06.Flat-bed v slide plus how we tested
Flat-bed scanners have the advantage of being able to scan reflective material as well, while a dedicated slide scanner can only cope with negatives and slides. But the buying decision also has as much to do with quality as it has with print size.
Until recently, flat-beds weren't able to provide the same resolution as a slide scanner. That's no longer the case, so printing up to A3 from a slide is quite realistic without having to resort to interpolated resolution (see Dictionary below), which can degrade the image. Size is only one factor; sharpness, quality of the colour reproduction and the ability to deal with lots of shades of grey (from almost pure white to almost black) are also important.
When their sharpening function was turned off, the images produced by the flat-bed Canon 9900F and Epson Perfection 4870 Photo weren't as sharp as their slide scanner counterparts. However, they produce acceptable images if their default sharpening functions are left on. If you need to further sharpen the image, this initial manipulation may cause problems. It's generally better to rely on a sharp lens rather than a software solution. The Canon FS 4000 US and Nikon V ED slide scanners impressed our panel with their sharpness.
You'll probably have to do some colour correction at the preview stage or after scanning regardless of the product you choose. The Epson 4870 Photo was a good performer in this area while the Canon 9900F scored OK. The slide scanners were generally good, but both the Konica Minolta scanners only managed OK scores. The Microtek Artixscan 4000tf and Nikon V ED were the most consistent performers in this area.
If you've limited space, the flat-beds are probably not for you. They're quite bulky (see Results Tables for sizes) and need space above for their substantial lids. The lid on the Epson 4870 Photo felt unstable when upright and had to be held it in place when positioning slides, which could be annoying.
How we tested
We scanned several slides, a black and white negative, and a colour negative at the scanners' default and best optical settings with the cleaning function (if available) on and off. The resulting files were printed using a Canon i950 printer on high quality photo inkjet paper using the software supplied with the scanner. We appraised the install and uninstall procedure the clarity and comprehensiveness of the paper and on-screen the help files and the scanning software. We also assessed the ease of use of the scanners for features such as slide carriers or mounts, buttons and controls.
We measured the time it took to scan a slide and the resulting prints were appraised by a panel of three experts for sharpness, colour and exposure.
We used the same Pentium 4 3.0GHz computer running Windows XP Home for each scanner. The quality of the two flat-beds was also appraised for reflective material (see Dictionary below). Our testers rated them superior to the top products in our last flat-bed scanner test).
Bit depth: A measure of the number of colours that a scanner can recognise and capture. 42 bit = 14 levels of intensity per colour (Red, Green and Blue) 48 bit = 16 levels of intensity per colour.
Interpolation: is a software trick that increases or replaces detail in an image by adding pixels between those measured by the optical resolution. When used to increase resolution this can create very big files.
Reflective material: normal paper photographs, magazine pages etc. reflect light, whereas light passes through transparencies (slides).