Focal Length and Depth of Field (Patreon)

This is a continuation of the topic that I started when I posted the image of the Bush Stone Curlews on July 1st 2021. It occurred to me, as I discussed how little depth of field you can achieve at a focal length of 400mm (even when stopping down to f/11), that I should present the 'flip side of the coin', i.e., how much depth of field you can achieve at wide apertures when using shorter focal lengths.

The first two images in this post were captured when I reviewed the FE 12-24 F2.8 GM. Those of you who are not interested in such an ultra wide-angle zoom may not have seen these images. Some people looking at these images without the metadata may assume that the aperture has been stopped down to achieve focus in the foreground and distant subject matter. The aperture, however, is wide open at the 12mm focal length - f/2.8.
I spent most of the review shooting hand-held with the aperture wide-open in dark alleyways. Sony has a cheaper FE 12-24 F4 G and I wanted to use the review to educate photographers as to how useful the wider f/2.8 aperture was on a lens that has a 12mm focal length. Some photographers were stopping down to f/11 when using these lenses out of force of habit.

The third image was captured with the FE 14mm F1.8 GM at the widest aperture and I wanted to to illustrate, that with considerable effort, it is still possible to force the background to blur when the focus was less than a metre (3 feet) from the lens.
The final image was captured with the RX100 VII that has much smaller 1-inch sensor (for reasons I won't go into here the sensor is actually smaller than an inch). When shooting at a 9mm focal length on this pocket camera it has a full-frame equivalent angle-of-view as a 24mm focal length on a full frame camera, but its 9mm actual focal length gives this camera amazing depth of field even when the aperture is wide open (f/2.8).

The 2.75 x crop factor of the 1 inch sensor has to be applied to the aperture as well as the focal length, so f/4 is equivalent to using f/11 on a full-frame camera. There is little reason to ever stop the aperture down on the RX100 cameras and this is useful because the ISO performance is not great over ISO 640. It's just as well that the crop factor does not get applied to the aperture in terms of exposure so the f/4 aperture of the final image (captured on a beach in Vietnam) meant that I could capture this hand-held at ISO 100.

My review of the RX100VII can be viewed here: https://youtu.be/d9rOUUPWVQI
As with many of my reviews I try and pack in as much education as possible, so this RX100 VII review focusses on how to extract the best performance when shooting with a camera with a very small 1 inch sensor.

Interesting Note > Other cameras that features this 1-inch sensor is the tiny RX0 II (a waterproof micro camera). This camera has no way to adjust the aperture - you shoot everything at F4. The RX10 also features this 1-inch sensor and features a zoom lens that has an equivalent full-frame zoom of 24-600mm (a whopping 25 x optical zoom). It just goes to show that small sensors still have their place in the imaging market. The 1 inch sensor of the RX100 is actually a stacked sensor and has been so successful for Sony that even Canon (a sensor manufacturer) purchases this sensor from Sony to use in their own compact cameras. I often get asked by non-photographer friends what is a good point-and-shoot camera to purchase. I say that if they are not prepared to own an interchangeable lens camera then the only camera left on the market that offers better performance than their mobile phone is an RX100 or RX10.