Technical Information

A home colour photo quality ink jet printer may typically print at up to 300 pixels (or lines) per inch, which is adequate to produce a smoothly graded image. This is the physical resolution. In general any higher resolution quoted is what is known as "virtual resolution", which uses technology trickery with color blending to achieve a better print. For example, a printer may be quoted as giving a resolution of 9600 dpi. Usually this means it can deposit up to 9600 droplets per inch, however a droplet may be as small as 1 picolitre and a pixel may need typically up to 32 droplets. 9600 divided by 32 = 300.

The scanning resolution required depends not only on the printer's capability but also to a large extent on the paper and ink type. However, as a rule of thumb: A 35mm scan at 2700 dpi will approximately match a typical printer on A4 paper with no margins. Scanning at 1350 dpi will produce a good print at 8 " x 6 ". A 4000 dpi scan will allow good quality printing at least to A3. Typically APS will produce good prints at a bit over half that of 35mm, so for A4 prints from APS you would need 4000 dpi.

Scanning at a higher resolution than needed for the way the scanned file will be used can produce unexpectedly lower quality results due to "pixel skipping" - and conversely if the image is scanned at a lower resolution than needed then image quality will suffer in the final result as the missing pixels need to be "invented".

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This is the number of dots per inch scanned on the 35mm slide or negative. In all cases the raw image will be cropped slightly after scanning to remove rough edges at the extremities of the scan.

At 1350 dpi the raw scan is 1296 x 1947 pixels (picture area 2,523,312 pixels). This is larger than most display screens in current use, and will provide excellent quality images on-screen and good quality home printing for most requirements. To view the complete picture on screen you will need to use a viewing programme that resizes the image automatically to fit.

At 2700 dpi the raw scan is 2592 x 3894 pixels (picture area 10,093,248 pixels) and at 4000 dpi it is 5782 x 3946 (picture area 22.8 MPixels).

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This is the number of dots per inch scanned on the APS negative. In all cases the raw image will be cropped slightly after scanning to remove rough edges at the extremities of the scan.

At 1350 dpi the raw scan is 1502 x 984 pixels (picture area 1,477,968 pixels) and cropped will typically be 1427 x 842 approximately, or 1,201,534 pixels. This is larger than most display screens in current use, and will provide excellent quality images on-screen and good quality home printing for most requirements. To view the complete picture on screen you will need to use a viewing programme that resizes the image automatically to fit.

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(Tagged Image File Format) A lossless uncompressed image file format that produces no artifacts as is common with other image formats such as JPG, a common format for exchanging raster (bitmapped) images between application programmes. Tiff will support 8-bit or 16-bit per colour (R, G, B) resolution = 24- or 48-bit overall. Typical file sizes are shown below:

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The results delivered by the scanning process are dependent upon a number of factors, principal of which is the quality of the slides or negatives. The main influencing factors and their effects are listed below. Correction of many of the problems can be achieved in the BasicPlus (dust / scratch removal) or Enhanced Services, and we will often spend more time to try and achieve better results for you. Basic Service scans are returned as-is after rotation and cropping.

• Properly exposed, well stored slides and negatives will usually produce excellent results.
• Under exposed film produces dark scans, and with that the film grain together with low levels of noise from the scanner's CCD become more noticeable, particularly in blues and more particularly large areas of blue (the sky). In the Enhanced Service option we can minimise this graininess by marking off any large affected areas like the sky and applying a noise filter. The technique can only be applied to limited areas of the scan as one side effect of this filter is that it softens the image, so details can look a little out of focus.
• Over exposed films are washed out and lack detail. We can adjust the brightness and contrast levels to reduce the effect, but detail is often completely missing and cannot be 'invented.'
• Out of focus photographs can sometimes be improved with sharpness filters, but in general little can be done to correct poor focus.
• 'Tunnel vision' effects are sometimes visible and usually caused by long lenses and lens hoods producing a circular shadow evident in the corners of the image. Over time this effect is often exaggerated as film emulsions deteriorate. Irregular patterns such as grass can be improved by cloning other patches of grass into the corners, but the continuous colour and brightness variation in most skies makes it very difficult to remove this effect.
• Film emulsions deteriorate over time, some more than others, and influenced by storage condition over the years. Much of this deterioration can be compensated for in the enhanced service by combining some automatic sensing of the colour changes during scanning against stored information on a large number of film types, with additional manual levels compensation in Photoshop. High levels of deterioration can only be corrected so far, depending upon how much original colour information is still present.
• Slides in particular are prone to fungal growth over time. This fungus shows as spidery trails emanating from a small discoloured area, or as patches of the image that are totally discoloured. The effects can be reduced within the Enhanced Service, but total elimination would often require large amounts of time and in the worst cases the image could end up more as an 'artist's impression' than a photograph. We will always do the best we can, but miracles do take longer!
• Fingerprints scan extremely well and are very difficult to remove. Sometimes we can remove the worst from the slide or negative using iso-propyl alcohol, but old fingerprints tend to stay. After scanning the worst effects can be removed in Photoshop but full removal can take considerable time and is not possible within normal pricing levels.
• Minute dust particles are evident on most slides and some negatives, attracted by static electricity and stubborn to remove before scanning. Digital ICE technology can eliminate dust pollution almost entirely, and we can remove any left-overs manually.
• Film negatives in particular are prone to scratching of the emulsion, producing white streaks and patches in the scanned image. Again, Digital ICE can remove the worst of these scratches automatically with any left-overs removed manually.
  

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For most purposes a single pass scan will produce excellent results. The sensor technology used in our scanners is CCD (Charge Couple Device), which can occasionally fire pixels at random, but these are rare and usually not noticed. In order to guarantee elimination of these random pixels, we can scan the slide or negative up to 16 times. The images are then compared and combined digitally, so the rogue pixels are removed. Multi-pass scanning adds considerably to the time required to produce the final image. This technique will only provide benefit to excellent quality originals.

The choice of storage medium largely depends upon the size of the files to be saved, the number of files you are comfortable with on one disc, and the compatibility of your computer. The actual number of pictures you can store will vary depending upon picture content, the following are provided as guidelines. Unless you specify otherwise, we will use the storage medium appropriate to the total file size of your scanned images, either CD-R or DVD-R. Typically, Jpeg images will be stored on CD-R, whilst anything but a small quantity of Tiff images will be saved to DVD-R. If you prefer a specific medium (for example, if your PC does not have a DVD Drive, or if you know that you need DVD+R for compatibility), please use the Additional Information field on the order form to tell us your preference.

A recordable CD (Compact Disk) will provide between 620 and 700 MB of space. This represents anywhere from 500 to over 1000 images scanned at 1350 dpi depending upon picture content and level of compression. At 2700 dpi perhaps 100 to 300 or at 4000 dpi 30 to 150 (this is rough guidance only). Jpeg images optimised for the web can be up to 10x smaller than high quality Jpegs, therefore you can potentially store 10x as many in the same space.

Saved as Tiffs, the number you can store depends upon scan density and colour resolution. The following table provides approximate file sizes - these vary depending upon the amount of cropping of the original scan. A CD-R will accept about 75 Tiffs at 1350 dpi and with 8-bit resolution, but only three at 4000 and 16-bit.

A DVD (Digital Versatile Disk) will provide 4.7 GB of space. Using the same parameters as above, you can store about 7 times as many files..

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Digital ICE3 technology can identify defects (scratches and dust) independently of the picture data. The resulting defect map is then used to correct the damaged or obscured parts of the image. The use of the defect correction technology can produce scans from unusable, scratched or mis-handled film at a quality that is close to the state of the original image. It is designed to be used with dye-based films (i.e. C-41 or E-6 process films) and can not be used with silver based black and white films. This is due to the fact that the defect correction relies on the dye layers being transparent to the detection signal. Most black and white file uses metallic silver as the pigment, and this element blocks the defect detection signal.

Monochrome C41 process film such as Ilford XP2 or Kodaks T-Max CN may be used with the defect correction system as metal pigments are not employed in this type of film.

Previously, Digital ICE could not normally be used with Kodachrome films as degradation to the image quality occured. Our upgraded scanning equipment now includes a Kodachrome setting to allow its use.

Very badly scratched or marked negatives or slides will normally need considerable additional effort in Photoshop, particularly black and white films where digital ICE cannot be used. We will always do our best within a reasonable time frame, but may need to quote for additional processing time in such circumstances. Fingerprints and the spidery marking caused by fungus growth are not removed by Digital ICE. Where these occur we do try our best to remove them as part of the BasicPlus or Enhanced Services but cannot guarantee to remove them all within the standard scanning price.

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A DVD Slide Show will play on your television through most DVD players, or on your computer via its own DVD player software (you will need a computer with a DVD drive and the relevant software installed). You will need to c heck your DVD player's compatibility with DVD-R before ordering!

The DVD Slide Show can include the images we have scanned for you, or images that you send us on CD, or a combination of both. The DVD is created in a standard format with menu. Each slide show can have a maximum of 99 images, and we we recommend a maximum of 8 slide shows per disc, each of which has its own menu selection. You specify which images go into which slide show, what each show is called, and what the DVD's title should be.

An audio track can also be added to your slide shows, due to music licensing restrictions we ask that you send us your chosen music on CD. A slide show with 99 images lasts about 10 minutes.

The images are resized as they are added to the DVD to the full PAL studio standard (CCIR-601 D1) of 720 x 576. We are unable to produce DVDs to the HD standards.

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