Photography

The Lens Ratio

When you look upon the front end of your lens barrel, you'll see a ratio number (1:2.8, 1:2.8-4, 1:3.5-5.6, etc), which is the maximum aperture of the lens.

A lens with a low f-number (wide maximum aperture), is a better quality lens and allows you to do more with it.

High quality zoom lenses deliver a constant f-stop throughout the focal range (i.e. a f/2.8 at 35mm and a f/2.8 at 80mm); whereas on a lower quality lens, the f-stop varies as you travel up the focal range (i.e. a f/3.5 at 28mm, but a f/5.6 at 80mm).

It is to be noted that any lens that is f/2.8 or lower is considered to be a professional lens, and will have a correspondingly higher price tag.

Filter Thread

Or Filter size. Almost all lenses have a threaded section on the front that allows you to screw on filters to achieve certain effects. When referring to a len' specifications, it should tell you the diameter of the filter thread and then you can purchase your filters in the same diameter. Common thread sizes include 49mm, 52mm, 55mm, 58mm, 62mm, 67mm, 72mm, 77mm and 82mm.

Standard (or Normal) Lens

The standard lens has a fixed focal length (50mm, 85mm, 100mm), and reproduces fairly accurately what the human eye sees -- in terms of perspective and angle of view.

For a 35mm film camera or a full-frame DSLR, the 50mm lens is considered standard.

At higher focal lengths (85mm or 100mm) you have an ideal lens for portraiture because when coupled with a wide aperture they thoroughly soften any background detail, thus making it less likely to distract from the main subject.

Wide Angle Lens

A wide-angle has a shorter focal length (10 thru 42mm) when compared to a standard lens.

This enables you to capture a comparatively wider angle of view. A wide-angle lens is a natural choice for capturing outdoor landscapes and group portraits.

You can use wide-angle lenses to capture a deep DoF (Depth of Focus, the opposite of the "distraction from the main subject").

Telephoto Lens

Telephoto lenses (100mm -- 800mm) can provide you with a narrow field of view.

These long lenses enable you to compress a distance (and compress the sense of depth, as well) and pick out specific objects from far off.

They have a strong resolving power and an inherent shallow DoF, where the slightest lateral moment can take a subject out of view.

Macro Lens

Macro lenses are used for close-up or "macro" photography (ie., designed for short focus distances).

They range in focal lengths of between 50-200mm. These lenses obtain razor-sharp focus for subjects within the macro focus distance, but lose their ability for sharp focus at other distances.

These lenses enable the photographer to obtain life-size or larger images of subjects like wasps, butterflies, and flowers.

Zoom Lens

Zoom lenses have variable focal lengths, and are extremely useful.

Some can range between a wide-angle and a telephoto (i.e. 24 to 300mm) so you have extensive versatility for composition.

The trade-off with zoom lenses is the aperture. Because of the number of elements required in constructing these lenses, they have a limited ability to open up and allow in light.

So unless you're prepared to outlay a lot of money, you will give up lens speed.

Image Stabilization

These lenses contain small gyro stabilizer sensors and servo-actuated lens elements, which purportedly correct for camera shake that occurs with longer focal length lens or in low-light conditions when you need to have slower shutter speeds to achieve an effective EV.

It is claimed that these lenses enable the user to shoot hand-held at 2 to 4 stop slower shutter speeds (exposure 4 to 16 times longer) than the minimum required for a sharp image (ie., exposure of 1/25 sec or longer).

Extension tubes

They work as macro (zoom) lenses, allowing standard lenses to reduce their minimum focus distance. However, the lens loses the ability to focus at infinity.

Normal and Cross-Type Focusing Points

Look through the viewfinder of any DSLR camera and you will see several dots, or squares, that represent individual points at which the camera is capable of focusing. The purpose of these focusing points may seem fairly obvious, but not all of them are created equal. When you press the shutter button (or back button) halfway, some of these points will light up, indicating that everything at that specific spot is crystal clear and your photo will be nice and sharp.

However, the speed at which your camera can focus on one of the points, as well as how accurate the focus will be, depends greatly on whether the individual focusing point is a single or cross-type. Understanding the differences in how they operate can help you decide which ones to use to take better photos.

Most DSLR cameras use whats's called a phase-detection focusing system -- whereas most mirrorless cameras, point-and-shoots, and mobile phones use a separate system called contrast-detect. In a DSLR, most of the light coming through the lens is reflected upwards by the mirror, to the optical viewfinder, which lets you see precisely what the camera lens sees.

However, a tiny bit of light is also sent downward to a series of sensors that are capable of figuring out whether the image is in focus. The science behind this involves splitting the incoming light, and comparing two beams, to essentially see if they match up. If not, an electronic signal is sent to the focusing motor, to adjust the lens until the image is in focus. All this happens in a fraction of a second, but these fractions matter in photography, and can often be the difference between a tack-sharp image and a blurry shot.

The problem with traditional phase-detecting systems is they get a bit stumped if there are a lot of vertical lines in the spot where they are trying to focus. To see how this works for yourself, print a sheet of paper on your computer, with nothing but vertical lines. Tape it to a wall, and try to focus on it with your camera. If you are using one of the focusing points on the outside edge of your camera's viewfinder, your lens will likely spend a few seconds hunting for focus but will probably never find it. However if you turn the paper sideways and try again your camera will likely get things focused fairly easily. This is because when light is sent to the phase-detection sensors in your camera, the sensors don't have enough information to determine focus, if all it sees is vertical lines.

While most of the time when you are out taking pictures, you are probably not shooting images of vertically-lined paper, this example does illustrate how your camera's autofocus can get slowed down, and become unreliable under certain conditions. Ironically, in this test, your camera will find focus much better if you use the live view function. That employs a contrast-detection focusing method which is also used in most mirrorless cameras, and while it is a bit slower, can have some advantages over traditional phase-detect systems.

Test your camera's focus sensors with nothing but a lined piece of paper.

To address this issue, most camera manufacturers have implemented cross-type focusing sensors that work fine when focusing on images with horizontal and vertical patterns. On high-end models (like the Nikon D5 or Canon 5D Mark III) there are several clusters of cross-type focusing sensors, but lower-end models (like the Nikon D3200 and Canon Rebel T3i) usually have just one, right in the center. This means that the center autofocus point will likely be significantly faster, and more reliable, than the points on the edge. You can see the results yourself by repeating the test from earlier with the center focus point, instead of one on the perimeter of your viewfinder.

The real-world implications of this are quite significant, and may very well change how you approach your photography. Many people use an automatic setting that allows their camera to look at all the available focus points, and determine which one should be used to set the focus. But, if you know that the the cross-type points will give you consistently better results, you might try using them more often.

This is especially useful with sports and fast action, but other types of photography situations can benefit from utilizing cross-type points also. Portrait, family, and wedding photographers often utilize the focus-and-recompose method to nail focus with a cross-type sensor, then shift their camera's field of view to get precisely the composition they want. If you shoot landscapes you might not need speedy autofocus, but using your camera's cross-type sensors may help your focus be more accurate.

Of course all this doesn't mean that the normal focusing sensors on your camera are worthless, just that knowing which ones are cross-type can often give you an advantage you might not have otherwise had.

One other point worth noting is that mirrorless cameras use phase-detection focusing more than they used to, and some are implementing cross-type sensors too. Just because this technology started with DSLRs does not mean it will be forever limited to these types of cameras, and as manufacturers continue to innovate we will likely see more, and better, focusing options in the years ahead.

Cameras and lenses

• Very complete benchmarks for photography!!! https://www.dxomark.com
• Cameras comparison https://cameradecision.com/

Optics Vocabulary

• Anti-alias (AA or low-pass) filter: in photography, removing anti-alias filter increases the sharpness and level of detail but at the same time, it increases the chance of moire occurring in certain scenes. Many Nikon sensors (including D5300) lacks anti-alias filter (see Moiré).
• Baffle: is an opto-mechanical construction designed to block light from a source shining into the front of a optical system and reaching the image as unwanted light. Optical systems which have stringent requirements on stray light levels often need optical baffles. There are many designs, depending on the desired goals. Generic optical baffle designs and their advantages for stray light control can be classified as reflective or refractive; reimaging and nonreimaging systems. A lens hood is a basic baffle (see Lens Hood).
• Barrel: a type of distortion where the image magnification decreases with the distance from the optical axis (see Distortion).
• Bokeh: is the aesthetic quality of the blur produced in the out-of-focus parts of an image produced by a lens (see Depth of Field).
• Chromatic Aberration: usually found at long focal lengths and on the corners of the field (see Distortion).
• Depth of Field (DOF): is the distance about the plane of focus (POF) where objects appear acceptably sharp in an image. Although an optical imaging system can precisely focus on only one plane at a time, the decrease in sharpness is gradual on each side of the POF, so that within the DOF the unsharpness is imperceptible under normal viewing conditions (see Bokeh). Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture (see Bokeh).
• Distortion: perspective or radial distortion is a warping or transformation of an object and its surrounding area that differs significantly from what the object would look like with a normal focal length, due to the relative scale of nearby and distant features. It is classified as i) Barrel, ii) Pincushion, and iii) Mustache distortions (see also Foreshortening).
• Do-It-Yourself (DIY): in photography, usually associated with easy trick you can do with you camera to make your photos more professional.
• Exposure value (EV): is a number that represents a combination of a camera's shutter speed and f-number, such that all combinations that yield the same exposure have the same EV (for any fixed scene luminance). The film sensitivity (ie., ISO) isn't considered in the EV.
• Flare: or lens flare occurs when a point of light source such as the Sun is much brighter than the rest of the scene. Depending on the position of this bright light source, it can result in a lot of haze/lack of contrast, orbs and polygon artifacts scattered throughout the image, semi-round shapes with rainbow colors, or a combination of all of the above (see Ghosting Flare).
• Focus breathing: or just Breathing, refers to the shifting of angle of view of a lens when changing the focus. Some (often higher quality) lenses are designed to lessen the degree of this effect. Lens breathing does not prevent one from racking focus or following focus with this lens, but it lessens the desirability of any type of focus adjustment, since it noticeably changes the composition of the shot. So, in a photographic camera, when the object is focused close, the lens is far from the detector. When focused at infinity, the lens is in the closest position to the detector. When changing its focal length, the camera change distances internally and with respect to the detector. These different distance configurations are related to the "focus breathing" with the corresponding change in focus distances.
• Ghosting Flare: or just "ghosting" represents all the artifacts that are visible in the image beyond the bright hazy, whether it is reflections of the bright source, or shapes that is similar to the lens diaphragm.
• Foreshortening: is the perspective effect (or optical illusion) that causes an object or distance to appear shorter than it actually is because it is angled toward the viewer (see Perspective Control).
• Lens hood: In photography, a lens hood or lens shade is a device used on the front end of a lens to block the Sun or other light source(s) to prevent glare and lens flare. Lens hoods may also be used to protect the lens from scratches and the elements without having to put on a lens cover (see Baffle).
• Moiré: moiré pattern or moiré fringes are large-scale interference patterns that can be produced when an opaque ruled pattern with transparent gaps is overlaid on another similar pattern (see Anti-alias filter).
• Mustache: a type of distortion where the image magnification increases and decreases in different distances from the optical axis (see Distortion).
• Panning: in cinematography and photography panning means swivelling a still or video camera horizontally from a fixed position. Probably Nikon VR is not able to handle panning.
• Perspective Control: is a procedure for composing or editing photographs to better conform with the commonly accepted distortions in constructed perspective (see Foreshortening).
• Pincushion: a type of distortion where the image magnification increases with the distance from the optical axis (see Distortion).
• Teleconverter: sometimes called "tele extender", is a secondary lens mounted between a camera and a photographic lens which enlarges the central part of an image obtained by the objective lens. Teleconverters are typically made in 1.4x, 1.7x, 2x and variants. They effectively increase by that factor the focal length of a given lens. Using a teleconverter with an existing lens is usually less expensive than acquiring a separate, longer telephoto lens, but as the teleconverter is magnifying the existing image circle, it also magnifies any aberrations. The use of a teleconverter also results in a darker image. The degradation of (angular) resolution can be noticeable.
• Vignetting: is a reduction of an image's brightness or saturation toward the periphery compared to the image center.

Types of cameras

• Point-and-shoot (or P&S): is a still camera designed primarily for simple operation. Most use focus free lenses or auto focus. Also, their viewfinder passes through a separate lens.
• Bridge (or SLR-like): often comparable in size and weight to the smallest digital SLRs (DSLR), but lack interchangeable lenses, and almost all digital bridge cameras lack an optical viewfinder system. The phrase "bridge camera" has been in use at least since the 1980s, and continues to be used with digital cameras. The term was originally used to refer to film cameras which "bridged the gap" between point-and-shoot cameras and SLRs.
• Digital Single-Lens Reflex (D-SLR or DSLR): The reflex design scheme is the primary difference between a DSLR and other digital cameras. In the reflex design, light travels through the lens, then to a mirror that alternates to send the image to either the viewfinder or the image sensor. The traditional alternative would be to have a viewfinder with its own lens, hence the term "single lens" for this design. The ability to exchange lenses, to select the best lens for the current photographic need, and to allow the attachment of specialized lenses, is one of the key factors in the popularity of DSLR cameras.
• Mirrorless Interchangeable-Lens Camera (MILC): this cameras features a single, removable lens and uses a digital display system rather than an optical viewfinder. The word "mirrorless" indicates that the camera does not have an optical mirror or an optical viewfinder like a conventional single-lens reflex camera (SLR), but an electronic viewfinder which displays what the camera image sensor sees. In many mirrorless models, the mechanical shutter remains.

Flash

• Flash configurations:

  • Bare Flash
  • Shoot Thru (Umbrella)
  • Reflective Umbrellas

• Slave Mode: this mode on your flash will allow you to fire that particular flash when it senses the flash from another speedlight. All you need to make sure of is that there is a clear line of sight to another flash.
• Speedlight (or speedlite): An on-camera flash, provides additional light when conditions become too dark to handhold your camera comfortably, allows you to achieve more balanced exposures in daylight, permits freezing of fast-moving subjects, and can also be used to control or trigger other flash light sources.
• Through-the-lens (TTL) Flash metering: Automatic in-camera calculation of flash metering is usually done using a TTL method. This method of determining proper flash exposure is very similar to the way a camera's exposure meter works, but it takes into account more variables, such as flash power and even subject distance, if used in conjunction with a compatible lens.
• Fill-Flash and Dragging the Shutter: While flash is often used to illuminate a scene entirely, flash can also be used in combination with ambient exposure to provide additional creative benefits. An example would be photographing a field or bush at dusk; while the foreground and surrounding areas are very dark, there is more light available in the sky regions of the scene. A way of rendering this type of scene would be to use your flash to illuminate the nearer regions, and then let your shutter stay open longer to capture the ambient light of the sky. This technique is called "dragging the shutter" and can be utilized to highlight specific objects or subjects in a scene. Similar in concept, but using the opposite protocol, is to illuminate the background. To properly use "fill flash", first meter your subject and then meter the background. This difference in exposure values is what is to be made up by use of flash exposure.

Filters

• UV: Film and a digital CCD are more sensitive to UV light than our eyes are. This often shows up in images shot from high altitudes and long distances especially over water. This filter will remove the UV light and more importantly protect your lens from moisture, scratches, and damage.
• (Circular) Polarizer (or CPL): provides color and contrast enhancement. Reflected light often shows up as a whitish glare that washes out color in an image. A polarizing filter will correct this problem creating deep blue skies. It also removes glare from non-metallic surfaces such as windows and water.
• FLD: provides color correction when shooting under fluorescent lighting. It will remove the greenish tint from the image, providing pleasing skin tones and true to life color renditions.
• GND: Graduated Neutral Density.
• ND: Neutral Density.

Thin lens equation

(1)/(o) + (1)/(i) = (1)/(f)

where:

• o is the object distance
• i is the image distance
• f is the lens focal length

Field of View

FoV = 2arctan(S ⁄ 2f),

where:

• f is the lens focal length
• S is the Sensor Size

f-number

f-number is usually calculated by the f-stop definition N = 2^i ⁄ 2 , where i = 1, 2, 3,... for f/1.4, f/2, f/2.8,...

Depth of Field

Hyperfocal distance: H = (f²)/(Nc) + f

Near distance of acceptable sharpness: D_n = (s(H − f))/(H + s − 2f)

Far distance of acceptable sharpness: D_f = (s(H − f))/(H − s)

where:

• H is the hyperfocal distance, mm
• f is the lens focal length, mm
• s is the focus distance, mm
• Dn is the near distance for acceptable sharpness
• Df is the far distance for acceptable sharpness
• N is the f-number
• c is the circle of confusion, mm

Exposure Value

E_V = log₂(N²)/(t) = ES

where:

• N is the f-stop
• t is the shutter speed
• E is the (incident-light calibrated) illuminance
• M is the ISO arithmetic speed

ISO, f-stop and Shutter Speed correlation

f-stop units i follows N = 2^i ⁄ 2. Here there is a factor 0.5x with the unit because the flux goes with the square of the aperture diameter.

ISO units j follows: M = 50*2^j

Shutter Speed units k follows: t = 2^− k. However, it has a 'non-standard' round method:

• (1/8 = 1/8);
• 1/16 = 1/15;
• 1/32 = 1/30;
• 1/64 = 1/60;
• 1/128 = 1/120;
• 1/256 = 1/250;
• 1/512 = 1/500;
• 1/1024 = 1/1000;
• and so on and forth.

So, in principle, for a constant illumatation of the scenery, the sum combination of i, j and k units produces the same image lighting results.

The equivalence of the exposure value is tricky:

• high ISO makes the images noisy;
• slow shutter speeds blurs moving objects (such as in sports) and the slower ones require tripod;
• changes in f-stop changes depth of the field (Bokeh).

Nikon Lenses Acronyms

Pentax Lenses Acronyms

Nikon lenses

Canon PowerShot S30

My acquisition date: ~2002-Sep

My rate: 8.0/10.

My comments: My first digital camera. Canon quality to start learning photography.

Fujifilm FinePix HS25EXR

My acquisition date: ~2012-Mar

My rate: 5.0/10.

My comments: a very complete camera. Good optics. However, the detector quality is horrible. It is impossible to take sharp images, specially with ISO above 800. The manual focus also has problems. It is very hard to do something very simple, that is to focus at infinity. Video auto-zoom is very unstable. Decent batteries (4xAA) consumption (350+ frames).

Nikon D5300

My acquisition date: 2019-Jan

My rate: 9.0/10.

My comments: The camera specs created a very high expectation. In particular, multiple exposure and time-lapse control are great resources. All camera options are not so easy to handle. To be fast requires practice.

Lens tools

Other accessories

Planned:

• Extension tube set for Nikon (7, 14 and 28mm)**
• Directional microphone w/ windscreen for cameras**
• V-shape triple 3 shoe mount bracket for cameras**
• LED light for cameras**
• Extension tubes = $36
• Var ND 55mm filter = $18
• Mic = $27
• Mount bracket = $11
• Light = $37
• 58mm CPL (kit) = $15

Flash

• Flash is useful to make the exposure faster. Useful when below 1/60 sec and the object is within your flash coverage distance.
• The combination of short focal lengths and close objects can cause vignetting when flash is used.

• When using flash, if the background is too bright:

  • Increase distance between subject and background.
  • Decrease distance between flash and subject.
  • Configure flash power/distance.

The future (at early 2020's) of the digital cameras

DSLRs largely replaced film-based SLRs during the 2000s, and despite the rising popularity of mirrorless system cameras in the early 2010s, DSLRs remain the most common type of interchangeable lens camera in use as of late 2018.

However, this trend shall change in the 2020's as mirrorless camera are gaining popularity. This is clear with the recent (2018) announcements of great products from three major camera manufacturers, namely Nikon, Canon and Sony.

In early 2018, Sony announced the A7III mirrorless camera, bringing the 693 auto-focus points of the A9 model at a much lower cost. In August 2018, Nikon announced its new full-frame mirrorless Z6 and Z7 cameras, both using a new lens mount. Canon announced its first full-frame mirrorless model, the EOS R, and its own new lens mount in October 2018.

Entry-level DSLR vs Mirrorless in Jan 2019

In Jan 2019 I had a budget of USD~800 and I decided to buy a (Nikon) DSLR instead of a (Sony) mirrorless camera. The main reason for this choice was that mirrorless cameras are more expensive at this moment. The DSLR choice allowed me to buy a kit of different lenses (although my budget also excluded Canon DLSRs).

I believe my start was an ideal one. I bought a decent body (Nikon D5300, USD~400) which contains many important features for me (including a fully articulated screen for selfies and time-lapse control) with 3 lenses to cover multiple applications. Here are the lenses selection:

• Standard zoom lens 27-83mm f/3.5-5.6, for landscape and portraits (USD~100);
• Telephoto lens 105-450mm f/4.5-6.3, for nature and close-up (USD~150);
• Normal lens ~50mm f/1.8, for night sky and low-light environments (USD~200).

See "my gear" for more details.

Weather / Dust Sealing

Unless you need to photograph under severe weather conditions, or have substantion amount of money to spend, it is not so useful to make and investiment on a weather sealed body camera. To have full protection, you would also need to buy sealed lenses, which are extremely high cost.