56 mp fx ?

Started Feb 23, 2013 | Discussions thread
Rick Knepper
Rick Knepper Forum Pro • Posts: 16,121
Re: I think you should reconsider...
1

J Mankila wrote:

Grevture wrote:

noirdesir wrote:

Grevture wrote:

noirdesir wrote:

If we stay within reasonable levels of FOV (eg, 200 mm FF equiv.), already 12 MP required at least 1/400 s. Staying at base ISO, eg, 200, that is f/11 in bright sunlight. Going to 100 MP, ie, quadrupling in linear terms, we are at f/5.6. And that is in bright sunlight.....

Look, we can successfully handhold compact cameras with way, way, way higher pixel densities, and with their flimsy weight, they are actually more difficult to handhold then a reasonably heavy DSLR.

I think be both agree that it is not the pixel density but the total number of MP and the AOV. Handholding a compact camera or a FF DSLR for the same AOV and the same MP poses exactly the same challenges (well having a viewfinder or not influences posture).

No, I do not agree on that What amount of camera shake you can detect is a factor of pixel density at any given focal length, pure and simple.

No, unfortunately it is not that simple. Although it is quite simple, as I shall demonstrate.

Take the angle of view of a lens. An effective focal length of 300mm gives you 6.9 degrees of horizontal angle. If your hands give you 0.1 degrees of horizontal movement per the given shutter speed, you can do the calculation easily. If both cameras have, say 24MP, which handily gives us 6000 pixels in the horizontal dimension, both cameras will give you 0.1 / 6.9 * 6000 = blur of 87 pixels wide.

Look again at my example with the SX50 below: Shooting with that zoomed to 200 mm focal length and then looking at the image in 100% is exactly the same as looking at a 6.2 x 4.5 mm crop at 100% from a 36 x 24 sensor with 370 megapixels and a 200 mm lens.

But the real focal lengths of the two cameras will be vastly different, and this is what overthrows your "pure and simple geometry".

Take Nikon 1 cameras and see how focal lengths change when you use the same lenses on FX and CX sensors. The effective focal length is increased 2.7x and the angle of view is divided by 2.7x. Then again, using 2.7x shorter focal lengths on the Nikon 1 camera will produce wider angle of view on the sensor and, thus, lessen the impact of camera shake.

.....

As long as we look at 100% magnification, the sensor size becomes irrelevant, and it is all about the pixel size for any given focal length. Because at 100% magnification we look at the AOV of the pixels, not the AOV of the sensor.

Note the bolded part. The real, actual focal lengths vary greatly between compact cameras and DSLRs. Actual focal lengths of lenses that give you the same effective focal length can differ by an order of magnitude - depending on the sensor size.

The math aside, I proved to myself that using a tripod (in most situations) is preferable to handholding if the ultimate IQ was desired (and of course, ultimate IQ is always desired) back when I was using the 6 MP Canon Rebel by actually testing my ability to handhold against the same scene on a tripod.

The problem with a tripod is that some situations do not allow for tripod use. The problem with general statements about handholding is the variable ability of each individual's technique in this regard. The shutter speed threshold for each individual must be arrived by actual testing preferably before one gets oneself into a critical shooting situation. The whole handholding/D800 "issue" on the Nikon forum was way overblown.

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Rick Knepper, photographer, non-professional, shooting for pleasure, check my profile for gear list and philosophy.

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