To answer the question of why a lens hood is needed, let's look at how it looks. The device is more often a plastic or rubber, less often a metal, hollow attachment for a lens of various shapes with thin walls. The shape is conical, cylindrical, petal or in the form of a pyramid.
Functions
A lens hood of any shape and type performs two main functions: the first is protection from unwanted glare of light, which significantly reduces the quality of the photo, and the second is protection against various mechanical damage.
If shooting is carried out in conditions of excessive lighting, the rays of light that do not participate in the formation of the image fall on the front lens and therefore create glare of light or iridescent glare in the final image, which are not removed by any graphic editor in post-processing.
In addition to glare, such "harmful" rays affect the image with low contrast, even if you use, or incomprehensible fog. She insures against such unnecessary rays, with her walls protecting from the rays. At the same time, it does not fall into the frame, no matter what focal length you stop the lens at.
A camera with a lens hood installed looks quite impressive and solid, this impressiveness protects the front lens from various smears by hands, damage from small splashes, dust, pebbles, and so on.
It is also very convenient to carry a camera with a lens hood, putting it on the lens backwards. This is also a kind of additional protection, especially if the device is very expensive. If you accidentally drop the camera, it will surely fall on the lens, and if a lens hood is put on it at the same time, most damage can be avoided due to depreciation. She will take a hit on herself, in whatever position she is put on.
Form differences and their meanings
The quality of the images will directly depend on the shape and size of the lens hood.
Petal - the most common in use, it protects well from side rays, although more often it is useless in protection from corner rays. Also, it cannot be used at some focal lengths, its scope is the focal length up to 55 mm.
This species has such a complex shape in order not to create blackouts at the edges. It is also best not to use the lobe lens where the front lens rotates, again because of its shape, which, when rotated, can easily miss the beam that you are trying to hide from.
Solid, round or otherwise mounted on models with focal lengths over 55mm, when using solid is pale at shorter focal lengths, severe edge shading, or vignetting, cannot be avoided.
There are also some kind of “intermediate options”, solid for focal lengths of 40-80 mm, as well as universal in shape, suitable for all focal lengths, it has a round shape and, as a rule, metal, so that you can already install a suitable filter on it.
They also differ in the way they are attached. There are universal ones, they are suitable for any device of the corresponding size and reserve the ability to attach a light filter directly to the lens hood itself.
Universal ones are much cheaper than the original ones, but they have a major minus - it takes much more time to install them. Screw the original one faster, sometimes these seconds can be important and more convenient, and this will save your nerves.
Features of use
Having figured out why you need a lens hood for, it remains to choose the right one for your lens in size and shape. Of course, it is better and more convenient to take the original model, it certainly costs more, but this is such a detail that you can not remove it at all.
Of course, subject to work in the range of suitable focal lengths. You can not pay much attention to the choice of material at all, a variety of options exist only for the breadth of the assortment, take what you like, metal or rubber. None of the functions of the lens hood is affected by what it is made of, but the final amount is affected.
At the right time, any will perform the function of protecting against unwanted light, and will also be permanent. This simple accessory is the first assistant on the way to great pictures.
The photographer's bag contains many different accessories, including a lens hood. What it is, why it is needed, we will consider in the article.
What is a lens hood?
This is an additional accessory made of plastic or other material (rubber, metal), often it is already included with the lens, but sometimes it needs to be purchased separately. Outwardly, it looks like a flask with a thread, thanks to which it is screwed onto the lens. In the working position, the hood protrudes beyond the edge of the lens. The forms are different: in the form of a cylinder or a cone, a tetrahedron, which tapers on one side, or in the form of a complex figure with petals.
Sometimes you can find a lens hood that is already built into the lens. If necessary, it is enough to simply push it out. Another option that exists, but is found and used very rarely, is a folding hood.
Often, people who have only recently plunged into the world of photography express bewilderment about this accessory, asking the question: “Do I need a lens hood?” - and do not use it at all. Or they wear it with the other side wound on the lens, not working, but intended for storage mode. This is a big misconception.
For example, if you shoot against the sun, you may experience a faded and low-contrast frame. The hood will cut off unnecessary streams of light, make the picture more contrasting and expressive.
But this does not mean that if you are shooting on a cloudy day, then using a hood is useless. There is another, not the most obvious task that it performs - to protect the optics from mechanical damage. In practice, it has been verified that even when a camera falls from a tripod height onto a concrete floor, if the lens hood takes the blow, it breaks, and expensive optics remain intact.
Also, the lens hood saves the lens from dust, splashes of water and dirt, snow, raindrops and other unwanted particles that can ruin the frame or optics.
It creates ease of use. Because the lens hood is protected, you don't need to put the lens cap on when you put the camera down. This saves time, makes work more comfortable, and you won't have to worry about losing or forgetting the protective cover somewhere in the heat of shooting.
Now you understand why a lens hood is needed, and you realize the need to use it.
Blend material
As mentioned above, three types of material can be used to make a hood: plastic, rubber and metal. Metal blends are quite difficult to find on sale. They are, of course, very strong and reliable, but also heavy. For professional work that lasts for several hours, extra weight is useless.
The most popular option is plastic. It is a lightweight, inexpensive material. With proper care, the plastic hood will last a very long time, but even if it breaks, it is easy to replace.
An alternative option is rubber lens hoods. It is a light material, but at the same time guarantees a high degree of protection both against impacts and against natural elements.
Mounting options
There are only two of them. And they depend on the model of your lens:
- Bayonet mount, usually it is provided for professional optics. This type of attachment allows you to work with a hood and a light filter at the same time. Another plus is that you can install the lens hood not only in the working position, but also vice versa, which allows you to compactly store lenses in your work bag.
- Threaded mount. This is not the most convenient solution if you use filters in your work, since the hood takes up the slot intended for it.
Examples with photos
Let's now look at examples of what a lens hood looks like. Photos consistently show the different shape of this accessory.
In this photo you can see a petal hood that is used for short focal length lenses as well as for wide angle lenses.
Here is a cylindrical hood, which is usually used with telephoto lenses.
In this picture, a rather rare variety is a folding hood.
How to choose a hood?
You need to select it based on the characteristics of the lens, focal length and viewing angle. A petal hood works best for short and medium focal length lenses. This shape is also suitable for wide-angle lenses, it allows you to avoid the appearance of vignette in the pictures, which means it reduces the time spent in Photoshop.
For long-focus optics, a cone-shaped or cylindrical lens hood would be the best option. Unfortunately, it is impossible to choose one option for the entire fleet of optics. Such a model simply does not exist.
There are lenses that are not suitable for working with a lens hood. These are fisheye lenses. Their viewing angle is so large that the lens hood, even the smallest one, falls into the frame. But this is perhaps the only exception to the rule.
In order to take really high-quality photographs, it is not enough just to buy a good camera. In addition to the necessary knowledge and skills, in the arsenal of any self-respecting photographer you will find many additional accessories: filters, flashes, interchangeable lenses, extra batteries, memory cards, tripods, camera care products and many other nice additions. And if the opinions of experts differ regarding the advisability of using light filters, then no one will deny that a hood is a necessary thing. But what is a hood, and why is it needed? Let's figure it out.
What is a hood?
Lens hoods come in a variety of shapes and sizes, and each lens has to be matched to the perfect lens hood. The problem here is that the diameter of the front lens component, just like the angle of view, is different for each lens, so not every lens hood will fit.
Types of blends
Blends primarily differ from each other in shape, as well as in the material from which they are made. On sale, you can most often find hoods made of plastic, less often - made of metal or rubber. Plastic hoods are light, durable and can serve their owner faithfully for many years.
petal hood
Petal blends are the most common. They are mounted on medium-focus and short-focus lenses. On wide-angle and ultra-wide-angle lenses, petal hoods are used to eliminate vignetting (partial obscuration of oblique light beams) at the corners of the frame. This kind of hood best protects the frame from glare, since the size of the petal hood takes into account the aspect ratio of the camera's digital sensor.
Conical lens hood
Tapered lens hoods are most commonly seen on telephoto lenses. By the way, a lens hood is needed not only to correctly cut off the light, but it also serves as additional protection for the lens during a fall, if that happens.
Pyramidal (square) hood
Lens hoods for professional video cameras most often have a pyramidal shape. A pyramidal hood is more effective than a round hood, but assumes that the lens barrel does not rotate when focusing, otherwise you will get the exact opposite effect.
Cylindrical (round) hood
If your lens is a rotating front lens, this means that you can only use a round lens hood, otherwise, at minimum magnification, a lens hood (for example, a petal hood) will be clearly visible in the frame, causing vignetting.
In the photo above, you can see how the petal hood enters the frame when shooting on a camera with a rotating front lens.
“Nothing paints a photographer like a hood” - folk wisdom
The main task of the lens hood is to protect the front lens of the lens from direct sunlight. It can be compared with a headgear visor that protects the eyes from bright light. What is the danger of direct rays falling on the front lens of the lens?
There is such a phenomenon as "light scattering" of the lens. Its essence is that the numerous lenses that make up the lens not only transmit light, but also reflect it with their surfaces.
1. Glare. Surely everyone saw spots of solar "bunnies" on their frames after shooting in the backlight;
2.Loss of image contrast. The frame becomes as if covered with a gray haze with greater or lesser intensity;
3.Reduce color saturation;
4.Loss of fine image details.
An example of one of the flare options in the frame. On the left is a normally exposed frame. On the right is the same shooting point, but the lens was turned slightly to the left, which led to the high brightness area entering the frame.
I cannot explain this phenomenon in a deeper way in the framework of a short article. If there is a desire to delve deeper into the essence of the light scattering of the lens, I suggest downloading and reading the textbook for students of VGIK by the author P.A. Nogin “Camera technique”. The book is of course ancient, but very sensible. In my opinion, everyone who writes about optics on the network “tear” from there. Download a book.
There is an opinion that a hood is needed only when shooting on a sunny day. This is not entirely true. Because even in cloudy weather, the gray sky sometimes has a very high brightness, which can also degrade the quality of the future image. I hope that I have already scared you enough? Don't worry, we'll fix it.
The right lens hood will help improve the quality of your shots.
A modern lens is made of lenses with a special coating, the so-called "enlightenment", which significantly reduces light scattering.
But even the most advanced optics need to protect the front lens from bright light. Like no one else, professional cameramen know this. See what deep blends they use. 
With adjustable length and sliding shutters to make the protection as effective as possible. Lens hoods are made much more compact. This is a forced measure of the developers. But it does not always provide maximum protection.
For example, for budget zoom lenses with a focal length of 18-55 mm, the so-called "whale ones", the branded lens hood is generally ineffective. It's a little useful at wide angle, but doesn't affect anything at all at 55mm.
The only way out for the owners of such lenses is probably to buy a second lens hood specifically for the 55 mm position, choosing it among analogues, which are now a great many on sale, as well as experimenting with home-made designs, about which I will give advice at the end of the article.
Various types of lens hoods for zoom lenses
First of all, this applies to zoom lenses. But for fixes, you can choose any universal analogue of a branded hood. Go to the nearest photo store and see what they have in stock for your lens mounting thread.
Just before buying, be sure to try on the lens hood, fixing it on the lens and taking one shot. If the lens hood is too small, then the edges of the frame will be masked, that is, darkened.
However, a completely different type of lens hood can provide more reliable and maximum protection for the lens, for example, the LEE Filters universal lens hood with adjustable length.
It has more additional features, read and see here Universal Hood - Part of the LEE Camera Filter Range Surely there are other manufacturers of such blends. I would be grateful if you share information.
But what if you shoot with a compact camera, for example, a “soap box”, for which a lens hood is not provided at all? I advise such amateur photographers to take an umbrella for shooting. It will serve you on occasion as an excellent hood, save you from glare and help you make high-quality shots.
By the way, an umbrella will also be useful to owners of DSLRs, especially when shooting in backlight, when a standard lens hood is not enough
Well, for a snack, the funniest thing. Our desire to at least somehow save on the purchase of photo accessories is true for the lens hood. It turns out that the lens hood can not only be bought, but also downloaded. And what? We're downloading gigabytes of movies. So why don't we download some kind of lens hood? It only weighs 50 grams! However, jokes aside
How to download lens hood
There is an interesting resource site lenshoods.net on the Internet. It contains data on most modern lenses and their respective lens hoods. And there you can download a scan or, if you like, a pattern for a future hood. We go to the site, look for our type of lens and the scan corresponding to it, download it as a PDF file.
Carefully read the instructions for your next steps. The main thing is to print our pattern on the printer without changing the scale, otherwise the size will not match. The resource advises to print it on thick dark-colored cardboard.
For an experiment, I tried to download, print and glue a lens hood for one of my 18-200mm lenses. The hood material was a sheet of black cardboard A4 in size and with a density of 160 g/m.
Of course, I would like it to be denser, but I did not find another black cardboard in stationery stores. I printed the scan on a regular sheet of writing paper, cut it out, and transferred the contours to cardboard.
This sheet was bent along the long side in half and glued the sides together with double-sided tape, thus obtaining a denser cardboard. Then I cut it out along the contour, bent it and glued it together. 
It turned out like this. Well, what can I say? The hood had to be fixed on the lens with an elastic band. Moving back and forth, I chose a position so that the edges would not vignette. The material for the hood is of course thin. It is advisable to take cardboard even denser.
But on occasion, of course, you can use it. By the way, on the same site you can calculate the sweep according to your individual sizes. I hope that this idea will inspire someone to experiment on their own.
Everyone knows that the main thing in the work of a photographer is light. After all, even the word "photography" in Greek means "light painting". Therefore, it is extremely important that the amount of light entering the lens is optimal. As a rule, the most sensitive lenses are also used for this. But what if there is too much light or it hits the lens almost at a right angle, creating unnecessary glare? Do not shoot now in semi-darkness, completely turning away from the sun. That's what a hood is for! This is a round plastic piece that is screwed onto the lens.
A lens hood is usually used when shooting against the sun or other light source. This helps to improve the contrast and color of the resulting images by blocking the light rays that can hit the sensor, as well as avoiding vignetting (darkening or lightening the edges of the image). This improves the quality of the resulting photos. Lens hoods also prevent flare from appearing in images. Protection from light rays hitting the matrix is the main one from the list of reasons why a hood is needed.
Also, many photographers use ultraviolet, neutral gray and others. The smallest scratches and damages become visible when they are quite easy to hide - that's what a hood is for. It prevents direct light rays from reflecting off damaged areas, so they cannot affect image quality. Of course, if we are not talking about cracks in half of the filter.
Speaking of damage. The lens hood also protects your optics from them. No one is safe from accidents (and from the banal touch of fingers on the lens, which gives a greasy print), so a hood can save you and your lens more than once.
And, of course, nothing can replace a lens hood when shooting in rainy or snowy weather! You can not even explain that drops of water flowing down the lens will not lead to anything good. Therefore, having a hood with you in case of bad weather is not exactly necessary, but it does not hurt.
It is also worth noting that hoods for different lenses differ from each other in shape. They can be cone-shaped, petal or cylindrical. It is best to consult with the retailer or a professional photographer about which lens hood is right for your shooting purpose and lens. It is important to take this carefully, because an incorrectly chosen lens hood will not only not perform its functions, but will also bring a lot of unnecessary inconvenience to the photographer.
So, we found out what a hood is for. In practice, it is used when oblique rays of light hit the lens, when photographing against the light, sea and snow landscapes (since snow and water strongly reflect the rays), in bad weather, sunsets, and simply to protect optics. If these types of shooting are not in your circle of interests, you will not lose anything by refusing to purchase a lens hood. And if you regularly work in these genres and are looking for a way to improve the quality of images - well, now you know a great way!