Lenses. So many of them. There is no best.

Focal Length

Lenses are categorized by their focal length in mm. More or less that number relates to angle of view which dictates the ideal use of a lens. 


Lenses that have an angle of view somewhat similar to human eyes are called normal or standard lenses. This is around 35mm for crop sensor dSLR's or 50mm for full-frame dSLR's and (35mm) film SLR's. Normal lenses are great for taking people in general. You use it also for portraits, candids, pets and most anything that interests you.


Wide angle lenses see more than normal. This makes the objects in the picture smaller but the scene wider. Less than 25mm to around 12mm are considered wide angle in crop sensor dSLR's while around 35mm to around 18mm are wide for full-frame and (35mm) film SLR's. These lenses are very good for taking landscapes and large group shots.


Super wide angle lenses are those that have lower than 12mm for crop sensor dSLR's and lower than 18mm in full-frame and (35mm) film SLR's. These lenses have pronounced distortion making straight lines curve inwards. The best example of this is the fisheye lens. Aside from special effects, super wide angle lenses are used for cramped spaces. You can see more without backing away too much.


Telephoto lenses have a narrower angle of view than normal lenses. They usually range from 50mm to 100mm for crop sensor dSLR's and 75mm up to 150mm for full-frame and (35mm) SLR's. Subjects appear bigger to fill up the picture more easily. Lenses like these are good for closeup shots where you focus more on detail.


Super telephoto lenses are used to pull very far objects closer to you. They are those with focal lengths higher than 100mm for crop sensor dSLR's and more than 150mm for full-frame and (35mm) SLR's. Super telephotos are important in wildlife, nature and for sleuthing.


Prime lenses vs. Zoom lenses

Lenses that have only one focal length are called prime lenses. They do not zoom. An example is the 50mm lens below. Those that have variable focal lengths are called zoom lenses. Zoom lenses are indicated by their minimum and maximum focal lengths like the 18-55mm.

Generally, prime lenses have better optical quality than zoom lenses. That's the reason you will find that most demanding professional photographers use prime lenses exclusively.


Zoom is the ability of the lens to change focal length. There are wide zoom lenses like the 10-20mm, standard zoom lenses like the 18-55mm or 28-75mm, telephoto zooms like the 80-200mm and 100-300mm and super zooms like the 28-300mm and the Tamron 18-250mm.

13+X zoom lenses

(X) Zoom Factor Computation (and the insignificance of it)

To compute for the zoom factor of a lens, use the following formula:

Zoom factor = maximum focal length / minimum focal length

An 18-55mm zoom lens will be computed as 55/18 resulting to 3X. The 18-250mm super zoom lens can be rounded to 14X. That is very high for dSLRs. The longest at the time of writing (9/2012)is the Nikon 18-300mm 16.67X zoom lens. It's harder to make large zoom factor lenses for dSLRs due to cost and physical constraints.

Zoom does not equate to magnifying power. Take note that a 1000mm non-zooming lens (1000/1000 = 1X) will make a far object seem exactly four times closer to you than that 14X 18-250mm super zoom. It's all in the focal length.

Focal Length / Angle of View Comparison

Here is a guide on focal lengths and their resulting angles of view so you can compare them more visually. Again, the site is here.


Aperture, Lens Speed

When buying lenses, you may also be concerned with speed. Aperture is the size of the hole. It is indicated by f/values. The lower the f/number, the larger the maximum aperture size of the lens, the faster you can set the camera's speed and take the shot, the faster the lens is but the more expensive it becomes. F/1.8 is fast enough and affordable, f/1.4 is great, f/1.2 is heaven while f/0.7 is mind-blowing. These very large aperture sizes will produce very shallow depth of field (DOF) making blurry backgrounds easy as pie. They also make shooting in low light a lot easier. You can usually find these low f/numbers with (but not limited to) 50mm lenses.

With some zoom lenses, the maximum aperture may also come in a range like the 18-55mm f/3.5-5.6. That's just the maximum aperture in the focal length range. The minimum aperture is different and usually not indicated in the naming of the lens. Those kind of zoom lenses are referred to as "variable aperture" zoom lenses and aperture size changes as you change focal length. There are faster (meaning wider aperture) and more expensive (yes, more pricey) zoom lenses that don't change aperture size as you change focal length. They are called "constant aperture" zoom lenses.


Special Purpose Lenses

There are some specialized lenses for different purposes. If you are concerned with making very small objects seem large, you will need a macro lens. Most macro lenses are normal or telephoto. Check the minimum focusing distance when buying a macro lens to suit your needs.


Another specialized lens is the tilt-shift lens. This is usually a wide angle lens that has controls to move the mount sideways and up or down to allow optical correction for maintaining straight lines. This is very important for architectural shots. On this picture on the right, the left side is uncorrected while the right is with tilt-shift applied.


The Kit Lens

Believe it or not, the 18-55mm kit lens is enough for most of the common shooting conditions you will encounter. The 18-300mm 14X zoom lens might be the lens with longest zoom range in the dSLR world but it definitely is not the best in glass quality. Optically, the best lenses are those that don't zoom. To zoom non-zooming lenses, the secret is to use your legs. Walk.


Crop Factor

Digital sensor size will play a role on the angle of view of a lens. Canon crop sensor dSLRs have a crop factor of 1.6X while Nikon, Sony and Pentax have it at 1.5X. The smaller sensor size changes the angle of view of the lens compared to a 35mm film camera or a full-frame dSLR by the crop factor. This means that on a 1.5X crop sensor dSLR, the 50mm lens will act like a 75mm lens on a full-frame dSLR.

50mm x 1.5 = 75mm

Take note that the 50mm lens is still 50mm on the crop sensor dSLR. The only difference is that it's angle of view on the crop sensor dSLR is equal to the angle of view of a 75mm lens on a full-frame dSLR or a 35mm film camera.

This is important to those who are used to film SLR focal length terms. If you are just starting, you shouldn't have any problem unless you use mixed full-frame and crop sensor bodies. You only need to remember what is the normal focal length of your camera, 35mm for crop sensors and 50mm for full-frame. Lesser than that number is wide angle while more than normal is telephoto.


On a side note, I have to mention 35mm film because there are other film sizes. Do not confuse it with a 35mm lens. 35mm film is the standard reference for comparison. This is what is referred to when you read "Equivalent" under focal length in some spec pages.


This page is just about the numbers. If you are concerned with the letters, I have only a few helpful links so far which personally concerns me. For Nikon, see this and this. For Pentax, click here.

Now you know!



  1. Thanks for this information... It really has helped me a lot!

  2. Gr8 Pics...I just wanted your help to find out which is the best Cell Phone Maker is terms of Camera Quality?
    Is it Nokia, Samsung or Sony Ericsson?

  3. @tan30, only the sunset is mine. The rest aren't. As for cellphone cameras, just go along with this line of thinking. Nokia is purely a cellphone maker, Samsung makes great TVs, while Sony is one of the pioneers in digital camera technology.

  4. Hi Keerok, I got a nikon d5000 camera and 18-55 mm lens along with 55-200mm lens.But irrespective of which setting I choose, auto-portarit, aperture priority, manual etc, am unable to get the shallow depth in the pics i take, where the focus is only on the person or thing and everything else is blurred.I tried max aperture i.e f3.5 on my cam and still can't get the blurred background effect.Please let me know how can I take the pic with shallow depth.


  5. Position subject as far as possible from background. Position camera as near as possible to subject.

    Try using 55mm at f/5.6 (if that is the largest aperture at your lens) with in a couple of feet from your subject with the background 5 meters away.

  6. great information! thanks man, good job. :)

  7. Thank you so much! I am new to this game and appreciate any information that helps me understand digital photography. I have been able to take some 'ok' pics but this has been down to luck more than skill!

    Your blog has made a lot of grey areas much clearer.

    Please keep up the good work :-)

  8. Hi Keerok,
    I'm having a bit of a problem understanding the letters and numbers used when people are advertising their lenses. I have a Nikon D3000 and I am looking to get something with a more powerful zoom as I'm finding this one a little disappointing in that area (however, I've not taken the leap to use it in manual yet :/ ) I know that Nikon uses an F-mount, but a lot of sellers aren't aware of what mount their lenses use, only the brand the brand of camera it fits. I want to buy a Sigma 400mm (prime) f/5.6 (I figure the more mm it has, the closer zoom it'll have? and therefore I'll be able to take pictures from a longer distance, like animal and nature pictures)
    Do you have any tips as far as amateur lens shopping goes?
    I'd like to go pro at some point, but don't currently have the depth of knowledge or the budget to do so.

    Thank you very much, Robyn

  9. Lens numbers mean the same whatever brand so 400mm and f/5.6 would be the same whatever brand. Letters are really confusing so you will have to research on it a bit to understand fully what features they represent. Your main concern is autofocus and with Nikon lenses, only AF-S and AF-I lenses do that. There are equivalent letter designations with third-party brands but I'm not familiar with them. What's important is that the lens must have an internal motor to autofocus with your camera.

    You are correct, the more mm a lens has, the closer you get to a distant subject. It's not zoom. It's called telephoto. Manual focusing is easy but needs getting used to but no matter how good you are in focusing, you won't get razor sharp photos compared to AF with VR.

    When buying lenses, the cheaper you go, the more you have to work with it. In photography, you get exactly what you pay for.

  10. Thank you Keerok, I appreciate the help.

  11. i have searching the net for a basic explaination of lenses and zooming etc.. and this has been the best! thanks!

  12. Hi! Just discovered your blog while researching lenses - great post! I've got a question for you, if you have the time: I'd love to be able to take crisp, close-up shots of objects for my blog, preferable focusing on the subject and have the background be blurry and out of focus. Which lens is best for this? the 30mm or 50mm? And, which lens or setting is best for when sight-seeing, meaning taking photos of buildings, etc. Thanks!!! Greetings from Switzerland :)

  13. Mabuhay Switzerland!

    Close up of small objects? Macro lens. What focal length exactly will depend on how far you will be from the subject. The nearer you are, the shorter the macro lens. In general, 50mm would do fine for both APS-C and full frame. Macro lenses have very pronounced blur effects that the subject itself will get blurred in some parts. If you find blur too much, use a larger f/number and more light. If you're not shooting small objects, the kit lens will do. See this ( http://keerok-photography.blogspot.com/2011/05/how-to-blur-background.html ).

    For sight-seeing, the best is the 18-55mm kit lens. The wide end (18mm) would be most useful for taking most of the scenery. Settings will depend on the lighting condition. If you don't know how, set everything to Auto then if you want the picture brighter, simply move exposure compensation to the plus side or to make it darker, to the minus side.

  14. Hi Keerok,

    I am a big fan of photography, I found your blog is very helpful and informative to photographers.
    I am beginner to DSLR photography, and I myself want to have one.
    I have zeroed in on Nikon D5200 and D3300 to buy.
    Can you please help me to choose one in them.
    Thanks in advance.

    1. Hi Praveen Naganur! It really is a toss up between those two models but I would prefer the slightly higher-classed D5200 over the bottom of the barrel D3300.