Lens Buyers Guide

Discussion in 'What Camera Should I Buy?' started by Eliwood, Feb 20, 2007.

  1. Eliwood

    Eliwood Digital Camera Consultant

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    Lens Buyers Guide
    Version 3.5 - Last Updated February 19th, 2007

    Table of Contents

    (0) Preface
    (1) Introduction
    (2) Figuring out your needs
    (3) What determines price?
    (4) Apertures and IS
    (5) Extenders
    (6) MTF Charts
    (7) Lens Recommendations
    (8) Conclusion
    (9) Links/Resources


    This is the same guide that I posted over at DCRP under the alias of Rex914, and a lot of people found it useful, so I'm posting it here too.

    I. Introduction

    Buying a lens for your new DSLR can turn out to be a much more difficult decision than deciding which DSLR or brand to buy. For each system, there are dozens upon dozens of choices on the market ranging from a lowly $50 all the way up to a bank breaking $10,000+.


    This guide will help you choose the right lens(es) given your needs and more practically, your budget.

    II. Figuring out Your Needs

    The first step towards buying a lens is asking yourself what kinds of subjects you shoot the most. That’s where the bulk of your investment needs to go initially. Ask yourself questions like the following...

    - Do I shoot indoors or outdoors?
    - Do I take pictures of closer things or farther things?
    - Do I take photos of fast moving objects (i.e. action, sports)?
    - Do I want to take portraits or do weddings?
    - Do I like hiking around to take pictures of wildlife and nature?
    - Am I into macro photography?
    - Do I take pictures of landscapes, interiors, and/or architecture?
    - Do I prefer more compact, convenient lenses or more bulky, inconvenient lenses that will help me take "better" pictures?

    These are the kinds of questions you need to ask yourself. Once you find out what your needs are, you need to decide what your budget is and how many lenses you plan to buy. If your lens budget is in the range of…

    Under $300

    In this range, a solid 3rd party all-purpose lens will be your best bet. Hopefully, you won't be in tricky situations like indoor sports, concerts or indoor venues where flash is prohibited.


    In this range, you have a little more room to work with. You still can’t afford a “premium” first-party (Canon/Nikon) lens, but you can comfortably buy a top-grade 3rd party lens with money to spare for a 50mm prime (for low light situations).

    Above $600

    When you have a little more money to work with, you can start looking at entry-level premium lenses like Canon’s 17-40 f/4 L and 70-200 f/4 L. However, these won’t do for tricky situations like indoor, low-light photography. For those situations, you will want to look at premium lenses with large apertures of at least f/2.8. You may also want to opt for a prime to complement your choice.

    Either way, refrain from buying more than 2 lenses at the outset. Buy slowly and constantly evaluate what you need. You may end up changing your mind once you start shooting.


    Whichever lens(es) you decide to purchase, be sure to actually try them out in the store before buying! Make sure you’re comfortable with the build of the lens as well as its weight. And most importantly, make sure that its optical quality meets your expectations.


    Bring along a memory card
    and see how the shots come out at home. There's no way you can evaluate image quality through the preview LCD, even a 2.5" one!

    III. What determines price?

    If you are looking at lenses and their prices for the first time, you may be quite bewildered at the pricing scheme. It may be counterintuitive at first to see that the lenses with the widest ranges (the highest "optical zoom") tend to be the cheapest while the ones with the most restrictive ranges tend to be the most expensive. But once you understand how several key factors play into the final cost of a lens, you’ll understand why certain lenses can cost thousands while seemingly similar ones can cost only hundreds.

    There are two primary factors that determine the price of a lens. These are focal length and aperture.

    Focal Length

    The cheapest lenses are the ones that are easiest to make. The easiest lenses to make are those that are close to the 50mm mark*. The farther the focal length deviates from 50mm (percentage-wise), the more costly it will be. It is much trickier to design say… a 10mm or a 500mm lens than a 35mm or an 85mm lens.

    Moreover, we must take into account the fact that most digital SLR's use sensors whose area is smaller than that of 35mm film, and this is where the crop factor originates.

    * Precisely speaking, the "normal" focal length is defined as the length of the diagonal dimension of the medium. For film this is approximately 43.2mm (24mm x 36mm). Calibrating this to 50mm is a simplfication, so that we can make our calculations easier.

    (Comparison between a 50mm to a 1200mm lens)


    The bigger factor into cost is how large the aperture is. The larger the aperture is (indicated by a small f-number), the more costly a lens is. This is why two lenses with the same focal lengths can differ by $1000. Notice how the lenses with large apertures have huge, fat barrels while the small aperture lenses are skinny and compact.

    (Comparison between a small aperture and large aperture lens)

    There are other features that factor into the final cost such as build quality and the inclusion of ED (extra low dispersion) elements for reducing CA ("purple fringing").

    IV. How big an aperture do I need? Do I need IS?

    Bigger apertures are better, but they cost you a lot of extra money. Why do you need a bigger aperture anyways? There are several reasons for wanting a big aperture.

    Bigger apertures are most commonly used in situations where there’s poor lighting and if you cannot use flash. To take a picture, the camera will either need a bigger aperture or it will need to make the shutter speed slower to expose the shot properly. Using a larger ISO value (1600, 3200) will help too, but going too high may sometimes introduce unwanted noise into the picture. If you are handholding the shot in this situation, the need for a bigger aperture is that much more important because a slower shutter speed will lead to camera shake and blurriness.

    You will also need a bigger aperture when you want to blur the background in a shot. When you use a larger aperture, the depth of field becomes shallow, placing only closer things (to the focus point) in focus, leaving the rest out of focus, or blurred. Conversely, when you use a smaller aperture, the depth of field becomes deeper, making a larger part (or in some cases the entire) image in focus.

    Diaphragm Blades and "Bokeh"

    The other major factor when it comes to blurring the background is how many diaphragm blades there are. This affects the the "bokeh" (a Japanese word which literally means "blur"), describing how well a lens handles out of focus areas of an image. Having more blades (7-9) is better than having fewer (5). Bad bokeh can be characterized by the presence of distinct geometric shapes (like pentagons or hexagons) instead of smooth circles when certain elements are blurred out.

    Do I need IS?

    Image Stabilization (IS) is a technology that can reduce the need for a larger aperture if you are handholding shots in low light. In layman's terms, it is a "virtual tripod." In situations where you cannot bring along a tripod, IS can make a difference between a photo that's a keeper and one that heads to the trash bin.

    In practice, IS will gain you about 2 full stops, but your mileage will vary depending on how advanced the technology in the lens is. To put things into context, I've heard of people who were able to handhold shots at ridiculous shutter speeds of 1/4 sec!

    (Right - IS off, Left - IS on)

    Beware that IS does NOT help when the subject moves.
    While IS may still help you handhold the shot, you will still need a fast lens to obtain a faster shutter speed that will freeze the action.

    What apertures do I need?

    If you are doing available-light indoor photography, f/2.8 is the bare minimum. I recommend f/2.0 and larger.

    If you are doing indoor sports or action photography, f/2.0 and larger is virtually required, so you can get fast shutter speeds to freeze the action in addition to bumping up the ISO to 800 or 1600.

    If you are working in decent light (i.e. outdoors), f/4 will work just fine. If you work mostly outdoors in great lighting, f/5.6 and above will suffice. If you plan on bringing a monopod or a tripod to stabilize things, you can even get away with even smaller apertures.

    V. What is an extender?


    An extender is a special kind of lens which mounts itself between the main lens and your camera. As its name suggests, an extender increases the focal length of your lens by some set amount. At this moment, there are two kinds of extenders, 1.4x and 2.0x. As a quick example, if you have a 100mm lens, the 1.4x and 2.0x extenders will transform the focal length into 140mm and 200mm respectively.

    For this reason alone, extenders can be quite useful in extending the reach of your lens at a relatively low cost and also taking less space than an equivalent lens.

    As always though, there's a tradeoff when you gain convenience. You sacrifice image quality, and the lens becomes "slower." Here's an explanation for both points.

    1) You might recall that f-stop is a simple ratio between the diameter of the aperture of the lens (how big the hole is) and the focal length of the lens. For example, a 50mm lens with a 25mm diameter has an f-stop value of 2, hence the f/2 branding. Naturally, this means then that doubling the focal length will double the f-stop value, causing you to lose TWO whole stops. Using a 1.4x extender makes you lose ONE stop. If the f-stop value gets too high, sometimes auto focus will no longer function (check with your manufacturer for exact details).

    2) Extenders also degrade image quality, especially if you use a 2x extender. Think of an extender as a magnifying glass for a moment. If an extender is a magnifying glass, all of the "faults" in a lens will effectively become that much more noticeable. For examples, images may be softer, or they may lack contrast. But this is the price you pay for convenience. I'm sure that most of us would be happy lugging around a 200mm lens with an extender rather than a 400mm lens and a tripod.

    To sum it up, extenders are useful tools for getting more utility out of your lens collection. I personally recommend buying a 1.4x converter as the degredation in speed and more importantly, in image quality, is hardly noticeable. If you start with a very good lens, you may not notice a difference at all!

    VI. How do I read MTF charts?

    (Read this section if you are interested)

    MTF stands for Modulation Transfer Function. You don't need to understand what the heck that means to read an MTF chart.

    An MTF chart gives us a visual representation of how well a lens performs. It gives us a good idea of how contrasty and sharp a lens is in laboratory testing.

    Here are two sample MTF charts from Canon. For simplicity, I have chosen 2 primes. The first chart is for the 135 f/2 L. The second chart is for the 50mm f/1.8.

    [​IMG] [​IMG]
    (Source: Canon USA)

    The vertical axis represents contrast, ranging from 0% to 100%. An ideal lens would take in 100% of the light, but that never happens in practice. So, the higher a line is, the more contrast the lens has, which is good.

    The horizontal axis represents the distance for a sample point from the center of the image in millimeters. It is typically the case that quality suffers as you move towards the edge, but that isn't always true as you can see with the 135L.

    Ignore the dotted lines for a moment. The black lines represent the lens performance wide-open. The blue lines represent its performance at f/8. Obviously, stopping a lens down will result in better contrast and sharpness. The best lenses will differ little when stopped down, meaning they can be used wide-open! This means you want the black and blue lines to be as close to each other as possible as you can see once again with the 135L.

    If you look carefully, you'll notice that for each pair of lines (black and blue), there is a thicker line and a thinner line. The thick line tells you specifically about contrast while the thin line tells you specifically about sharpness.

    Finally, what do the dotted lines represent? Rather than go into the technical jargon of what they are, you are looking for these lines to be close to each other. They represent the quality of the "bokeh."

    MTF charts shouldn't be taken as the ultimate word on everything as they are yet just another bunch of numbers, but they are usually pretty accurate. Their weakness though is that they don't reveal everything about a lens. A good MTF chart doesn't necessarily lead to great performance in real world photos and vice-versa.
    Last edited by a moderator: Feb 20, 2007
  2. Eliwood

    Eliwood Digital Camera Consultant

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    Part II

    VII. Lens Recommendations

    These recommendations are mostly geared towards a budget-minded DSLR buyer with a few nicer lenses for those looking to step up to nicer gear.

    The prevailing theme is, "Less is more." Spend your money on fewer lenses (up to two) if you're strapped for cash rather than spreading your money out. The other big idea is to acquire slowly but steadily. Buy one lens at a time and evaluate your needs. Never buy a lens for the sake of buying a lens!

    A) Common Setups


    The following 4 setups are the among the most common starting kits I've come across.

    Setup A ($250 - $350) - Convenience Lens


    Sigma 18-125 or Sigma 18-200 - Recommended for those who want one lens to handle it all, particularly when traveling. Quality is compromised because of the large range, but the upside is that you can figure out what focal lengths you use the most and work from there.

    Setup B ($350 - $450) - "Walkaround" Lens


    Sigma 17-70mm f/2.8-4.5
    - This is an excellent alternative to the kit lens. It's sharp and it's fast at the wide end. Highly recommended as a walkaround lens.

    Alternatives to the Sigma 17-70 include the Tamron 17-50mm f/2.8 and the Sigma 18-50mm f/2.8 if you desire a faster lens.

    Setup C (add $80) - "Walkaround Lens" + Prime


    Pair any of the lenses above with the 50mm prime (for low light or available light photography), and you've got a powerful duo that can handle most normal conditions.

    Setup D ($1250) - Baby Lens Kit


    Canon 17-40 L + Canon 70-200f/4 L - This is a popular combo for Canon shooters who want to jump straight into the L class lenses. These 2 lenses cover the majority of situations except for those in low light.

    B) Convenience Lenses

    The rest of this guide splits up lenses into various categories. This category contains compact, super-convenient lenses which are good for outdoor shots and for budget-minded photographers.

    Sigma 18-125mm f/3.5-5.6 ($250) – It's not without its flaws, but it's a convenient starter lens and also good for vacations. For $100 more, you can get the 18-200, a similar lens with longer reach.

    Canon EF-S 17-85mm f/4-5.6 IS ($500) - A popular (but overpriced) alternative to the kit lens. It has its flaws, but it's a very convenient lens. The Canon 28-135 IS is a similar lens for $100 less, but it's less suitable for cameras with the crop factor.

    Nikon 18-200mm f/3.5-5.6 VR DX ($700) - This is a very good lens relative to other "convenience lenses." That is, if you can get hold of it. Right now, it's back-ordered at most stores.

    C) Walkaround Lenses

    If you want a wide or standard zoom lens, these are the ones to put atop your list. These are less versatile than the do-it-all lenses, but they are faster and of higher quality.

    Sigma 17-70mm f/2.8-4.5 ($350) - An excellent alternative to a kit lens at a slightly higher price. This lens is sharp throughout its range and roughly replicates a classic 28-105 lens!

    Tamron 17-50mm f/2.8 ($430) - A spectacular lens that's similar in image quality to the 28-75 but more suitable for APS-C based cameras. The 28-75 ($330) is about the same in quality, but the focal length is less convenient on cropped cameras.

    Canon 17-40mm f/4
    L ($650) – Arguably Canon's most popular lens, this great wide-angle walkaround lens can be used everywhere as long as the lighting is good. While third party alternatives are budget friendly, the Canon still trumps them in focus speed/accuracy and build quality.

    Pentax 16-45mm f/4 ($399) - A great lens for a budget price, especially if the $100 rebate is available. Similar in price and quality to the Nikon 18-35mm f/3.5-4.5.

    Canon/Nikon 28-105mm f/3.5-4.5 ($230) - This is one of the best bargains out there and is easily one of the best consumer zooms available. It beats a kit lens by a long shot, but it's less convenient due to the crop factor.

    D) Telephoto Zooms

    Need that extra reach to capture distant subjects? If you are on a tight budget, I highly recommend buying a decent walkaround lens first and then dealing with telephoto later. In addition, you'll learn how to use the camera and be able to better evaluate your situation when the time comes to buy your second lens.

    Up to 200mm

    Canon 70-200mm f/4
    L ($570) - An entry-level L lens which is a big leap up from consumer telephoto lenses. Stunning optical quality as long as you aren't taking low light shots. Lightweight and compact enough to bring everywhere. One common use of this lens is for zoo/short-range wildlife photography.

    Sigma 70-200mm f/2.8 EX DG ($770)
    – An alternative to the first party offerings for hundreds less. Recommended for those low light shots or if you shoot action. There's an updated "Macro" version with brand new optics, and it costs $50 more. It's allegedly replacing this model.

    Nikon 80-200mm f/2.8 ($870) - Equivalent in quality to the Canon 70-200 f/2.8 L (non-IS). Focusing isn't quite as fast since this is not an AF-S lens.

    300mm+ (Remember that these are sub-$1000)

    Sigma 70-300mm f/4-5.6 APO DG ($200)
    - This is the only budget telephoto lens I can recommend. If you need a telephoto lens and only have $200 to spend, this is the lens to buy. Be sure to buy the APO version.

    Canon 70-300mm f/4-5.6 IS ($550)
    - Canon has replaced its popular 75-300 IS with a brand new version that contains a UD element, an updated IS mechanism and an updated body. This is a much sharper and better lens than the old version.

    Nikon 70-300mm f/4.5-5.6 VR ($530) - Status pending.

    Sigma 100-300mm f/4
    EX DG ($850) - Think of this as a longer version of Canon's 70-200 f/4. While this is arguably Sigma's best lens, take note that there's no IS which does limit this lens' appeal. It's also quite heavy.

    E) Ultra Wide Zooms

    With the advent of digital bodies with a crop factor (20D, D70) came the need for ultra-wide lenses to make up for lost coverage at the wide end. Consequently, almost all of these lenses are only suitable for such bodies and if used on a full-frame camera, will exhibit vignetting. In general, there are a lot of ultra-wide lenses on the market, and most of them are pretty good. The first party offerings are better, but like always, they may not be worth twice the price.

    What may sway your decision most (besides price) may be how each lens fits into your current lens lineup. Because each one starts and stops at different focal lengths, you may want to avoid overlap (or gaps) if at all possible.

    Canon EF-S 10-22mm f/3.5-4.5 ($650) – This is a sharp, relatively distortion-free (for this focal length) lens that has L-class optics. Don't be misled by the f/3.5-4.5 designation. It's f/3.5 up to 20mm and f/4.5 for the last 2mm.

    Tokina 12-24mm f/4 ATX-PRO ($470) – This lens is a great alternative to first party ultra wide lenses. Build quality is superb, and the image quality is similar.

    The other good third party lens to look at is the Sigma 10-20mm f/4-5.6 EX ($470). It's not perfect, but it's similar to the Tokina. I would avoid the Tamron 11-18 which is more expensive and has more faults than the Tokina and Sigma.

    F) Primes

    Primes are the best bangs for the buck if you need them. You lose flexibility, but you gain it all back in sharpness (especially wide-open), low distortion, less lens flare, and less ghosting.

    Do you shoot indoor sports like hockey or indoor action? Do you shoot indoors in low-light in places where flash is prohibited? If you work in these kinds of tricky conditions, consider these lenses. Primes are also superb for portraits though high grade zooms also do the trick.

    I am only listing shorter primes (less than 200mm) here.

    Sigma 30mm f/1.4 EX ($420) – A cheaper, sharper alternative to the expensive first-party f/1.4 offerings. If $420 is too much to spend, Canon and Nikon offer cheaper 35mm f/2 lenses for about half the price.

    50mm f/1.8 (< $100)
    – The "nifty fifty" should be part of everybody’s collection. If you use this prime a lot and you own a Canon body, step up to the f/1.4 version for the better build quality and better optics.

    85mm f/1.8 ($340)
    – An ideal lens for portraits. Also works as a short range telephoto lens in low light. Canon offers a similar 100mm f/2 lens for about the same price if 85mm is too short for you.

    Canon 135mm f/2 L ($900) – This is one of Canon’s best lenses. This gem will serve you extremely well if you shoot indoor sports or concerts. It's also a superb portrait lens. Nikon has a similar lens, but it costs more.

    Canon 200mm f/2.8 L ($630) - This lens is very similar in quality and size to the 135 and is a great, compact alternative to a 70-200 f/2.8 zoom which is heavy and attention grabbing. For $630, it's a steal.

    G) Macro Lenses

    In a gist, macro lenses let you get closer to your subject than a normal lens can, effectively letting you fill up the frame with a small subject. This is how small subjects like bees and flowers can appear "magnified." Macro lenses can also double as standard lenses. The downside? They tend to have higher f-stop numbers than an equivalent lens, and they also tend to hunt a bit in low light.

    Sigma 50mm f/2.8 EX Macro ($230) – A good bang for the buck. This lens renders life size images (1:1) as opposed to the Canon model which only has 0.5x magnification (1:2).

    Canon EF-S 60mm f/2.8 Macro ($350)
    - Although it's an EF-S lens, this is a spectacular macro lens made to replicate a classic 100mm macro lens. Sharpness is top notch, and the build quality is quite good. Great for product photography.

    Tamron 90mm f/2.8 Macro ($400) – Popular telephoto macro. The Canon/Nikon 100mm versions are better (particularly in focusing) but cost more. The Sigma 105mm f/2.8 EX ($350) is also very similar to the Tamron.

    Sigma 180mm f/2.8 EX APO Macro HSM ($650) - Sharpness is undeniably good though focusing speed is lacking compared to first party choices. Sigma also makes a popular 150mm macro lens if 180mm is a bit too long.

    Summary: It's hard to go wrong with any dedicated macro lens. Just pick the focal length(s) you need, and you're set!

    VIII. Conclusion

    I hope that you now have a better idea of what lenses to get for your brand new DSLR. Even if you are still unsure about what to get, you should now be a more informed buyer, and you will make a better decision about what lens to buy in the end.

    IX. Resources

    These are sites that supply ratings and/or reviews for various lenses. Take what they say with a grain of salt. They’re good for doing a “sanity check” and making sure the lens you want isn’t a dud, but don’t take what they say as the absolute truth. Look for general trends in what users say and see if those comments really affect you.

    Lens Specification Charts

    - Canon
    - Nikon

    Lens Reviews

    - Our lens reviews (DCRP)

    - Photozone (Full reviews)
    - Lightrules (Detailed Lens Comparisons)
    - The Digital Picture (Full Reviews and Comparisons)
    - Fred Miranda (numbers and user comments)
    - Photodo (all numbers)
    - William Castleman (lens comparisons)
    Last edited by a moderator: Feb 20, 2007
  3. Ben Stafford

    Ben Stafford Site Admin

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    Thanks! This is awesome!
  4. Eliwood

    Eliwood Digital Camera Consultant

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    I've got a minor request. The personal site on which I host these images will be expiring in about 2 months. Is it possible to upload the images here, so they don't get lost when my site goes down?
  5. Ben Stafford

    Ben Stafford Site Admin

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    All taken care of.
  6. Wail

    Wail Well-Known Member

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    What a wonderful guide. I say it's 6 out of 5 stars ...
  7. UFG

    UFG Member

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    Wow, excellently stated and extremely comprehensive!
  8. khanhfat

    khanhfat Member

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    nice work in writting up the review. I might need a F1.8 85mm and a L class Zoom for sports.
  9. gubak

    gubak Active Member

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    Nice topic and very helpful informations!
  10. AaronM

    AaronM News/Review Writer News/Review Writer

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    One Macro addition

    I'd just add as an addendum to the Macro list the Canon MP-E. It is somewhat unique in its fantastic 5:1 high end. It is not for the casual user, as focusing essentially requires a sliding tripod head, but it is unsurpassed in taking close-ups
    Here is a brief explanation of how to use it(not by me) and some example pictures(it helps to have a Zenith 135 handy)

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