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What's the advantage with fixed lens over vari lens

Discussion in 'Lens Matters' started by Keith Jones, Jan 14, 2021.

  1. Keith Jones

    Keith Jones Active Member

    Hi all,
    Now starting photography again after 25 years, at the moment I've got Nikon 18-55 & 55-200 lens , so wondering what is the advantage of having of say a 30mm fixed lens when my 18-55 covers 30mm.
    Apologies if that sounds a dumb question
  2. GeoffR

    GeoffR Well-Known Member

    A 30mm lens will be optimised at that focal length a zoom is always a compromise at any focal length however zooms are very good. Thus the aberrations present in all lenses will be minimised in the prime lens, resolution and sharpness across the field may be higher. Shading at the corners of the frame (vignetting) will be better controlled.

    The other factors are maximum aperture, a prime (fixed) lens will probably have a wider maximum aperture than a zoom. and weight a prime lens will be lighter than a zoom and certainly lighter than a zoom of the same or similar maximum aperture. Zooms, even the fastest, tend to have maximum apertures around f2.8 (there are some f1.8 zooms) Nikon make a 35mm f2.which is considerably lighter than their 17-55 f2.8 or 24-70 f2.8 zoom lenses.
  3. Andrew Flannigan

    Andrew Flannigan Well-Known Member

    Little or none. Modern lens design has removed most of the shortcomings that zooms once had and with digital cameras having a great deal of processing power, they can adjust the image data to make up for any optical shortcomings of the lens provided the correction data has been programmed into their firmware.

    I only use fixed focal length lenses for fun, these days.
    Terrywoodenpic and Keith Jones like this.
  4. Keith Jones

    Keith Jones Active Member

    Many thanks for your reply Geoff, what in your opinion would be the best fixed lens for portraits ?
    RogerMac likes this.
  5. beatnik69

    beatnik69 Well-Known Member

    Are you shooting on a cropped sensor camera? You can use any focal length for portraits, but they will have different effects. A shorter length will faces look broader and rounder (if you are shooting head shots). On an APS-C camera a 50 mm lens is quite good for portraits, but I've also used a 90 mm lens with good results. The short answer is that there's no "best" lens.
    RogerMac, Zou and Keith Jones like this.
  6. PeteRob

    PeteRob Well-Known Member

    Hi Keith, these is no such thing as a dumb question.

    Geoff answered you well. In theory fixed focal length lenses (prime lenses) can be better than zooms for some definition of “better” (optical quality, size, weight, maximum aperture). It is a trade off with flexibility really. I prefer to use zooms for general photography.

    I own some primes but they were bought for dedicated purposes. I have a wide angle perspective control lens for architecture and a short telephoto prime for macro. I also have some longer telephoto primes because, historically, telephoto zooms (to 300 mm+) were not as sharp at their longest focal length as a prime. This is no longer true of the latest zooms.
    Keith Jones likes this.
  7. Keith Jones

    Keith Jones Active Member

    Hi PeteRob,
    Thank you for your comments, think I might invest in a 50mm or 80mm fixed for portraits as Geoff said they are lighter and also have other advantages over zoom.
    RogerMac likes this.
  8. PeteRob

    PeteRob Well-Known Member

    It all depends! When you take portraits one thing to consider is how far away you want to be. A short focal-length lens used close up for a head photograph is unflattering, it makes the nose more prominent. A short telephoto lens is more flattering to most eyes but you need a lot of room, especially if doing full body shots or groups. I think, on full-frame, anything between 35 mm (for groups) and 135 mm for tight head shots would be considered game for portrait. There are optimised wide aperture 85 mm “portrait” lenses which can produce very shallow depth of field which can be used to effect in some portraiture studies. For an APS-C camera (a x1.5 crop factor ) and family pictures I’d say a prime 35 mm or 50 mm would do. The shorter if fuller figure/group pictures are the main object. The longer for head and shoulder. I don’t do much portraiture, mainly kids, now grandkids, running around outside. I tend to use a 70-200 zoom on a full frame camera.
    Keith Jones likes this.
  9. GeoffR

    GeoffR Well-Known Member

    In my opinion and limited experience an 85mm lens would be about right but 105 is good too. However, before you rush out looking for either of those, I have full frame cameras. On your camera that would be 60 and 75, now the other disappointment my 105 is the DC (Defocus image Control) version, which is why I like it for portraits, and there is no DX equivalent. For convenience and economy why not get a 50 f1.8 AF-S.
    Keith Jones likes this.
  10. PeteRob

    PeteRob Well-Known Member

    I forgot to say that it also depends on whose portrait. A new born baby in arms presents different challenges to the working portrait of a 30 st sumo wrestler in terms of focal length choice.
    Keith Jones likes this.
  11. Keith Jones

    Keith Jones Active Member

    I'll bear that in mind haha
  12. Keith Jones

    Keith Jones Active Member

    Thanks again Geoff , does sound as if the 50mm is about the best choice
  13. PeteRob

    PeteRob Well-Known Member

    That should work well. You can use your 18-55 zoom to tell if 50 mm gives you the sort of framing that you want at the distances you want to work from. There are some exceedingly sharp 50 mm lenses on the market. I don't know what camera you have. If it is a newish one with a high resolution sensor be prepared to do some post-production work, portrait sitters don't necessarily want to see every pore!
  14. Andrew Flannigan

    Andrew Flannigan Well-Known Member

    The last time I did any portraits the Beatles had just released an album called "Abbey Road"! But I've always liked pictures of people. I find that any lens works if the interest is there...

    300mm on full frame...
    Young woman in Hall Austria 5758.JPG

    400mm on APS-C...
    Young woman smiling at Swindon Mela CAN_4279.jpg

    80mm lens on 6x6 film...

    85mm on 35mm film...
    Vicar in Straw Hat Canon F1 Ilford Film 1996-13_ 21.jpg

    65mm on 645 film...

    75mm on 6x6 film...
    Keith Jones likes this.
  15. Keith Jones

    Keith Jones Active Member

    Hi PeteRob,

    It's a Nikon D7000 second hand as I'm getting back into photography after 30 years , I'm used to roll film, so this digital lark is all new to me , going by what Geoff has said, a 50mm fixed is the way to go to, but welcome any other input before I purchase, obviously I don't want to cause argument
  16. gray1720

    gray1720 Well-Known Member

    What's the story behind the chap with the bang-seat blind?
  17. Keith Jones

    Keith Jones Active Member

    That's very true Andrew, I've taken pics of trees, bushes or anything which interests me, not necessary other people , whether that's right or wrong I don't know ? But I like your pics , do you prefer B/W or colour, that's just out of interest.
  18. Andrew Flannigan

    Andrew Flannigan Well-Known Member

    For film: black and white, because colour's too much like hard work. I'll desaturate digital if the shot looks better that way but usually I leave the colour in.

    By the way: here's a shot made through a 28mm lens on 35mm film which I think shows that even a wide angle works for people shots, in the right circumstances...

    Pentacon FM 67-9006.JPG
    Last edited: Jan 14, 2021
  19. PeteRob

    PeteRob Well-Known Member

    I didn't mean to cause any alarm! Coming from film to digital now is more of a jump than when I moved over in 2007 and was surprised to find that a 12 MP Canon 5D with, admittedly a good 24-105 mm L lens, was pretty equal to the 6x6 I was using. Today I use a Canon 5Ds which is 50 MP and sayings like "count the hairs on" don't even come close to describing the resolution. Should I take a people picture these days (rare) with it then I usually smooth skin texture a bit in post-processing as it can be a bit revealing :).

    Digital is pretty wonderful really. I adapted to saving only the raw image files and doing post-processing myself on most pictures. This came originally because I liked to explore the effect of the different picture options on the Canon - e.g. whether a picture shot using "portrait" colour settings looked better than using "standard" colour settings or "landscape" colour settings. These can be set in camera but I found it easier to flip through them on a computer after the picture was taken, rather than take 3 pictures out in the field and let the camera do the work.
  20. ChrisNewman

    ChrisNewman Well-Known Member

    Welcome back to photography, Keith. I agree with all that GeoffR stated, and also:
    For myself, I’m not interested in portraiture. I have two prime macro lenses (an old DX from when I used a D90, the Nikon D7000’s predecessor, and subsequently an FX). There’s little benefit in being able to zoom a macro lens; it’s usually better to get the advantages of a prime, and generally straightforward to adjust the camera-to-subject distance to fill the frame. I also have a Sigma Art 50mm f/1.4 for best possible image quality, as I like that perspective for subjects such as buildings or trees, if I can set up at the right distance (30mm to 35mm would be similar with your DX D7000). Most modern DSLR zooms have image stabilization, an advantage over most primes other than telephotos. The f/1.4 lacks image stabilization, so currently I rarely carry it unless I’ve also taken a tripod. But if I replace my DSLR with a Nikon Z-series mirrorless camera, I could mount the f/1.4 on an adapter, and use the stabilization built into most mirrorless bodies. Anyway, currently I take nearly all my hand-held shots, other than macro, with one of my zoom lenses.

    Last edited: Jan 16, 2021
    Keith Jones likes this.

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