Sensor Size Myth – “A bigger sensor gathers more light.”

If I hear this crap one more time either my head’s going to explode or I’m going to do some really nasty things to someone!

A larger sensor size does NOT necessarily gather any more light than a smaller sensor – END OF!

What DOES gather more light is BIGGER PHOTOSITES – those individual light receptors that cumulatively ‘make up’ the photosensitive surface plane of our camera sensor.

Above we have two fictional sensors, one with smaller physical dimensions and one with larger dimensions – the bottom one is a ‘larger sensor size’ than the top one, and the bottom one has TWICE as many photosites as the top one (analogous to more megapixels).

But the individual photosites in BOTH sensors are THE SAME SIZE.

Ignoring the factors of:

• Micro Lens design
• Variations in photosite design such as resistivity
• Wiring Substrate
• SNR & ADC

the photosites in both sensors will have exactly the same pixel pitch, reactivity to light, saturation capacity and base noise level.

However, if we now try to cram the number of photosites (megapixels) into the area of the SMALLER sensor – to increase the resolution:

we end up with SMALLER photosites.

We have a HIGHER pixel resolution but this comes with a multi-faceted major penalty:

• Decreased Dynamic Range
• Increased susceptibility to specular highlight clipping
• Lower photosite SNR (signal to noise ratio)
• Increased susceptibility to diffraction – f-stop limiting

And of course EXACTLY the same penalties are incurred when we increase the megapixel count of LARGER sensors too – the mega-pixel race – fueled by FOOLS and NO-NOTHING IDIOTS and accommodated by camera manufacturers trying to make a profit.

But this perennial argument that a sensor behaves like a window is stupid – it doesn’t matter if I look outside through a small window or a big one, the light value of the scene outside is the same.

Just because I make the window bigger the intensity of the light coming through it does NOT INCREASE.

And the ultimate proof of the stupidity and futility of the ‘big window vs small window’ argument lies with the ‘proper photographers’ like Ben Horne, Nick Carver and Steve O’nions to name but three – those who shoot FILM!

A 10″x8″ sheet of Provia 100 has exactly the same exposure characteristics as a roll of 35mm or 120/220 Provia 100, and yet the 10″x 8″ window is 59.73x the size of the 35mm window.

And don’t even get me started on the other argument the ‘bigger = more light’ idiots use – that of the solar panel!

“A bigger solar panel pumps out more volts so because it gathers more light, so a bigger sensor gathers more light so must pump out better images………”

What a load of shite…………

Firstly, SPs are cumulative and they increase their ‘megapixel count’ by growing in physical dimensions, not by making their ‘photosites’ smaller.

But if you cover half of one with a thick tarpaulin then the cumulative output of the panel drops dramatically!

Also, we want SPs to hit their clip point for maximum voltage generation (the clip point would be that where more light does NOT produce more volts!).

Our camera sensor CANNOT be thought of in the same way:

We are not interested in a cumulative output, and we don’t want all the photosites on our sensors to ‘max out’ otherwise we’ll have no tonal variation in our image will we…..!

The shot above is from a D800E fitted with a 21mm prime, ISO 100 and 2secs @f13.

If I’d have shot this with the same lens on the D500 and framed the same composition I’d have had to use a SHORTER exposure to prevent the highlights from clipping.

But if bigger sensors gather more light (FX gathers more than DX) I’d have theoretically have had expose LONGER……….and that would have been a disaster.

Seriously folks, when it comes to sensor size bigger ones (FX) do not gather more light than smaller (DX) sensors.

It’s not the sensor total area that does the light gathering, but the photosites contained therein – bigger photosites gather more light, have better SNR, are less prone to diffraction and result in a higher cumulative dynamic range for the sensor as a whole.

Do NOT believe anyone anywhere on any website, forum or YouTube channel who tells you any different because they a plain WRONG!

Where does this shite originate from you may ask?

Well, some while back FX dslr cameras where not made and everything from Canon and Nikon was APSC 1.5x or 1.6x, or APSH 1.3x. Canon was first with an FX digital then Nikon joined the fray with the D3.

Prior to the D3 we Nikon folk had the D300 DX which was 12.3Mp with a photosite area 30.36 microns²

The D3 FX came along with 12.1Mp but with a photosite area of 70.9 microns²

Better in low light than its DX counterpart due to these MASSIVE photosites it gave the dick heads, fools and no-nothing idiots the crackpot idea that a bigger sensor size gathers more light – and you know what……it stuck; and for some there’s no shifting it!

Hope this all makes sense folks.

Don’t forget, any questions or queries then just ask!

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Andy