The Quality-Versatility relationship in cameras 6 March 2020

We are endlessly informed by photographic experts most of whom are self appointed that a camera with  a larger sensor and more pixels will make better pictures than one with a smaller sensor and fewer pixels.

My practical experience using many cameras with a range of sensor sizes leads me to the view that the superiority of larger sensors and more pixels is:

a) true in the technical sense but overstated and in practice much less clear cut than some pundits would have you believe and

b) comes with costs. The obvious ones are price, size, weight and  the need to buy, carry and mount several interchangeable lenses.

Less often discussed is that increased sensor size comes with decreased versatility.

The relationship between sensor size and image quality is not linear. 

The graph below is my attempt to illustrate the relationship visually.

There are no numbers on the axes of this graph. It is conceptual, based on my practical experience.

The 15.9mm (so-called “one inch”) sensor in the Sony RX10.4 and several other models from Sony, Panasonic and Canon delivers mostof the imaging quality of larger sensors while giving camera designers the freedom to create fixed zoom lens models of high versatility.

You can see that there is a big jump in image quality as sensor size increases from 7.67mm (diagonal) to 15.9mm.  But further increases in sensor size deliver progressively declining increments of improvement.

If we bring depth of field into the equation the superiority of larger sensors is further challenged.

Consider the attached photo “feeding time at the zoo” which shows humans eating junk which would never be offered to the animals. Actually if the zoo offered such rubbish to the animals its operators would be dismissed.

This was made hand held with a Sony RX10.4 at f2.4 and ISO 500. You can see that there is plenty of detail and that everybody is rendered clearly.

If I were to make the same picture with a full frame camera and wanted to achieve the same depth of field I would have to set f8 or thereabouts. This is 3.3 stops smaller than the f2.4 used on the RX10.4.

My tests show that My Nikon Z6 full frame MILC has about three stops (EV steps) less luminance noise at around ISO 3200 than the RX10.4.   

At f8,  ISO 4000 will be required.

The result from the RX10.4 at f2.4 and ISO 500 will be difficult to distinguish from that obtained with the Z6 using f8 and ISO 4000.

So using the full frame camera will get us exactly nowhere as to image quality and depth of field.

Now compare the RX10.4 with the Z6 with respect to versatility. My Z6 has the 24-70 f4 S zoom lens which is often sold with the Z6 body. This is a 2.9x zoom of very good quality.

The RX10.4 has a very sharp 25x zoom and much higher performance especially when following fast moving subjects.

There is a large spectrum of long lens/high speed/high performance capability which the RX10.4 manages easily but which the Z6 cannot do at all. Even if I mount a long lens on the Z6 it can’t keep up with the RX10.4.

Many of the discussions which I read or watch on Youtube about the merits of various cameras are like watching people debate the number of angels which might be able to dance on the head of a pin. 

In other words a complete waste of time and effort.

Most current model cameras and smartphones can make fine pictures if used thoughtfully.

Camera makers want you to buy their most expensive models because that delivers them greater profits.

I think it is worth noting however that they generally do not  say camera A will make better pictures than camera B. They just put their products out there and let the self appointed experts pontificate at length often in support of big sensor, big pixel count models.