Hasselblad Digital Camera, Manual

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Image Size and Format in Digital Imaging and Film Photography
13
or poor quality. The topic of DAC is discussed more in the chapter on lenses where you can
also fi nd an MTF diagram that shows how much DAC improves the quality in an image cre-
ated by a 35 mm HC lens on H cameras.
Pixel Size
Digital cameras are promoted, separated, and distinguished mainly by the pixel number with the
conveying message that a camera with a higher pixel number produces a sharper image. While
the pixel number increases resolution, the number of pixels is only part of the quality story. The
pixel number can be increased in two ways, either by placing more pixels on the same size sen-
sor in which case the pixels need to be smaller, or by increasing the size of the sensor in which
case the pixel size may not have to be reduced or can even be increased. It is no problem for
a manufacturer to increase the number of pixels and produce a digital camera with a fabulous
megapixel number but the more pixels the manufacturer puts on the same size sensor the
smaller the pixels need to be. The benefi ts in image quality from such a sensor where tiny pixels
are cramped onto a small sensor then become questionable because larger pixels do perform
better photographically with increased information gathering power. A larger pixel collects more
light and its signal needs to be less magnifi ed thus creating less “noise,” as it is called in digital
imaging. Small sensors are more susceptible to noise especially when used at higher ISO val-
ues. The increase in the sensor's dynamic range produces images with a better tonal range from
the deepest shadows to the brightest highlights, better colors, fi ner tonal gradation, and more
attractive shadow details allowing for the production of gigantic prints. The improvements are
usually especially noticeable in the highlights. The larger Hasselblad sensors offer these improve-
ments because they not only allow a larger pixel number but also pixels of a much larger size.
Hasselblads provide 16
more information with a 16-bit depth providing 65,536 shades of gray
compared to a 12-bit depth with 4096 shades of gray on a typical DSLR camera.
Because of the danger of creating noise, digital photographers are advised to photograph
at the lowest possible ISO setting. This is certainly good advice, but it also means that in low
light situations you may have to choose between using a higher ISO which allows shorter
shutter speeds or a lower ISO which may require longer shutter speeds that may create
unsharpness due to camera motion. In such a case a higher ISO is defi nitely recommended
especially with Hasselblad. The larger sensor with larger pixels can produce better image
quality at ISO 400 than a smaller sensor with smaller pixels at ISO 100 just as the newer 400
ISO negative or transparency fi lms produce considerably sharper images with fi ner grain than
the older fi lms at ISO 100. A fi le with all the information from the larger sensor with larger
pixels will also survive post manipulations much better.
Sensor Size
The size of the pixel needs to be considered seriously and is determined by the size of the
sensor. A typical DSLR camera may have an APS-C sensor with 8 megabytes on the image area
of about 340 square mm. The Hasselblad 36.7
49 mm sensor of 39 megabytes has more than
4 as many pixels on an image area that is also 5 larger. There are not only more pixels but
all the pixels are larger. The greater number of larger pixels is what sets medium-format digital
imaging apart just as the medium format did in comparison to 35 mm in fi lm photography.