Now that I am finally getting a fast zoom (Tamron 17-50mm 2.8) I've been considering a fast prime to go with it, specifically a Sigma 50mm 1.4. Despite its shortcomings, it still does really nice subject isolation past f/2, which is important to me. I was wondering if it might be redundant since my zoom is already a pretty fast fixed aperture. Of course, 1.4 is two stops faster than 2.8, but as with all primes you have to stop it down to get sharp results.

The main thing I am worried about is that if I drop $500 on a Sigma, it won't get used because there is already something O.K. in that range. Basically, is two stops difference enough to make you want to switch lenses?

EDIT: Perhaps I should add and as may have already been mentioned, these $500 could go to a nice speedlight which could sove the low-light 'issue' you get with f/2.8 vs f/1.4.

  • 2
    You have to stop down zooms as well to get decent sharpness and reduce halo... May 3, 2011 at 20:39
  • Are you shooting a Canon? If so, the EF-50/1.4 is noticeably cheaper than the $500 price tag you mentioned.
    – ysap
    May 5, 2011 at 23:16
  • 1
    You could check your need for a certain prime by taking some (typical) pictures with your zoom and then use ExposurePlot to analyze if you prefer a certain focal length or walk all over your zoom-range all the time.
    – Leonidas
    May 6, 2011 at 0:29
  • In addition to (or instead of) worrying about aperture and image quality, check out this article, entitled "The Case Against Zooms" theonlinephotographer.typepad.com/the_online_photographer/…, which is an interesting read even if you don't end up agreeing for your own use.
    – mattdm
    May 6, 2011 at 3:22

9 Answers 9


f/1.4 is very useful if your other lens is f/2.8. I would certainly pull out my bag and grab the f/1.4 lens when the need arises. Indoor portraits, indoor sports, low light anything etc all will greatly benefit, if not require f/1.4. On the other hand, you aren't going to find a 17-50 f/1.4, so that is why you will need the prime.


If you're only going to shoot your 50 f/1.4 at f/2.8 then yes it is redundant.

but as with all primes you have to stop it down to get sharp results

I'd replace "primes" with "f/1.4 lenses", plenty of primes are sharp wide open. Few ultra wide aperture lenses are really sharp. The Sigma 50 is actually pretty good. #Certainly sharp enough to consider using wide open, I have the Sigma 30 f/1.4 and was blown away by the sharpness wide open.

In short a 50 f/1.4 isn't redundant as it's two stops faster, which can mean shooting ISO400 instead of ISO1600, or 1/50s compared to 1/12s. You don't have to stop it down for sharpness, a little softness is really not that big a deal.

  • 4
    Sharpness is relative, even within an image. I'd certainly have no problem using the Sigma wide-open, particularly for portrait/beauty type shots -- with one caveat: keep the out-of-focus elements behind the subject when you can; the bokeh in front of the plane of focus at f/1.4 is, um, a little busy (to put it politely).
    – user2719
    May 3, 2011 at 18:13

Have you given any thought to how you use your lenses? The biggest benefit of a zoom is that it can do the walking for you. You'll be able to find all sorts of threads talking about how great primes are, and that you should move yourself to frame your shots, and so on. There are settings where that makes a ton of sense, and then there are photos that you're just going to miss if you don't have a camera ready to snap a shot within a second or two -- so which kind of photos are you shooting?

I'd say that if you find yourself taking photos where you can set up the shot and frame it to fit a 50mm lens, you'll probably love the prime - this would seem to be the case for your portraits, for instance. On the other hand, you mentioned candid shots -- if you need to grab your camera and take a snapshot in a hurry, the zoom might save a lot of shots that you'd just miss with a prime.


Primes are typically much sharper, and often brighter than zooms. No matter what brand or price you pay for a zoom, there are inherent trade-offs made in the design to get a zoom to be reasonable at all focal lengths. In every situation, a similar quality, and often lower quality prime will out perform a zoom at all focal lengths. If you want the absolute best quality image with no compromise, you should choose primes over zoom.

Of course, having a bag of 20 primes can get a bit expensive and be inconvenient, which is why many of us go with zooms instead.

A recommendation is to choose a few primes that will help you in focal lengths you most often use. If you shoot lots of portraits, then perhaps an 85mm would be useful. Lots of landscapes? then consider a 24mm or 35mm. Need a bright, all around lens for indoors? Try a 35mm or 50mm. Both Nikon and Canon make a respectable 50mm f1.8 that is surprisingly cheap and outperforms most zooms of any price.


I would use the new zoom for a while, to see where in the focal length range you are taking the shots you like. If you're gravitating towards the long end, by all means consider getting a longer prime. If you haunt the wider angles you might want to go even wider with another zoom (zoom, because there are precious few affordable primes below 17mm).


Sometimes I think people's reliance on asking question on the internet is getting out of hand...

Look, the only way you can know if the prime or ther zoom will better satisfy your need for a 50mm lens is if you actually make the plunge and get both. Yes, 1.4 is 2 stops faster, but at 2.8 you'll be sharper than the zoom at 2.8 - zooms aren't sharpest wide-open either. There's really nothing more I can add, other than:

Buy lenses at new focal lengths because you're not getting the image you want, not as a technical exercise.

  • Ok I've changed the question to get rid of the middle paragraph as it is kind of a derailment. May 3, 2011 at 13:34
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    I don't think this is an unreasonable beginner question.
    – mattdm
    May 6, 2011 at 2:17

Just returned from a 2 week trip. Deliberately left my f/2.8 zoom at home and took a bunch of primes instead. Bit more cumbersome to use (changing lenses regularly), but the savings in size and weight (the primes combined were slightly smaller and about a third less heavy as compared to the zoom I'd otherwise have taken) were well worth it. Plus it forces you to think and compose with your feet, yielding overall higher quality pictures.

As is, after this trip I am seriously considering buying one more prime (to cover the gap in my prime coverage remaining) and storing the zoom semi-permanently (keeping it as a spare) or selling it (depending on the money I can get for it).

Mind I still have zooms for other purposes, talking only about the 28-70 range here.

  • Out of curiosity what primes where you using at what focal length where you looking to fill in the 'gap'?
    – mundeep
    Aug 30, 2012 at 16:36

I suspect that, if you are anything like me, that if you have a zoom and a prime in the same range you will end up using one or the other almost exclusively. When I used Canon cameras my 24-70 f/4 L was almost permanently on the camera and the 50 f/1.8 rarely saw any use. Only if I made a special effort to go out for the day with the prime and leave the zoom at home did I use the little 50mm lens.

The 50mm might resolve more detail, but not so much that you'd ever notice except with your nose up against wall sized prints. In fact the zoom, even though less "sharp" in the centre, had more even resolution across the frame - a big advantage for landscapes and technical illustrations or if shooting multiple images to stitch together.

[An aside, for the benefit of Canon shooters. This edge to edge consistency is also an advantage of the f/4 zoom over the more expensive and non-stabilised f/2.8 zoom, which is significantly poorer in the corners than in the centre AND has noticeably more chromatic aberration.]

As for the extra speed of a prime lens, the IS of the f/4 zoom more than made up for the 2 and a bit stops of the prime.

For me the real reason for carrying the prime when the 24-70 f/4 was on the camera all the time was as a backup in case the zoom lens failed (unlikely) or got damaged (more likely) which is why I chose the lightweight f/1.8 lens over the faster but heavier f/1.4 and f/1.2 lenses that, in any case, performed hardly better, if at all.

I hope this helps.

  • Tripod ?
  • Will your camera work with an f:1.4 ?
  • Old low-end models have AF and focussing-screens that only work well between f:2.8-5.6.
  • Nikon D40, D40x gave me <10% sharp at f:1.4 D3100 is >90%.
  • Best to borrow a lens or try it in the shop.
  • Amazon f:1.4 reviewers tend to keep sending the lenses back, but it's the camera's fault.
  • 1
    -1 because your answer doesn't make any sense
    – gjb
    May 21, 2011 at 10:50
  • 1
    There's a kernel of sense in it: rent, borrow, or try a lens in the shop. Bring your family, so you don't spend 10 minutes taking pictures of carpets and advertising like I did.
    – Michael H.
    Oct 18, 2011 at 16:56

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