are competitive.

Helpful Companies: Various people have found the following companies helpful:

ProjectorPoint: Based at Richmond. Have a very wide range and are very helpful on the phone. Very competitive prices. Web: Phone: 0800 073 0833

Hocken AV: Based at Kingswood. Very helpful. Web: Phone: 01737 370371

Pinnerton: Based in Woking. Very helpful. Web: Phone: 01276 488111

If you have found a particularly helpful company when you were purchasing a digital projector or related equipment, please let me know so we can add their details here.



Purpose: It is worth trying to anticipate the uses to which the equipment will be put. Some clubs have been interested in using the laptop for Digital Imaging demonstrations as well as image display for competitions. A higher specification computer is needed in that case. Other clubs (Selsdon CC) have been keen to run international competitions and to send CDs or DVDs of the competition, complete with judges commentary to the other clubs involved.

Laptop: Generally laptops are chosen as they are more convenient to transport. Mac or PC laptops are equally useful and the choice really depends on the preferences of club members and budget.

Main Memory: Most machines these days have at least 256MB (megabytes) of main memory, but if you are planning to use it for Photoshop demonstrations too it is best to increase it to 512MB or 1GB (gigabyte).

Hard Disk: Images for competitions will be relatively small so disk space will not be an issue, but if using Photoshop do not go for less than 40GB of hard disk space.


CD/DVD: It is worth getting an internal CD/DVD writer with the machine to allow exchange of data with others and for backing up. A free-standing external drive (USB2) costs about £150, similar to the cost of a built-in one. The choice depends on whether the CD/DVD drive is to be shared among several machines.

Keyboard/mouse: One way of reducing the cabling problems is to keep the laptop close to the projector and have a cordless keyboard and mouse so that the demonstration/competition can be controlled remotely. Standard wireless mice and keyboards work well, but their range is limited to about 5-6 feet. "Bluetooth" keyboards and mice claim a range of up to about 30 feet, but they are more expensive. (Don't forget spare batteries!)

Audio: Small PA systems with radio microphones are available for £200-£300. Selsdon bought theirs from Sound Dynamics Ltd.

Display Connector: If possible, choose a machine that has both DVI and VGA connectors for attaching a display or projector. The DVI connector should give (slightly) better image quality.



The package that has been used in FSLPS Competitions such as Jack's Jug and the Vic Smith Trophy is DiCentra. It is costs £35 for a club licence. It provides facilities for loading images from entrants and checking that they comply with the competition rules. Facilities are provided for setting up the projector prior to judging. Marks are accumulated during the competition and selected images can be held back to be marked at the end. The scoresheet can be displayed at any stage and a 'Lightbox' can be used to select images for awards.

Some people use MS Powerpoint for producing presentations, although it is relatively expensive if used just for that purpose. There are many other packages including PicturesToExe for about $30.

Slide shows can also be made with Photoshop and displayed in a browser such as Internet Explorer.

Digital Competitions

Here are a few points about gathering and presenting images for digital competitions.

Image Size : Most affordable digital projectors have a displayable area of 1024 pixels wide by 768 pixels high. Some wide screen projectors provide a wider image but none provide more than 768 pixels height (to my knowledge). Let us suppose we have a portrait format image and a landscape format image, both with a 2:3 (35mm) aspect ratio. If the landscape image fills the screen horizontally it will be 1024 x 682 pixels, while if the portrait format image fills the screen vertically it will be 512 x 768 pixels. If you do the arithmetic this means that a portrait image is only 56% of the area on screen of the landscape. If they were slides, the two images would be the same area on screen.

For this reason I advocate that the maximum dimension (width or height) of an image should be 768 pixels with today's projectors. It can be argued that you are losing some of the available resolution/quality in the landscape format. But if the full 1024 pixel width is available for landscape format, portrait format images suffer the same problem, and are only 56% of the size.

A number of digital competitions seem to be allowing images up to 1024 x 768 to be submitted, so that format will probably prevail even though portrait format images are at a disadvantage.

No Interpolation: Entries should be displayed as submitted, so that there can be no arguments that detail has been lost due to interpolation (re-sampling) or compression. Files should be prepared to a maximum dimension of 768 or to a maximum size of 1024 x 768 pixels or whatever other standard the organisers choose. (Some software may put a 1 or two pixel border around the image so that needs to be considered.)

Entrants should be warned that if they fail to submit to the correct size, jagged edges may appear (so-called interpolation or compression artifacts) or some of the image may be arbitrarily cropped by the software.

Colour Space: Projectors cannot display the full gamut of Adobe RGB. Submitted images should be converted to sRGB by the author so that they can preview the image and deal with any problems due to the reduced gamut of sRGB. Entrants should be advised to view their images on a colour calibrated monitor before submission. Monitor profiling devices are now easily available at prices from £90 (e.g. Colour Confidence).

File Format: Entries should be submitted as JPEG or TIFF files. JPEG files can be smaller, which may be an advantage if images are being emailed to the competition organiser, although even with uncompressed TIFF the file sizes should not be too great. TIFF files should not include layers or transparency.

Projector Colour Management: Just as monitors can be calibrated, so can data projectors. The main problem is that the calibration is affected by the ambient conditions, so the black-out conditions and screen need to be in place before this is done. Although a calibration done some time earlier may be adequate, it really should be done for the competition conditions. Projector calibration takes up to about 20 minutes.

The Gretag Macbeth Eye One Photo has facilities for projector calibration A new Color Vision Spyder2Pro kit is available and includes projector calibration. The Gretag Macbeth kit is expensive but does printer profiling as well ad display and projector calibration (£800). The Spyder2Pro costs about £180.

Projector Setup

There are a number of charts that may be useful in evaluating a projector for purchase or when setting up the projector for a competition. There are three sets here that you can download:

Black Chart : By comparing the blackness of the projected area to the outer, un-illuminated parts of the screen, the depth of black can be assessed. This needs to be done in a darkened room.

Grey Chart: This is good for identifying colour shifts introduced by the projector. They show up well on a grey chart because the human eye is very sensitive to small shifts away from neutral greys.

White Chart: Essentially the equivalent of the open gate in slide projectors. It is useful for measuring the brightness of the image. For slide projectors an open gate measurement using an exposure meter should show 50 lumens/square foot at the screen centre. There are no accepted standards for digital projectors yet, but using an exposure meter at 100 ISO pointing to the centre of the screen, a reading of 1/60th at f/16 gives a similar illumination to that used for the Vic Smith competition in 2006.

PAGB Wedges: These give 5 steps for each of the primary colours and grey. More details can be found on the PAGB web site( The third PAGB report on Digital Projected Images is particularly useful and contains information on projectors, software and competitions.

Photodisc Chart: This is a freely available colour test chart that contains many features including standard colour and monochrome step wedges, as well as many 'memory' colours such as skin tones. The versions called PDI-target 768 and PDI-target 1024 lscape have been scaled to fit a standard 1024 x 768 monitor in portrait and landscape orientation, respectively. Please note the license terms in the Read Me file. (The original test chart is a rather larger TIF file. It can be downloaded from the PAGB site.)

Grey Wedge: This is a 21-step grey wedge. If the projector is properly set up each step should be distinct.

Projector 1024 x 768 size: If this is shown at full size on a screen you should be able to see an alternating yellow/black line around the edge of the projected image. Its purpose is to ensure that the projector (or software being used) does not lose any pixels at the edge of the image.

Projector Focus and Contrast: Part of this includes a variety of 21-step grey wedges near the edge of the screen. There are also bars at 1, 2 and 3 pixel spacing that may help with focusing and in diagnosing problems with focus at different parts of the screen.