Hi all, every so often I see articles or discussions about photography and there will be a photo and then a cropped version of the same photo, sometimes 2 or 3 different crops getting closer each time. It often says 50% or 100% crop. What is 100% crop? To me if you cropped something by 100% there would be nothing left!
Any way if someone can tell me what 100% cropped means it would appreciated, thanks.
With most things their dimensions are described simply in physical lengths - 6 inches, 30 cm or whatever. That applies to photographs, of course - a FF sensor is 36x24mm, prints might be 8"x10" etc.
However, with digital photos there's another way of measuring: the number of pixels. A 24MP sensor has an array of pixels that's 6000x4000: On a FF sensor that's 36x24mm the pixels are each bigger than a 24MP sensor that's APS-C (about 24x16mm) or any other size.
Similarly, a common
pixel size for monitors is 1920x1080 pixels although the physical size varies 22", 27" etc. If I post a picture here it might be 6 inches wide on my monitor but only 5 inches wide on yours. But its number of pixels stays the same. It's therefore common to describe digital pictures in terms of their pixel dimensions.
It isn't always necessary to count the pixels, if what we want is to know the relative size of what we're looking at. The percentage terms you ask about relate to the relative pixel sizes: 100% means that the relative numbers of pixels between image and monitor are equal: 1 image pixel is displayed on one monitor pixel. 50% means that 4 image pixels (2x2) are displayed on one monitor pixel, and so on.
If you look at an image posted here such as this you see it downsized to fit the window but if you click on
original size you see it at the full pixel size - 100%.
But once it opens for you, you may not be able to see all of it (unless your computer resizes it again). If I wanted to draw your attention to just the eyes I might save you the bother of going to
original size by cropping out a small section around the eyes.
It's that crop - a crop designed to show you the 100% pixel view - that we call a 100% crop. In other words, 100% crop means "cropped
from a 100% view" and not "cropped
by 100%".
This term, like most terms (or jargon) in any specialist subject comes from practical reasoning. Although, as you say " if you cropped something by 100% there would be nothing left" is logical things just don't happen that way: if I wanted to remove the whole picture I'd say something like "delete it", not "crop it by 100%". If I wanted to describe what I actually did, changing it from the native 3:2 aspect ratio of the sensor I'd describe it as "crop to 16:9" rather than cropping to some %age ratio.
Note too that a ratio N:M has long been used photographically for aspect ratio. 1:1 means square, so while there is a 1-to-1 correspondence between image and monitor pixels confusion might arise if we said
1:1 crop, whereas
100% crop doesn't have any other meaning when used in photography.
Incidentally, ratios such as N:M are also used to describe the magnification - the ratio between the size of an image on the sensor and the real size of the object. Thus, to say
view at 1:1 could cause confusion between viewing at pixel size or at an actual physical size. Note that aspect ratio and magnification are so different that there isn't confusion: it's clear what the context is.
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Gerry
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First camera 1953, first Pentax 1985, first DSLR 2006
[email protected]
