Recently, in the war of marketers of photographic equipment manufacturers for the wallets of users, there is a clear trend towards the increased number and pixel density of digital camera sensors. Of course, by increasing the number of pixels supported by a digital camera, it is possible to capture higher resolution images. But the more pixels, the smaller their size, the more blurring defect will be noticeable when the images are enlarged on a computer monitor. Is it possible to avoid or minimize this effect?
Let’s find out what you need to know when buying such a camera and what the manufacturer is silent about.
- A sensor with a large number of pixels has a smaller pixel size than one with a small number of pixels. Thus, using the same lens, cameras with a large number of pixels can reproduce finer details of the subject compared to cameras with a small number of pixels. However, the more detailed the images conveyed by the lens, the lower the detail contrast. The degree of contrast reduction depends on the lens. Therefore, if you magnify images taken with a camera with a large number of pixels when you view them, the image may appear blurred due to a decrease in the contrast of individual details depending on the characteristics of the lens you are using.
- Reducing the aperture increases the depth of field in the image, reducing lens aberrations and improving contrast. Setting the aperture too small, however, can lead to diffraction (which I will discuss below), which, like aberrations, reduces contrast. The aperture value that provides the highest contrast and optimal low aberration with minimal diffraction depends on the lens. It is usually recommended to reduce the aperture value by 2 or 3 steps from fully open. Be sure to consider camera shake, as reducing the aperture results in longer shutter speeds.
- As the number of pixels increases, the size of an individual pixel decreases. When you view images on a computer monitor at 100%, images from a camera with a higher pixel density are actually larger compared to images taken with a camera with a larger pixel size. Even if the images are captured under the same conditions with similar hand or camera movement, the blur defect in the images from the camera with the higher pixel density actually increases several times, hence it will be more noticeable when the images are displayed. It can therefore be argued that cameras with a higher pixel density are more sensitive to minor movements. Try to keep hand and camera movements to a minimum during shooting.
- The smaller the pixel area, the fewer photons of light it picks up. Photons are elementary particles, a quantum of electromagnetic radiation (light in the narrow sense). The smaller they are, the worse is the signal/noise ratio, the worse is the camera sensitivity. Maybe technologists make new cameras with more sensitive sensors, but so far cameras with lower pixel density are less noisy and more sensitive.
- Also don’t forget about dynamic range – the ability of the sensor to convey the brightness of objects in a real scene. Dynamic range is very closely related to noise, as it limits it in shadows. A smaller pixel means a smaller dynamic range. Conclusions everyone will draw for himself.
- We want to warn about one more insidious enemy, that will always be waiting for those who likes megapixels. This is diffraction. I will not lay out here a theoretical course of optics, I will only say that after passing through the aperture, the rays do not go straight as we would like them to, but a little “split”, diverge to the sides. As a result, each ray forms on the matrix surface not just a point, but “circles and circles on water” – diffraction rings. Such disks can climb onto neighboring pixels if they are dense enough. And when they climb onto neighboring pixels, we say goodbye to good sharpness.
The conclusion to this situation is disappointing. Despite manufacturers’ software tricks, high-quality photography with high-resolution interchangeable optics (SLR or system cameras) requires high-end lenses (to avoid contrast reduction phenomena), the price of which may be several times higher than the price of the camera itself, especially for amateur cameras.
When shooting with compacts with fixed optics and high density sensors you have to decrease the aperture value at manual camera settings, sacrificing the desired small DOF. Again, you have to set the aperture to avoid diffraction and slow shutter speeds.