How to make DSLR photos stand out in your circle of friends?

My friends, the Spring Festival is just around the corner. The traditional Spring Festival involves family gatherings and walking around the streets, but now young people seem to like to travel during the Spring Festival. After all, there are only two long holidays in a year. , even Xiaopang’s parents have planned to go on a self-driving trip, and the photo contest in Moments during the Spring Festival every year must be the most topical. As the old joke goes: meeting friends unexpectedly at the breakfast shop downstairs I didn’t dare to say hello when I met him, because in the circle of friends, I was in the United States and he was in Paris. Although it is just a joke, it fully shows that high-quality photos are enough to attract the attention of most people. So the question is, what is the highest level of posting pictures in Moments? It’s probably what girls say: “Wow, were they taken with a DSLR?!” But how can you make your travel photos escape the frame of the mobile phone APP filter, so that even people who don’t understand can see its difference at a glance? Woolen cloth? Today Xiaopang is here to give you some advice.

In other words, how to take advantage of the camera on your mobile phone? From shallow to deep, the first is the focal length. The biggest advantage of the camera is that it has everything from fisheye to cannon, just for travel photos. , the tension of the ultra-wide lens is completely unmatched by the panoramic mode of mobile phones. In addition, the detailed small scenes at the telephoto end are also beyond the reach of mobile phones. Therefore, if you want to reflect the advantages of SLR in the circle of friends in the simplest and most crude way, then you can Let’s make more fuss about both the long and short sides. For example, from the perspective of the picture below, even if the shot is not very good, the momentum is already here.

What if you think this is too simple and crude, and maybe you don’t have an ultra-wide or telephoto lens at all? You also have a shallow depth of field. The most intuitive manifestation of the frame advantage of SLR and mirrorless is the depth of field. You said that your 18-55mm telephoto end is only F5.6, and it seems that the depth of field has no advantage? But in fact, even this most basic kit lens can achieve a shallow depth of field of less than 1 cm at the minimum focusing distance of 25 cm on the 55mm end. Photographing flowers and plants can fully demonstrate the innate advantages of the SLR's large CMOS. If It is an APS-C frame with a 50mm F1.8. When shooting close-ups of portraits from about 1.5 meters away, the depth of field is only 2 centimeters, and the blur effect is equally impressive after avoiding cluttered backgrounds. If you are interested in knowing, the following is the depth of field calculation formula:

There are 4 factors that affect the depth of field: object distance u (distance from subject to lens), focal length f, aperture value N and maximum circle of confusion diameter C . The C value is defined as the quotient of the CMOS diagonal divided by 1500 (so C is related to the frame). The 1500 here is an experimental value, and some manufacturers use other values. For example, Zeiss uses 1730. The larger the value, the more stringent it is. Under this definition, the full-frame circle of confusion diameter C=0.0289mm. Taking Nikon DX as an example for APS-C format, the circle of confusion diameter C=0.0201mm. 4/3 frame C=0.144mm. The total depth of field = foreground depth - back depth of field, so there are:

Of course, there are also directly available depth of field calculation tools online. In addition, the camera lens is not a single lens, so the calculation of object distance and image distance is actually also It is very complicated, so the depth of field formula can only be regarded as an approximation, and accuracy should not be overly concerned. But Xiaopang’s meaning is still the same: Don’t underestimate your kit lens. If you want to shoot a depth-of-field effect that can catch people’s eyes in the circle of friends, it’s still no problem. And compared with the blur effect of dual-camera mobile phones, the authenticity of SLR is much stronger (the picture below is 18-55mm@55mm F5.6).

If you don’t want to PK based on the perspective, and don’t want to challenge your aesthetics with mindless blur, for travel scenery films, SLR, or full frame/APS-C format. An obvious advantage is sharpness. Sharpness can be said to be positively correlated with frame size. The larger the frame, the higher the sharpness. Let’s talk about the theory next:

Lens imaging is to transfer object plane information to The image plane is an analog signal. Due to the limitation of lens resolution, this analog signal has a maximum frequency. The function of CMOS is to perform analog-to-digital conversion through sampling. In order to restore the analog signal without distortion, the sampling frequency should not be less than the frequency of the analog signal. 2 times the highest frequency.

We know that point light sources will be converted into Airy disks on CMOS. There are countless point light sources in the photos we take, which correspond to countless Airy disks. What is reflected on the CMOS is each pixel. Combined with the previous The sampling law mentioned is that one MTF line pair corresponds to 2 pixels (Airy disk). The width of a CMOS line pair with MTF=0.5 = diameter of the diffusion circle, that is, 1 pixel = Airy disk radius = 1.22F. A lens with an aperture of F=2.8 captures yellow-green light with a wavelength of 555nm. When used in the Airy disk calculation formula, the pixel width is approximately 1.9m. Therefore, each CMOS size has its own upper limit of pixel density. If you add pixels without increasing the CMOS area, the extra pixel sampling information will be directly lost as high-frequency data. Therefore, large-size CMOS is inherently more conducive to With high sharpness, you can enlarge a photo taken by a 20-megapixel mobile phone by 100%, and you will easily find that the pixels are basically blurred and have no details, while a SLR will not have this problem.

When taking landscape photos, how can you ensure high resolution throughout the entire frame? In other words, keep the entire frame "in focus" and magnify it 100°, or crop and recompose the photos later. Without losing sharpness, you need to learn the so-called "hyperfocal distance" method. The so-called hyperfocal distance is to push the back depth of field to infinity (as shown in the picture above, the grass in the foreground and the farthest mountains in the background are both clear image). There is a formula:

When shooting with a 24mm lens at F2.8, when the focus point is at 10.234 meters, the back depth of field reaches infinity. If the focus point is closer than it, the back depth of field is It will fall out of focus, start to blur, and the focus position is further away? Because the foreground depth of the hyperfocal distance is still limited, it is the focus point distance/2, which is 5.117 meters in this example. The panoramic depth of the entire hyperfocal distance starts from this distance, and there is still foreground blur within this distance. If your focus position is further away, the starting point of the deep foreground will also be pushed forward, which is not worth the gain.

And you can see that the larger the aperture value (that is, the smaller the aperture), the closer the focus point will be, and the deeper the foreground will be closer to the camera. For example, if this 24mm lens is shot at F8, the focus will be 2.5 When it is about 1.25 meters to infinity, the depth of field will be within the range. At the same time, the longer the focal length of the lens/the larger the frame, the farther the focus distance and the depth of the foreground will be. Even if the full-frame 85mm lens is stopped down to F16, it must focus to 15 meters away to achieve the hyperfocal distance starting from 7.5 meters.

So if you want to achieve a clear image throughout the photo, use a wide-angle, small aperture and roughly calculate the focus distance to avoid too close foreground, so you can take a photo that is completely in focus like the picture below.

But be careful not to narrow the aperture too much even at hyperfocal distances, because too small an aperture will cause diffraction problems that affect image quality. In addition, you should try to shoot with a low ISO and be able to use a tripod. In addition, if you want to show your professional photography skills in your circle of friends, you must also use the RAW format, because most of them need to be edited in post-production. Publish, so you can post a few "work pictures" of photos taken while traveling to warm up the scene, which will naturally attract more people's attention. Of course, the disadvantage is that if you really don't take the photos well, posting them will conflict with expectations. There is a gap, and if you don’t feel it, you will give up. It is suitable for those who are already relatively confident in their own skills.

Finally, I hope everyone has a happy Spring Festival. Although it is still more than a month away, I believe many people’s hearts have already flowed~~