a 35 mm digital SLR, but exposures of up to about an hour at room temperature and as long as 17 hours in extremely cold situations can remain noise-free on a digital camera back. In practice a 30-second exposure on a Sinar 75 evolution with a built-in fan-assisted Peltier-cooled CCD represents the state of the art for practical purposes. The resolution of digital camera backs (in 2017, up to 101 megapixels, IQ3 100) is higher than any fixed sensor digital camera (in 2017, up to 51 megapixels, Hasselblad X1D). and captures more detail per pixel due to the omission of an anti-aliasing filter. Each pixel is also able to capture more dynamic range due to higher quality electronics and larger pixel pitch. The use of active cooling systems such as internal fans and Peltier effect electric cooling systems also contributes to image quality. The Sinar eXact creates images in excess of 1 GB in multi-shot mode from a 49 MB sensor. Alternatives There are alternative ways to create a high-resolution digital image without a digital back. Scanning film If a high-resolution digital image is required, it can be achieved inexpensively without the use of a digital back by taking a large-format photograph on film and scanning the result; for best results a high-quality drum scanner is required. This can be used to create a much larger very high resolution computer file than is feasible with a single-shot digital back, and quality is high, though it has been argued that the resolution is not much better than a digitally photographed image. A detailed comparison in 2006 by a professional photographer of drum-scanned 10 × 12.5 cm (4 × 5″) images and digital 39-megapixel images on a medium-format camera found resolution very similar, with the scanned images slightly better. Color accuracy was not compared as digital profiles for the digital back were not available, but the author was of the considered opinion that the digital camera would ultimately be more accurate. For sustained professional use the apparent cost advantage of scanning film was very much reduced on careful analysis; including expensive 10 × 12.5 cm (4 × 5″) film and processing and the cost of use of a drum scanner brought the projected cost over three years to about 80% of the cost of a digital back at the time. The digital back also had the advantage that the incremental cost of