Announcement

Collapse
No announcement yet.

Lenses: relative length & diameter

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Lenses: relative length & diameter

    I am no expert in the physics involved in lens-making but always thought that with same-fit lenses having the same max apertures, the lens with a longer focal length would be longer and larger than the other one. If that is the case, how is it that the Sigma 56mm f1.4 DC DN is significantly shorter than the Sigma 30mm f1.4 DC DN (which I own and do NOT think is too big like some people do)?

  • #2
    Re: Lenses: relative length & diameter

    Originally posted by Loup Garou View Post
    I am no expert in the physics involved in lens-making but always thought that with same-fit lenses having the same max apertures, the lens with a longer focal length would be longer and larger than the other one. If that is the case, how is it that the Sigma 56mm f1.4 DC DN is significantly shorter than the Sigma 30mm f1.4 DC DN (which I own and do NOT think is too big like some people do)?
    It's quite trendy with lenses designed for digital sensors to be physically long. Look at, say, the new 50mm Nikon and Canon mirrorless lenses and compare them to something like a Zuiko (film era) 50mm lens - the new ones are more than twice as long.

    Ian
    Founder and editor of:
    Olympus UK E-System User Group (http://e-group.uk.net)
    Four Thirds User (http://fourthirds-user.com)
    Digital Photography Now (http://dpnow.com)
    Olympus camera, lens, and accessory hire (http://e-group.uk.net/hire)

    Twitter: www.twitter.com/ian_burley
    Flickr: www.flickr.com/photos/dpnow/
    Pinterest: www.pinterest.com/ianburley/
    NEW: My personal BLOG ianburley.com
    sigpic

    Comment


    • #3
      Regards,
      Mark

      ------------------------------
      http://www.microcontrast.com
      Too much Oly gear.
      Panasonic GM5, 12-32, 12-35, 15. Laowa 7.5.
      Assorted legacy lenses, plus a Fuji X70 & a Sony A7S.

      Comment


      • #4
        Re: Lenses: relative length & diameter

        That sounds encouraging. What I'd love Sigma to do then is to design a 150-400mm f4.5-5.6 MFT lens that is only 125mm long and has no more than 72mm filter thread up front. With that, a weight of up to 500g would be fine.

        Is that physically even possible?

        Comment


        • #5
          Re: Lenses: relative length & diameter

          Originally posted by Loup Garou View Post
          That sounds encouraging. What I'd love Sigma to do then is to design a 150-400mm f4.5-5.6 MFT lens that is only 125mm long and has no more than 72mm filter thread up front. With that, a weight of up to 500g would be fine.

          Is that physically even possible?
          Regards,
          Mark

          ------------------------------
          http://www.microcontrast.com
          Too much Oly gear.
          Panasonic GM5, 12-32, 12-35, 15. Laowa 7.5.
          Assorted legacy lenses, plus a Fuji X70 & a Sony A7S.

          Comment


          • #6
            Re: Lenses: relative length & diameter

            BTW the huge mount diameters in both the new Nikon and Canon full frame systems are necessary to meet the market demand for faster and faster lenses (one or other of them has an f0.95 50mm on the horizon, which is going to be huge and will weigh a ton). Never mind that real photographers are rarely going to need gear like this (and the Nikon hasn’t even got eye-detect AF, I believe, so most normal people won’t be able to get them in focus for portraits at full aperture, anyway).

            As ever, people may regret what they’ve been asking for.

            Since the bayonet end of the matching lenses are going to have to be large and heavy, this is going to work against them producing compact lenses, so Olympus may maintain more of a size advantage than many commentators have spotted.

            The Sony EF full frame bayonet is much narrower and has apparently needed some optical compromises to cover the sensor, but this has allowed them to build more compact lenses (although looking at the new 400 f2.8 you’d wonder).
            Regards,
            Mark

            ------------------------------
            http://www.microcontrast.com
            Too much Oly gear.
            Panasonic GM5, 12-32, 12-35, 15. Laowa 7.5.
            Assorted legacy lenses, plus a Fuji X70 & a Sony A7S.

            Comment


            • #7
              Re: Lenses: relative length & diameter

              My Panasonic 100-300mm f4-5.6 is 126mm long, has a 67mm filter thread and weighs just over 500g. That fits well into my camera bag inside its padded JJC case. The way I am thinking, that is a design over 6 years old, is a 3X zoom and a larger aperture range than what I am thinking of. It works very well in all departments.

              That is what makes me wonder if Sigma (or someone similar) could design the 150-400mm f4.5-5.6 lens within the same dimensions - at least the length with the new tech available. It has less than 3X zoom.

              Comment


              • #8
                Re: Lenses: relative length & diameter

                One thing that mystifies me is Olympus's 25mm and 45mm f/1.8 lenses. Both are lovely - but how come the 45mm is only fractionally longer, fractionally narrower, significantly lighter (116g vs 137 according to the spec) than the 25, and even more significantly cheaper (GBP199 vs 299 at Wex at the moment). It is the same aperture, nearly twice the focal length and of excellent optical quality so I would expect it to be bigger in all respects.

                John

                Comment


                • #9
                  Re: Lenses: relative length & diameter

                  I never had the Olympus 25mm f1.8 but having owned the 45mm f1.8 for 5 years, often wondered about its compact size. The price per se

                  Comment


                  • #10
                    Re: Lenses: relative length & diameter

                    Originally posted by Loup Garou View Post
                    I am no expert in the physics involved in lens-making but always thought that with same-fit lenses having the same max apertures, the lens with a longer focal length would be longer and larger than the other one. If that is the case, how is it that the Sigma 56mm f1.4 DC DN is significantly shorter than the Sigma 30mm f1.4 DC DN (which I own and do NOT think is too big like some people do)?

                    There are a couple of crafty lenses designs that were invented around 100 years ago:
                    Telephoto lenses use a design that allows the lens to be physically shorter than it's focal length. Today the term is often missused to just mean a long focal length lens. Not all long lenses are telephotos & some normal lenses are in fact telephoto.



                    The opposite arrangement retro focus designs allowed wide lenses to have more distance behind the lens that it's focal length would suggest. This was VITAL when you had to get an SLR's viewing mirror into the gap.
                    With modern mirrorless camera designs that reasoning for a retrofocus lens is no longer significant - but I suspect there are other advantages such as having the light more perpendicular to the sensor.


                    Todays lenses are often much more complicated & can be retrofocus at short focal lengths and telephoto at longer focal lengths.

                    There are practical advantages of compact lenses causing some designers to make smaller lenses even at the expense of slightly inferior optics.
                    Mike
                    Compulsive photographic Dabbler.
                    Flickr

                    Comment


                    • #11
                      Re: Lenses: relative length & diameter

                      Originally posted by Loup Garou View Post
                      ...........how is it that the Sigma 56mm f1.4 DC DN is significantly shorter than the Sigma 30mm f1.4 DC DN (which I own and do NOT think is too big like some people do)?

                      Most 'long' lenses use the so-called 'telephoto' design, which makes the overall length of the assembly shorter than the focal length would suggest. Conversely, many wide angle lenses use a 'reverse telephoto' design, which makes the front lens smaller in diameter than would otherwise be needed to collect light out into the corners of the image but also makes the overall assembly longer than the focal length suggests.



                      In fact, 'fast' wide angles can be quite large, such that, for portrait photographers, who want a shallow depth of field, there is little advantage, in terms of size and weight, to be gained from using smaller formats. That's why we see lenses such as the 42.5mm f/0.95 lenses for MFT cameras, which provide similar values for both angle-of-view and depth-of-field to an 85mm f/1.8 lens on 'full frame'.
                      Mike
                      visit my Natural History Photos website:
                      http://www.botanicdesign.co.uk/Natur...story/home.htm

                      Comment

                      Working...
                      X