Some dumb questions I have been wondering about

Started Mar 28, 2013 | Discussions thread
FractalFlame Regular Member • Posts: 159
Re: Some dumb questions I have been wondering about

Wellington100 wrote:

1) Why are camera sensors not square? Surely a square sensor is the most efficient way to get the best out of a lens?

Humans tend to look left right more than up down - our field of vision is rectangular.

Not necessarily by eye limitation, more of a brain limitation. When we look up we lift our chin and use our head to look. when we look sideways we turn our eyeballs (peripheral vision is generally accepted as side to side).

Note that a few groups of people have bypasses this - usually martial arts (not meaning kung-fu type, but military arts AND kung-fu type). People who are extraordinary aware of surrounding, some sports where you have to be aware of incoming balls, military (enemy up top), etc.

The general, average man-on-th-street is a horizontal viewer more than a vertical viewer - our dangers are level with our eyes but sideways (cars, pedestrians, doors, etc).

That's why, I believe, the rectangular film frame came about - dig sensors are just an extrapolation of them.

Even 6x6 format is often cropped to rectangular.
Some people even feel unusually 'unsettled' by a square painting or photo.

2) Does using a Polarising filter reduce the Dynamic Range of an image taken in sunlight with a digital camera?

Yes, unlike a ND filter (which just 'shifts' the light downwards, blocking all evenly), a pol filter actually blocks some areas more than others.
If a bright reflection is polarised then you will get a DR shift.

Bear in mind how it works - a pol filter stops certain wave directions from passing and lets other wave directions through.
A differential blocking of light = DR change. A ND filter does a non-differential light block.

3) Why do most cameras have IQ reducing AA filters when the few cameras that don't have them jump in IQ and moire is nowhere to be seen in 99.99% of the images?

I can only offer a surmise here -  consumer cameras are aimed at ordinary people.
If they take photos and end up with a lot of moire in them they will not know how to remove it and might turn away from the camera (of even digital photography in general).

So they make them with the AA filter, accepting that the loss of resolution is offset by the loss of aliasing... ??

4) What is the optimum resolution for small camera sensors? High resolution sensors seem to add significant file size for little discernible improvement in resolution, so what is the cut off for a functional and well rounded small sensor?

A sensor is more than just the resolution - it's about the actual size (and quality, et al) of the sensor sites.

You are physically limited by the sensor size:

A 1" square sensor at 10 Mpxl might have the sensor sites at 30 microns = good light gathering ability but lower actual image resolution.

A 1" square sensor at 20 Mpxl might have the sensor sites at 15 microns = lower light gathering ability but higher actual image resolution.

A 4" square sensor at 20 Mpxl might have a sensor size of 60 microns = good light gathering AN high resolution.

(No, I didn't do the math - that's why i chose 1" and 4" - these numbers are examples only!)

This is why an apc-c camera of 16 mpxl can sometime outperform an acp-c camera of 20 mpxl.

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