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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. Terrywoodenpic

    Terrywoodenpic Well-Known Member

    I would save your money until you know that you need a particular lens.
    Modern Zooms are so good on digital cameras that a vast majority of people can not see any difference at all in sharpness.

    However longer focal length and wider apertures allow you to throw the back ground out of focus more easily than shorter focal lengths and smaller apertures.

    Moderate telephotos like a 90 or 135mm on full frame give more pleasing and natural drawing of the Features in portraits. But zooms in this range do equally well if the Aperture range is also suitable. Which on entry level Zooms may not be the case, especially if you want the backgrounds to be soft.

    On an Aps camera a 50mm or thereabouts wide aperture lens F1.4 or so makes a very good small studio portrait lens.

    However I find that my Fuji 18-55 f2.8-f4 zoom serves very well indeed, and is fully usable wide open.

    For the time being I would use what you have to see if it serves well enough, I hate to have lenses that I never get round to using, just sitting there.
  2. Keith Jones

    Keith Jones Active Member

    Hi Chris,
    Thanks for the comments, think i'm going stick with the zoom lenses a bit longer until i'm up and running and then maybe get a 50mm f1.8 later

  3. Bipolar

    Bipolar Well-Known Member

    I bought a Canon 40mm f2.8 pancake lens a couple years ago.
    I took it off my 50D yesterday for the first time since i bought it.
    Its a great lens and very sharp wide open.
    Keith Jones likes this.
  4. Petrochemist

    Petrochemist Well-Known Member

    Primes don't have to be as complicated optically to get the same image quality. This means they can be smaller, lighter & cheaper. In many cases they will also be faster but this is less the case now, in the past few years Sigma have produced a series of f/1.4 zooms which is fast enough for most users!

    In the earliest days of zooms primes had noticeably better image quality, but today's zooms are much improved. There probably are less distortions from a typical modern prime compared to a typical modern zoom but these are much harder to spot and probably not relevant to most photographers.

    If your 18-55 works nicely for you there's not much reason to go for a 30mm prime, but if you find it doesn't go fast enough for the lighting conditions you meet or subject separation you want then a 28mm/2.8 might be enough of an improvement, (if not, I'm sure there are faster options, but 28/2.8 is a very common set up).

    The weight & cost advantages of a prime is only really relevant if you're not carrying a zoom that can do the same job as well.
    Keith Jones likes this.
  5. Keith Jones

    Keith Jones Active Member

    Hi Petrochemist,

    Many thanks for your comments , most appreciated , might give the 28mm a look

  6. ChrisNewman

    ChrisNewman Well-Known Member

    I was surprised to read the above. I’ve just looked on the Sigma website, and the fastest zooms I found were the Art 18-35mm F1.8 DC HSM and Art 50-100mm F1.8 DC HSM (but they are very fast for zooms, and primes faster than f/1.4 are pretty exotic).

  7. Andrew Flannigan

    Andrew Flannigan Well-Known Member

    His name was Tony Svenson and he held the unenviable record (at one time) for the fastest ejection, coming out of a Mirage III over the Australian desert at somewhere north of Mach 1. Other people have done it faster since but Tony's two years in hospital suggest that it isn't a sport for the faint hearted!

    I heard that he died in a car crash some years ago.
  8. Keith Jones

    Keith Jones Active Member

    Hi Chris,
    Thank you for your time looking this up, trouble is after taking up photography again after a 25 year gap and obviously lenses have improved to what they were , I really need to think do I really need a fixed focus , I've read so many pro's and con's which is great to read people's opinions , if I do go for fixed I'll probably go for the 50mm f1.8

  9. gray1720

    gray1720 Well-Known Member

    Thanks - it's some story!


    Died in 2009, it seems.
  10. GeoffR

    GeoffR Well-Known Member

    A mere inconvenience considering the alternative.

    Full story
    Squadron Leader Tony Svensson, R.A.F., was a test pilot on loan to the Royal Australian Air Force. Flying from R.A.A.F. Avalon near Melbourne, he was testing Mirage III supersonic fighters. On 7 December 1964 he was testing a Mirage III at 35,000 feet, when something went wrong and control was lost, and with the engine shut down the aircraft headed earthwards. The following was reported in The Sunday Express of 30 April 1967:
    “‘For the next 90 seconds I was very busy. I kept a running commentary going to the ground station saying what I had done, what was happening to me and what I was trying to do to get the plane out of its downward plunge. ... At 7,000 feet I decided it was time to get out and I pulled the blind which fires the ejector seat.” Three seconds later the Mirage, still accelerating, hit the ground. ... So late had Svensson left his ejection that he landed only 600 feet away. As Sir James Martin, the designer of the seat which saved Svensson’s life wrote to him: “Your ejection at 932 miles an hour was by far and away at the highest speed we have ever recorded.” A fragment of a tape crash-recorded which was dug up ... revealed that Svensson’s ejection was a world record. This is what happened after he pulled the blind: First to go was the cockpit canopy which let in a hideous 900-plus miles an hour stream of air which hit Svensson like a brick wall. ... Next his rocket-propelled seat lifted from the cockpit into the cruel supersonic air stream, cracked his webbing leg restraining straps and broke both his arms as they flailed, and one leg in two places. Squadron Leader Svensson was by now unconscious. But the British designed seat took over. It gently detached him from his seat and automatically deployed his parachute. But he was to be further injured ... for his one remaining sound leg was also broken in two places on landing. Then he had a piece of luck. Six doctors who had been lecturing ... at a school were passing in a minibus on a road only 100 yards away ...’
    Whisked away to hospital Svensson was in a coma for 10 days. His lengthy treatment involved his legs having to be re-broken before they could be properly set. When his legs were properly mended, he was found to be two inches shorter.
    Last edited: Jan 16, 2021
  11. ChrisNewman

    ChrisNewman Well-Known Member

    Hi Keith,

    I’m entirely neutral as to what you buy, although your “i'm going stick with the zoom lenses a bit longer until i'm up and running”, suggesting you’re following Terrywoodenpic’s advice “For the time being I would use what you have to see if it serves well enough” seems wise.

    But having just looked for Sigma f/1.4 zooms myself out of curiosity, I just wanted to set the record straight (unless, of course, they do exist, but I missed them on the website), in case others reading this thread waste time trying to find and buy one.

  12. Chester AP

    Chester AP Well-Known Member

    Since your 'kit' lens is an 18-55, I assume you have a camera with a half-frame (APS-C) sensor, as I do. I never had an 18-55, since I purchased the my first DLR camera body and a Tamron 18-250 separately.

    However, I have since purchased three older 'prime' lenses second hand. Two that were originally wanted for closeup work, but have also proved very good for 'head and shoulders' portrait shots - a Sigma 50 mm F2.8 Macro (equivalent to 75 mm of a full-frame camera body), and a Tamron 90 mm F2.8 Macro (equivalent to 135 mm on a full-frame camera body). I have not found the F2.8 maximum aperture limiting on either of these, and it makes them cheaper and lighter than more modern F1.8 lenses.

    The third lens is a second hand Sigma 30 mm 1.4, purchased because I wanted a 'fast' lens for low light work indoors. It is the sharpest lens I own, but the cost of the F1.4 maximum aperture was wasted since I rarely use it 'fully open' because the depth of field is so shallow. If buying now I'd be tempted to look for an older second hand 28 mm F2.8 originally made for a full-frame camera.

    Before you spend any money, I'll ask my usual question: what do you want to do with your pictures? If they are only viewed on a PC monitor or handheld device with a small screen, the image quality from the lenses you already have will be more than adequate (unless you crave the very shallow depth of field that only an expensive large-aperture prime lens will provide). However, if you want to get large prints done to hang on a wall, the quality of the lens used will be important and may be worth the expense.
  13. PeteRob

    PeteRob Well-Known Member

    I didn’t believe it either. There are two F1.8 zooms for APS-C only. Still very fast for zooms where F2.8 or F4 are the usual max apertures for full frame lenses.
  14. Andrew Flannigan

    Andrew Flannigan Well-Known Member

    The way Tony told me the story, he was actually somewhat wider due to the air pressure bending his rib cage. He was a guy with an interesting sense of humour. When I met him, he was running a sail boarding school on Dartmoor and I did the story for the local papers.
  15. PeteRob

    PeteRob Well-Known Member

    Burrator reservoir I presume. I did a double take at the idea of sailing 0n Dartmoor but I think there is a water sports centre on Burrator although I don’t remember seeing sails there ever.
  16. Chester AP

    Chester AP Well-Known Member

    Some confusion here - the Sigma 30 mm F1.4 is not a zoom lens. It is a fixed focal length 'prime' lens and was made for half-frame (APS-C) DSLR cameras, and it's not a waste of time trying to find one. They are not the most common type of lenses you will find second hand, but they are available. My advice about 'what do you want to do with your pictures?' (above) is relevant - even second hand, these are not cheap lenses.

    This is the link to the Pentax forum lens reviews page for the Sigma 30 mm F1.4 and gives the details of the lens (this page features the Pentax mount version, but Canon and Nikon mount versions were made too).


    And the London Camera Exchange website currently (16.01.21) has two - one Canon and one Nikon fit.

  17. GeoffR

    GeoffR Well-Known Member

    Keith, being pedantic, you don’t want a “fixed focus” lens. That would be one where you are stuck with the lens focused at some set distance and rely on depth of field to achieve an in focus result. We know what you mean but these boards are public and a casual reader may be confused.

    What you are looking for is a fixed focal length lens, a prime lens, the Nikon 50 f1.8 AF-S will serve you well in this respect.

    You might like to consider the well known compatibility problems associated with Sigma lenses on Nikon cameras. Some lenses, usually those manufactured earlier than the camera, may not work properly. Sigma will modify lenses, where possible, but if you buy used there is a charge. Lenses manufactured later than the camera are rarely a problem. The difficulty of course is ensuring that the lens you are looking at is the newer version. Sigma lenses are optically superb but the reverse engineered interface is the seat of the problem.
  18. PeteRob

    PeteRob Well-Known Member

    He knows what he meant. But it is a good point to make, when buying 3rd party lenses secondhand, always try before you buy as compatibility between lens and body of different ages (especially newer body) isn’t assured.
  19. ChrisNewman

    ChrisNewman Well-Known Member

    I don’t think there’s been any confusion about Sigma f/1.4 Primes. There are lots of them, and I mentioned having the 50mm Art myself. But Petrochemist stated “Primes don't have to be as complicated optically to get the same image quality. This means they can be smaller, lighter & cheaper. In many cases they will also be faster but this is less the case now, in the past few years Sigma have produced a series of f/1.4 zooms which is fast enough for most users!” I don’t think Sigma offer any zooms with apertures as fast as f/1.4, and wanted to correct what I believe is a misleading claim from Petrochemist.

  20. Andrew Flannigan

    Andrew Flannigan Well-Known Member

    This would have been sometime in the middle of the 1980s. A lot of things have come and gone since then.

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