As a digital format, micro for thirds has increased in popularity over recent years. It is based on a system designed from scratch, a blank sheet of paper, by Alunpur's back in 2003. Then they decided that the physical size of a sensor should be roughly half that of a 35mm film frame. At the time, it was greeted with a certain amount of skepticism. But today, it has developed into a system of high quality, now widely used by photographers both amateur and professional. Sadly, photographers using other digital formats sometimes taint the system with fake news. One example of this concerns differential focusing. That is where the subject is in focus, but the background is out of focus. And apparently, we are told that this is not possible. This may be a problem for the smartphone technology, but with micro for thirds, this is utter plep trap. Sorry, because such nonsense only demonstrates an ignorance of traditional photographic values. Differential focusing or depth of field, as we used to call it, is controlled by aperture and focal length of lens. Appages do far more for photography than contribute to a correct exposure. Sometimes I meet photographers sporting very high-tech digital cameras, but they don't know that shutter speeds and apertures are the key components to achieving a correct exposure. As for their extended purpose, that is controlling movement and depth of field that is beyond their grasp. They believe that today's science of photography is achieved at the press of a button on auto, of course, and helped by a menu, only to achieve the perfect average. All of this, I find rather sad, because artistic success in photography, even in today's high-tech world, is still based on traditional techniques. So, now, let me show you a few photographs, which I hope will clarify what I am saying about differential focusing depth of field in connection with the micro for thirds system. This photograph of co-astles inside King's College Chapel Cambridge makes it abundantly clear that differential focusing is possible with micro for thirds, but it wasn't taken on auto. The focal length of the lens is 25mm, that is 50mm in film. So, depth of field is modest. However, this is greatly reduced with an aperture of F1.2 and manual focusing. A large aperture reduces depth of field, isolating sharpness to one small part of the image. Therefore, this is a presentation that I controlled in camera. Keeping to a shallow depth of field with a wide aperture still, that is F1.2, but now focusing on the background, an entirely different effect is created. Easily achievable, of course, with micro for thirds. Where confusion occurs with micro for thirds is sensor size. It is smaller than many other formats, but not as small as those found in most smartphones. The smaller the sensor, the greater the depth of field and overall sharpness. But my personal technical guru informs me that it is really down to the size of pixels that have to be accommodated in a smaller area. An unexpected benefit of micro for thirds is extended depth of field in low light, for example, inside a church. Because of lack of light, the camera has to use a wide aperture. Otherwise, the picture is going to be underexposed. But this reduces depth of field. Now for tripod users, a longer shutter speed allows the use of a smaller aperture to extend depth of field without increasing ISO. This would be difficult if handholding the camera without an image stabilizer. However, with micro for thirds, it is amazing. Yes, amazing how much extra sharpness there is from front to back at F4. And this can be increased further by using a wide angle optic either zoom or prime. But don't be fooled into thinking that differential focusing is not possible. Achieved with the right know-how, even to the point that everything that should be sharp is not. Taking a broad view of depth of field, a small aperture increases depth of field, a large aperture reduces it. A wide angle lens, either zoom or prime, increases depth of field at any aperture. A telephoto does the opposite. It reduces it. When the photographer focuses on a subject, depth of field extends twice as much behind the focus point than in front. The amount dictated by aperture and focal length of lens as above. For close-up photography, especially macro, depth of field is dramatically decreased, making aperture and lens choice very critical. Otherwise, the same rules apply. Smaller senses keep more depth of field at any of the above combinations. To the point that differential focusing with a smartphone is difficult if not impossible, but not with micro for thirds. All of this takes practice. It is not easy. And any sophisticated instant gratification control on a camera, even if it works, does not teach the photographer how to do it. It takes time, but to disregard how apertures and focal length of lens is controlled depth of field is like trying to perform music without understanding scales. Both are the rudiments, the bedrock of their art forms, out of which only true creativity under the control of the exponent is born, and a match else in photography. Sometimes I meet photographers sporting high-tech digital cameras who do not know their shutter speeds and... ...the paper has just fallen down my clip sheet. Sorry about that.