Beginning photographers often wonder why they only have one person in focus in a photo with a group of people, while the rest are blurry. Or how to take a photo of a school class so that everyone is sharp in the photo. Actually, this requires experience and a lot of practice. But if there is still little practice, but you want to figure it out, then the depth of field calculator will come to the rescue.

The calculator is convenient to have at hand, so if you have a modern smartphone, then here are more options:

Correct free calculators for Android http://android.lospopadosos.com/dof

Correct paid calculator for iPhone http://www.neuwert-media.com/dof.html

The iPhone disappointed me the most because I was able to find the only calculator that worked correctly, and that for money. Although, Apple fans, as you know, do not count money and are charged for every sneeze. The peak of idiocy was calculators, where the depth of field depends on the crop factor, and you also have to pay for it! Hello, we have arrived...

In fact, I understand where these misconceptions come from. It is assumed that if you change the crop factor, then the angle of view changes, and therefore the composition of the frame. People who try to preserve the composition of the frame naively believe that the depth of field, which changes with this procedure, depends on the crop factor. What actually changes is the object distance s or the focal length f. It is incorrect to say that the depth of field depends on the crop factor, because it would mean that, all other things being equal, changing the crop factor, the depth of field should also change, and we have no other equals. The swindlers and swindlers who claim this change, along with the crop factor, either the distance to the object, or the focal length, or both. It is correct to conduct an experiment only from a tripod, using one FX camera, switching between FX and DX modes, but this is tantamount to cropping the photo at the edges. Obviously, the depth of field will not change.

Attentive readers have already noticed keyword“slightly blurred” a little higher and pricked up. Indeed, when viewing photos, sharpness is a subjective thing. Everyone perceives it in their own way. It makes no sense to measure depth to the nearest millimeter, unless we are talking about macro, of course. Do not try to go deep into the depth of field in pursuit of specifications, as you will simply be sucked into the fractal of details and you will get even more confused.

The decision on whether the depth of field is sufficient or not must be made quickly and emotionally, otherwise it will turn out like in the well-known case with a patient who underwent surgery in the region of the frontal lobes: http://olegart.ru/wordpress/2011/07/05/3413 / By the way, this also applies to the choice of photographic equipment in general, the choice of which turned out to be the most difficult for the human brain:

Four windows can be opened in the program.

The program can be used as a simple calculator. In this case, use the arrows above and below the values ​​of the focal length, aperture value and the permissible circle of confusion, select the necessary parameters, use the arrows at the bottom of the window to select the distance at which the focus object is located, and read the value of the foreground and background. The bottom line shows in red the position before infinity and the foreground position when focusing at hyperfocal distance. The program allows you to graphically present the results. So, the focus point is marked by a green man on the road. Depth of field can be judged by which trees are sharply depicted on the side of the road. If the background is at infinity, the mountains on the horizon become visible. The distance can be changed by dragging the little man along the road. If the distance becomes less than 1 m, then a window opens that shows the value of the depth of field, the position of sharp plans relative to the flower, which can also be dragged around the screen. The red flag on the road marks the hyperfocal distance, the red stripe on the road marks the boundary of the sharply recorded foreground when aiming at it. This part of the program has not changed since the very first version. The calculation is carried out in accordance with the formulas below, which give an unambiguous result if the focal length, aperture and circle of confusion are set. All changes in the program are associated with additional reference information that facilitates the selection of an acceptable circle of confusion. This part does not serve to obtain an exact number, but for a rough estimate and a better understanding of the criteria that determine the choice of an acceptable circle of confusion. In the latest version of the program, a window has been added that allows you to evaluate the angle of the field of view and the size of objects that fall into the frame. The horizontal angle of view is displayed, indicated as hfov, and vertical, denoted as vfov. The angles are calculated for the frame, the size of which is displayed in red in the upper right corner of the screen. The display of angles and the expected picture on the screen can be turned off by clicking on the camera screen in the lower left corner of the screen. The angle of view is useful when shooting panoramas to estimate the required number of frames for a given focal length and sensor size. In addition, this parameter seems to me much more reasonable than the reduced focal length that is often used instead. Today, when the percentage of people with film experience SLR cameras with a set of lenses with different focal lengths is negligible compared to the shooting public, this does not make life easier for experienced photographers and misleads beginners, since it has nothing to do with the concept of focal length adopted in optics, and determines not the distance from the lens to the point at which the parallel beam converges, and the angle at which the object occupying the entire frame is visible. The calculation of angles in the program is made for normal (rectilinear) lenses and cannot be applied to fisheye lenses. The focal length in the program can be changed to unrealistic values ​​for some combinations of a normal lens + matrix, and, therefore, the picture that displays the expected image on the camera screen will also be unrealistic :-) So, a normal lens with a focal length of 15 when working with a 36x24 frame mm gives a horizontal angle of view of 100 degrees, and a fisheye lens with the same focal length is already 140 degrees. For more information about the difference in the angle of view of lenses of different designs, see the article "Ultra wide-angle lens Mir-47".

The assessment of the acceptable circle of confusion is carried out after clicking on the question mark in the upper right corner. To get the correct value, you must make a choice in the upper and one of the two lower drop-down menus. The top menu is used to set the frame size, the next menu allows you to set the number of pixels in the matrix, or the AgBr item, which implies the use of an average film with a relatively good lens. If you select a frame size of 36x24 mm in the top menu and AgBr in the next menu, the program will give values ​​close to those printed on the lens barrel. The bottommost drop-down menu allows you to set the desired print size. It's a good idea to use it if your camera has some pixel headroom, but you don't intend to print large prints. In this case, the evaluation is made from the printing condition, for example, on a sublimation printer with a resolution of 300 dpi. This is close to what the eye can see from the best vision distance of 25 cm. In the second window, in this case, the number of megapixels of the matrix, the size of two pixels of which is equal to the calculated circle of confusion, will be displayed.

I recommend taking a series of test shots of the world in order to determine the experimentally acceptable scatter circle for your apparatus. It is very likely that it will be determined by the capabilities of the lens, and not the matrix.

In the program, in addition to the allowable focus circle, the value of the linear resolution limit (dp) is also displayed. If the linear limit of resolution exceeds the specified size of the allowable focus circle d, then the background under the aperture values ​​of the allowable focus circle and the linear limit of resolution will turn pink. In this case, to get real values, you need to change either the aperture or the allowable focus circle.

1. Focal length
2. Diaphragm
3. Permissible circle of confusion
4. Linear resolution limit
5. Frame size
6. The number of pixels in the matrix
7. Print size
8. Distance
9. Foreground and background position
10. hyperfocal distance
11. Foreground position when focusing at hyperfocal distance

The program can be used without leaving this article, it can be written separately and run using Macromedia Flash Player or through a browser by running the rezkost.html file. The latest version of the program, when run on a local machine, allows you to edit the start values. To do this, edit the datarzk.txt file. For the matrix, you can set values ​​that are not available from the program menu, they will be valid until you enter new ones in the menu. Recording formats:

dn6=0.016&fn=35&dnr1=24&wc=3&hc=2&mp=9&
or
fn=35&dnr1=24&wc=3&hc=2&mp=9&

Where fn=35&- means that the initial focal length is 35 mm, and dn6=0.016&, that the allowable circle of confusion is 16 µm. This value of the circle of confusion is valid until the button with the question mark is pressed. After entering the menu for assessing the acceptable circle of confusion, priority will be given to the parameters set in this menu. If the allowable circle of confusion is not set, then it is calculated from the number of sensitive elements in the matrix, set in Mp. dnr1=24&- the size of the long side of the frame is 24 mm, wc=3&hc=2&- the ratio of the sides of the frame in this case is 3:2, mp=9&- the number of sensitive elements in the matrix is ​​9 megapixels.

Using a PDA imposes certain limitations due to the fact that you do not have the right mouse button, and the fact that the computer learns about the position of the cursor only when the pen touches the screen. It is not able to distinguish between the presence of the pen over the button and the actual pressing of the button, so it may be necessary to make an extra press when moving from one button to another.

The program uses the Latin font, since this allows, firstly, to use the PDA fonts without problems and not waste space on embedding the lettering in the program file, and secondly, I could not find a small Cyrillic font that would be clearly readable on PDA.

Theory and practice

The depth of field is calculated according to fairly simple formulas, however, it is not always convenient to do calculations during the shooting process; during the calculations, the bee may fly away. ; ; where p is the distance between the image plane and the pointing plane, A is the relative aperture, f is the focal length, d is the allowable circle of scattering, p 1 is the foreground position, p 2 is the background position.

The photographic resolution of a photographic lens is characterized by the number of parallel strokes (lines) that this lens can reproduce on a piece of photographic material 1 mm long. The resolution of the photographic material is determined in the same way. The linear resolution of a photographic lens is the reciprocal of the resolution in lines. To estimate the resolving power of the photo lens, taking into account the resolving power of the photo layer, the linear resolutions of the lens and the photo layer should be summed. To determine the depth of the sharply depicted space of objects, the permissible defocusing circle must correspond to the sum of the linear resolutions of the lens and the photo layer. However, no matter how well we focus on the object, and no matter how high the resolution of the lens is, the maximum resolution of the optical system to image two closely spaced points separately is limited by diffraction at the boundary of the pupil. According to the diffraction theory, a luminous point due to diffraction on the diaphragm is depicted as a circle of scattering. This circle consists of a bright central core, which is called the Airy circle, and dark and light rings surrounding it. Rayleigh concluded that two equally bright points are visible separately if the center of the Airy circle of one point coincides with the first minimum of the second point. It follows from the Rayleigh criterion that the resolution of an ideal photographic lens when using a world of absolute contrast and illuminated with monochrome light depends only on the ratio of the focal length to the diameter of the pupil, that is, on the aperture value. And the linear resolution limit of the optical system is: where K is the aperture value, f is the focal length, lambda is the wavelength. At a wavelength of 546 nm, we get a value equal to K/1500 for the linear resolution limit.

With regard to the matrix of a digital camera, it can be considered that 2 lines will be distinguishable if the diameter of the focusing circle is less than the linear size of the two sensitive elements. In this case, if the image of 2 white lines is drawn exactly to the centers of two non-adjacent sensitive elements, then the signal on them will be maximum, while in the element located between them, it will be minimal. Of course, the slightest shift of the image relative to the matrix will lead to the fact that we will not be able to distinguish the lines. If the strokes of the test object go at a certain angle to the columns of sensitive elements, then, examining the image line by line, you can see alternating solid and dotted lines. It turns out a structure resembling a moiré fabric.

My measurements of the lens + matrix system show that the real resolution is one and a half times worse than the maximum theoretical resolution for one matrix, and to obtain a linear resolution, the size of two sensitive cells must be multiplied by 1.6.

When shooting landscapes, knowing the hyperfocal distance, or the beginning of infinity, is very important. These terms denote the distance to the subject, when focusing on which the background is sharp at infinity. If we set the hyperfocal distance on the scale of the apparatus, then the background will lie at infinity, and the foreground will be twice as close to the focus point. If we point the camera at infinity, then the foreground will coincide with the hyperfocal distance. That. pointing the camera not at infinity, but at a hyperfocal distance, we bring the boundary of the sharp foreground twice as close.

For orientation in the permissible circles of scattering, the table below gives the characteristic values ​​of the linear resolution limits of typical lenses, films and matrices.

On good film, up to 100 lines per mm can be distinguished. Good lenses for 35mm film cameras have a center resolution of 40-60 lines per mm. To estimate the resolution of the lens + film system, the linear resolution limits for film and lens are added, i.e. in a typical case, about 50 lines per mm can be registered. Those. the allowable focus circle for this system is 20 microns.

Lenses designed for manual focus are usually marked with a depth of field scale. Using the program, it is easy to solve the inverse problem and determine the acceptable circle of confusion, which was taken to calculate the scale.

The sharpness scale on the Volna -3 lens for the Kyiv 88 camera with F = 80 mm. The scale is applied on the basis that the permissible circle of confusion is approximately 65 microns.



Depth of field table on a Welta camera with a Xenon F=50 mm lens. The table is compiled on the basis that the permissible circle of confusion is approximately 40 microns.

I analyzed the scales on the rest of my lenses, and this is what I came up with:

As we see in most cases, the scale is built on the assumption that the result will be a print of 10x15 cm. The largest variation in the size of the circle of confusion is observed for medium format camera lenses. That. if we want to get the most out of the film and the lens, then we should take into account that the depth of field will be less than the range indicated on the lens. Download latest version

License agreement

Now it is customary to precede any program with a license agreement. Following the spirit of the time, I did it in 2001 too. Summarizing someone else's experience of writing such a document, I came to the conclusion that it all boils down to the following statement:

Dear user, eat well.
If you choke, then you are an idiot.
If you feed others, forgetting about the cook, then get ready for a confrontation with Kuz'kin's mother.

This license agreement applies to all executable modules of the program. The latest version 2.1 can also be downloaded with source codes, in which case I found it necessary to change my wishes for its use and, therefore, the license agreement. The Free Software Foundation has done a great job of polishing the language, and I decided to take advantage of their work. This program is distributed under the same license as .

I'll try to explain why I didn't just use the GNU GPL license.

1) My understanding of the conditions put forward should be maximum. Obviously, this should be done in the native language, regardless of the level of foreign language proficiency and trust in the translator. Most people know their native language better than a foreign one, and they trust themselves more than any other :-).

2) The preface to the translation says:
"This Russian translation of the GNU General Public License is not official. It is not published by the Free Software Foundation and does not establish legally binding terms for redistributing software that is distributed under the terms of the GNU General Public License. The legally binding terms are set forth solely in authentic text of the GNU General Public License in English."

However, in my understanding, the hierarchy of conditions that determine the activity of the Internet is based first on and only then on all documents that do not contradict it.

The declaration reads:
"Governments derive their powers from the consent of the governed. You didn't ask for it, and you didn't get it from us. We didn't invite you. You don't know us, you don't know our world. Cyberspace is not within your borders. Don't think you can build it." as if it were a community building project.You can't do that.It's a natural phenomenon and it grows on its own through our collective actions.

You did not participate in our huge and growing dialogue, you did not create the wealth of our market. You do not know our culture, our ethics, our unwritten laws, which already provide more order to our society than could be obtained from any of your prescriptions.

You claim that we have problems that you must solve. You are using this claim as an excuse to invade our domain. Many of these problems simply do not exist. Where there are real conflicts, where there are offenses, we will identify them by applying our own funds. We form our own Social Contract. This leadership will arise according to the conditions of our world, not yours. Our world is different."

Thus, the question of legal force is eliminated. By violating my wishes expressed in this license, you are making an enemy. You cannot know what is essential and what is not, and what reaction will follow. You just need to follow the letter of the license or be prepared for what will follow, perhaps not an adequate reaction in your understanding. People are different - some live with the slogan Freedom or death, others are ready to agree to shmon at the airport for the sake of illusory security. As Benjamin Franklin, one of the creators of American nationhood, wrote: He who sacrifices freedom for the sake of security deserves neither freedom nor security. It seems that his descendants did not heed his precepts, and it is not worth idealizing modern American legislation and following it, distributing a license in English with the program.

• Version 2.1 for desktop -(rezk21f1.html, rezk21f1.swf, datarzk.txt)
• Version 2.1 with sources - Zip archive, including five files(rezk21f1.html, rezk21f1.swf, rezk21f1.fla, datarzk.txt, GPL russian translation.htm)
• Version 1.19 for older PDAs - Zip archive including three files(rezk19f4.html, rezk19f4.swf, datarzk.txt)

Version 2.1 dated September 9, 2009

Added reference ability to display the angle of the field of view and the size of the object that enters the frame in the plane of focus. The number of start parameters specified in the datarzk.txt file has been increased. Slightly optimized code.

The program is distributed for the first time along with source codes. The reason for this step, in the first place, is that I am gradually completely refusing to use the Windows family of operating systems in my work. And support for flash technology under Linux does not allow to continue its development, so if someone decides to improve or supplement the program, then the flag is in his hands. The Flash4linux program does not currently allow you to open and edit the text of this program. To work and modernize it, you probably need to purchase an Adobe software package and work under Windows, which is not included in my immediate plans.

Version 1.9 dated September 15, 2007

Fixed some issues related to the display when working for a long time without rebooting. The list of matrices for choosing a valid circle of scattering has been replenished. This version of the program, when run on a local machine, allows you to edit the starting values ​​of the focal length and the allowable scatter circle. To do this, edit the datarzk.txt file.

Version 1.5 dated January 11, 2005

Version 1.4 dated November 27, 2004

The starting values ​​of the allowable scatter circle, focal length and aperture have been changed.

Added the ability to estimate the allowable circle of scattering by the size of the matrix and the number of pixels, or the desired print size, assuming that printing takes place on a sublimation printer or photographic paper with a resolution of 12 dots per mm. The assessment of the acceptable circle of confusion is carried out after clicking on the question mark in the upper right corner. To get the correct value, you must make a choice in the upper and one of the two lower drop-down menus. The top menu is used to set the frame size, the next menu allows you to set the number of pixels in the matrix, or the AgBr item, which implies the use of an average film with a relatively good lens. If you select a frame size of 36x24 mm in the top menu and AgBr in the next menu, then the program will give values ​​close to those printed on the frame of Industar type lenses. The bottommost drop-down menu allows you to set the desired print size. It's a good idea to use it if your camera has some pixel headroom, but you don't intend to print large prints.

The version assumes the use of Flash Player 6.

Version 1.01 dated November 13, 2001

In order to install the program on a PDA, it is enough to unpack the archive and place its contents (two files, html and swf) into an arbitrary directory of the PDA. "Fit to Screen" must be selected in the Microsoft Internet Explorer preferences. This choice takes effect after the page is reloaded. When tested on the Cassiopeia E-125, it turned out that although the processor with a clock speed of 150 MHz seemed to be quite powerful, however, graphics processing caused significant delays. The PDA video system does not like translucent areas and the need to constantly recalculate the picture. Of course, not only the computer is to blame here, but also the Flash interpreter.

DOF and hyperfocal distance are some of the basic concepts that a beginner photographer needs to grasp. Let's sort it out in order - what it is and what it is used for in photography.

IPIG is an abbreviation for the words Depth of Field, she is Depth of field. In English, the abbreviation IPIG will be called Depth of Field or DOP. This is the region of space, or the distance between the near and far borders, where objects will be perceived as sharp.

Strictly speaking, ideal sharpness, from the point of view of physics, can only be in one plane. Where, then, does this region come from? The fact is that the human eye, despite all its perfection, is still not an ideal optical system. We do not notice a slight blurring of the image up to some limits. It is generally accepted that the human eye does not notice the blurring of a point up to 0.1 mm from a distance of 0.25 m. All calculations of the depth of field are based on this. In photography, this slight blurring of a point is called circle of confusion. In most calculation methods, the diameter of the circle of confusion is taken to be 0.03 mm.

Based on the assumption that the human eye does not notice some blurring, we will no longer have a plane of sharpness in space (called the focal plane), but some area that is limited by the allowable blurring of objects. This area will be called the depth of field.

What determines the depth of field

Only two parameters influence the depth of the sharply depicted space:

1. Lens focal length
2. Aperture value

How more focal length of the lens less depth of field. How wider aperture is open (smaller f-number), the less depth of field. Simply put, in order to get the greatest possible depth of field, you need to use a wide-angle lens and cover the aperture as much as possible, making its aperture smaller. Conversely, to obtain a minimum depth of field, it is desirable to use a telephoto lens and a wide open aperture.

In some sources, and positioned as very authoritative, one can come across the statement that the size of the matrix or film frame also affects the depth of field. Actually it is not. By itself, the size of the matrix or the crop factor does not have any effect on the depth of field. But why then the depth of field compact cameras with a small matrix size is much larger than SLR cameras with a large sensor? Because as the size of the sensor decreases, the focal length of the lens required to obtain the same angle of view also decreases! And the smaller the focal length, the greater the depth of field.

Depth of field also depends on the distance to the subject - the closer to the lens, the shallower the depth of field, and the blurring of the background is more pronounced.

How depth of field is used

The choice of the optimal depth of field depends on the shooting tasks. The most common mistake made by beginner photographers who have recently purchased a fast lens is to shoot everything as wide as possible. Sometimes it's good, sometimes it's not. For example, if you are shooting a portrait from too shallow depth sharpness, it may well turn out that the eyes are sharp, but the tip of the nose is not. Is it beautiful? The question is moot. If the person's head is turned to the side, then the near eye may be sharp, and the far eye may be blurry. This is perfectly acceptable, but a client who does not know what depth of field is may have certain questions.

Therefore, in order to obtain the optimal depth of field in portrait photography, you do not need to strive to always open the aperture. For most cases, it is better to cover it by a couple of steps. Then the background will be pleasantly blurred, and the depth of field is acceptable. When shooting group portraits, it is especially important to ensure that the depth of field is such that all people turn out sharp. The aperture in this case is covered more, up to f / 8 - f / 11 when shooting outdoors and in good lighting.

hyperfocal distance

What if we need, for example, to photograph a landscape where foreground and background objects should be equally sharp? This is where the ability to use hyperfocal distance. This is the distance to the front of the field of view when the lens is focused to infinity. In other words, this is the same depth of field, but when focusing on infinity.

Depending on where it is more important to get maximum sharpness - in the foreground or at the most distant objects, they focus either at hyperfocal distance or at infinity. In the first case, foreground details will be sharper, in the second - distant objects. Hyperfocal distance also depends on the focal length of the lens and aperture. The more the aperture is closed and the shorter the focal length of the lens, the smaller the hyperfocal distance.

This image is sharp both foreground and background.

Calculation of depth of field and hyperfocal distance

To calculate the length of the depth of field and hyperfocal distance, special tables are usually used. But I recommend using more modern way, namely, a specialized program . It works online right in the browser. The program is very easy to use and easy to figure out on your own. And most importantly, what will help you choose the right depth of field and hyperfocal distance is constant conscious practice!

DOF (depth of field) calculators are one of the most popular types of software designed to provide the photographer with specific information about shooting parameters and make it easier to get high-quality images. There are a lot of different implementations of depth of field calculators on the Internet, but the one created by Polish photographer and programmer Michael Bemowski is without a doubt one of the best.

The Bemowski Calculator has many settings, adjustable parameters, fixed presets and saved configurations. It not only calculates the parameters in numerical form, but also visualizes the results in a visual form.

First of all, you can set specific shooting parameters - lens focal length and sensor size, aperture, distance to the subject and to the background. By the way, these same object and background are also customizable - they are selected from several proposed options.

As you play with the shooting settings, the visualization (image in the window on the right) works out in real time all the changes you make.

Even background blur (bokeh) is simulated, the degree of this blur corresponds to the parameters entered (and calculated) at the moment.

At the bottom of the page is the actual depth of field calculator, which calculates the location and depth of the field of field and presents the results in a visual way.

If you accessed the site from a mobile phone, pressing the button in the upper left corner will change the interface to the "mobile" version. The application does not require a connection to the server to work, so the author also offers an offline version that you can download to your computer. The whole project is completely free, based on advertising and donations.

In our opinion, the calculator has not only (and even not so much) serious practical value, but, first of all, educational. We recommend that novice photographers play thoughtfully with the settings, and maybe return to this lesson more than once in order to better understand and feel - which lens should be taken, what aperture should be set, whether to approach the object closer or farther - in order to get the desired result, as with DOF and bokeh points of view, as well as the ratio of the scales of the object and the background.

The Depth of Field (DOF) Calculator is a useful photographic tool for estimating what camera settings are needed to achieve the desired degree of sharpness. This calculator is more flexible than the one given in the Depth of Field chapter, as the calculation parameters include viewing distance, print size, and visual power - giving you more control over what is considered "acceptably sharp" (the maximum size of the circle of confusion allowed).

To calculate the depth of field, you first need to set the appropriate value for the maximum diameter of the circle of confusion (KH). Most calculators assume that for a 20x25 cm print viewed from a distance of 25 cm, it is enough to keep details down to 0.025 mm (0.01 inch) to obtain acceptable clarity. This approach is often not a correct description of acceptable clarity, so this calculator allows you to specify other viewing options (although it adheres to this standard by default).

Using the calculator

rising viewing distance it is more difficult for our eyes to distinguish fine details in the print, and thus the depth of field increases (along with the diameter of the KH). On the contrary, our eyes can see more detail when magnified. printed size, and accordingly, the depth of field decreases. A photo intended for close viewing in a large size (for example, in a gallery) will most likely have a more rigid technical framework than a similar image intended for a postcard or large billboard on the side of the road.

People with perfect vision capable of recognizing details about 1/3 of the size set by lens manufacturers as the KH standard (0.025 mm for a 20x25 cm print viewed from 25 cm). Accordingly, changing the parameter " vision” has a significant effect on the depth of field. On the other hand, even if you can see KN with your eyes, the image can still be perceived as "acceptably sharp". This calculation can only serve as a rough estimate of the conditions under which details can no longer be discerned by our eyes.

Camera type determines the frame size of your film or digital sensor, and accordingly how much the original image must be enlarged to reach the specified print size. Larger sensors can usually allow larger diameter HFs because they don't require as much magnification in image size, but they require longer focal lengths to achieve the same field of view. Check your camera manufacturer's manual or website if you're unsure which camera type to choose from.

Lens focal length corresponds to the number of mm indicated on your camera, NOT the "effective" (true) focal length (calculated in 35mm camera equivalent) that is sometimes used. Most compact digital cameras use zoom lenses with focal lengths ranging from 6-7mm to about 30mm (often marked on the front of the camera on the lens side). If you are using a value outside this range for a compact digital camera, it is most likely incorrect. DSLRs are easier in this regard, as most of them use standard 35mm lenses that have a clearly marked focal length, but don't try to multiply the value printed on the lens by your camera's crop factor. If the picture has already been taken, almost all digital cameras write the actual focal length to the EXIF ​​data in the snapshot file.

On practice

You should not be attached to all these figures when shooting. I'm not recommending calculating DOF for each image, but rather suggesting that you get a visual representation of how aperture and focus distance affect the resulting image. You can get it only by getting up from your computer and experimenting with the camera. Once you have mastered the subject, you can use the DOF calculator to improve the quality of carefully selected landscape and landscape scenes or, say, macro photography in low light where range of sharpness is critical.