The F16 rule can also save your photos with your mobile: this is how it works

Throughout the history of photography we have worked with a rule to get the best shot from a technical point of view: that of f16. In mobile photography we have tried to adapt it with the help of the law of reciprocity. The only thing is that we will be very limited.

In the present photograph, the author has less and less to say in the technical section. Right now the Kodak motto ‘You shoot, we do the rest’ is true. The photographer has to choose two fundamental aspects: the subject and the frame. But we can almost forget about the technique with mobile phones.

Computational photography and the various advances allow us to forget about the most technical part of photography. But those of us who like to do things for ourselves still have some chance to achieve the full feeling of being authors.

What matters is the end result, without a doubt, and we will never underestimate a photograph for the steps that have been taken to make it. It only matters that the image is good and communicates what the author wanted. We are going to look for some technique that allows us to get the most out of our mobile camera.

The famous f16 rule

This rule has been essential for many photographers over time. If we did not want to depend on automation, there was no choice but to learn it to have total technical control. It is very simple and perfect for our mirrorless cameras.

The f16 rule comes from the times of the reel. And it is the perfect technique to know what shutter time to set based on the ISO sensitivity and the light we have at the time of shooting. When you get the hang of it you can look at the sun and be a veteran when it comes to setting the exposure.

It is very simple. It’s all based on how much light there is at the time. And depending on your needs, you choose some values ​​or others. The base is as follows:

On a totally sunny day you get a perfect exposure if you shoot at f16 with the inverse of the sensitivity as the shutter time. That is, you put an f16 diaphragm, and if you have ISO 100 the shutter time will be 1/100. It is not a mathematical rulebut it works quite accurately.

Best of all, thanks to the exposure triangle, you can adjust for each type of light. If a cloud covers the sun, you can open the diaphragm one stop (from f16 to f11) or slow down to 1/50… We have all kinds of combinations depending on what we need. The only important thing is to memorize the rule to know how to act.

In the table you can see how if we change a parameter of the exposure triangle, one can leave it fixed depending on what we want to achieve, more speed or more depth of field. It’s that simple. You just have to memorize the rule to get the picture you want.

The f16 rule in mobile photography

Some nostalgic person may want to do the same with their mobile phone. And when he tries to put it into practice, he’ll discover that phones don’t have diaphragms. Its lenses have a single diaphragm, as bright as possible, to compensate for the small size of the sensors.

It all depends on the shutter time and sensitivity. Computational photography does not let us act and always decides for us. But if we work with the Manual mode that some applications allow us, we have the opportunity to test the f16 rule with it.

The f16 rule with the iPhone 13

To put it into practice we only have to see the diaphragm of our mobile and do the pertinent calculations to see what the perfect exposure is with the nominal ISO. For the example, I am going to use the wide angle lens of my iPhone 13, the 26mm f1.6.

This phone has a ISO 40 nominal ISO. We don’t have integer steps, so the calculation of the f16 rule will be approximate. And we will have to adjust it through the classic trial/error. Let us begin.

A photograph on a summer day, with this mobile, it would be done with an exposure of f16, ISO 40 and 1/40. The problem is that it cannot close that much, so we have to open and adjust the time according to the law of reciprocity. The ISO is not modified:

f16 1/40>f11 1/80>f8 1/160>f5.6 1/320>f4 1/640>f2.8 1/1280>f2 1/2560>f1.4 1/5120

Rounding off the calculation, to achieve a perfect exposure with our mobile we should shoot, in broad daylight, with an ISO 40 and an f1.6 diaphragm, with a time of 1/5000. We should memorize this information.

Thus, if we have less light, we only have to raise the ISO one step, to 80 ISO, for example. But to make it clearer, I’m going to put a table.

Computational photography does this job for us. And you will surely do much better and get superior results. But being in control from start to finish and knowing we’re on the right track is priceless. We know that the important thing is photography, but everything changes depending on the path we take.