Photos

Inaccurate auto focus (with all lenses).
Slight chroma noise in light shadows, even when the environmental light is very good for photography.
Lots of noise at high ISO (beyond 400).
Inconsistent metering. The camera's metering system is easily fooled in bright light. It's quite common to get underexposure up to 1 stop.

Editing flow

It is essential to follow the same editing flow in order to get consistently good photos.

Make sure you put your name in the camera's settings, so that all the photos can have a known author.

Take photos in raw format! Taking photos in raw format and then adjusting them on a computer, compared to taking photos in JPEG, is as different as day from night.

From Lightroom, import the photos from the photocamera to a "Originals" directory, in a subdirectory named "YYYYMMDD", where "YYYYMMDD" is the date when the photo was taken. Name the files "YYYYMMDD_index".

Look (several times) through the photos and delete the bad ones and the redundant ones. Try to keep maximum 200 photos from a day's work in order to minimizes both the space taken by the photos and the time required to edit them. (Instead of Lightroom, you can use IrfanView because it loads the preview JPEGs from the RAWs, which is very fast).

Edit the photos: exposure compensation, black level, white balance (= color temperature and tint), sigma contrast (= the curves), sharpness, noise reduction, vibrancy (or saturation), crop, selective color correction, heal skin defects.

Rate the photos and tag them with keywords. Here are some examples of keywords: "Animals", "Landscape", "Making of photoshoot", "Models", "Objects", "People", "Print", "Vegetation", "Website"; some of them may have sub-keywords.

Export the photos in JPEG format to a "Exported" directory. Do not resize them and use ProPhotoRGB (if your display doesn't have a large gamut, use sRGB) and quality 90. (IrfanView can show color-managed photos.)

Export some of the photos in JPEG format to a "Print" directory. Do not resize them and use sRGB (printer have a much smaller gamut than displays) and quality 100. Print the photos on A4 paper.

Export some of the photos in JPEG format to a "Website" directory. Resize them (within 900 * 900) and use sRGB (because it's standard for the web) and quality 80.

Parameters

As a starting point, for outdoor daylight photos I use the default editor settings with the following changes:

Working color space: ProPhoto RGB.
Black level: 5.
Sigma contrast (from curves): Strong.
Sharpness: 50.
Luminance noise reduction: 20.

As the noise from the photos increases (usually because a high ISO was used), increase the chrominance and luminance noise reduction.

Display calibration

It is crucial to calibrate the display on which you'll see and edit your photos, in the environmental light that you are going to use, at the preferred display brightness.

Turn on your display with at least 30 minutes before you try to calibrate it.

The illumination from your room (at display level, non-incident) should be 40 lux and have 5'000 kelvin.

Change your display's settings by using its control menu: brightness = 100 cd / m2, color temperature = 6'500 kelvin, gamma = 2.2.

With current technology, a display can't show all the tonal range that a printed photo can at a given brightness. Therefore, the brightness of the display must be set much higher.

If possible, calibrate your display with a calibrating device. Hardware calibration will not make your display better, it just makes it display images according to a colorimetric standard, in the limits of its hardware capabilities.

Set the calibration target to D65 (color temperature = 6'500 kelvin, gamma = 2.2).

Printing

Do the printing on a photo printer.

A home printer provides all the necessary image quality, when the printing is performed at the maximum quality and with consumables (= paper and ink) of the highest quality. Disable all forms of photo processing within the printer software.

I prefer to use a folder with a ring binder as a photo album, even though I have to perforate each photo by hand, because:

The photos are not covered by anything when you view them.
Photos can be grouped in categories because photos made later can be easily inserted anywhere in between.
It's faster than sticking photos to an album's pages, and it doesn't waste the paper used for the album's pages.
The photos can be easily moved to a more appropriate album (like a thicker one).

Printing the photos with a border minimizes the effect of the perforations and of the fingers (used to hold the photos while flipping them).

The advantages of my home printer are:

Better color match to my display.
Immediate results (I don't have to go out to print).

The disadvantages of my home printer are:

The ink is sticky and that's a real fingerprint magnet. The photos have to be kept to dry in a covered place, so that dust would not stick to the fresh ink.

The advantages of a photo-developing machine are:

Many paper sizes.
The paper can be glossy or matte.
About 3 times cheaper than my home printer (for the same size).
Outputs photos 10 times faster than my printer.
The photos are safe to touch immediately.

The disadvantages of a photo-developing machine are:

Difficult to find one which outputs proper colors, and sometimes the results are not reproducible.

Because of the price, I prefer to output my photos on a photo-developing machine.

Knowledge

Exposure = The capturing of the light which goes through the lens, by the camera's sensor.

Exposure time (measured in seconds) = The time during which the camera sensor captures light.

Focal length (measured in millimeters) = The distance from the lens at which the image is formed. Increasing the focal length of the lens has a zoom-in effect, that is, it exposes the camera sensor to a smaller part of the subject.

Diaphragm = A circular mechanical device (in the camera) which controls the aperture of the lens.

F-number = The focal length of the lens divided by the diameter of the central circular opening of the diaphragm. A fast lens means a small F-number.

The amount of light which (goes through the lens and) illuminates the camera's sensor is inversely proportional with square of the F-number. You may be tempted to think that the amount of light should be proportional with the surface of the opening through which light enters through the lens, but it's not so.

Aperture (measured in millimeters) = The diameter of the central circular (really more of an octagon) opening of the diaphragm. The aperture of a lens is equal with the focal length of the lens divided by the F-number. A fast / wide aperture means a large aperture. A fast / wide / large aperture means a small F-number.

Shutter = A mechanical device (in the camera) which controls the time of the exposure of the camera's sensor to the light which goes through the lens.

Shutter speed (measured in exposures / second) = The inverse of the exposure time. A fast shutter speed means a small exposure time.

Stop = A doubling or halving of the amount of light which goes through the lens.

Stop up = A doubling of the amount of light which goes through the lens. This is equivalent with a halving of the shutter speed (because this means that the camera's sensor is exposed to more light), and with an increase of the aperture of 1.4 times (it's actually square root of 2).

Stop down = A halving of the amount of light which goes through the lens. This is equivalent with a doubling of the shutter speed (because this means that the camera's sensor is exposed to less light), and with a decrease of the aperture of 1.4 times (it's actually square root of 2).

In general, cameras display their shutter speed and F-numbers in (approximations of) thirds (or halves) of units in order to make it easier for the photographer to manually control the exposure, that is, to know how much the camera would expose an image.

Exposure compensation = A parameter which tells the camera how to adjust the exposure in a semi-manual mode (like "Aperture Priority"). If the taken image is too dark then set the exposure compensation to a positive value, and if the taken image is too bright then set the exposure compensation to a negative value.

Focus = The state in which the subject of a photo has maximum clarity / sharpness.

Autofocus = The automatic focusing process achieved by the camera and the lens. The precision of the autofocus is not constant and this is one of the factors which, at least in certain conditions, may turn photos into mere snapshots.

The autofocus is performed at a lenses physical aperture (for the current focal length), not at the F-number that you've set, which is very important in low light for focus speed and accuracy. Some autofocus sensors become active only if the F-number is smaller than a given value (like F2.8 for the center cross-type sensor).

Unit area = an absolute measurement unit for areas, like a square millimeter.

Circle of confusion (COC) = The amount of blur above which a person finds that the objects from a photo do not look sharp anymore.

The COC is in fact highly variable because it depends on the type of the viewed photo (on screen, printed or developed), on the size of the photo (which is normally 10...30 centimeters), on the viewing distance (which is normally 20...60 centimeters), and on visual acuity of the viewer.

Crop factor = The ratio of the diagonals of a reference camera sensor (36 * 24 mm, 43 mm diagonal, called full frame sensor) and a compared sensor; this number is normally higher than 1. Basically, a cropped sensor is a sensor which is smaller than the reference sensor, that is, it "sees" a smaller part of a subject; the margins of the frame are cut out from the photo.

The surface of a cropped sensor is inversely proportional with the square of the crop factor. For example, Canon EOS 40D has a crop factor of 1.6 and a surface 2.56 times smaller than the reference sensor.

Zoom = The ratio between two focal lengths. An increase of the focal length of a lens results in a decrease of its angle of view, which means that a smaller part of the subject is exposed to the camera sensor, which means that the subject is zoomed-in (that is, its size is increased on the sensor). A camera's crop factor doesn't affect the zoom.

Magnification = The ratio between the size a subject projected on a camera's sensor and its real size. Macro lenses typically have a magnification of 1, that is, a subject 10 millimeters tall also has 10 millimeters on the sensor; in such a case, if the sensor is 25 millimeters tall, the subject takes 40% of the photo's height.

Subject magnification = The percentage of a subject from the total photo height / width.

If a person is photographed with a camera sensor of a given size and a given focal length, and then with another camera with a larger sensor and the same focal length, the subject looks smaller in the second photo because the larger sensor literally has more sensor space around the smaller sensor.

In order to have the same subject magnification in the two photos, the second photo has to be taken either from a smaller distance or with a longer focal length; the proportion is equal with the crop factor between the two sensors (= the width / height / diagonal of the larger sensor divided with the width / height / diagonal of the smaller sensor).

Gamut = A subset of the entire range of colors perceivable by the average human eye.

When you hear that some display is able to show millions or billions of colors, that does not refer generally to the "amount" (= gamut) of colors which can be shown, but refers to the detail of the shown colors (which has little relevance because from some point the eye can't perceive the difference).

Color / white balance = The real color of objects, as seen by the human eye or photocameras, depends on the color of the light which reaches them. Color balance in general, and white balance in particular, refers to the adjustment of colors so that the colors from a photo look similar to those seen by the eye in normal daylight conditions.

Color balance is crucial for indoors photos, photos which have a color cast from the incandescent or fluorescent light bulbs.

Dynamic range (measured in stops) = The ratio between the brightest and darkest spots captured by a camera sensor, where detail is still visible in the resulting RAW image; this may be expressed on a logarithmic scale. For example, the dynamic range of a sensor can be 12 stops, which means a 2048 (= 2 ^ 12) ratio.

Tonal range = The number of tones which show detail throughout the dynamic range; this may be expressed on a logarithmic scale. For example, the tonal range of a camera sensor can be 14 bits, which means 16384 (= 2 ^ 14) intervals.

Noise = Random alteration of image information. The main reason why bigger camera sensors yield cleaner images is that for the same exposure (and subject magnification) they capture more light.

Depth of field

The depth of field (DOF, or depth of field of clarity) is the distance range in which the subject of a photo appears in focus.

The depth of field:

Grows with the distance to the subject.
Grows with the F-number. Shrinks with the aperture.
Shrinks with the focal length.

The depth of field beyond the subject is always greater than the depth of field in front of the subject.

The closer the camera is to the subject (in focus) and the farther the background is from the subject, the more the subject "pops" out from the image.

Use a high aperture (= small F-number) and a long focal length in order to blur the background and create a beautiful closeup (like a portrait). Use a low aperture (= high F-number) in order bring the entire range from the foreground to the background into focus.

The depth of field is very important for closeups because it can be responsible for a beautifully blurred background (which is called bokeh).

Angle of view

The angle of view is the angular extent visible in a photographed scene. The angle of view decreases as the focal length of a lens and the crop factor of a camera increase.

A photocamera (like the human eye) sees a scene in a conic manner, that is, the observed objects are within a cone which starts as a point at the lens (/ eye) and ends at infinity as a huge area.

Because a photocamera sees a scene under an angle of view, objects of a given absolute size appear to have different relative sizes (on the camera's sensor) when they are located at different distances from the lens (/ eye). For example, if you look at a mountain from its base, it will look massive to you (that is, it will occupy a huge portion of your visual field), but if you look at it from far away, it will look tiny (that is, it will occupy a small portion of your visual field).

Sometimes, it's not just an entire object that appears to have a different size, but also parts of an object. For example, when photographing a building from a small distance, at ground level, the top of the building will appear smaller than its base. This happens because the distance to the top of the building is significantly larger than the distance to the base of the building, and as such the top will occupy a smaller area (than the base occupies) on the camera's sensor. If you would photograph the same building from far away, the difference between the distances would be too small to be noticeable.

Perspective distortion

Perspective distortion is a visible alteration of absolute measures.

Think at photos taken of movie stars (on the "Red Carpet"). Their feet look thin and their heads look big.

Such photos must be taken from very close to the subject, or risk having obstacles in between, and therefore in order to frame the entire subject they must be taken with lenses with a short focal length.

Now think at the position of the camera. It's usually at the level of the subject's head.

Because of this, the distance from the camera to the subject's head is significantly smaller than the distance from the camera to the subject's feet. Therefore, X centimeters measured over the subject's head take a specific number of pixels on the camera sensor, and the same X centimeters measured over the subject's feet take a significantly smaller number of pixels on the sensor; this is because objects which are father away appear smaller (than closer objects).

This is why the feet of the subject appear so thin when compared to their head.

In opposition to this, when taking a photo of the same subject with a lens with a long focal length for farther away (in order to preserve the size of the subject on the sensor), the differences between the distances become insignificant (, making the photos look flatter / 2D).

To summarize, taking photos with a lens with a short focal length exaggerates the differences between the distances to the various parts of the subject, while taking photos with a lens with a long focal length flattens / compresses the differences between the distances to the various parts of the subject (relative to the distance to the subject, which keeps increasing).

Taking photos with a lens with a short focal length is not good for portrait photography, and a long focal length may require too much of a distance between the photographer and the subject, which is why the preferred focal length for this is somewhere between 85 and 135 mm, depending on the crop factor of the sensor. In portrait photography, a very shallow depth of field is also desired, which in turn requires lenses with a wide aperture.

Although taking photos with a lens with a long focal length flattens the differences between the distances to the various parts of the subject, thusly showing all the objects from a photo at their real proportions, this is still called perspective distortion because it's unnatural for the human eye to see this flattening of distances.

Here is an example of perspective distortion, and here is an example of perspective distortion in portrait photography.

Sunny 16

The sunny 16 rule says that when taking a photo of a front-lighted, average-reflective subject in bright sunlight, at F16, the shutter speed should be the same as the ISO.

For example, if you are using ISO 200 and F16, the exposure should be 1/200 seconds. Or if you are using F4, the exposure should be 1/3200 seconds.

F-number progression (each step represents a stop of light): 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16.

Light changes with focus

In some lenses, changing the focus range from infinity to the minimum focusing distance (MFD) decreases the amount of light that goes through the lens (even though all the other exposure parameters are the same). This is typical for macro lenses.

To experiment, set the camera and the lens in full manual mode. Focus-out completely, at infinity, point the lens at a white wall and take a photo. Now focus-in completely, at the minimum focusing distance of the lens and take a photo. If you compare the two photos you can see that the second photo is (much) darker.

For lenses whose barrel extends when focusing-in, it appears that the amount of light which goes through the lens decreases linearly with the length with which the barrel extends.

As an example of this, for the Tamron 90 mm (whose barrel extends when focusing-in) the second photo has about 2 stops less light than the first photo. When the barrel is half extended, the taken photo has about 1 stop less light than the first photo.

For the Canon 70-200 mm the second photo has about 1/3 stops less light than the first photo, that is, virtually no light loss.

Filters

A protection filter doesn't visibly decrease the amount of light that goes through the lens.

Use a polarizing filter to eliminate reflections from non-metallic objects, like vegetation. The lack of such a filter can, for example, ruin the photos you take to vegetation after a rain.

A circular polarizer filter decreases the amount of light that goes through the lens with 1...4 stops. For example, a Hoya HD Cir-Pl takes about 1 stop (regardless of its rotation angle).

Rotate the mobile part of the circular polarizer filter to achieve the effect that you want.

Use this filter with care because it may affect the colors in an undesired way.

Pixel count

Current photocameras with Bayer sensors, like the usual Canon and Nikon photocamera, claim to have resolutions of X pixels (like 10 mega pixels). However, this is virtually pure marketing. In fact, that is the number of photosites, not pixels.

A photosite is really a monochromatic sensor, normally for either red, green or blue colors. They are arranged in a matrix of RGGB patterns (that's two photosites for green).

The reason why photos taken with such camera sensors really have X pixels is because the software which converts the sensor data into an image interpolates each photosite to an RGB pixel, also using the data from the surrounding photosites. This means that while you expect the software to convert each RGGB pattern to an RGB pixel, it really doesn't do that; in reality, it upscales the image 4 times.

Exposure calculation and camera sensor size

The exposure of a photocamera is calculated per unit area (= a square millimeter) of the camera sensor because a unit area receives the same amount of light no matter what the total sensor area is.

In photocameras, the sensor size and the diameter of a lens used for it are proportional, so that for each unit area of the sensor there is a corresponding unit area of the lens, which means that each unit area of the sensor receives the same amount of light.

However, this means that larger sensors capture a higher total amount of light than smaller sensors, and that the images formed on larger sensors are brighter than the images formed on smaller sensors. This doesn't mean that the photos taken with larger sensors are brighter, since such photos are not viewed at a similarly increased size (they are viewed on the same displays and printed on the same paper).

There is, however, a consequence of this phenomena: the higher amount of light captured by the larger sensor overwhelms the noise, which means that the photos taken with it have lower noise levels if they are taken with the same subject magnification (which is usually what photographers do).

In theory, taking photos with sensors of the same size and with different pixel densities must produce photos with the same noise levels after scaling the photos to the same size. However, taking photos is not a theoretical case and this leads to differences where the photos taken with sensors with fewer pixels yields less noise. Yet, the differences are so small (with today's technology) that they simply are irrelevant.

Color perception

The most important properties of light are intensity (measured in lux), color temperature (measured in kelvin), and spectral power distribution (SPD).

The perception of colors depends on the properties of the illuminating light, that is, it depends on a large set of datas, not on just one or two values. For natural color appearance, the spectral power distribution of the illuminating light must be as close as possible to that of the natural sunlight.

The spectral power distribution is the reason why white balancing photos doesn't always yield the desired results. Each object from a photographed scene responds differently to the illuminating light, so white balancing a part of a photo may destroy the white balance of another part of the photo. This happens usually when the illuminating light is artificial.

The perception of colors depends on the intensity of the illuminating light. The color sensitivity of the human eye for red is high when the light is intense, but as the light gets dimmer, the sensitivity for red decreases in favor of blue, that is, all the colors are shifted toward blue.

Here is the usual light intensity for a few common cases:

Livingroom: 50...100 lux.
Overcast day: 1'000 lux.
Bright daylight (not the Sun itself): 10'000...25'000 lux.

The Kruithof curve correlates light temperature and intensity, from a visually pleasing point of view.

A light with a low color temperature gives a warm appearance (red, orange, or yellow), and a light with a high color temperature gives a cool appearance (blue or white). The sunlight at the noon of a bright summer day has a temperature of 5'500...6'500 Kelvin. Incandescent light bulbs have a color temperature of about 2'700 kelvin.

In photography, the temperature of light is upside down due to associative reasons. This means that a high temperature indicates a warm color (which is associated with fire), while a low temperature indicates a cool color.

Background blur

Here are some graphs which depict the background blur for several photo setups.

The X axis represents the distance from the point in focus (not from the camera) to the background, and is measured in meters. An X higher than 0 represents the background.

The Y axis represents the blur of the background (beyond the point in focus), and is measured in micrometers. The blur is 0 in the focus point (0 on the X axis), that is, the objects from that point are in perfect focus.

The higher the value on the Y axis, the higher the blur is and therefore the better the bokeh is.

The red line represents the COC for Canon EOS 40D: 18.

If the blur is smaller than the COC (of the camera) then the blur at that distance would be imperceptible in a photo.

We use the following formula (derived from here) for calculating the background blur: b = f ^ 2 / (s - f / 1000) / N * |x| / (s + x) , where "b" is the blur (in micrometers), "f" is the focal length (in millimeters), "m" is the subject magnification (on the camera's sensor), "N" is the F-number, "s" is the focus distance (in meters), "x" is the distance between the subject and the background (in meters). A negative "x" yields the foreground blur.

For the far background, the blur has an asymptote which can be approximated with: f ^ 2 / s / N . This asymptote is reached when the distance to the background is significantly larger than the focus distance.

We consider that all lenses take photos of a subject at the same magnification (= size in photo).

Magnification formula: m = f / (s - f) .

In order to preserve the magnification of lens 2 the same as the magnification of lens 1, we use the following formula to calculate at what distance from the subject should lens 2 be: s2 = s1 * f2 / f1 .

The format of the camera's sensor is not a direct factor of the equation. However, the magnification (and consequently the focus distance) and the COC depend on the format.

COC formula: coc = sd * va * d / pd , where "sd" is the sensor's diagonal, "va" is visual acuity of the average human eye, "d" is the viewing distance of the photo, "pd" is the photo's diagonal.

The average human eye can see (according to this), in normal light, up to 50 black-white line pairs, contained within 17.5 millimeters, from 1 meter away. This gives a visual acuity of 0.35 millimeters from 1 meter away, that is, approximately 1 / 3000.

A hand-held postcard-sized photo is usually seen from a distance equal with twice it's diagonal. Personally, I view postcards from a distance equal with 2 to 3 times the photo's diagonal. However, using the minimum viewing distance, yields more stringent sharpness requirements.

These give a simplified COC formula (which is in accordance with this): coc = sd / 1500 .

You can use the DOF calculator to calculate the depth of field.

Graphs are generated with WZGrapher.

The most important factor in generating a nice background blur is the focus distance, followed by the F-number.

In this graph you can see:

The blue curve represents the background blur for a lens with a focal length of 400 mm and F4.0, focused at 40 meters.
The green curve represents the background blur for a lens with a focal length of 200 mm and F4.0, focused at 20 meters.
The yellow curve represents the background blur for a lens with a focal length of 20 mm and F4.0, focused at 2 meters.

The formulas are:

18;
400 ^ 2 / (40 - 400 / 1000) / 4 * |x| / (40 + x);
200 ^ 2 / (20 - 200 / 1000) / 4 * |x| / (20 + x);
20 ^ 2 / (2 - 20 / 1000) / 4 * |x| / (2 + x);

You can see in the graph above that the curve of the 400 mm lens has the highest blur.

In this graph you can see:

The blue curve represents the background blur for a lens with a focal length of 400 mm and F5.6, focused at 40 meters.
The green curve represents the background blur for a lens with a focal length of 200 mm and F4.0, focused at 20 meters.
The yellow curve represents the background blur for a lens with a focal length of 20 mm and F1.4, focused at 2 meters.

The formulas are:

18;
400 ^ 2 / (40 - 400 / 1000) / 5.6 * |x| / (40 + x);
200 ^ 2 / (20 - 200 / 1000) / 4 * |x| / (20 + x);
20 ^ 2 / (2 - 20 / 1000) / 1.4 * |x| / (2 + x);

You can see in the graph above that the curve of the 20 mm lens has the highest blur for the close background area, but the lowest for the far background area.

Also, the curve of the 400 mm lens has the lowest blur for the close background area, but the highest for the far background area.

In this graph you can see:

The blue curve represents the background blur for a lens with a focal length of 340 mm and F4.8, focused at 34 meters.
The green curve represents the background blur for a lens with a focal length of 85 mm and F1.2, focused at 8.5 meters.

The formulas are:

18;
340 ^ 2 / (34 - 340 / 1000) / 4.8 * |x| / (34 + x);
85 ^ 2 / (8.5 - 85 / 1000) / 1.2 * |x| / (8.5 + x);

You can see in the graph above that the background blur is similar when the focal length and the F-number are multiplied with the same factor. Far away in the background, the lenses have the same asymptote.

In this graph you can see real lenses at their maximum aperture:

The blue curve represents the background blur for a lens with a focal length of 400 mm and F5.6, focused at 40 meters.
The green curve represents the background blur for a lens with a focal length of 200 mm and F4.0, focused at 20 meters.
The yellow curve represents the background blur for a lens with a focal length of 135 mm and F2, focused at 13.5 meters.
The purple curve represents the background blur for a lens with a focal length of 85 mm and F1.2, focused at 8.5 meters.

The formulas are:

18;
400 ^ 2 / (40 - 400 / 1000) / 5.6 * |x| / (40 + x);
200 ^ 2 / (20 - 200 / 1000) / 4 * |x| / (20 + x);
135 ^ 2 / (13.5 - 135 / 1000) / 2 * |x| / (13.5 + x);
85 ^ 2 / (8.5 - 85 / 1000) / 1.2 * |x| / (8.5 + x);

You can see in the graph above that the 85 mm and 135 mm lenses have the highest blur for the entire background area. This is why these lenses are preferred for portrait photography.

The depth of field gets thinner as the focal length gets longer, for the same F-number, although the difference is also getting smaller and smaller. For example, for Canon EOS 40D, with a lens set at F4, a 20 mm focal length focused at a distance of 2 meters has a 1.61 meters DOF, a 200 mm focal length focused at 20 meters has a 1.41 meters DOF, and a 2000 mm focal length focused at 200 meters has a 1.41 meters DOF.

However, because the asymptote of the blur grows with the focal length, the bokeh of far away background looks better when a long focal length is used.

The bokeh is better looking if the blur grows faster (/ more abruptly) because it creates a clearer (/ sharper) separation between the focused and background planes.

DOF calculator

DofCalc is web-browser based application which calculates the depth of field for a given set of photographic parameters.

DofCalc is an open source application developed in HTML and JavaScript, specifically designed for mobile devices (like PDAs).

You can download it on your computer by right-clicking here and choosing "Save link as". Then just click on that file to open it in your web-browser and use it.

First public release of DofCalc: version 1.0 on 09 June 2009.

Tips

Things which make a good photo

The Moment (= the event, the uniqueness), Action, Light, Color, People.

For me, a good photo is made by the subject, lens, camera and editing software, not by the photographer. The photographer is there to simply capture the moment, not make it.

The most important thing about light is not its amount, but its properties, like: color, the lack of reflections either in the atmosphere or from the photographed objects, the limited light contrast (between shadows and highlights), the high color contrast.

Other relevant things are: composition, framing, technical quality.

Things which may destroy a good photo

Missed focus: focusing either in front or behind the subject.

Inappropriate depth of field: too shallow for macros or too deep for close-ups.

Framing only a part of the subject: for example, the subject's legs are outside the frame.

Excessive light contrast: striking contrast between shadows and highlights.

Use both the landscape and portrait formats

The usual format of a photo is landscape because this is how the camera sensor is positioned in the camera, as the camera is held in its most comfortable position. Turn the camera vertically to take photos in a portrait format. Individual people or flowers are easier to isolate this way, so they may look better.

Use the flash outdoors

A strong sun light causes a strong light contrast. You can eliminate the shadow by lightening the subject with a flash. This is called a fill flash.

Be aware of the light

Avoid taking photos facing sources of strong light, like the sun.

Avoid taking photos of people facing strong sources of light because they will squint.

When taking photos of people in strong sunlight, position yourself to have the sun in front of you, 45 degrees at your side. Otherwise, the strong light will create strong shadows.

Early or late in the day fills the environment with a golden light.

Hold the camera steady

If you can't put the camera on something steady, like a tripod, hold it with a hand on the side which has the shutter, and with the other hand support the lens from beneath.

Shutter speed - focal length

In order to take sharp photos while hand-holding the camera, without image stabilization, use a shutter speed equal with or higher than the focal length.

For example, if you're using a lens with a 100 mm focal length then use a shutter speed equal with or higher than 100. If you're using a lens with a 200 mm focal length then use a shutter speed equal with or higher than 200.

Get to the subject's eye level

This may mean squatting so that the camera would be at the subject's eye level, like when you are photographing a child. This makes the photo more personal.

Get close to the subject

For photos with a more personal touch, fill the entire frame with the subject.

Use a simple background

A simple background makes the subject pop out more.

Don't center the subject

A slightly off center position for the subject is usually better than a perfectly centered one. This can be done later by cropping the photo more on one side.

Photographed subjects are not three-dimensional

Something which looks beautiful to your eyes doesn't necessarily look beautiful in a photo.

This is for various reason, but one of them is that a photograph doesn't show the subject three-dimensionally, as your eyes do. Therefore, you have to find an angle which gives depth to the subject.

For example, a flower looks beautiful to your eyes from front, but when you're taking a photo of a flower you should try an off-center angle.

Focus the entire subject

If the entire subject's depth appears in focus, the photo appears clearer / sharper. However, extending the depth of field too much makes the background look less attractive.

Generally, the closer you get to a subject, the higher the F-number must be in order to create a greater depth of field.

Long exposure times

When taking photos with a long exposure time (like 1/10 seconds), take them in continuous shooting mode. You'll have a greater chance to get one of them sharp.

Take photos of people when they are not posing

Taking photos of people who are not preparing to be photographed gives a natural look to the photos.

Photos can't be taken in all conditions

While pictures can be taken in any environmental conditions, to any subjects, photos can not because the conditions simply don't convey anything of importance to the viewer.

Never share bad photos

Never share bad pictures, especially of people. Delete them immediately. Make sure people get good photos of themselves. After a while you'll gain a good reputation and people will feel much more at ease with you taking photos of them.

Clear the skin defects, like zits, blemishes and moles. They distract the viewer's attention to an exaggerated level, and hide the underlying beauty of the bones, muscles and skin.

Long focal length

Taking photos with a long focal length produces a sensation of special harmony. This happens because:

Perspective distortion makes objects with equal absolute measures (in meters), located at different distances in the frame, occupy a similar number of pixels in a photo. This way, all the objects from a photo are shown at their real proportions. Even though this is not natural to the eye, it looks beautiful.
The viewer is "taken" / "flown" to the subject, as if zooming live into the frame of the photo, especially if the foreground is also blurred and the subject occupies only a part of the frame.

Cleaning glass

Wipe the entire surface of the glass (from a lens or a filter) with a wet microfiber tissue (moistened with ethanol), in a circular manner, in order to remove dust; a dry tissue may scratch the glass. The tissue must be label for cleaning glass.

Do this as rare as possible because the ethanol will eventually strip the delicate coating off the glass. Generally, dust will not show on photos, so there is no real need to remove it.

Then, before the moisture evaporates (which does quickly), wipe the glass with a dry tissue until all the moisture is gone.

If you exhale on the glass, you'll see the moisture from your breath condense on the glass and expose the cleaning pattern; this moisture evaporates quickly.

Various

Canon EOS cameras automatically lock the exposure when "Evaluative" metering and "One-Shot" auto-focus mode are used. Simply press the shutter button half-way and both the focus and the exposure will be locked. Good for shooting portraits: lock on subject, then recompose.

Look at photos on a professional display. A notebook display is usually limited in its capabilities to reproduce colors. A good choice is to print the photos.

Sometimes, colors look better if the photo is underexposed. I find this to be true even for an underexposure of more than 1 stop.

Edit photos

The most important thing that amateur photographers miss is the extra step that professional photographers are taking: photo editing with the explicit goal of making the photos consistent (with what the photographer wants).

The problem with the photos taken by the camera is that they are perceptually inconsistent. The camera's sensor records the reality with a number of hardware parameters: aperture, exposure time and ISO. These parameters are responsible for the technical quality of photos, and can't be change later.

Everything else done by the camera to output a photo is just post-processing, that is, the modification of photos after they were physically recorded, using software.

If you are taking photos using a semiautomatic photo mode, that is, a mode where the camera automatically computes at least one of the hardware parameters, the camera will miss (usually by a small amount) a lot of times to use the hardware parameters that a photographer would use if he would have the time to manually set them.

Moreover, reality is not consistent. Light (amount, spectrum and directionality) and subject colors vary all the time.

Reality is boring, grayish. When taking landscape photos, you're also facing the problem of atmospheric conditions, usually in the form of suspended dust particles which reduce the contrast of distant subjects (making them look grayish).

A significant part of reality is always lost in its path to be seen as a printed photo (or as one displayed on a computer screen). The factors which generate a loss of reality are: light, camera lens, camera sensor, camera hardware parameters, photo post-processing, printing photos (= paper, ink and quality), displaying photos on a computer screen, the light in which the photos are seen, the eyes of the viewers.

In the end, the reality seen by the eye of the photographer is less important than what the viewers of the photos see. The only good photos are the ones which look good to their viewers.

People see the grayish reality everyday, so why not make it look better in photos?

Edit your photos to fit your taste! Don't worry about details not looking right anymore (because, for example, you've increased the contrast), a photo looks good when viewed overall.