Everyone I speak to says that a 50mm lens is the best and beats them all as an all-rounder. I was wondering whether to get myself a decent, fast 50mm as well. However I'm still not 100% sure whether I really need such a lens.

I use a Pentax K10D and mainly shoot people (kids, portraits, some street shots). The lens I love and use most is the DA 70mm f/2.4 Limited. I often also use a DA 40mm f/2.8 Limited. They are great little lenses that produce very high quality images but they could be a bit faster.

Is is worth spending 400 quid on a Sigma 50mm f/1.4 in my situation? It seems like a good compromise between the 40mm and 70mm and much faster (in fact, 2 f-stops faster than the DA 70mm f/2.8!). On the other hand would the lens be sufficiently different from my current lenses?

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    Since you have a Pentax, what you really absolutely need is a 55mm F/1.4, 50mm is so unoriginal ;) Seriously, see the related questions suggest by Matt.
    – Itai
    Jul 25, 2011 at 1:26
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    No. I feel that a 50mm is best used on a full-frame. Being effectively 80mm on an APS-C body, it is not wide enough to be "all rounder". While on a full frame, 50mm is just wide enough for typical use. Another popular choice is 35mm. However these are very general preferences, and in the end, you should only buy when you are sure you will enjoy using it. Not for other people's sake.
    – Gapton
    Jun 27, 2012 at 4:54
  • For your type of photography, you need a lens that focus fast, for example the DA 40mm ltd. (the old one or the new HD one).
    – Max
    Oct 18, 2013 at 14:25
  • Simply buy an SMC Pentax-A 50mm F1.7 for 50$, and you'll be a lot happy ;-)
    – motoDrizzt
    Nov 16, 2018 at 20:22

11 Answers 11


No, you don't.

In some circles of photography, the 50mm has reached almost cult religion status. It seems to solve everything from focus problems to technique stagnation to global warming. Ask a question about photography, and chances are, someone will recommend a 50mm lens as the solution ("I want to take images of the space station crossing the sun" "The 50mm 1.2 is perfect for this! the narrow depth of field will give you a nice soft focus on the sun's surface")

In reality, for some types of photography, the 50mm is awesome; some portraiture, but more still life and item photography and places where the narrow depth of field can get the image a very strong focal composition. And if you do that kind of photography, then a 50mm is a good lens to add to your kit.

but many of us see no need for it, don't do photography that lends itself to a 50mm, and have no intention of ever buying one. And while we get shunned by some photographers who look in our kit and see the missing slot where a 50mm should go, we don't feel particularly deprived.

There's a lot of "religion" tied to the 50mm left over from the days when prime lenses were significantly better than zooms, when film was slow and cameras were manual and lenses were slower and your choices were limited. Today, it's a lot different landscape than it used to be, and so some of these "givens" aren't really as true as they used to be.

So here's the hint: anyone who tells you to get a 50mm without knowing what kind of photography you do or how you plan on using it is wrong. it's not a panacea, it's not a given it'll improve your photography. It might, depending on your interests.

But it's certainly not a given that you need one.

So here's the question back: what would you use it for? How often are you shooting your existing lenses in the 20-80 range wide open and what are you trying to do then that you find you can't? If you aren't fighting to create an image under those circumstances and failing because your lens won't do what you need to do, then a 50mm probably won't solve the problem you're trying to solve. It might, however, be an interesting lens to add if you want to start exploring new techniques or styles of photography -- but either way, don't buy it because someone said to, buy it because you've analyzed what you're doing, thought about how you'll use it, and decided that it will help you do whatever you are wanting to do with your camera (that your existing gear can't).

I always tell people to never buy gear unless they can explain what that gear will do for them that their existing ear can't (or can't do well, or easily enough). too often we get into gear lust, and too often, that's what ends up gathering dust...

(by the way, if you have an aps sized (or crop) sensor, it's not even a 50mm any more. that works for full frame sensors, but if you have a crop sensor camera, it's about a 35mm lens... 50mm on a crop sensor acts more like an 85mm lens).

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    To be a little fairer, the suggested lens is often the "nifty fifty", the cheap-as-chips 50mm f/1.7-1.8. It's not only a versatile focal length and close-focusing (while not being in real macro territory), but it's a stop or two faster than anything near its price class. (Anything faster is "special gear"; buy it if you really need it.) Of course, it's not something everybody needs, but it is the cheap ticket into the territory and can help you decide whether you'd want to go in a particular direction without breaking the bank. (You still get +1.)
    – user2719
    Jul 25, 2011 at 3:07
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    Gear lust ... ends up gathering dust. I'm going to have to remember that one. Jul 25, 2011 at 3:08
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    +1 for global warming. I had no idea my nifty fifty was so awesome!
    – Tim Post
    Jul 25, 2011 at 3:33
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    My fifty imbues me with super powers.
    – rfusca
    Jul 25, 2011 at 4:15
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    @Om: You're wrong. The focal length stated is in actual millimetres, not in "full-frame equivalent units". Pentax sensors are the same size as Nikon APS-C sensors and will have the same crop factor, so a 50mm Pentax lens on a Pentax DSLR will have about the same field of view as an 85mm Pentax lens on a Pentax 35mm film camera.
    – user2719
    Jul 25, 2011 at 11:21

Possibly - but the real answer lies in whether you find yourself limited by your current lenses in available light and portrait situations.

Two stops is a lot of shutter speed and DoF, but I rarely find myself shooting my Sigma 50mm wide open at 1.4. Not because its too soft (its still plenty sharp for me there), but because the depth of field is so narrow its difficult to nail focus on a subject that's moving at all. You'll focus on the eyes and then they barely move and suddenly its the nose. I find myself much, much more often in the range of 2-2.8 for the kids and portraits - I can't even remember the last time I felt the need to go down to 1.4. This is really a stylistic decision though, some people like the depth so shallow that the ears are out of focus. So for me its really a question of more like 0-1 stops in many, many situations.

My gut tells me its probably not worth it given the lenses you already have. The 70mm should be a great portrait lens and the 40mm should be great to walk around with. (In fact, I'm jealous of those two lenses for those purposes.)

I see a fast 50mm recommended for 3 typical reasons:

  1. On a full frame, its the 'normal' focal length that best represents the perspective of the world you normally have. In fact, on your crop sensor, the 40mm better represents this.
  2. Its a prime lens, so it helps beginners focus and think about composition since they'll have to physically move their bodies to change it. Both lenses cover this as well.
  3. The large aperture provides the chance to do low light shots and get shallow depth of field shots. Given the paragraph I discussed above, I think you're probably OK here but this is where you need to make your decision.

A big negative against the Sigma 50mm compared to your current lenses is that its HUGE compared to them. It is quite a bit larger and you definitely start to feel the weight of it after a bit.

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    ... and many are relatively light compared to the zoom lenses we have all become accustomed to carrying around. The extra stop+ can add weight. Consider the Canon 1.8 50mm (4.6 oz) versus 1.2 50mm (1.3 lbs or 20 oz). The 1.8 is so much lighter, it's a joy to use. A Canon 24-70mm zoom is 2.1 lbs or 33.6 oz, so the prime lenses are quite a bit lighter. I presume Pentax, Sigma, Tokina, Tamaron, etc., are in line with this kind of weight / performance.
    – Steve Ross
    Jul 24, 2011 at 23:09
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    @Steve True, the Sigma is going to be a beast compared to his Limited edition pentax primes. They're tiny!
    – rfusca
    Jul 24, 2011 at 23:12

No you don't

The number one reason for a beginner to get a 50mm lens is that on Canon and Nikon (don't know about other brands) the 50mm f/1.8 is cheap (the Canon 50 1.8 is the cheapest, smallest and lightest lens they make) - so it's a cheap introduction into the world of fast primes and it's so much better than the kit lens.

You already have a 40mm and a 70mm - do you find yourself wishing you had something in the middle? do you struggle with low light situation or wish you had shallower depth of field? - if the answer to one of this question is yes you should consider getting a fast 50mm.

But you should also consider other focal lengths, if what you want is a faster 40 get a faster 40, if what you want is something in the middle there are a lot of non-50 lends out there (especially for Pentax, they don't make the same "standard" focal lengths as other brands)

There's nothing magic about the 50mm focal length.


You may not "need" one but wow am I enjoying mine! It is not the lens to have in your bag but definitely fulfills a space! Just as in the kitchen, you don't have to have an old cast iron skillet, but it definitely fills a need that only it can!

I have shot for several days with my new Sigma 50mm f/1.4. I love it! Tired of waiting on the Nikon 50mm. Liked the price, bokeh...

But then, I don't have a long time to live. Sure glad I added this lens. It's a keeper!

  • I can't say you will love my girlfriend since I think she is such a lovely person, can I? While I am glad that you enjoy using the 50mm 1.4 , only the OP will know if he will enjoy using one. I like my 50mm 1.4 but the OP seems to be wanting to buy it for the sake of buying it. So for me I wouldn't recommend buying something that you are not gonna use.
    – Gapton
    Jun 27, 2012 at 5:02

Not "necessary" to get 50mm lens. That depends on what you like to shoot and your style. You may, for example, like to shoot portraits with a longer or shorter focal length... Your choice. I DO think a fast lens is worth what you can afford to pay! You will be amazed at the results you can extend yourself to with anything faster than f/2. The faster the better, depending on what you can afford. Combined with the amazing sensitivity of the latest sensors and ever decreasing noise at higher ISO settings, why not expand your horizons with the fastest lens you can get? There are some great buys out there on used lenses... BTW, I shoot Pentax and I'm using vintage glass. My first film camera was a Ricoh in 1978 with a 50mm, f/2 lens which works beatifully!


Haven't used a 50mm in going on 20 years, so you indeed don't need one (and of course your 40mm is pretty close to 50 in focal length...).
That said, I've been considering getting one and ditching my heavy 28-70 f/2.8 (which, with a 50 in the collection, will have been completely covered by primes at all important focal lengths). But that's a convenience thing, I'd rather take a few light weight primes with me than that big heavy zoom (4 primes to cover it would together weigh less and be about the same size as that 28-70), not because I urgently "need" a 50mm because without one I can't take the shots I want.


No, you do not need a 50mm lens. I have checked my photo collection (35 years worth of pictures) and the only time I used the 50mm was when I just bought my first SLR at age 14 and could not afford any other lense. As soon as I had a 35mm and a 135, that's all I used. Then when I got older I bought a 35mm and a 85mm (and later a 200mm) and I loved using them, while my 50mm was collecting dust. Then even later, I switched to DSLR with good zooms (Canon L) and I can now check what focal lengths I zoom to, and it is always either < 40 or > 80. Apparently, I do not need a 50 mm, and to be honest, I am not too impressed by others using it either. It is a horrible flat characterless focal length. Not the intimacy of tele, not the overview of wide. So if you want my 50mm, you can have it.

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    It would be helpful to understand whether you were using a full frame or crop sensor DSLR, as the 50mm would be the equivalent of 80mm on the latter and fall into your preferred range.
    – ab.aditya
    Jun 27, 2012 at 4:30

Yes, if you consider 1.8 fast. There is no reason not to spend approx $100 to get a lens under f/2.8. To go to 1.4 or 1.2 you're going to spend exponentially more though! Also keep in mind the "crop-zoom" factor. The 50mm 1.8 was my first fast lens and I don't really use it too much anymore, but later on I grabbed a 28mm 1.8 which is closer to a 50mm range on a crop-sensor, and I use that all the time. I still love both and when I go to full-frame 5DmkII I'll probably mess around with the 50mm/1.8 again or splurge on a really fast 1.2 or 1.4. For doing natural light shots in tight spaces/at weddings, you can't beat them.

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    That's a good argument for Canon/Nikon, but unfortunately not for Pentax - there simply is no cheap 50mm/1.8 or similar (except second-hand; with AF, even those cost far more than $100).
    – Imre
    Jul 26, 2011 at 17:42
  • @Imre This is a good point. Pentax has its own way of designing and pricing lenses and the "standard" primes seem to be quite expensive ones wen compared to Canons or Nikkors. Jul 26, 2011 at 20:48
  • That makes sense, sorry I spaced into the world where only Canon and Nikon exist. I have used the old K1000(100?) film cameras with a 50mm. I forget if Pentax takes old lenses, but I believe they do. If you could deal without the auto-focus, you could get a K series film cam and lens for about $100.
    – Andrew B
    Jul 28, 2011 at 15:13

I don’t think you need one. I’m personally not a fan of the focal length...I like 35mm/40mm lenses better as a standard lens then go longer to something like an 85/105 or wider to something like a 21/24 from there.

  • Are you taking sensor size into account? Field of view of a 50 on FF wouldn't be too different from a 35 on a crop sensor.
    – OnBreak.
    Nov 16, 2018 at 16:41


If you expect to also expand your night photography capabilities that way, know that not all f1.4 or f1.2 primes are made equal. For example, classic 50mm designs without aspherics are known to behave quite differently from aspherical designs like the Sigma you mentioned, or the f1.8 AF G Nikkor, when challenged with a typical urban nightscape scene, due to very different contrast performance and correction of coma aberration when wide open.


As many other have said, 50mm f/1.4 is not really needed. I have had one from when I first started photography and honestly, I never really use it anymore. I really just bring it out for when I want to improve my skill of improvisation of using a fixed focal length - which I sometimes do when traveling.

But in reality, 50mm focal length, in my opinion anyway, it kind of a boring focal length. It is standard POV, which unless you are a street photographer, doesn't often inspire much creativity. I honestly prefer much wider to have more dramatic compositions. The lenses I have been using a lot lately is my 15-30mm F/2.8, where it is mostly always at 15mm. Also my 85mm F/1.4 is quite frequently used and if I need longer, I would use my 70-200mm F/2.8 - which honestly is not very often now with a 85mm F/1.4.

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