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Frequently Asked Questions and Answers
Lenses
Mar 20, 2021 00:48:32   #
Rongnongno Loc: FL
 
Lenses are more important than your camera.

They can be expensive and will usually lock you onto a brand due to the investment made.

Since lenses are cross-body compatible or compliant within a brand and will last longer than the camera body you need to be really careful when you plan a purchase. If there is a 'full frame' camera in your future consider your options carefully.

If you have a 'cropped sensor' by example and know you will upgrade to a 'full frame' investing in lenses that will not adapt well to your projected camera upgrade you will be stuck with inferior results. The solution here is simple: Purchase a wife range zoom for your 'cropped sensor' camera and all other lenses should be for the future 'full frame' camera.

There is an advantage of doing that. When you use a 'full frame' lens on a cropped camera you use the center of the lens only which has the best optical quality this lens can offer. That you also get a magnifying factor is beside the point, we are talking $$$ here.

 ► Camera/Lens axes
 ► Calibration
 → Type
  ► Fisheye
  ► Mirror telephoto
  ► Normal
  ► Other
  ► Prime lens
  ► Telephoto
  ► Tilt/Shift
  ► Wide angle
  ► Zoom

Breaking down a lens
 ► Element
 ► Element Group
 ► Iris (Diaphragm)
 ► Diameter

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Mar 20, 2021 00:49:10   #
Rongnongno Loc: FL
 
Lens Calibration

Calibrating a lens for sharpness is optional but should be done systematically and periodically by professional photographers.
Depending on the camera brand and model this option might not be available.

How to calibrate Generic link

Calibration name per brand...
→ Nikon – AF Fine Tune
→ Canon – AF Microadjustment
→ Sony – AF Micro Adjustment
→ Pentax – AF Adjustment
→ Olympus – AF Focus Adjust

It is likely that you will find a youtube video for your camera.

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Mar 20, 2021 01:10:08   #
Rongnongno Loc: FL
 
Lens type

Lens are defined by their purpose. When you read or hear 'walking camera' this usually refers to a zoom that can adapt to many situations.

A lens is usually described by its focal length in mm and its maximal aperture as F-Stop when wide open. The F-Stop is particularly important. Lenses with a F-stop below 2.0 usually offer a better quality in optics and build. Currently, I believe the widest aperture is 1.1 meaning that the glass inside is near transparent and let in more light regardless of aperture. This in turn influences sharpness, color rendition...

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Mar 20, 2021 01:21:29   #
Rongnongno Loc: FL
 
Fish eye lenses

A fish eye lens is a specialized wide-angle lens that produces strong visual distortion intended to create a wide panoramic or hemispherical image. (Wikipedia)

Fish eye lenses have limited use, yet they have their place.


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Mar 20, 2021 06:40:15   #
Rongnongno Loc: FL
 
Normal lens

These refer to lenses who create images similar to an eye field of vision.

They are identified as 50mm or 50mm equivalent depending on your camera sensor type.

To test your camera, use a zoom or zoom function. Look at the scene with one eye and through the lens with the other. Adjust the zoom so that both eyes see everything at the same scale. Take a picture. Use software to identify the length value created by the zoom and there you have it.

Use of it? I am not sure.

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Mar 20, 2021 06:44:17   #
Rongnongno Loc: FL
 
Other lenses

Other lenses cover all the odd lenses created for their optical properties like the Lensbaby.

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Mar 20, 2021 06:57:07   #
Rongnongno Loc: FL
 
Prime lenses

Prime lenses are fixed length lenses.
The glass quality is superior to regular lenses, even other fixed length lenses.
The maximal aperture is usually below 2.0*
They are usually highly specialized.
Some prime lenses offer a greater number of blades (9 instead of 7 or even 5 in cheap lenses) in the iris that controls the aperture.

Prime lenses exist in the 35 mm to 200 mm range. They are usually heavier due to their build.

While not a criterion prime lenses can cost two to three time regular lenses of the same fixed length. Sometimes they are even more expensive.

These lenses 'sweet spot' varies depending on their specialty.
An 80 mm macro lens will not have the same optimal focusing distance as an 80 mm portrait lens by example.

Prime lenses can be used as 'regular lenses' for anything, you just will not get the optimal sharpness taking a portrait with an 80 mm macro lens. You will not be able to shoot a macro subject with an 80 mm portrait lens.

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* The maximum aperture - expressed in f-numbers or f-stops (for example f/2.8) - is the limit to how wide a lens can be open. Basically, it is the hole in your lens with the largest diameter, allowing the most amount of light to travel through the lens to the film plane.

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Mar 20, 2021 07:15:31   #
Rongnongno Loc: FL
 
Telephotos

In plain English a telephoto is a lens that magnifies a scene by an x factor same as when using a scope. The difference is that a telephoto is described by its length in mm. They are also referred to as 'long lenses'.

Anything above a 'normal lens' length can be considered a telephoto.

Telephotos can be divided in three major types:
► Short telephoto; 85 mm to 135 mm or equivalent*
► Medium telephoto; 135 mm to 300 mm or equivalent
► Super telephoto; longer than 300 mm or equivalent

Optical particularities
► As the lens length augments the focus plane appears two-dimensional, same as the afore mentioned scope.
► Objects do not appear bloated as they do with shorter lenses. This is why prime portrait lenses length vary from 80 to 180 mm.
► A telephoto quality depends on its brightness or maximal aperture.

The brighter the lens the more expensive (wide aperture).

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* Length value will vary depending on your camera type.

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Mar 20, 2021 07:30:13   #
Rongnongno Loc: FL
 
Mirror telephotos

Advantages:
► Light weight
► Typically shorter than a 'normal' telephoto of the same length
► Use of a tripod (creates good habits)

Issues:
► Fixed aperture
► Heavy vignetting
► No stabilization or VR
► Focus is manual and due to the absence of stabilization relatively painful.

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Mar 20, 2021 13:51:26   #
Rongnongno Loc: FL
 
Tilt/Shift

These lenses modify the Z (principal) axe of a lens. These are great for panorama and architecture photography.

Used in view cameras they have been adapted to regular cameras, usually full frame.

When tilted
► Changes the plane of focus
► Optimizes the DOF (maximize or minimize as needed)

When Shifted
► Controls the perspective

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Mar 20, 2021 14:07:16   #
Rongnongno Loc: FL
 
Camera Axis

Cameras have three axes
 ► X Tilt up or down
 ► Y Rotate left/right (correctable in post-processing)
 ► Z Direction

Camera lenses have only the Z axe. Only a tilt/shift lens can modify it.
A camera lens Z axe is perpendicular to the camera sensor array center.
Tilt/Shift lenses are the only lenses that can modify the Z axe orientation and location.

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Mar 22, 2021 15:05:37   #
Rongnongno Loc: FL
 
Wide angle

Wide angle lenses are lenses that offer a wider field of view than 50 mm lenses or equivalent.

Wide angles lenses have subclasses like the telephotos' lens.
 ► 28 mm ~ < 50 mm Wide angle
 ► 12 mm ~ < 28 mm Ultra wide angle
 ► < 12 mm fish eyes lenses

Use:
 ► Mainly landscape, architecture
 ► Subject that cannot be captured from a longer distance.
 ► Special effects.

Advantage:
Deep DoF

Issue:
Optical distortion. Many aspherical wide angle correct part of it but cannot prevent the foreground objects to appear larger.

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* Depends on your camera type.

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Mar 25, 2021 22:36:13   #
Rongnongno Loc: FL
 
Zoom

Zoom are lenses with a variable length. They are described by their minimal/maximal length.

While versatile as walk around lenses and wild life shooting they do not offer the quality of prime lenses, but they are close.

Their maximal aperture is rarely below 2.8.

The 'pump' lens are now rare and replaced by 'twist lenses'.

A zoom that changes its length by itself suffers from what is called 'Zoom-creep'. It is not unusual.

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Mar 28, 2021 17:39:46   #
Rongnongno Loc: FL
 
Aberration

This relates to inability of light to focus a single point.

This 'defect' leads to several issues, the most common is a discoloration on the corner edge of a capture. One less common is field curvature. This field curvature by the way is part of the Lensbaby appeal, if you are into this.

Pincushion and barrel are distortions created by a lens aberration.

B&H has a great article on this.

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