Most images are used in a rectangular format rather than square, and a square sensor would be expensive and much of the image would be thrown away when making a rectangular image.
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If I may comment on this, just as a heads up for Creativity over Numbers
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You are of course right in your line of thought for what os 99.9% the actual product we will see! I agree with that
So you argue that the square Hasselblad images where a waste of area,,, Your line of thought here is a little tightly bound to a cool calculation of numbers, rather than freedom to express yourself
Sure as the photographer you decide on the crop, in principle often this is the case yes, however in reality for many photographers they deliver an image to be used elsewhere, where the image is cropped and used together with text graphics etc. so a lot of the times it's anway cropped if we like it or not. Sometimes this is know before the shoot, but often not so I usually alway have to shoot the same subjects both on portrait and landscape orientation to make sure there is both versions,,,
There are several benefits of starting out with a square image, your freedom to crop in post processing is greatly enhanced the more area you have top and bottom or right left, very often layout or design requires many different shapes apart , not just a rectangle.
Art directors and the like, really like to have the ability to crop, and the high MP count of today greatly gives more opportunity for this.
As I recall several of the digital Medium format cameras has formats, sensors that are more square-ish that rectangular.
I see a huge benefit of supplying a square image as a base for some medium format jobs,,,
Square images could be used much more creatively especially with the two industri standard formats that are rapidly taking over much of the way we see images, smartphones and wide computer and television displays, sure rotating the smartphone does work but functionality suffers,,, most app's really doesn't support rotating fully.
I often see these 'auto' generated square thumbnails online, often resulting in very silly looking images
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if not a human has been involved,,,
Most likely there will not be a square sensor in the new Nikon, i agree, but please leave us the freedom to crop as we please
IMG_0546 by
Erik Gunst Lund, on Flickr
My favorite layouter