Basic knowledge literacy of digital SLR photography

Since I became the moderator of Nikon plate a few months ago, I found that many people often post and ask some roughly the same questions. Of course, netizens are very enthusiastic and will take pains to answer them, but I always feel that some questions belong to basic common sense or experience, so I have the idea of putting them together to answer them uniformly.

Of course, the so-called basic knowledge here is not the basic concepts such as aperture, shutter and depth of field that can be found in any introductory photography books, but the practical problems that people often encounter in use, with the purpose of practicality.

In addition, this is for beginners. The old bird is rich in knowledge, so there is no need to look down.

First, the frame of the camera

Recently, because Nikon introduced FX Quan Huafu digital SLR, there are many problems around the concept of frame. So let's explain the concept of camera border first.

Simply put, the so-called frame is the size of the negative film for the traditional film machine and the size of the photosensitive device for the digital camera. The larger the film used, the larger the frame.

The traditional 135 film SLR camera we used before used 35mm film with a frame of 36mm×24mm. Because the film used by 135 camera is the predecessor of cinematographic film, and the width of cinematographic film (including upper and lower perforations) is 35mm, so this film used by camera is also called 35mm film.

In addition to the 35mm 135 format, there are 6×4.5, 6×6 and 6×7 medium formats and 4×5 and 8× 10 large formats. As shown in figure 1:

There is a long-winded sentence here. Never use numbers to judge the size of a frame. For example, never think that a 4×5 frame is smaller than a 6×7 frame, because the size units of various frames are different. 135 frames are in millimeters, middle frames are in centimeters, and large frames are in inches.

What is Quan Huafu? Quan Huafu's concept refers to the frame of 135 camera. Because the predecessor of the digital SLR we are using now is 135 film SLR. If the size of the photosensitive device of the camera is the same as or very close to that of 35mm film, it is Quan Huafu, also called FX frame. Such as Nikon D3 and D700. However, Nikon's digital SLR did not use the specifications of 35mm film from the beginning, but first introduced the SLR in APS-C format, that is, DX format, and the size of its photosensitive device is about 24× 16mm, such as D80, D200 and D300.

In addition, in the camp of digital SLR, Olympus and Panasonic use 4/3 format, but what are the specifications of small digital, such as 2/3 inch, 1/2.5 inch,11.8 inch and so on? This is very complicated. For a more intuitive explanation, we borrow a schematic diagram to make the relationship between Quan Huafu and various specifications smaller than Quan Huafu clear at a glance (Figure 2).

Second, Quan Huafu lens and DX frame lens.

Because Nikon's digital SLR has two specifications, it is necessary to study the corresponding lens.

Broadly speaking, Nikon's 135 lens can be divided into two types: Quan Huafu lens and DX lens. In the past, Nikon's 135 lenses were all used by film machines, so we can call Nikon's old lenses and new Quan Huafu lenses Quan Huafu lenses.

In recent years, in order to adapt to Nikon's DX format camera, Nikon has introduced some DX format lenses for D200, such as 18-200VR/f3.5-5.6 and 17-55mm/f2.8, etc. In addition, Sigma, Longteng and other foundries have also introduced lenses with similar specifications.

Therefore, at present, when we choose the lens, we often hesitate between Quan Huafu and DX. People will ask:

1. What if the Quan Huafu lens is used in a digital SLR camera?

It should be said that digital SLR cameras have basically no problem with Quan Huafu lenses. Even if it is used in Quan Huafu digital SLR, there are only some dark corners around it at most, because of the characteristics of the photosensitive device of digital camera, it is sensitive to oblique light. If it is used in a digital SLR in DX format, it is not a problem, because DX format only uses the image field in the middle of the Quan Huafu lens, and the image field in the middle of the lens is often the part with the highest resolution.

2. Can 2.DX format lens be used in Quan Huafu digital SLR?

Due to the small image field of DX format lens, it is impossible to fill its image with the size of Quan Huafu. In other words, you can only take pictures with the middle part of the photosensitive device of a full-frame camera. If you have to use it as a Quan Huafu lens, then this is the following result. At this time, the surrounding is not a dark corner, but a serious black circle:

Therefore, in order to solve the problem that FX digital SLR continues to use DX lens, both D3 and D700 adopt cropping format, that is, when you put DX lens, only about 5 million pixels of 1200 pixels are used for imaging. In fact, this is a last resort, and it is very uncomfortable to use. First, it's very uncomfortable psychologically, because can you be happy when you spend a high-pixel camera bought at a high price as a low-pixel camera? Second, only a small piece in the middle is bright when shooting, and the field of vision is greatly reduced. Can you feel comfortable? I only tried it once and never used it again.

3. Are the past standard lenses and portrait lenses still standard lenses and portrait lenses after they are used in APS-C cameras?

After understanding the concepts of frame and lens, we discuss the relationship between lens and frame in detail, taking the standard lens and portrait lens often used in the film era as examples.

I found that many netizens should equip their DX cameras such as D200 or D80 with a standard lens, and also listed the benefits brought by various standard lenses as the basis. So let me talk about the standard lens first.

We can't simply judge whether a lens is a standard lens by its focal length. The so-called "standard" in the standard lens means that the image in the photo is basically the same as that seen by the human eye, that is, the human eye is the standard.

In order to explain this feeling of human eyes, the definition of a standard lens still depends on the frame of the camera. Because people find that when the focal length of the lens is close to the diagonal length of the film or photosensitive device, the photos taken are basically the same as those of the eyes. If the frame is large, the diagonal is long, otherwise, the diagonal is short. For a 135 film SLR camera or FX Quan Huafu digital SLR, the diagonal length is close to 50mm, so any lens with a focal length of 40-60mm can achieve this effect, and any lens within this focal length can be regarded as a standard lens.

However, if the frame is not the specifications of 135 camera or the Quan Huafu of 135, that is to say, the size of the negative or the size of the photosensitive device is not 36×24mm, big or small, then a lens with a focal length of 50mm is definitely not a standard lens. For example, a 4×5 frame camera has a large frame and a long diagonal, so the standard lens is a lens with a focal length of150 mm. 8× 10 frame camera, with larger frame and longer diagonal, the standard lens is a lens with a focal length of 300 mm. ..

Similarly, Nikon's APS-C camera, such as D200 or D300, has a much smaller photosensitive device size and a shorter diagonal than digital SLR's 135 film or FX frame. At this time, if you want to use a standard lens with a focal length of 50mm for the 135 camera, it is definitely not a standard lens. Because the actual focal length at this time is already 75mm, or in popular terms, it is equivalent to 75mm, which is much larger than the diagonal size. According to the above statement, this focal length has exceeded the definition that the focal length range of a standard lens should be within 40-60 mm When you take a picture or film with a DX camera and a +50mm lens, you will also find that the field of vision seen by your eyes is different and much smaller. Therefore, in terms of clarity and effect, for DX format cameras, the 50mm lens is not a standard lens. In other words, for an APS-C camera, if your lens focal length is multiplied by the magnification of 1.5, and it is between 40 and 60 mm, it can be used as the standard lens on an APS-C camera. ..

Let's talk about what a portrait lens is first.

In fact, for portrait photography, any lens can shoot portraits, such as wide angle, pan/tilt, medium focus, telephoto and even fisheye. Depends on what kind of effect you want.

But the concept of portrait lens usually mentioned here generally refers to the lens used when taking pictures at a distance of 1.5-2 meters, and basically considers the shooting effect of close-ups or busts of people. Because according to the general aesthetic point of view, people's facial features are the most beautiful within this distance, because the perspective effect of this distance makes people's nose look slightly smaller than the real one, and their faces are not peaceful. If the distance is too close, the nose will deform and become too large. Just like comics, if the distance is too far, the three-dimensional sense will weaken, and it is not good to communicate with the subject when shooting, which is not conducive to mobilizing the subject.

For 135 camera or FX Quan Huafu digital camera, a lens with a focal length of 85- 135mm can play a good role at this working distance. Therefore, any lens with this focal length is generally called a portrait lens.

A lens with a focal length of 85mm is a portrait head when used on a 135 film machine or FX Quan Huafu digital SLR, and a portrait head when used on an APS-C format camera. Multiplied by the multiple of 1.5, it is127.5mm. Because it is still within the focal length range of 85- 135mm, it is still a portrait head. It's just that when you are framing and composing a picture, if you want to make people the same size as photos, you may only need a working distance of 3 meters with a full-frame camera and 4.5 meters with an APS-C camera. This change is not obvious when there is enough space outside, but indoors, such as at home, using the same 85mm lens on APS-C camera may feel "a little stuck" (of course, if your house is big or you have a big studio).

As far as Nikon's portrait lens is concerned, there are two people who can be called portrait kings. One is 85mm/f 1.4, and the other is 135mm/f2 DC, and many people think that the latter is better and more outstanding, and it is the real king of figures. But people think this is based on using it on 135 camera or Quan Huafu SLR. I'm afraid it may not be used in APS-C format cameras. Because the working distance is too long and the operation is inconvenient, it is even more difficult to play indoors. Secondly, its actual focal length becomes 202.5mm, which is far beyond the definition of the focal length of a portrait lens of 85- 135mm, and its perspective effect is greatly reduced, so it cannot be used as a portrait head.

4. What's the strange light in my photo?

Some netizens' photos often have the following situations, such as two circular spots in the middle and an oval spot below:

This phenomenon often occurs in the case of backlight shooting. But not everyone will have this situation when taking photos against the light. Why? I have answered this question many times. The reason for this phenomenon is often your UV mirror. Either your UV mirror is inferior or your UV is fake.

The solution is to buy the best UV mirror you can afford, or not to use it at all. I used the latter method.

5. What's with the black spots in my photos?

Some friends often send such photos and ask what is going on? Is the lens dirty?

Note that there is an inconspicuous circular black spot on the left of the rider in the picture below, but the black spot on the right is not. It proved to be a bird after enlargement.

The same position, that is, the left side of the yurt below, is still the round black spot:

This means that there is dust on your CCD or CMOS, which has nothing to do with the dust on the lens. No matter how dusty your lens is, it won't be reflected in the photo.

Solution:

Install a newly charged battery on the camera, lift the mirror, with the lens mouth facing down, and blow it with air several times. If the dust is stubborn and can't be blown off, take it to Nikon maintenance department for cleaning. It is said that it is free during the warranty period. My practice is to gently dust off the dust with a lens pen, which will get immediate results, but many netizens think it is dangerous, so I don't recommend my own practice.

Sixth, the characteristics of photosensitive devices to ash

How do you know it's dust on CCD or CMOS? Because its characteristics are very obvious, that is, the smaller the aperture, the more obvious it is, and the position is the same.

This is in the case of aperture f 13, pay attention to the lower right corner:

This is the case of the aperture f 19, or pay attention to the lower right corner:

This is in the case of aperture f32, or pay attention to the lower right corner:

As you can see, as the aperture shrinks, the dust becomes clearer and clearer, and then even the shape is seen and the position is fixed.

Seven, matters needing attention when replacing the lens

Nine times out of ten, the camera on CCD or CMOS goes in when you change the lens, so it is very necessary to change the lens correctly.

My approach is to find a direction facing away from the wind (of course, it is best to stand indoors), turn off the power of the camera, take off the lens of the fuselage, face down, and quickly replace another lens. Note: Be sure to bring a hair dryer. After opening the back cover of the lens to be replaced, first carefully check whether there is dust in the back group of the lens. If there is, be sure to blow it clean before loading it on the fuselage. In addition, don't throw away the back cover of the lens even if it is not used at ordinary times, because if there is dust on the back cover, it will be brought to the back group of the lens when it is used in the future, and finally transferred to the photosensitive device of the camera.

Eight, I haven't changed the lens, how can there be dust on the photosensitive device?

This seems unreasonable in reason, but this phenomenon is very likely to happen. Take my personal experience as an example. At first, I bought only one lens for my D200, that is, 18-200VR. I never took it off the fuselage, but when I used it, I found dust on the CCD. Because the dust comes from inside the camera. It may be some micro-fragments falling from your lens, the aperture on the lens, the shutter of the fuselage and other mechanical structures.

Aside, this is why some small DC's, such as Canon's G7, can't change the lens, but there will be dust on the CCD in the end.

9. What should I do if I see one or several black spots in the picture?

Generally speaking, that's dust on the reflector. How to solve it? Just like cleaning CCD or CMOS, blow with air. If it still doesn't blow out, that's fine, and it won't affect imaging anyway. Don't try to wipe the mirror yourself, because rubbing or scratching the mirror is common.

10. What is the dust between my lenses?

This situation mainly occurs in zoom lenses, especially telescope lenses with large zoom ratio, such as 18-200VR or 70-300VR (small bamboo cannons and the like generally do not occur because the lens length does not change when zooming). Because when your wide angle becomes telephoto, pull out the lens, and when you put away the camera or lens, you have to pull it back to shorten it, and pull it repeatedly to suck in the dust. In jargon, it is called negative pressure effect or bellows effect.

Solution: Do not affect the imaging, ignore it, or send it to the maintenance department for cleaning.

My 18-200VR has been seriously grayed out, because I often take that lens to climb mountains and take pictures in windy weather in winter. But I found that the front of the lens was easy to fall off, so I cleaned it myself several times. People who are not sure should not do this, so it is not recommended.

This explanation also applies to small DC with long zoom ratio.

Tip: In order to reduce the appearance of this kind of lens dust, you should pay more attention to cleaning the lens at ordinary times. But please note that when I ask you to clean the lens, I don't want you to clean the front lens, but to pull out the lens body and clean up the dust in several telescopic parts of the lens barrel, so that the dust on it can be greatly avoided when the lens is retracted.

1 1. When my lens is in focus, will there be a "click" in it?

This usually happens on the anti-shake lens, that is, the VR lens. This is the result of turning on the anti-shake function, which is a normal phenomenon. If there is no such sound, there is something wrong with the lens. If you don't believe me, turn off the anti-shake switch on the lens and the sound will be gone.

Twelve. Why does my 60mm or 105mm macro lens sometimes fail to reach the maximum aperture of f2.8?

I won't say much about this question, two words: normal.

Thirteen, how to directly view the shooting information in the forum pictures?

Note: when I say direct viewing, I mean direct viewing, and there is no need to download or save the pictures on the computer.

Every digital photo has an Exif message hidden outside the picture. The latest version used at present is version 2.2, which means that digital cameras often support Exif2.2 in the specifications. Not all image formats can save Exif information, such as BMP images. But the original file, JPG file and TIF file are all supported. Photos on web pages are generally in JPG format, so they can be viewed by special tools unless there is an error in post-processing or the Exif information is deliberately deleted.

Here is a small tool called Exifshow, which must be installed by yourself. Click here to find more than n download addresses to download.

This is the Chinese version. After the installation is completed, restart the browser and you can use it. When you want to view the Exif information of a photo, you don't need to save it to your hard disk. You can right-click the photo you want to view, and then a window will pop up. If you are prompted "This picture has no EXIF information", there is no way to explain that the person in the above picture has not saved the information. Otherwise, a window similar to the following will appear:

The photos in my post are marked with model, lens, aperture, shutter, ISO, shooting date and other information below. But how do you know whether the camera is directly released or exported JPG film after NX adjustment? It can also be roughly judged by this tool.

Let's take a closer look at the first three lines in Figure 1 and Figure 2: camera manufacturer, camera model and software. Let's compare the contents after "software" in the third line

If the content of this line is "Ver. 1.00", as shown in figure 1, it means that it is a JPG film directly produced by the camera, where 1.00 is actually the firmware version number of the camera. If the content of this line is "Capture NX 1.0. 1 W", as shown in Figure 2, it means that it is a JPG piece exported after adjusting the RAW format file by NX software in the later stage.

Give two more examples:

If "Nikon Capture Editor 4.4.0 W" is displayed, it means that the pictures are JPG exported after NC adjustment, such as some films I took with D200.

If "silky pix (r) Developer Studio Version 3" is displayed, it means that the picture is a JPG that was adjusted and exported by Silkypix software, such as some movies I shot with LX2.