HDR pour High Dynamic Range : mais c'est quoi ?
HDR (high dynamic range, grande plage dynamique ou grande gamme dynamique) est devenu au fil du temps un terme photo un peu fourre-tout, qui regroupe des méthodes et des techniques permettant de réaliser des images à grande plage dynamique. On rencontre souvent les dénominations « photo HDR », « image HRDI », « prise de vue en HDR »… mais de quoi parle-t-on, au fond ?
Although we will see that in the end, methods to maximize the dynamic range of a photograph does not begin with the advent of digital photography, HDR techniques as perceived and used today have their origin in digital imaging and computer-generated images (including the work of Professor Paul Debevec in ICT Graphic Lab California in 1997). There followed a whole bunch of software, filters, techniques and other IT artifacts to literally create images with optimal exposure from multiple photos.
HDR (high dynamic range, grande plage dynamique ou grande gamme dynamique) est devenu au fil du temps un terme photo un peu fourre-tout, qui regroupe des méthodes et des techniques permettant de réaliser des images à grande plage dynamique. On rencontre souvent les dénominations « photo HDR », « image HRDI », « prise de vue en HDR »… mais de quoi parle-t-on, au fond ?
The dynamic range of a photo is the difference between the darkest and the strongest light in the image (sometimes called extended tones). The important thing to keep in mind before you start is that nature is well done, the human eye has a very wide dynamic range (called visible spectrum or optical spectrum, which covers wavelengths from 380 nm to 780 nm from violet to red, before and after ultraviolet infrared): in other words, looking at a landscape or any scene, we are able to discern the infinite shades between light and the shadows ... Difficult to make both these strong contrasts with a camera and a display screen or paper printing.
In the end, this is not the actual photo whose dynamic range is evaluated, but the media or instrument capture and restores: human eye, screen, paper, sensor digital camera, movie ...
Principle of HDR photography
Although we will see that in the end, methods to maximize the dynamic range of a photograph does not begin with the advent of digital photography, HDR techniques as perceived and used today have their origin in digital imaging and computer-generated images (including the work of Professor Paul Debevec in ICT Graphic Lab California in 1997). There followed a whole bunch of software, filters, techniques and other IT artifacts to literally create images with optimal exposure from multiple photos.
You read that right: to create a HDR high dynamic light, you need more input photograph of the same scene differently exposed. The principle is actually very simple. Indeed, sometimes our photos are underexposed, sometimes they are a bit overexposed, sometimes very over-exposed, etc.. : Why not take the best of several differently exposed photos to create the "perfect" show? That's the HDR.
Technically, "take the best of several differently exposed pictures" is not so simple and it is not possible natively with our usual file formats 8-bit per channel (256 shades) or 16 bits per channel (65,536 shades) . This is why the HDR fusion will be performed in a file 32 bits per channel (sometimes referred to as HDR container in shades 4294967296), that we will then "compress" (nothing to do with compression JPG) to fit in a 16-bit encoded file (a computer screen do not have sufficient dynamic range to display an HDR image): this is called tone mapping. Area by area, HDR fusion algorithms will choose the best exposed pixels in each shot, to compose an image in which all pixels are properly exposed.
Above all: know what you want to do with HDRI!
We will see that the HDR technique can produce very different from the same set of source images pictures. First of all, so you just need to know what you want to do!
There are roughly speaking two reasons that can motivate a photographer to make HDR:
Exceed the capacity of its digital camera to produce a photograph closer to the perceived vision and emotion felt by the human eye (sometimes called "photo-realistic" or TTHDR for "True Tone HDR")
Use the technique to create a surreal image typical "HDR Impressionist" or "texture extraction" close to a real painting or drawing
Here are two images produced from the same basic picture and the same picture without the use of HDR technique:
Depth of field: definition
The depth of field (PDC) is the area of space in which to find a topic that we can get an image that the human eye accepts as "net". It is bounded by the two extreme points where the image will be sharp.
Okay for the theory on the PDC, but in practice?
All this is nice, but what's the point? Again, it's very simple! When you take a photo, we do not always think, but there are two possibilities to us:
I take a landscape, or a close subject (animal, person ...) with a nice background: I rather like the subject and the background are clear both. For this, I will try to maximize the depth of field!
I take a close subject (portrait for example), and the background does not interest me, I want my subject looks sharp and stands a blurred background. I must then minimize the depth of field.
A picture is worth a thousand words ...
Here are two pictures taken with the same framing, playing only on the depth of field:
The first photo was taken in order to minimize the depth of field to emphasize the subject. The second image, however, was achieved by maximizing the depth of field.
How?
Ok, we now know the concept of depth of field, and its concrete manifestation in the image. Let us now proceed to obtain an image with shallow depth of field or on the contrary, a photo with great depth of field.
Aperture Priority
To play on the depth of field of a photo, we will use a setting that typically offer all cameras: the aperture.
To do this, we will use the Av mode (or A, depending on the aircraft), which will allow us to specify the opening of the diaphragm, while the camera will do the rest (for the curious, the "rest", c is the shutter speed!).
THE rule!
The rule, simple is as follows:
To maximize the depth of field, I chose a small aperture opening (it is often said "I shut up" ...).
To minimize the depth of field (have the background blur), I choose a wide aperture.
and ... THE trap!
Enough is enough. It was too easy! So there is a trap in there, you will require a little brain gymnastics, at least initially ...
Indeed, the aperture is expressed as a ratio, the "1 / x" style. However, the cameras do not show "1 / x", but "x". Mathematicians in the grass will include: to specify a large opening, I have to give a small x, and specify a small opening, I have to specify a large x. That's it!
Conclusion
To play on the depth of field, I select the Av mode (aperture priority), then I give a low value to minimize the depth of field, or a high value to maximize depth of field.
On your device, and keep this information in mind for your group photos (large depth of field so that everyone is net), photos of flowers (shallow depth of field so that the flower stands out from its background ) your portraits (ditto), your landscapes (great depth for all the plans are clear) ...
Questions about depth of field?
You have finished reading this mini-course on the depth of field, but you do not quite understand what it's all about or how to apply these tricks? You can come and talk and ask all the necessary questions on the forum of photographers, a thread devoted to it!
The depth of field (PDC) is the area of space in which to find a topic that we can get an image that the human eye accepts as "net". It is bounded by the two extreme points where the image will be sharp.
Okay for the theory on the PDC, but in practice?
All this is nice, but what's the point? Again, it's very simple! When you take a photo, we do not always think, but there are two possibilities to us:
I take a landscape, or a close subject (animal, person ...) with a nice background: I rather like the subject and the background are clear both. For this, I will try to maximize the depth of field!
I take a close subject (portrait for example), and the background does not interest me, I want my subject looks sharp and stands a blurred background. I must then minimize the depth of field.
A picture is worth a thousand words ...
Here are two pictures taken with the same framing, playing only on the depth of field:
The first photo was taken in order to minimize the depth of field to emphasize the subject. The second image, however, was achieved by maximizing the depth of field.
How?
Ok, we now know the concept of depth of field, and its concrete manifestation in the image. Let us now proceed to obtain an image with shallow depth of field or on the contrary, a photo with great depth of field.
Aperture Priority
To play on the depth of field of a photo, we will use a setting that typically offer all cameras: the aperture.
To do this, we will use the Av mode (or A, depending on the aircraft), which will allow us to specify the opening of the diaphragm, while the camera will do the rest (for the curious, the "rest", c is the shutter speed!).
THE rule!
The rule, simple is as follows:
To maximize the depth of field, I chose a small aperture opening (it is often said "I shut up" ...).
To minimize the depth of field (have the background blur), I choose a wide aperture.
and ... THE trap!
Enough is enough. It was too easy! So there is a trap in there, you will require a little brain gymnastics, at least initially ...
Indeed, the aperture is expressed as a ratio, the "1 / x" style. However, the cameras do not show "1 / x", but "x". Mathematicians in the grass will include: to specify a large opening, I have to give a small x, and specify a small opening, I have to specify a large x. That's it!
Conclusion
To play on the depth of field, I select the Av mode (aperture priority), then I give a low value to minimize the depth of field, or a high value to maximize depth of field.
On your device, and keep this information in mind for your group photos (large depth of field so that everyone is net), photos of flowers (shallow depth of field so that the flower stands out from its background ) your portraits (ditto), your landscapes (great depth for all the plans are clear) ...
Questions about depth of field?
You have finished reading this mini-course on the depth of field, but you do not quite understand what it's all about or how to apply these tricks? You can come and talk and ask all the necessary questions on the forum of photographers, a thread devoted to it!
Very often botched or overlooked, yet the composition has a fundamental role in the final result of your photograph: a well-composed photograph allows it to be "readable" and understandable, that a subject takes all its importance, to give meaning to a movement to beautify a landscape avoiding signage panel, etc..
Although no absolute rule makes faith in photography (and fortunately), there are a few simple tips that will help you make sure you fit! Your topics will be highlighted and attract the eye ...
The rule of thirds (or golden rule), the lines of force
The rule of thirds, also called golden rule is the rule of rules in picture ... Everyone knows it, few people respect. The principle is very simple: to fit well, always trying to put the subject of your photo (what you want the viewer to look first) on a strong point of the image.
The crossing points of the red lines are the highlights
s of the image. In most cases, place the main subject of the photo on one of these points is a good thing.
When we discover the digital camera with any less evolved DSLR or compact hybrid expert case, it is sometimes difficult to navigate. The functions are many, menus loaded settings play a lot of rendering images and early it is common to be completely lost. Do not panic, this is normal!
With a little method, patience and work, you can quickly move forward and take pictures of a good standard. The technique is not everything, and the desire and taste will help you a lot, but a minimum of training is essential to understand how your equipment works and to make the best.
Here are 12 subjects, lessons, tutorials to learn more and get started with your digital camera. Follow the guide!
- Start by learning the basic essentials of the photo
- Then Learn to use a flash
- If you do not have flash, learn how to set your camera for low light
- Train yourself to take pictures of children outside
- And take the opportunity to test the macro capabilities of your case on flowers and insects nearby
- If the weather is bad, practice taking pictures of objects inside
- Use creative lighting and photographing bottles
- The housings have a manual mode, try the long exposure photo
- If you love sports and action, learn how to make yarn for a dynamic rendering
- Look for the right location for your photos, the result will be much better
- Enhance your photos, learn to work in RAW
- Finally, make prints and learn to improve rendering
With a little method, patience and work, you can quickly move forward and take pictures of a good standard. The technique is not everything, and the desire and taste will help you a lot, but a minimum of training is essential to understand how your equipment works and to make the best.
Here are 12 subjects, lessons, tutorials to learn more and get started with your digital camera. Follow the guide!
- Start by learning the basic essentials of the photo
- Then Learn to use a flash
- If you do not have flash, learn how to set your camera for low light
- Train yourself to take pictures of children outside
- And take the opportunity to test the macro capabilities of your case on flowers and insects nearby
- If the weather is bad, practice taking pictures of objects inside
- Use creative lighting and photographing bottles
- The housings have a manual mode, try the long exposure photo
- If you love sports and action, learn how to make yarn for a dynamic rendering
- Look for the right location for your photos, the result will be much better
- Enhance your photos, learn to work in RAW
- Finally, make prints and learn to improve rendering
To fix his choice, there are a number of points, in addition to the price on which to consider:
Size, do you prefer a compact "jewels" or a full-size, bigger but can be
be better in hand.
The possible settings, the number of scenes mode, the manual settings, disabling and
specific flash settings.
Zooming, as a rule, are compact wide angle, ie their purpose allows
to shoot wide shots (landscapes, groups of people, etc.).
So the zoom level that will make the difference. It will be sure to check the amplitude of
Optical zoom (x10 x5 etc., the higher the number, the more you can shoot things
distant). Why focus on the optical zoom? Because it is a clever game with lentils
superimposed on each other within the lens that what we want to photograph far
seems very close. The magnification is mechanical, so there is no loss of image quality.
Digital zoom, it means that the unit will grow each point of the image artificially. such as
a magnifying glass. The picture taken with digital zoom so often present a pixelation effect ("noise").
In any case, if you want to buy your camera online, I suggest you go see
shop front. To go the fiddle, the weighing, the grind. See if the size is right for you, if you
well in hand, if the wheels are easy to access.
The race to the number of megapixels is not a selection criterion. From the moment you can print
no picture beyond 20x30 (A4), 6 megapixels is plenty.
Size, do you prefer a compact "jewels" or a full-size, bigger but can be
be better in hand.
The possible settings, the number of scenes mode, the manual settings, disabling and
specific flash settings.
Zooming, as a rule, are compact wide angle, ie their purpose allows
to shoot wide shots (landscapes, groups of people, etc.).
So the zoom level that will make the difference. It will be sure to check the amplitude of
Optical zoom (x10 x5 etc., the higher the number, the more you can shoot things
distant). Why focus on the optical zoom? Because it is a clever game with lentils
superimposed on each other within the lens that what we want to photograph far
seems very close. The magnification is mechanical, so there is no loss of image quality.
Digital zoom, it means that the unit will grow each point of the image artificially. such as
a magnifying glass. The picture taken with digital zoom so often present a pixelation effect ("noise").
In any case, if you want to buy your camera online, I suggest you go see
shop front. To go the fiddle, the weighing, the grind. See if the size is right for you, if you
well in hand, if the wheels are easy to access.
The race to the number of megapixels is not a selection criterion. From the moment you can print
no picture beyond 20x30 (A4), 6 megapixels is plenty.
A USER IS INTENDED If TYPE THE COMPACT?
The compact digital camera is for everyone. the
beginner to expert, through the amateur. Its main advantage
is its small size allows to keep in a pocket or
corner of the bag and take it everywhere and for always having
on itself.
Thanks to its small sensor, it is also ideal for the
Macro (photos taken from very close).
It is especially designed for beginners, who will appreciate its compactness, its
built-in flash and ease of use. Indeed, the models
basis there are usually few buttons and guaranteed automatic mode
successful picture in virtually all situations. it is
ideal for those who want to take pictures without worrying about
the art.
For amateurs, a little more sophisticated models offer
semi-automatic and / or manual menu to learn
gradually with the settings, without necessarily bridge,
the hybrid or reflex, much more cumbersome.
Finally, there is often much more expensive models for experts. They do not necessarily
superior image quality, but most importantly they emphasize the possibilities of manual settings
compared to automatic mode and therefore rarely modes "scene." They also allow
to get photos in RAW format that corresponds to the "raw sensor" image that the photographer
can then "develop" at will using specific software.
The compact digital camera is for everyone. the
beginner to expert, through the amateur. Its main advantage
is its small size allows to keep in a pocket or
corner of the bag and take it everywhere and for always having
on itself.
Thanks to its small sensor, it is also ideal for the
Macro (photos taken from very close).
It is especially designed for beginners, who will appreciate its compactness, its
built-in flash and ease of use. Indeed, the models
basis there are usually few buttons and guaranteed automatic mode
successful picture in virtually all situations. it is
ideal for those who want to take pictures without worrying about
the art.
For amateurs, a little more sophisticated models offer
semi-automatic and / or manual menu to learn
gradually with the settings, without necessarily bridge,
the hybrid or reflex, much more cumbersome.
Finally, there is often much more expensive models for experts. They do not necessarily
superior image quality, but most importantly they emphasize the possibilities of manual settings
compared to automatic mode and therefore rarely modes "scene." They also allow
to get photos in RAW format that corresponds to the "raw sensor" image that the photographer
can then "develop" at will using specific software.
If you want to develop in the digital photography beginners or if you want to have some photography tips for beginners photography. Digital photography, especially when using an SLR, is a whole new world. Here are some photography tips for beginners photography that I think will help get you going in the right direction.
Choose a camera
Choosing an SLR can be confusing. Sites and forums or companies like B & H Photo can help you choose the one that suits your specific use, whether personal or professional.
Learning the basics
There are a few basic rules of photography beginners that will help you get started on the path to success in digital photography. The first is to learn the relationship between aperture and exposure of the shutter speed. In digital photography, the aperture controls the size of the aperture and the shutter speed control the time the shutter is open. To get the right amount of light, it is necessary to control these parameters correctly. A wide opening with leaving open for a long time makes your picture too exposed to light and will be washed and colorless shutter. The reverse is also true. Using this guide, you will learn how to change these settings so that the right amount of light into the lens.
Practice, practice, practice
Once you have your camera and photography has taught beginners basics you need to get out and practice. This process can be long and frustrating, but stick with it and not give up! The more you practice, the more you will learn from them. Sites like digital photography school.com have forums where you can have your pictures and learn criticized suggestions from professional photographers.
Earn Money
Once you have the basics and practiced and received professional advice, use their digital photography skills to start earning extra income. Find websites, forums and other resources that allow you to use their newfound skills in photography for beginners to generate extra income on my website below. Even people with little knowledge of photography beginners can earn extra money by learning the fundamentals and practices
Choose a camera
Choosing an SLR can be confusing. Sites and forums or companies like B & H Photo can help you choose the one that suits your specific use, whether personal or professional.
Learning the basics
There are a few basic rules of photography beginners that will help you get started on the path to success in digital photography. The first is to learn the relationship between aperture and exposure of the shutter speed. In digital photography, the aperture controls the size of the aperture and the shutter speed control the time the shutter is open. To get the right amount of light, it is necessary to control these parameters correctly. A wide opening with leaving open for a long time makes your picture too exposed to light and will be washed and colorless shutter. The reverse is also true. Using this guide, you will learn how to change these settings so that the right amount of light into the lens.
Practice, practice, practice
Once you have your camera and photography has taught beginners basics you need to get out and practice. This process can be long and frustrating, but stick with it and not give up! The more you practice, the more you will learn from them. Sites like digital photography school.com have forums where you can have your pictures and learn criticized suggestions from professional photographers.
Earn Money
Once you have the basics and practiced and received professional advice, use their digital photography skills to start earning extra income. Find websites, forums and other resources that allow you to use their newfound skills in photography for beginners to generate extra income on my website below. Even people with little knowledge of photography beginners can earn extra money by learning the fundamentals and practices
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