The real advantage of Full Frame.

Started May 17, 2008 | Discussions thread
monte12345 Senior Member • Posts: 2,672
Nope, consider the size of the image area.

With the Dx format the image sensor is basicaly 16 x 24mm, the FX is 24 x 35mm. Eight inches is equal to 203.2mm. So 203.2/16 = 12.7 and 203.2/24 = 8.47. Image sensors are now nearing the point where the resolution of the sensor will exceed that of the lenses at any aperture. The D300 is currently right about at the diffraction limit for f8, at apertures smaller than this the image sensor actually out resolves the lenses. With the D3, the diffractiion limit is probably in the range of f11 to f14 because of the larger image area. Point is, once the image sensor can exceed the resolution of the lens, the only constraint on magnification will be the size of the final image.

BTW, 35mm film hit this point ages ago so this isn't anything new. Generally, 35mm film would hit the resolution wall at about a 16 x 24 inch print size if you examined the print closely with the naked eye and used a lens aperture in the f5.6 to f8 range. But back then we didn't have ready access to sharpening methods that worked as well as Unsharp mask. So it's possible to make an acceptable looking print from digital which is larger than what was once considered normal for 35mm film. However, if you use a magnifying glass on those digitally enhanced prints you'll quickly realize that there is a lack of real detail at the very fine level. So, if you try an magnify an image too much, it will "break up" and look soft on close examination no matter how many mp you have or how much you manipulate it. The simple fact is that there is a distinct theoretical limit to how much detail a lens can resolve and it's a barrier that just cannot be breached. So, once you hit that barrier, the only answer is to use a larger imaging format and reduce the total magnification of the final image to what is within those limits.

BTW, with film that limit was just about 16 to 20X with common photographic lenses and techniques. With the enhancements available in digital, I would say that limit is about 25 to 30X but the level of fine detail will basically match that of a film print at the same magnification. These digital tweaks cannot make detail out of nothing, all they can do is make the detail that does exist look more distinct.

Bottomline, there is a distinct limit to how much you can magnify the image that is projected by the lens on the image sensor. So, if you need a really large print that can withstand critical examination, the only answer is to use an image format that won't require an extreme magnification for that final print.

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