Help with lenses.

Discussion in 'Native Lenses' started by sebs_color, Feb 16, 2014.

  1. sebs_color

    sebs_color Mu-43 Regular

    Jan 5, 2014
    Virginia Beach, Virginia
    So I'm just wondering... If you can have a 14-42mm, which can be set at 20 or 25 or 35, why would someone buy a, for example, 20mm 1.7?
    Is it because of the aperture?
    I really am just curious. Thanks for any feedback people!
  2. The 20mm does have a wider maximum aperture. It also is smaller and lighter. Some people also like the challenge of composing with a prime.
    • Like Like x 1
  3. 50orsohours

    50orsohours Mu-43 Hall of Famer Subscribing Member

    Oct 13, 2013
    Portland Oregon
    In most cases, primes are sharper.
    • Like Like x 1
  4. sebs_color

    sebs_color Mu-43 Regular

    Jan 5, 2014
    Virginia Beach, Virginia
    So basically the overall quality is better in some cases it's seems like.

    Thank you!
  5. Generally, primes are sharper but it's definitely on a case by case basis.
  6. Drdave944

    Drdave944 Mu-43 All-Pro Subscribing Member

    Feb 2, 2012
    Sharper ,faster, smaller. I like the 20mm f 1.7 but some people say it is slow to focus,whatever that means.I mean it takes a fourth of a second.
  7. jamespetts

    jamespetts Mu-43 Top Veteran

    May 21, 2011
    London, England
    Ahh, the debate as to the relative merits of zooms as against fixed focal length lenses has been around as long as zooms have been around. The actual relative merits of the two depend to a large extent on the individual lenses in question: the Olympus 12-40mm f/2.8 zoom, for example, has better optical quality at 17mm and f/2.8 than the Olympus 17mm f/2.8 fixed focal length lens.

    The basic underlying economics, however, are these: for any given price, bulk and weight, a fixed focal length lens can be made at higher optical quality and with a faster maximum aperture than a zoom lens, where higher optical quality includes sharpness, tendency to flare, vignetting, distortions and many other things. The optical quality of a zoom lens is often inconsistent throughout its range, generally being higher at the wide than at the long ends. Also, for any given F-stop on a zoom lens, it tends to have a lower T-stop than the equivalent in a fixed focal length lens.

    Relatively inexpensive zoom lenses tend to have slow maximum apertures and noticeably inferior optical quality than fixed focal length lenses in the same range. The Olympus 14-42mm (Mk. II) lens, for example, I found to lack sharpness and contrast throughout the zoom range, and had a maximum aperture of f/5.6 at the long end (although it is noteworthy that the Panasonic 12-32mm compact zoom lens is said to have considerably better optical quality). I do not have experience with all of the "kit zooms" (the inexpensive zoom lenses of slow variable apertures bundled with mid and low end cameras), but certainly I found that the Olympus 14-42mm Mk. II was poor enough for the images from it to look disappointing even on my computer monitor at normal viewing distances. I do not know whether the latest 14-42mm "EZ" compact zoom is any better - it might be.

    By contrast, there are a number of fixed focal length lenses that are quite inexpensive, either small or very small indeed, and which have very high optical quality. The Panasonic 20mm f/1.7 is a notable example, and the Panasonic 14mm f/2.5, although in some respects not quite as good as the 20mm f/1.7, is still considerably better than the relatively inexpensive kit zooms. The Olympus 45mm f/1.8 is small, light and relatively inexpensive and is known to have outstanding optical performance.

    There are some more expensive zoom lenses, however, that have optical performance close to or sometimes even in some respects in excess of fixed focal length lenses of equivalent focal lengths. The Panasonic 12-35mm f/2.8 and 35-100 f/2.8 together with the Olympus 12-40mm f/2.8 lenses are all notable examples of this type, and Olympus plan to release three more "PRO" series zooms in the next two years. The 12-40mm lens has superior corner sharpness to even the "premium" fixed focal length lenses of equivalent focal lengths (such as the 12mm f/2.0 and 17mm f/1.8), although the overall sharpness is less than the 45mm at 40mm. This comes at a cost, however, and this lens is much more expensive, larger and bulkier than the individual lenses that it replaces (although much cheaper than all of them together). It is also more prone to flare (as any zoom lens would be) than fixed focal length lenses, and is 1 to 1 1/3 of a stop slower as measured in F-stops, and more again in T-stops. Although to a large extent a matter of preference, many report that the out of focus rendition is not as pleasing with the 12-40mm lens as with, for example, the 17mm f/1.8 lens.

    The great and obvious advantage of the zoom lens is the ability to change focal lengths without changing lenses, and to have a single lens in place of multiple lenses, meaning that, whilst the lens is larger, bulkier and more expensive than one of the lenses that it replaces, it is cheaper, smaller and lighter than all of them together. However, it can be useful on occasions to take the camera out with just one lens attached, in which case a single fixed focal length lens of small size is an advantage over a zoom. Some people, moreover, find it helpful to have a fixed focal length, either for reasons of creative restriction or as an aid to learning; the extent to which this is a worthwhile thing is likely to vary considerably from person to person and depend on how each person's individual mind interacts with the tools of the hobby, but this is clearly of use to some people.

    Finally, there are several specialist types of lens that tend only to be made in fixed focal lengths, including macro lenses, fish-eye lenses and tilt and shift lenses (the latter of which does not currently exist in Micro Four Thirds, but the former of which are well represented). A macro lens, for example, is designed from the ground up to excel at that specific task, and for that reason, having the ability to zoom would compromise that ability. That is why both of the true macro lenses in the Micro Four Thirds system (that is, those capable of a 1:1 reproduction, being the Olympus 60mm f/2.8 and the Panasonic 45mm f/2.8) are fixed focal length lenses.
    • Like Like x 3
  8. sebs_color

    sebs_color Mu-43 Regular

    Jan 5, 2014
    Virginia Beach, Virginia
    James, I really appreciate you taking the time to write all that info!

  9. Whtrbt7

    Whtrbt7 Mu-43 Veteran

    Jan 7, 2014
    This is a great starting post. I started out with zooms then went all primes and now I use a mix of both primes and zooms. Why? It's because each lens has a different usage and some lenses are better than other ones at certain things. There a multiple things to consider with each lens. Sharpness, color rendition, depth of field control, weight, size, weather sealing, low light capabilities, autofocus vs manual focus, angle of view, bokeh, and rendering/feel of the lens all play a role in selecting the right lens for what you want to shoot. Zooms are generally more flexible and have narrower apertures due to physics and cost. They are good for shooting a variety of things when you don't know what you are going to be shooting or in the cases of weather sealed zooms, they are great for bad weather. Primes generally tend to be more specialized and allow for different uses including wider aperture/thinner DOF/more light gathering power for low light shooting. There are other prime lenses that allow you to do microscopic shooting, architectural shooting, macro photography, etc... There are so many reasons to own different lenses that it becomes a subjective decision to choose lenses for what you want to do/accomplish. Also, rules are meant to be broken so just because someone says that a lens is a perfect "portrait lens", it means it's just a perfect portrait lens for them. You can always use other lenses than for their "intended" purpose.
    • Like Like x 1
  10. OzRay

    OzRay Mu-43 Hall of Famer

    Jan 29, 2010
    South Gippsland, Australia
    Ray, not Oz
    There is another aspect to it as well and that relates to the work that you are doing. In a professional/semi-professional field, you can't always afford to work with fixed focal length lenses and change them around, you need flexibility to change your perspective rapidly because you may not have the room or time to move about. This is where zooms excel and why you find them more often than not in the pro-photographer's kit.
    • Like Like x 1