A Beginner’s Guide To Lenses · A Beginner’s Guide to Lenses Camera systems Once you have selected a Camera manufacturer and system, you will only be able to use lenses designed

A Beginner’s GuideTo Lenses

A Beginner’s Guide to Lenses

What is a lens?


What is a lens?Simplified:

It’s an optical method of focusing the light from your subject onto your sensor to give the desired image.

A camera “lens” is actually made up of a series of lenses to focus the image and remove as much distortion, both in shape

and colour, as possible


Your camera and lensYou’ve got your camera, so you should have a lens. Whether it came already attached to it, separate in a box or built into the camera, it’s got a lens.

With compact cameras or bridge cameras, it’ll be built in and that lens is what you’ve got. Like it or lump it.

The glory of DSLR, Micro 4/3rd or system cameras is that these lenses are interchangeable within it’s own system so that you can choose a lens to suit your needs.


Your sensorThe type of sensor in your camera has an effect on what type of lens you need to buy for your camera.

A full frame sensor is the same size as an old 35mm film frame.

A crop sensor is 2/3 the size of a full frame sensor.

A micro 4/3rds sensor is 1/2 the size of a full frame sensor.

Full Frame

Crop SensorMicro 4/3rds

Sensor Sizes


Your sensorIf you’re unsure about the sensor in your DSLR, as a general rule if your camera body cost less than £1000 when new, it’s likely to be a crop sensor.

A crop sensor is often labelled as APS-C. Nikon use FX to denote full frame sensors.

If you’re in any doubt, check the manufacturer’s website, a review site or your manual.

Full Frame

Crop SensorMicro 4/3rds

Sensor Sizes


“Kit” lensA kit lens is a description of a standard and/or telephoto zoom lens that is usually bundled in when you purchase a DSLR. They are normally at the lower end of the range of lenses offered by your camera’s maker.

They are perfectly usable and produce great results but they may have limitations and the optical quality may not be up there with the best.

Nikon 18-55mm


Camera systems

Once you have selected a Camera manufacturer and system, you will only be able to use lenses designed for that system.

You may be able to buy adapters to fit other lenses, but they may or may not work. You may lose some of the features.

Buying lenses is a minefield at times, so always check to make sure that the lens you want will work with your camera body.


Third party lensesAs well as the manufacturer of your camera, there are a number of manufacturers who produce lenses for a variety of systems.

Examples of these are Sigma, Tamron and Tokina.

They are often a lot cheaper than their brand equivalents and are quite close in quality. Camera manufacturers are often known to make small profit margins on the cameras and hope to make more on the lenses.

Lens Manufacturers


Different types of lenses• Prime

A fixed length lens with no zoom

• Standard Zoom Your common all garden zoom lens

• Telephoto Zoom One of those that zooms in a long way to get close to things

• Specialist A lens designed specifically for one main job


Prime lensesThese are the simplest type of lenses that are available.

They have no zoom so they are mechanically less complicated.

They have less lens elements meaning that they are lighter and less likely to suffer from colour bleeding, known as chromatic aberration.

Pentax 50mm


Prime lensesThey tend to have a very good image quality and are often fast lenses.

They are an ideal lens to challenge you in composition terms and make you think about a shot a lot more.

With no zoom, they give you additional exercise!

Small prime lenses are compact and lightweight.

Nikon 35mm


Prime lenses

They come in all sizes and focal lengths.

Small prime lenses are great for portraits.

Large prime lenses can be used for wildlife or sports photography.

Prime lenses are sometimes used for macro (close up) work.

Pentax 40mm


Standard ZoomsThese are your standard zoom lenses and most likely to be included as your “kit” lens.

Covering the wide to low telephoto level, they give plenty of flexibility and a little bit of zoom to get closer in.

Lower cost models are relatively slow and have high-ish f numbers.

Pentax 18-55mm


Standard ZoomsThey are also available in more costly, faster varieties. The increase in optical quality and lower f numbers make images sharper and low light photography easier.

This also makes them larger and heavier than their lower counterparts.

The versatility of the standard zoom means that most photographers will have one in their kit locker.

Sigma 17-50mm


Telephoto ZoomsThese are for those higher level zoom factors. With focal lengths of up to 500mm plus, they give you close up views but are very large and heavy.

Most do not cover the wider angles so you start at around the 70mm level.

Less expensive models have lower image quality and are slower at the telephoto end of the range.

Sigma 70-300mm


Telephoto ZoomsLonger zoom lengths are bulky and heavy and you may need a tripod to keep things steady.

Faster telephoto zooms have less reach but are also more heavy.

Telephoto lenses are flexible but you will lose out on the wider angles.

Sigma 50-500mm


Travel ZoomsNot exactly a real term, but something that I’d call your all in one zoom lens, covering everything from wide angle at the low end, all the way through to the high telephoto range.

They’re not that expensive, but they do come with compromises. Distortion and optical quality is sacrificed slightly as the lens is trying to do everything.

Tamron 18-270mm


Travel ZoomsThe good thing about these lenses are that they will do everything for you in one lens. It means that you don’t have to carry around a couple of lenses and you won’t have to swap them over mid way through the shoot when you want a certain shot.

It’s great as a travel lens but don’t expect fantastic quality from it. It’s trying to do a lot of things to an acceptable level, rather than a few to a good level.

Tamron 18-270mm


Specialist LensesThere are a LOT of different lenses out there on the market and there are some which have specific areas of use.

A wide angle lens gives emphasis on landscapes and is good when it comes to interior shots as you can pack a lot into the image.

Wide angle lenses do give a lot of distortion away from the centre.

Sigma 10-20mm


Specialist LensesTrue macro lenses are designed to give an exact size reproduction of the subject on the sensor (known as a 1:1 macro). They allow you to get very close to subjects.

Other lenses may have a macro function, but this only indicates that they are close focusing and they will not achieve a 1:1 magnification. Most true macro lenses are prime lenses.

Macro lenses are also good general prime lenses.

Nikon 105mm


Specialist Lenses

Fisheye lenses distort the image into either a circle or bend the edges of a rectangle.

These are heavily distorted and are only used for artistic purposes and, as such, can’t be used for any other purposes.

They have an extreme field of view, often up to 180 degrees.

Sigma 10mm Fisheye


Specialist LensesTilt shift lenses allow you to change the focus plane and will give a model like effect. More specialised models allow you to remove distortion when taking images of buildings.

Selective focus lenses, like the Lensbaby, allow you to move the focus point and steadily blur the area surrounding it. It’s a creative lens and therefore not really suited to normal photography.

Lensbaby Composer 35mm


What is a “fast” lens?A fast lens is one that allows a lot of light into the camera so that it can use a faster shutter speed.

Generally, a fast lens is of f/2.8 or less (that is a wider aperture). Prime lenses can generally be a lot faster due to their simplicity and lack of zoom.

An f/2.8 lens lets in four time more light than one at f/5.6 and requires a quarter of the time to get the same exposure.

Sigma 28-70mm f/2.8


Lens Construction

A camera lens is not just one piece of glass or plastic like the lenses in your glasses.

Each lens has a number of elements in groups which are designed to focus a crisp image onto the sensor.

Different types of glass are used to do different jobs.

Nikon AF-S 18-55mm


Lens ConstructionEvery lens will have a movable group of optics to achieve the focusing.

Zoom lenses will have an additional set of optics to increase and decrease the focal length of the lens.

The more movable parts, the greater the likelihood of the image degrading.

Nikon AF-S 70-200mm


Lens ConstructionEach piece of glass that the light passes through will diffract light in the same way as a prism does. This needs a number of correcting optics to bring the light back together.

The quality of the glass makes a huge difference and there is always a chance you will get chromatic aberrations or fringing around bright objects.

Nikon AF-S 35mm


What is focal length?The focal length of a lens is the distance between the centre of the lens and the sensor. As all camera lenses are complex, it’s a theoretical distance.

The focal length of a lens determines its field of view (FOV), the angle between which the image is captured.

As focal length increases, the angle becomes smaller and that gives a zoom effect.


What is focal length?On a crop sensor, the focal length is 2/3 of that on a full sensor. To get a 35mm equivalent, you will need to multiply the focal length by 1.5.

So a 200mm lens on a crop sensor will give you the same field of view as a 300mm on a full frame sensor. 18mm on crop will give you a 27mm on full.

Field ofView(FOV)

FocalLength

Lens CropSensor

Full FrameSensor


What is focal length?On a full frame sensor, the focal length needed to give you the same field of view will be longer as the sensor is bigger.

A crop sensor on most cameras (Nikon, Pentax, Sony) is 23.6mm wide, a full frame sensor is 36mm wide.

Canon’s sensors are slightly smaller

Field ofView(FOV)

FocalLength

Lens CropSensor

Full FrameSensor


The problem with lensesA lens that is designed for a full frame sensor will always fill the frame as it is designed to do.

This is because the openings at both ends of the lens are wide enough to let the light in and the optics inside the lens have been manufactured to focus the light correctly.

Field ofView(FOV)

FocalLength

Lens Full FrameSensor


The problem with lensesIf you take that full frame lens and put it onto a crop sensor body, the lens is still capable of working as the optics all work within those outer boundaries.

In effect, you’re getting the same image but it is being “cropped” inside the camera.

Field ofView(FOV)

FocalLength

Lens CropSensor


The problem with lensesIf you take a lens that is designed specifically for a crop sensor, the angles are limited by the construction of the lens.

Although it is perfectly capable of filling a crop sensor, it may not be able to do so outside those boundaries.

Field ofView(FOV)

FocalLength

Lens CropSensor


The problem with lensesAny light outside the crop sensor boundaries (grey on the image) may not be transmitted onto the full frame sensor and you will get vignetting (dark areas) on the outer edge of the image.

It is not advisable to use a crop sensor lens on a full frame body for this reason.

Field ofView(FOV)

FocalLength

Lens Full FrameSensor


Field of viewAs shown before, as the focal length increases, the field of view gets smaller and that is what creates the zoom effect. The image on the sensor is still the same size.

That means that small focal length lenses are generally known as wide angle lenses as they give the largest field of view.


Field of viewCrop

Sensor 23.6mm FullFrame 36mm

10mm 99.44° 15mm 100.39°18mm 66.49° 28mm 65.47°35mm 37.26° 50mm 39.60°50mm 26.56° 70mm 28.84°85mm 15.81° 120mm 17.06°105mm 12.82° 150mm 13.69°150mm 9.00° 200mm 10.29°200mm 6.75° 300mm 6.87°300mm 4.50° 500mm 4.12°500mm 2.70°

Popular lens focal lengths and fields of view


Field of view

Crop Sensor

Focal Length:

10mm

FOV: 99.44°


Field of view

Crop Sensor

Focal Length:

18mm

FOV: 66.49°


Field of view

Crop Sensor

Focal Length:

35mm

FOV: 37.26°


Field of view

Crop Sensor

Focal Length:

50mm

FOV: 26.56°


Field of view

Crop Sensor

Focal Length:

85mm

FOV: 15.81°


Field of view

Crop Sensor

Focal Length:

105mm

FOV: 12.82°


Field of view

Crop Sensor

Focal Length:

200mm

FOV: 6.75°


Field of view

Crop Sensor

Focal Length:

300mm

FOV: 4.50°


Field of view

Crop Sensor

Focal Length:

500mm

FOV: 2.70°


Camera ShakeThe ability to hold your camera steady varies from person to person but even the steadiest of hands can make minute movements to the camera.

With wide angle lenses, a small movement of the camera will equate to a small movement of the image.

As the focal length increases, the movement in the image gets amplified.


Camera ShakeAs a general rule, to make sure that your image is blur free from camera shake, you will need a fast enough shutter speed to eliminate it.

On a full frame sensor, your shutter speed needs to be faster than 1 over the focal length of your lens at its current zoom setting.

On a crop sensor, you will need to add another half on to take into consideration the crop factor.


Camera ShakeLet’s take a full frame camera set to 28mm, a default wide angle.

You will need a shutter speed of faster than 1/28 of a second to reduce the risk of camera shake. So 1/30 of a second or faster would suffice.

A crop sensor set to 18mm will need a shutter speed faster than 1/(18x1.5) or 1/27 of a second. So again, 1/30 of a second should be OK for most people.


Camera ShakeWith a telephoto lens on a full frame camera set to 200mm, you will need a shutter speed of faster than 1/200 of a second.

A crop sensor set to 200mm will need a shutter speed faster than 1/(200x1.5) or 1/300 of a second.

A crop sensor set to 500mm would be 1/(500x1.5) or 1/750 of a second.

As you can see, increased focal lengths require a lot faster shutter speeds.


Camera ShakeCrop

SensorFull

Frame10mm 1/15s 15mm 1/15s18mm 1/30s 28mm 1/30s35mm 1/60s 50mm 1/60s50mm 1/80s 70mm 1/80s85mm 1/160s 120mm 1/125s105mm 1/200s 150mm 1/160s150mm 1/250s 200mm 1/200s200mm 1/320s 300mm 1/320s300mm 1/500s 500mm 1/500s500mm 1/1000s

Popular lens focal lengths and shutter speeds


Vibration CompensationA lot of lenses for Canon and Nikon cameras come with an inbuilt system to reduce camera shake.

They can be known as Optical Stabilisation (OS), Vibration reduction (VR), Vibration Compensation (VC) or Image Stabilisation (IS).

It uses a set of gyroscopes and motors to adjust a set of optics and reduce the likelihood of camera shake and can give you a 2 or 3 stop advantage when hand holding the camera.


Vibration CompensationPentax and Sony models have a similar system which controls the sensor inside the body of the camera but effectively they do the same job.

If you have a system in the body and one in the lens, it’s advisable to use only one as they may interfere.

Turn off vibration compensation when using a tripod. The lack of movement will confuse the electronics and will actually introduce camera shake.


Vibration CompensationSpeed Two

StopThreeStop

1/15s 1/4s 1/2s1/30s 1/8s 1/4s1/60s 1/15s 1/8s1/80s 1/20s 1/10s

1/160s 1/40s 1/20s1/200s 1/50s 1/25s1/250s 1/60s 1/30s1/320s 1/80s 1/40s1/500s 1/125s 1/60s

1/1000s 1/250s 1/125s

Speeds with vibration compensation turned on


Lens HoodsIf your lens comes with a detachable hood, it’s advisable to put it on when possible.

A lens hood cuts down on lens flare, bright spots of light that appear in your images. Light coming in from a very wide angle can bounce around the optics inside the lens and cause this. The hood shields light from those angles and will reduce the likelihood of it occurring.

Lens Hood


Lens HoodsA lens hood also cuts down on some ambient light which will affect the clarity and the contrast of an image.

The use of a hood can, in some situations, make a dramatic difference in the quality of your image giving it a punchier, more dynamic result.

The only time that it should not be put on the camera is in overcast conditions but it won’t do any harm to leave it on.

Lens Hood


FiltersNearly all lenses allow you to put filters on the front of them.

Each lens has a specific diameter and that is normally indicated on the lens itself.

You will need a filter with the same diameter to screw onto the front of the lens.

You can also use step-up rings to bring the diameter of the lens up to the diameter of the filter.

Screw in filters


FiltersTo cut down on cost and the amount of equipment you carry, it’s probably best to get filters for your largest diameter lens and then some step up rings to fit them to the smaller diameter lenses.

Using step down rings is not recommended as they reduce the amount of light entering the lens around the edges and will result in vignetting, especially on wider angle settings.

Step up ring


FiltersTry and get slim filters if possible. The slimmer the filter, the less likely that vignetting will occur.

Anything that protrudes from the front of the lens may affect the field of view, especially at the wide angle end.

At the extreme end (below 20mm on full frame, 14mm on crop), consider getting a larger filter and step up ring.

Thicker CPL filter


FiltersDon’t be tempted by cheap “no name” filters. Their optical quality may be poor compared to the big names.

Anything that you put on the front of the lens will affect the optical quality of the image and a cheap bit of glass will do no favours.

The named brands aren’t that expensive. Hoya and Hama for instance will only cost a couple of pounds extra.

Filter cases


UV FiltersThese cut out Ultraviolet light and can reduce some haze in bright conditions. Other than that, they are clear and will allow light to pass through.

Get one and fit it to your lens. They are a cheap way of protecting the front elements from dust, marks and damage.

You can leave it on all the time that you are not using another filter.

UV Filter


UV FiltersA UV filter can be around the £15-20 mark.

If you scratch a filter, you can buy another one. If something hits the front of the lens, the filter will take the hit.

If you clean the filter, you’re not touching the lens. Water droplets aren’t going to mark.

The small price to pay is better than having to replace a £500 lens

UV Filter


ND FiltersND filters, or neutral density filters, effectively act like sunglasses for your camera.

They reduce the amount of light entering the lens.

They are primarily used to lengthen the exposure time of an image, allowing lower f numbers, shallower depth of field or to get longer shutter speeds.

ND2 Filter


ND FiltersBy far the common way of describing the strength of a filter is using the NDx format.

An ND4 filter will give you two stops of light reduction. An ND32 filter will give you five stops.

There is also a filter called a big stopper. It is labelled as an ND100 or ND110 but really, using the above formula, it should be an ND1024 or more. It will give you 10 stops of light reduction.

ND8 filter


Variable ND FiltersVariable ND filters allow you to rotate one ring on the filter to vary the amount of light entering the lens.

They can effectively act between ND2 and ND400 which changes the exposure by 1 stop up to 8 stops.

Towards the maximum end of the variance, it is common for them to create a black X band across images so it is wise to only use them to a certain level.

Variable ND Filter


Polarising FiltersPolarising filters block light coming in from oblique angles.

They are rotating filters so that you can adjust the angle of blocked light. They are sort of like Venetian blinds.

By looking through the viewfinder and rotating the filter, you can adjust the effect.

Polarising filter


Polarising FiltersPolarising filters are great for adding vividness to images.

They can make a sky look bluer, colours in objects more punchy and this is done by blocking out some of the ambient whiteness or haze in a scene.

They can also be used to eliminate reflections or, indeed, enhance them in windows, mirrors or on the surface of water.

Polarising filter


Polarising FiltersThe only problem is that polarising filters are angle specific. The effect is only for that angle on the lens.

If you change from portrait to landscape, you will need to readjust the filter.

If your lens has a focus system that rotates the end of the lens, every time you focus, you will need to readjust. It is better to use a lens with internal focusing.

Polarising filter


Square FiltersThe other option for filters is to use a set of square filters such as Cokin or Lee.

These consist of a holder that screws onto the front of the lens and a set of square glass or perspex filters that slot into the holder.

They tend to be a bit bulky and will require an adaptor to fit the diameter of your lens.

Filter holder


Square FiltersYou can’t get variable filters in this variety but you can get ND filters which work in the same way.

You can also get graduated ND filters which vary in strength from top to bottom which is ideal if you have a bright sky and dark land. It will even out the exposure across the image when you align the graduation with the severe change in brightness, normally along the horizon.

Square graduated ND filter


Cooling and Warming Filters

These are pretty much redundant with modern digital cameras as you can adjust the white balance either in camera or (with RAW) at post production.

They were used to either warm (more red) or cool (more blue) an image especially when you had no control over that when using film.

Cooling and warming filters


Special Effect FiltersYou can also get a number of effect filters.

Star filters will create stars around points of light in an image.

A soft focus filter will blur the outer areas of an image while keeping the centre sharp.

There are also images for creating rainbow bursts from light sources.

Star filter


Lens careA lens is a precision optical instrument, so it will need careful care and handling.

Always place lens caps on both ends of the lens when not in use, even for short periods. It’s amazing how much dirt and dust can get on a lens just by walking around.

Don’t touch the front or rear elements. A finger print or grease from your hands will affect image quality and attract dirt and dust.

Lens caps


Lens careDon’t get water on the elements if at all possible. It will leave stains and marks.

Use an air blower or brush to get rid of dust or a microfibre cloth lightly brushed over the surface.

If after removing dust there are stubborn marks, use a microfibre cloth with even pressure rubbing with a circular motion from the inside to out of the lens element.

Air blower


Lens careIf dirt is still present, consider using a LensPen. Always ensure that you get a genuine product or one from Hama. Don’t get sucked in by cheap versions as the carbon in the cleaning head may actually scratch the lens.

Microfibre cloths are easy to come by. Use microfibre ones as they don’t cling onto dust increasing the risk of scratches.

LensPen


Lens careFit a UV filter and leave it on. If it’s the same diameter as your lens, the lens cap will fit onto that instead of your lens. Periodically remove it and clean the reverse side and the lens element to make sure that it’s all clean.

Use the lens hood as a protector so that if you bang your lens against something, the hood will take the impact rather than the lens itself.

UV Filter


Lens careWhen changing lenses, remove the inner cap of the lens that you are fitting and have it in your hand ready.

Remove the lens on your camera with the camera facing downwards and as soon as the lens is removed, place the cap on the lens.

Take the replacement lens and put it on the camera quickly.

Changing lenses


Lens careThe reason for doing this is to prevent any dust or dirt getting onto the lenses inner element or inside the camera.

Any dust inside the camera may settle on the image sensor and cause constant blots on your images.

Always change lenses in a sheltered, non dusty, calm area.

Don’t change lenses here


What lens do I buy?There’s no easy answer to this, really.

Obviously, and as a good starting point, it has to fit your camera, work with your camera and be the correct format, either crop or full sensor.

What is your aim? What type of photos do you want to take? These questions need answering before making a selection. Choose a lens that is going to perform well in the situation that you want.


What lens do I buy?How much do you want to spend? Is quality important to you? More expensive lenses tend to be better optically but if you’re budget is limited, you may have to sacrifice a bit.

Do you go for the big names or the third party lenses? With the Canon or Nikon lenses, you’ll pay a premium. Sigma and Tamron offer better value for money but you may lose some quality. Check the review sites to see what people think about the lens.


What lens do I buy?Are you going to actually use it? There’s no point spending money on something that is going to sit in a cupboard.

Consider second-hand. There’s always a risk that you’ll get a dud, but there’s some corkers out there and you can save a bit of cash.

Think of it as an investment. A good lens will last a lot longer than a camera body. Prices of lenses remain buoyant for longer so as long as you keep to the same system, you can use them on your next spangly model.


What lens do I buy?My suggestions are:

• A good, fast standard zoom (Sigma 17-50mm f/2.8)• A “travel zoom” (Tamron 18-270mm)• A prime lens (Nikon 35mm)

Why? They cover a good range of abilities. The prime lens is an ideal way to learn about photography and composition, the travel zoom is a bung-it-on and go lens, and the fast standard lens will give good quality in most conditions including low light.


What lens do I buy?Don’t get bogged down by lenses. You’ll only be able to carry about three comfortably with your camera.

If you have a selection, make a choice based on your location and purpose.

Select a “default” lens. The one that you use the most and leave it attached to your camera after every shoot.

If your selection is wrong, vow to return to the location with a different selection of lenses to try out.


What lens do I buy?Occasionally, travel light. Take your camera and one lens out and work within its limits.

You’ll find it rewarding and it will make you think more. Best to do it with the prime lens as that really does get you moving about and testing your composition skills.

Minimise the filter clutter by taking what you need and use step up rings and large diameter filters to reduce space.


What lens do I buy?Research.

Read reviews of lenses before you buy. Ask people at the Group for advice. They may be able to let you have a play.

Consider buying from a local shop (like Cameraworld in Chelmsford or London Camera Exchange in Colchester) so that you can get one-to-one advice.

Watch out for “grey imports” that come from overseas and will probably not have a UK guarantee.


What lens do I buy?Remember:

It doesn’t matter how good your camera is or how good your lens is. It doesn’t matter how much you spend on your camera equipment.

The most important part of the camera is the nut on the back.Sure, better quality cameras and lenses may improve YOUR shot. If you don’t practice, improve your skills, test yourself and learn how your camera works, then that shot may not be the best.

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A Beginner’s Guide To Lenses · A Beginner’s Guide to Lenses Camera systems Once you have selected a Camera manufacturer and system, you will only be able to use lenses designed