What is a Fast Lens?

What is a Fast Lens?

Fast-Lens-1‘I keep hearing about ‘fast’ lenses and how great they are, but I’m not sure what they are and why I need one. Is it something to do with how fast its shutter speed can go or how fast it focuses? Can you shed some light on it?’ – Theresa

The speed of a lens and how ‘fast’ it is refers to the maximum aperture of the lens. The larger the maximum aperture the faster the lens is.

When a lens is talked about it generally is described with its focal length (for example it could e a 50mm lens or a 300mm lens) as well as its maximum aperture (usually it will be a number with an ‘f’ in front of it – for example f/1.8 or f/4 or f/5.6). The smaller the number is the bigger the maximum aperture is.

Remember that aperture is the size of the hole in the lens that lets light in when you hit the shutter. So the bigger the maximum aperture – the more light that your lens will allow in.

The reason that a lens with a big maximum aperture is referred to as fast is that it lets more light in and therefore you can use faster shutter speeds even when there might not be much light around.

Why would you want a fast lens?

Fast lenses can be advantageous over slower ones in certain shooting conditions and types of photography. They really come into their own where there is either low light (for example if you need to shoot indoors but can’t use a flash) or where you need to use a fast shutter speed (for example in sports or even wildlife photography). They are especially useful when you need both a fast shutter speed in low light (ie indoor sports).

In general – a fast lens is any lens with a maximum aperture of f/4 or more (ie f/2.8, f/1.8, f/1.4 etc). The lens pictured above is a Canon 50mm f/1.2 lens – very fast but also quite expensive.

Keep in mind also that because you’re using larger apertures that this has an impact upon the depth of field that you get in your shots. Larger apertures lead to shallower depth of field which can be a great thing if you’re wanting to make your subject really stand out from its background (more on this in our introduction to aperture tutorial).

Fast lenses can be really useful to have but unfortunately they can also be quite expensive to buy. However if you’d like a more economical fast lens you might like to check out 50mm lenses. For example both Nikon and Canon have some lovely fast lenses in this focal length.

Here are a few:


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Darren Rowse is the editor and founder of Digital Photography School and SnapnDeals. He lives in Melbourne Australia and is also the editor of the ProBlogger Blog Tips. Follow him on Instagram, on Twitter at @digitalPS or on Google+.

Some Older Comments

  • Manmohan Sreedhar April 6, 2013 05:58 am


    I have a different reason for why a lens is called a 'fast' lens. It may not be necessarily because a lens with a maximum aperture allows the use of faster shutter speeds in poor light. An f/1.2 setting is going to be of practically no use in most circumstances due to the extremly shallow depth of field. So these 'faster' mens do not really give the advantage of shootingin poor light that it is credited for.

    I belive the phase detection autofocus is faster when the lighting is good. All SLRs always have the aperture wide open during focusing and automatically stops down to the set aperture value only when you release the shutter. So a lens with a larger aperture allows you to focus faster in low light and this perhaps justifued calling them a fast lens more than the possibiluty using a faster shutter spped.

    I am not sure I am correct. This is justmy thought.

  • alex mills February 28, 2013 08:42 am


    I hope somebody may be able to advice. I need to buy a new lens for concert photography and portraits
    I can't afford a fast lens with a f/2.8 but I need a zoom lens for the situations when I can't get near the stage
    in dark lighting would these lenses manage ? got a Canon
    Tamron AF 18-200mm F/3.5 or 55-200mm ? 135mm ?

  • George Slusher December 7, 2012 08:26 pm

    @john r: The reason you read more about the Canon and Nikon lenses is that either of those brands outsells all others combined, excluding the other. (Canon is the largest seller.)

    it sounds like your lenses are pretty slow--the kit lens and a slow (high aperture or f-number) zoom. They won't be much good for birds in flight unless you are very, very good at tracking, as the bird's motion will lead to blurring.

    Even with a faster lens (and thus faster shutter speeds), it takes a LOT of practice to do shots of birds in flight. You have to be able to find them quickly and anticipate where they're going. Start with soaring birds, which move fairly slowly and stay either in straight lines or gradual circles. It also helps to be fairly close to the birds and to shoot larger birds--pelicans are fine! Shooting smaller birds and/or further away will require longer focal lengths, which makes tracking even harder. Serious bird photographers might use a 500mm lens, but mounted on a tripod with a gimbal head for tracking. I used to use a Canon 100-400mm lens but now a Sigam 120-400mm lens for birds. Neither is lightweight; they're just barely useable handheld.

    A trick: keep your zoom at the WIDE end (75mm). That will make it a lot easier to find a bird in flight. Once you're tracking the bird, zoom in to get the framing you want. Also, exposure against the sky will probably make the bird look dark, so use exposure compensation as you would for backlighting (about +2 stops). A bird on the ground shouldn't need this, unless it's on a sandy beach. A bird on water could probably use some exposure compensation--experiment to see.

  • John R December 7, 2012 02:02 am

    I see a lot of talk about cannon and Nikon. I have been very happy with my NEX 3. I have what I think are some awsome photos. I'm still learning a lot. I have 16mm, 18-55 mm and a 75-200 mm lenses. I just got my wide angle to try. I'm mostly into nature photos so far. Usually involving water at sunset or sunrise. At this time I'm only out to please me.

    I've heard others say the NEX 3 is good for walking around. It is hard to catch birds in flight though. The pelicans have to stand still.

  • shaheen December 14, 2011 06:58 pm

    hi larry. your comment seems to be incomplete.

  • Larry Miller December 14, 2011 08:53 am

    What Shaheen said....

  • shaheen September 9, 2010 05:36 pm

    Hi Sherry,
    Whether you buy a Canon, Nikon, Tamron, Sigma or any other brand lens, make sure that it is at-least a f/1.8 50mm, or a f/1.4 50mm or a f/1.2 50mm lens. If the lens offers image stabilization, the better. the f/1.2 50mm is the fastest lens and the f/1.4 50mm is the second fastest and will allow blur-free hand held photography in as low light conditions as found in a room lit by a single candle! whereas the a f/1.8 50mm lens, will require a slightly more lit conditions. a 50 mm lens is perfect for urban and street scenes shooting as well as a perfect portrait lens. it will offer a lot of versatility. :-)

  • Sherry September 3, 2010 01:00 pm

    Does anyone have an advice for the type of lens needed for low-light, urban shooting, i.e. street scenes, neon, etc?

  • Rowland April 25, 2010 07:21 am

    A little tardy replying, and I didn't mean to start a flame war over lenses.

    I did eventually join an astronomy forum and quote "astrophotography is a slippery slope of escalating costs." Some beautiful shots taken by one of the members with an L-Series Canon lens - but the camera was modified - removal of the factory IR filter - and the use of Hydrogen alpha and Oxygen III filters. I was hoping to avoid the costs, but that's just not possible.

    After weeks of research, and this may be of interest, there are several ways to artificially improve images taken in high contrast. A Minus Violet filter for camera lenses and the "Fringe Killer" filter for achromatic refractor telescopes, or just get a purpose built telescope.

    I have since ordered an 80mm apochromatic refractor - f/6.3, FL 480mm, Hoya glass FPL-51 flourite triplet, with very good focus in the RGB wavelengths to eliminate fringe colour. The other option was to buy a Canon L-Series lens for around 750, but I went with the refractor - its sole purpose is to focus stars at infinity.

    I also purchased a OIII filter for eliminating sodium and mercury wavelengths - street lighting - and increasing contrast when photographing nebula, and a field flattener to have nice circular stars throughout the FOV and a T-ring adapter and ..... you get the picture - so maybe the Leica lens was not such a bad idea after all!

    The next purchase will be a good equatorial mount for precision tracking, the Leica lens is looking even better - this will be a huge improvement on my home made barn door tracker.

    Many thanks for your advice.

  • george slusher April 7, 2010 08:50 am


    Chromatic aberration is often a problem with high contrast subjects. (They don't get much more contrasty than pure black to pure white in a pixel or two.) Chromatic aberration is even more of a problem if the lens is not precisely focussed. (You cannot just set the lens to "infinity" and expect it to be in focus for starry skies. Different lenses will behave differently; some can be set to BEYOND infinity, for example.)

    You really need to find a good astrophotography forum and ask there. You would probably do best with a real telescope and an adapter to mount the camera. Astrophotography is much more complex than this site would even dream of.

    From a pure optics standpoint, I expect that the best Canon lens for you might be the 85mm f/1.2L. Unfortunately, it's also expensive and heavy--$1970 at B&H and 2.25 lb. You can read reviews of the lens by Ken Rockwell and Bryan Carnathan for more information. Do check on astrophotography forums, though.

    The Canon 50mm f/1.2L is probably not as good for your use as the 85mm f/1.2L, though you should think about both.

    You'll also need a rock-solid tripod. Carbon fiber is better than aluminum at absorbing vibration and is lighter, but you should care more about stability than weight. I have a Feisol FT3372 that is quite stable but isn't all that heavy (under 4 lbs) and "only" $500. (If you check out comparable Gitzo tripods, you'll see why I said only. The Feisol is, IMO, better-made than Gitzo tripods and costs a lot less.) Mine has 3 leg sections, rather than 4, for more stability (and a bit less weight) and does NOT have a center column, again for better stability and less weight. (You can get a column, but the tripod goes to almost 5 ft. With a ballhead, it's more than tall enough for me at 5'9".) Check out other tripods, including aluminum and other metals.

    You'll also want to hang a weight (e.g., your camera bag) on the tripod's hook.

    Be sure to put a very good head on the tripod. A geared head like the Manfrotto 405 would probably be easiest to adjust precisely. Next down might be a 3-way head (each axis has a separate control and lock) like the Manfrotto 229. A very good ballhead would be more versatile, if you do other kinds of photography, but could be harder to line up precisely. You'd want a top-rated ballhead, not some cheap thing. The Really Right Stuff BH-55 or maybe their BH-40, Markins M-20 (or maybe M-10, the one I have), and similar heads could be worth checking out.

  • Sime April 7, 2010 05:29 am

    Sure, but it's just not even worth mentioning really... Have you ever tried focussing at f/.95 or even 1.2 / 1.4 much fun :-) -- if someone needs to ask "what is a fast lens" they're not going to be in the Market for a Noctilux, are they... 15k for a lens when you don't know what aperture is could be a bit over kill perhaps... ;-)

  • shaheen April 7, 2010 05:14 am

    my friend, don't look at "LEICA", look at "f/0.95" printed on the lens. I hope then you realize that how fast the lens is.

    To quote from "http://www.dpreview.com/news/0809/08091505leica_50mm_f0_95.asp", it is the world's fastest aspherical lens. The wide maximum aperture gives extremely shallow depth of field and very low light capability. The wide maximum aperture gives extremely shallow depth of field and very low light capability. Hand assembled in Solms Germany, this lens is designed to retain its value and usability for decades.

  • Sime April 6, 2010 10:22 pm

    Having "LEICA" printed on it doesn't make it "The Best" it just makes it very expensive... ;-)

  • shaheen April 6, 2010 09:48 pm

    Well I did not mention it because i did not realize that dollars would be a problem here. You asked for a really good fast lens and this is what I knew about so informed you. Best things in life ain't cheap buddy :-) rest is upto you.

  • Sime April 6, 2010 05:52 am

    Yeah, Shaheen - you missed "and costs $10,450 USD" from the end of your comment ;-)

  • shaheen April 6, 2010 05:27 am

    Hi Rowland, if you are looking for a fast lens then look no further than the LEICA NOCTILUX-M 50 mm f/0.95 ASPH. When used in available light photography, the lens exceeds the perception of the human eye. Even the light from one candle can be sufficient for handheld photography.


    Hope this solves your problem.

  • Rowland April 5, 2010 09:07 am

    I'm looking for a fast lens for astrophotography. It doesn't need to be telephoto, but it does need to have excellent internal characteristics; i.e., as little ghosting and chromatic aberration as possible. At the moment I'm using a standard canon 18-55, and a cheap 55mm - 250mm telephoto on a 1000D. I love the low noise characteristics of the CMOS, but the lens lets me down every time. I have been told that a prime lens - fixed focal length - would be preferable for my task. Depth of field is not important, because a starry sky is at infinity.

    I use bulb for exposures of up to 10 mins - the fasest arpeture is f4 - f5.6 depending on the lens.

    This image is noisy because of colour adjustment without a dark frame - chromatic aberration is apparent - focus is also difficult with these cheap lenses.

    [eimg url='http://www.synergous.com/wp-content/uploads/2009/10/EtaCarinae2.jpeg' title='EtaCarinae2.jpeg']

    This image of Jupiter and its moons highlights the ghosting problem.

    [eimg url=' http://www.synergous.com/wp-content/uploads/2009/10/JupiterMoonsTreeTops2.jpeg' title='JupiterMoonsTreeTops2.jpeg']

    In short I'm looking a lens that will provide a clean crisp image.

  • vilas October 25, 2009 09:48 pm

    we talk about the speed of the film e.g. 100asa, 200asa, 400asa and so on. as the number increases, the film is called faster. similarly in case of lenses, I suppose, more light passes through the lense, that lens becomes faster. Am I correct? If not please correct me. Thanks!

  • George Slusher July 3, 2009 06:58 am

    The "other George" makes a good point. Autofocus can be difficult with fast lenses, though I have no problem choosing where the lens focuses on my Canon 30D. I can choose any of 9 focus points. I can also let the camera do the job, but, as George says, that can mean that the camera focuses on something other than the main subject. It may pick up the most contrast, or the closest point, etc. The most current Canon autofocus systems have "face detection," but they can sometimes "detect" something that's not a face. (My Canon G9 has this and usually works well with groups of people.)

    The problem of manual focus with very fast lenses is real and can be a major pain. Some DSLRs with interchangeable focus screens have a special screen for fast lenses. That would be a great idea for wedding photographers, for example, probably one of the primary groups who use very fast lenses like the Canon 50mm f/1.2 and 85mm f/1.2.

    What is "very fast" also depends upon the focal length. Short focal length lenses can be "faster" than longer lenses because of size limitations--not to mention cost! The fastest long telephoto for Canon cameras today is the Canon 200mm f/2L IS. It weighs 5.6 lb and costs $5,300. (In contrast, the 35mm f/2 lens weighs 0.46 lb and costs $300.) Go beyond 200mm and the fastest lens for Canon DSLRs is f/2.8 (300mm & 400mm), then f/4 (500mm & 600mm), then f/5.6 (800mm). Even with "slower" apertures, supertelephoto lenses are huge and incredibly expensive.

    300mm f/2.8L IS: 6 lb, $4,100
    400mm f/2.8L IS: 11.7 lb, $6,800 (the favorite lens for many sports photographers)
    500mm f/4L IS: 8.53 lb, $5,300 (probably the #1 favorite lens for pro bird & wildlife photographers)
    600mm f/4L IS: 11.8 lb, $7,600
    800mm f/5.6L IS: 9.9 lb, $10,999

    One has to wonder if the 400mm & 600mm lenses come with their own forklifts. They make my "behemoth" zooms--70-200mm f/2.8L IS @ 3.5 lb with collar, 3.2 lb without and 100-400mm f/4.5-5.6L IS @ 3 lb--seem dinky. Those zooms are at about the upper limit for handholding, even with IS. Anything heavier should be used on a tripod or monopod. Pointing my 100-400mm up to try to catch birds in flight (e.g., soaring hawks) shows me that I need to hit the gym! Even worse would be the Sigma 50-500mm f/4-6.3 at 4.1 lbs (no wonder it's called "Bigma"), which doesn't have image stabilization.

  • George E. Norkus July 3, 2009 05:03 am

    My turn for an error. Here is the link to the photo of my mother.

  • George E. Norkus July 3, 2009 05:01 am

    So far no one has mentioned that many really fast lenses are not for beginners and "faint at heart". It doesn't matter what brand camera you have they all work the same.

    Many of the fast lenses used in portrait work, are manual or set to manual focus. Automatic focusing lens are nice and seemingly easy to use but think about what really is going on. You might find the camera focusing on another portion of the subject. The end result could be that your camera chose another main subject and that may not be your initial intentions.

    For example, the Pentax SMC-A, 50mm f/1.2 that I used on my Pentax K20D. It’s not the easiest to use properly at the “faster end”. Should you desire allot of boken, (shallow depth of field), to bring out a subject, that also means you will need to be very exact when you focus. That can be difficult for many people, especially for the older foke out there with aging eyesight! (I’m included in that bunch! LoL)

    One example is a photo of my mother.

    In this picture, notice how shallow the depth of field really. This was a quickly taken shot that I thought was properly focused. Many portrait photos will have the eyes in focus, my original intention. The end result here was great looking teeth and nose but not the eyes. I’m lucky this was not a paying customer but if it was, I would have had more time to properly set things up. It’s not often I get to take her photo so I’ll have to live it.

    Remember the difficulty focusing before running out to purchase a really fast lens for big bucks. Leave that to the advanced amatures and professional.

  • George Slusher February 1, 2009 11:39 pm

    OOPS! I can't edit the above, but I made an error in the boldface. The first boldface lens (the ones that I have) should be the 70-200mm f/4 L. I wish that I had the others before that, but, alas, do not.

  • George Slusher February 1, 2009 11:36 pm

    Re: Mike Lao, "Canon 17-40 f4 L" Most people wouldn't consider an f/4 lens in that range to be "fast." The "fast" Canon lenses in that range are the 16-35mm f/2.8 L II and the EF-S 17-55mm f/2.8 IS (useable only on the 20D/30D/40D/50D and the Digital Rebel series). In the "L" series, Canon has two 'families," f/4 and f/2.8. The numbers in brackets are the prices at B&H. (Lenses in bold,/b> I have.)

    16-35mm f/2.8 L II [$1450]
    24-70mm f/2.8 L [$1190]
    70-200mm f/2.8 L (IS and non-IS) [$1699 & $1190]


    17-40mm f/4 L [$700]
    24-105mm f/4 L IS (the "kit" lens for the 5D, for example) [$1059]
    70-200mm f/4 L (IS and non-IS) [$1100 & $600]
    (The 70-200mm f/4 L IS has been called the "best zoom lens, anywhere" by several reviewers, including some who mostly use Nikon equipment.)

    Canon has two other L zooms, with wider ranges and non-constant maximum apertures, but these are harldy "fast" lenses.

    28-300mm f/3.5-5.6 L IS [$2300]
    100-400mm f/4.5-5.6 L IS [$1460]

    The other "fast" lenses (f/2.8 or larger) by Canon are all primes:

    14mm f/2.8 L II [$2020]
    15mm f/2.8 Fisheye [$610]
    20mm f/2.8 [$445]

    24mm f/1.4 L [$1170]
    24mm f/1.4 L II [$1699]
    24mm f/2.8 [$305]

    28mm f/1.8 [$420]
    28mm f/2.8 [$180]

    35mm f/1.4 L [$1180]
    35mm f/2 [$240]

    50mm f/1.2 L [$1400]
    50mm f/1.4 [$325]
    50mm f/1.8 [$90]
    50mm f/2.5 Macro [$250]

    85mm f/1.2 L [$1870]
    85mm f/1.8 [$355]

    100mm f/2 [$410]
    100mm f/2.8 Macro [$470]

    135mm f/2 L [$935]
    135mm f/2.8 Soft Focus (actually quite sharp!) [$295]

    200mm f/2 L IS [$5300 !]
    200mm f/2.8 L [$695]

    300mm f/2.8 L IS [$4100]

    400mm f/2.8 L IS [$6500]

    (N.B.: At 300mm +, many would consider f/4 lenses to be "fast.")

    Let's make some comparisons to show the penalties for "ultra-fast" lenses. The first number is the price at B&H, the second is the weight, the third is the filter size, which translates into cost, as well:

    50mm f/1.2 L $1400 19.2 oz 72mm
    50mm f/1.4 $325 10.2 oz 58mm
    50mm f/1.8 $90 4.6 oz 52mm

    F/1.2 and f/1.8 are a little bit more than 1 stop apart. That stop will really cost you: 15+ times the price, 4+ times the weight, plus more expensive filters.

    The 50mm comparison is probably the "worst," but other one-stop differences are also instructive. (I didn't compare IS or Macro lenses to non-IS):

    35mm f/1.4 L $1180 20.5 oz 72mm
    35mm f/2 $240 7.4 oz 52mm

    85mm f/1.2 L II $1870 36.8 oz 72mm
    85mm f/1.8 $355 14.9 oz 58mm

    70-200mm f/2.8 L $1190 45 oz 77mm
    70-200mm f/4 L $600 25 oz 67mm

    and the real shocker:

    300mm f/2.8 L IS $4100 5.6 lb rear filter
    300mm f/4 L IS $1059 2.6 lb 77mm

    So, if you want really fast lenses, be prepared for a major hit on your wallet and sore arms, to boot.

  • shaheen January 25, 2009 04:52 am

    Hi, can anyone tell me that what does "gain an effective 2-3 f stops" really means?

  • eB Photography January 20, 2009 01:38 am

    For indoor & low light candids I love the 50mm f/1.4 and 85mm f/1.8 combo. Once you've shot around with fixed focal length lenses you get pretty familiar with the working distance and framing. The sharpness and bokeh, if not just being able to shoot in lower light without a flash, might just get you hooked.

    For wedding & event coverage I find myself in some dim interiors so I pack up the Nikon glass in these arrangements:

    f/1.4 - 50mm
    f/1.8 - 85mm
    f/2.8 - 10.5mm,17-55mm, 70-200mm

  • Eric July 19, 2007 04:31 am

    I just bought a 20mm f1.8 Sigma lens for my Canon 20D, I already knew this but Ill say it anyway, I shoot mostly nightlife photography, and with a 3.5-5.6 (zoom) you would probably need to bump your ISO setting to at least 400-800, or in extreme cases 1600, just to get a shot.

    1.8 does a good job of bluring out the background, while letting an extensive ammount of light in, so you can shoot at a faster shutter speed, and acheive the same level of brightness, etc, as you would on a 3.5 or 5.6 F. Plus its sharper too because theres less blur, and less grain.
    -Hope that helps someone out there.


  • Dave New May 30, 2007 06:20 am

    I have a triumphirate of Canon f/1.8 lenses for use on my 1.6x crop-factor Canon 20D:

    28mm f/1.8 (45mm equivalent, or 'normal' view)
    50mm f/1.8 (80mm equivalent, or 'portrait' view)
    85mm f/1.8 (136mm equivalent, also useful for portrait work)

    These are all useful for available light work, and of course, for those situations where you want a shallow depth of field, but I also find them useful for flash work, as well.

    Consider that you gain an effective 2-3 stops of flash range over the more typical zoom lenses. This equates to stretching your flash range out quite a bit, as well as helping to avoid that 'dark cave' look where the background brightness falls off sharply. Coupled with the Canon DSLR's ability to take practically noise-free shots at ISO 400, 800, or even 1600 with some of the latest bodies, you have a really flexible setup for natural light or flash situations.

    Try shooting in Manual mode, or at least Av (Aperture preferred) and experiment with the camera and flash settings to see how you can balance the background room light with the lighted foreground subject.

    When you want to understand exactly how the Canon EOS flash system interacts with your flash and camera settings, check out:


  • Simeâ„¢ May 3, 2007 06:58 am

    I use my Canon f1.4 50mm on the 30D pretty much all the time.. lovely lens, good fun DOF... Thanks, Steve for the point on the weight of the 400mm... i'm really wanting the 100mm-400mm.. will go rent one for a shoot and see how my bicep is afterwards!


  • Andy Ferra April 26, 2007 03:56 am

    Personally, I think 'fast' is a misnomer.

    It's a 'bright' lens.

  • Stanley April 22, 2007 04:04 pm

    Wire, the Pentax shooter,
    Start at the B&H site, look at the fast ones, then go to the used part of the B&H site. Check KEH, and your local pro store's site. Look for a while before you leap.

    I do not shoot Pentax, but this is what I do. Research, and research some more.

  • deeleea April 21, 2007 10:07 pm

    I recently hired a fast telephoto for my Nikon D100 as I was shooting an indoor conference with a lot of action going on. I already own a 50mm f1:4 which is awesome but requires me to be a lot closer than I need to with the tele.

    I don't know how I'm going to manage without the tele now... or how I ever managed to do it before with my old lenses... It made a massive difference.

    I'm shooting a lot of events so the hire place will be seeing a bit more of me until I've enough dosh to get a fast tele of my own...

  • bailey April 20, 2007 10:50 pm

    I have loved photography for a long and have just recently gotten a little more serious with it, I think I have a good eye but I am still have a hard time when it comes to all these different lenses, I have a Canon Rebel Rebel XTi with the Canon 17-85MM I do a lot of sport photos (my son races motorcycles) and I would really like a little better lens for this, but I also like to take nature photos and want to get into some portrait photography as well.
    Are there any good informative sites, etc to find more info on just lens?

  • Phil April 20, 2007 01:14 am

    I just got the Sony/Minolta (Sonolta? Minony?) 50mm f/1.4 prime lens for my (also new) Sony Alpha 100 (replacing a KM Maxxum 5D). Check back in a week or two...

  • Maclean Patrick April 19, 2007 01:26 pm

    I own a Canon 50mm f/1.8 and it's my primary lens. This lens almost never leaves my Canon 10D. It's an all rounder and worth every penny I invested. I prefer natural lighting over using flash so a fast lens does the trick. With it's ability to handle DOF, it's really good for potraits, wildlife and sports photography.

  • Wire April 19, 2007 07:59 am

    I'm lookig for a big aperture, not very expensive, but useful.

  • Steve April 19, 2007 12:39 am

    I highly recommend renting an expensive lens before you buy. I was seriously considering an investment in the Canon 2.8 400mm and decided to rent it for a week to try it out. That's a huge chunk of change, and I was glad I rented it first.

    I took it out for a day-hike in the woods for wildlife photography and found it to be a beautiful lens. The downside (and what changed my mind about buying it) is that the thing weighs a ton. My arm is still sore. So by renting it first I saved some money. Maybe one day I'll decide to buy it after all, but not now.

    I'll plug the place I rented it from because they had great service: http://www.lensrentals.com/

  • ty April 19, 2007 12:31 am

    For those looking for a fast Canon lens that wont break your wallet, I must recommend the Canon prime 35mm f/2 wide lens. Its under 300$ at most places (I found it for about 250$ on Amazon) and it has been nothing but excellent. It takes super sharp images and with a f/2 max aperture I get some really nice DOF and nice looking bokeh. I am pretty new to photography but this lens has caused me to stick the kit lens in storage and keep this one on my cam at all times.

  • clarkee April 19, 2007 12:26 am

    i treated my self to the Canon EF 50mm f/1.2 L USM Lens for my 5D a few weeks ago and its hardly been off the body.

    its a great lens to use, and gives fantastic results.

    it is an expensive addition to my kit, but well worth the money in my oppinion.

  • Matthew Miller April 19, 2007 12:20 am

    Wire -- there's lots of great fast lenses for Pentax, and generally of very high quality. What are you looking for?

  • Greg Furry April 18, 2007 11:01 pm

    If you haven't got a fast lens and shoot indoors or in low light situations go get a lens now. You will be amazed at the difference. If you want to dip your toe into the water and have a Nikon camera check out the Nikkor 50mm f/1.8. You can find them for just over $100 brand new.

    Nikkor 50mm f/1.8
    Nikkor 85mm f/1.4

  • Fraser April 18, 2007 08:46 pm

    'very fast but also quite expensive'

    how about:

    very fast but also 'very' expensive . . .

  • Wire April 18, 2007 02:12 pm

    Can you tell me some lenses for Pentax?

  • Brian Auer April 18, 2007 12:19 pm

    Like Puplet said, older fast lenses are plentiful if you look in the right places. I've got my eye on a few f/1.4's on eBay that might go for around $50. Once you hit the 1.2 mark, expect to pay the big bucks -- no matter how old the lens is.

  • Daniel April 18, 2007 11:23 am

    I've always thought the term "fast lens" to be quite a misnomer. I think this post does a lot to help clear that up.

  • Mike Lao April 18, 2007 09:59 am

    They can be pricey but they are worth it. Once you get used to a fast lens (i.e. fixed aperture), it's hard to go back to variable aperture lenses.

    Lenses I use:
    Canon 85mm f1.8
    Canon 17-40 f4 L

    I noticed that I am taking a lot more portrait shots after I got the 85mm lens!

  • Puplet April 18, 2007 08:42 am

    Expensive, yes - but don't forget there's a ton of older, manual focus lenses that offer fast apertures, if you're willing to meter and focus manually on your dSLR.

    These older lenses can be a little soft when it comes to detail - but hold their own against the latest digital glass when it comes to low light conditions.

    Not a bad trade-off for something a fraction of the cost of new lenses!

    Lenses I use:

    Nikkor 50mm f1.4 (£45)
    Nikkor 105mm f2.5 (£60)

  • Silverhalide April 18, 2007 06:47 am

    "is that it lets light in faster"

    Wow. Fast lenses change the laws of physics? How'd they do that? special glass?

    No. Fast lenses let more light in. More light means a shorter (faster) shutter speed is needed, thus "a fast lens".

    Another advantage of fast lenses that isn't mentioned is depth of field. The larger the aperture, the shallower the depth of field. Shallow depth of field is useful for isolating a subject from the background (think portraits, athletes, birds -- the subject is in sharp focus while the backgound is nicely blurred out of focus and free of distractions).

    A distinct disadvantage of fast lenses is their size -- a 50mm f/1.8 needs a front element of at least 28mm (50/1.8); a 300mm f/1.8 needs a front element of 167mm (6-1/2"). A 6.5" lens is a big, heavy piece of glass. This is the reason that fast lenses are so expensive. Lens manufacturers can use higher (optical) density glass or other tricks (Canon's DO lenses) to reduce the size of the lens elements behind the first one, but the first element needs to be that big to capture the light.