Take better photos with your Pi
Mike Bedford explains how to get the most from the Raspberry Pi HQ Camera and learn the basic principles of photography at the same time.
Mike Bedford on how to get the most from the Raspberry Pi HQ Camera while learning the basic principles of photography.
hen Raspberry Pi launched its HQ Camera in 2020 (see reviews LXF264), it introduced something very different from their previous two cameras. While the other two camera modules are made up of a sensor and its interfacing electronics together with a lens, the HQ Camera doesn’t have an integral lens. This means that you need to buy one or more lenses separately, and Raspberry Pi offers a couple of alternatives that we look at here. In that way, it’s similar to digital SLRs (D-SLRs) cameras, but different from the cameras in phones or compact standalone cameras.
Our aim here is to introduce the HQ Camera for those who haven’t yet taken the plunge, and to follow this up by investigating how to use some of its lessfamiliar features, and at how to choose lenses as alternatives to those provided by Raspberry Pi. Armed with this information, we trust that many of you will decide to try your hand with the HQ Camera, and that it will form the basis of some fascinating new projects. Indeed, we already have some plans to present some exciting things you can do with it in the coming months.
The new sensor has a higher resolution – specifically 12MP, which compares to 5MP for the original camera module and 8MP for the v2. But although that megapixel figure is the one that most users concentrate on, the size of the sensor is also significant because the larger the sensor, the more light it gathers, and this also improves the image quality. So we should point out that while the original and v2 camera modules both had 1/4inch sensors, the HQ Camera has a 1/2.3-inch sensor. These figures don’t relate directly to the sensors’ width, height or diagonal, but the area of the sensor in the HQ Camera is about three times greater than that of the earlier RPi cameras. For reference, consumer D-SLRs have sensor that has a 12-times larger area again, and that increases by a factor of another 2.3 in professional full-frame D-SLRs.
The HQ Camera supports lenses with C or CS mounts, which are standards commonly used in CCTV cameras. While these are widely available – although not always affordable – Raspberry Pi has picked a couple of third-party lenses that are the “official” offerings. One has a focal length of 6mm and the other 16mm – see the boxout (left) for more details.
Manual controls
All cameras except the most basic point-and-shoot models offer a degree of manual control over focusing, shutter speed and aperture. The HQ Camera’s lenses,
on the other hand, don’t support automatic focusing or automatic aperture control. This might sound like a drawback, but being forced to use manual controls means the user learns about some of the basics of photography and gains the artistic benefits that aren’t available by using a fully automatic alternative.
Next up we need to consider exposure and this is controlled by three factors: shutter speed, aperture and ISO rating. Shutter speed is exactly what it sounds like, how long the shutter remains open. Typically this can vary from as little as a thousandth of a second to several seconds, and the amount of light admitted into the camera is simply proportional to the shutter speed.
Next is the aperture, which can be thought of as the effective diameter of the lens, and which is controlled by an iris shutter. This is specified as a so-called f-number and might vary from f/2.0 through f/2.8, f/4, f/5.6, f/8, f/11 and f/16, to f/22. To cut a long story short, the larger the number the smaller the aperture, and each f-number in the above sequence represents a halving of the amount of light admitted. (See below for more)
Finally there’s the ISO rating. This is a measure of how much the camera’s electronic circuitry amplifies the signal. It might range from 100 to several thousand, but to 800 for the HQ Camera.
Balancing act
Since there are three factors that affect the exposure, there will be several combinations that will provide a correct exposure. So, for example, if a correct exposure is achieved with 1/60 seconds, f/8 and ISO 100, it will also be correctly exposed with 1/120 seconds, f/5.6 and ISO 100, or with 1/240 seconds, f/5.6 and ISO 200. However, the results of these various combinations will not all be the same because these factors each impact the photo in various ways.
Shutter speed is probably the most obvious. The slower the shutter speed, the more likely it is that there will be some blur due to motion, either because you moved the camera while the shutter was open, or because something in the scene moved. The likelihood of blurring due to camera shake is almost eliminated if you use a tripod, although as a rule of thumb if you’re shooting hand-held you need a shutter speed faster than 1/60 second with a standard lens, and faster with a telephoto. Blurring due to something moving in the scene is quite different, and while this is usually a bad thing, there are exceptions. For example, if you’re shooting a waterfall, you might choose to use a shutter speed of 1/30 or slower so the blurring of the water imparts a feeling of motion.
Aperture effects something called depth of field, with the depth of field increasing as the aperture decreases – in other words, as the f-stop figure increases. A small depth of field means that only objects close to the distance you’re focused on will be in focus, but a large depth of field means that objects over a greater range of distances will be sharp. A large depth of field would often be suitable for landscape photography, so that everything from the foreground to the far distance is in focus. Conversely, a small depth of field might be preferred for portraits, to ensure that the subject is in focus while a distracting background is blurred.
Finally, we come to the ISO rating, and here the rule is that the greater this figure, the more noise – which manifests itself as a graininess to the image – is imparted to the picture. While there are pros and cons to slow/fast shutter speed, and large/small aperture, it’s hard to think of a reason that you wouldn’t choose the smallest ISO rating required to enable your ideal shutter speed/aperture combination.
While the aperture is controlled manually using a ring on the lens, the shutter speed and ISO rating are
The HQ Camera has a blanking cap that you have to remove to attach a lens, but when there’s no lens attached, replace the cap to prevent dust contaminating the sensor. The lenses are supplied with front and rear lens caps which have to be removed when the lens in use and these should also be replaced whenever possible to guard against damage or fingerprints on the glass.