difference between digital back and scanning back

I'm new to digital photography and would like to know what the difference is between

a "digital back" and a "scanning back". I would be using it on a 4x5 camera

The older 4x5 digital backs; such as the 35 megapixel PhaseOne Photophase; have a scan bar; that takes minues to transit across the "film plane". Here th one I use is 5000x7000 pixels; the 5000 pixel dimension is th scan bar dor of like a flatbed scanners bar; that moves during the exposure. These are/were common in studio 4x5; for still life. The Photophase requires an IR filter over the lens; the sensor is sensitive to IR. <BR><BR>In the MF backs; there is a physical sensor; and no lead screw; and stepper motor. Here the exposure of the pixels is about the same time.<BR><BR>Many times of big backs are tethered to a PC; a SCSI cable; etc.

What's commonly referred to as a digital back consists of a large sensor array (CCD or CMOS) that covers the entire capture area (which is much smaller than 4x5). The entire sensor array is exposed at once, just like film.<br>

A scanning back is very similar to a film scanner. The sensors are arranged in a thin row that physically moves across the film plane to capture an image (making the process slower, but requiring a much smaller number of individual sensors which keeps the price down).<br>

Large CCD or CMOS arrays are extremely expensive to manufacture (using current technology, I suppose that might change at some point) which is why you're not likely to see 4x5 sized sensors on the consumer market any time soon.<br>

<br>

Guy<br>

<a href="http://www.scenicwild.com">Scenic Wild Photography</a>

You can gain some insight into scanning backs at the Better Light website (http://

www.betterlight.com). Because they operate similar to a scanner, they are sensitive to the

motion of the objects being photographed but the results are stunning; plus you get to

see the results quickly. Stephen Johnson uses this back for his work (www.sjphoto.com).

 

Angelo

I too was going to recomend the Better Light site. However, another difference is that a single shot back uses a Bayor matrix and interpolates color. A scaning back has three rows of sensors red, green and blue so color should be way more accurate. A scanning back also uses large photo diodes for pixels instead of CCDs. This also give better dynamic range than most (or all) CCD arrays.

 

See my web site (if the server can be bothered to reply today)

 

http://truckgenerator.com/subdomain/sueandneal/pixelgrain-copy.jpg

 

This shows a Bayer array compaired to dye clouds in film.

 

This shows two of three rows of photo diodes on a scanning sensor from a Better Light back.

 

 

http://truckgenerator.com/subdomain/sueandneal/6003chip_small.jpg

 

 

If you really want to know all there is to now about scanning backs get a bottle of asprin and read this:

 

http://www.kodak.com/global/plugins/acrobat/en/digital/ccd/products/linear/KLI-6013LongSpec.pdf