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Fotografie: ? Zoom versus Prime Lens ?

Copyright by Michael Bockhorst 09 01 10 - 20:35

Is there a unique answer? Or are both primes and zoom lenses the right choice - depending on the field and preferences for your photography?

The physical image quality

It is much easier to build an excellent prime lens than building an excellent zoom lens. There is no magic behind. Primes are optimized for one focal length. This reduces the number of compromises drastically

  • A smaller number of lenses is needed resulting in a lower number of glass-air boundaries leeding to less flare and higher contrast.
  • A smaller number of lenses leaves more space between lenses/lens groups increasing the freedom to place each lens element/group at the optimum location.
  • A simple floating element approach with 1 or 2 groups moving during focusing gives better precision at a given price/weight/size.
  • The diaphragm placement is easier, it has not to be moved according to some zoom settings to control distortions.

Prime lenses allow high maximum apertures which have two big advantages for all photographic discipines:

  • Available light photography is possible because short shutter times can be realized to avoid sharpness loss due to shaking, e.g. for low light photography where a flash is not allowed or disrupting like wedding photography. A short shutter time is needed to freeze motion, necessary in sports photography, some disciplines of technical photography.
  • A high aperture value corresponds with a shallow depth of field. A shallow depth of field with standard or tele photo lenses allows the isolation of a subject from the background.

That doesn't mean, that primes are generally better than zoom lenses. But the limits of physical image quality can be extended by using primes which are really optimized for one focal length.

Quality of the Photographs

Is there some influence of zooms or primes for the artistic quality of photographs? Shure, but let as find some clear points where a prime or a zoom is recommended:

Choose a prime, if

  • ... you need the optimum physical quality (sharpness, contrast, low/no distorsion)
  • ... you need a high aperture for available light photography or artistic support by blurred backgrounds
  • ... you want a compact package (2.8 24mm prime is much smaller and lighter than 24-70 2.8 zoom)

Choose a zoom, if

  • ... you need flexibility, e.g. scenes with single persons, small groups, different distances etc.
  • ... you have to take photos where you cannot change the location
  • ... you want to reduce lens changes (due to limited time to do that, external conditions like moisture, dust, etc.)
  • ... you want one more or less compact package to solve your photographic "problems"

If you know what you do there is no principal difference between primes and zooms. Focal length has two strongly different meanings for a photograph and the photographer:

  • The variation of the focal length can be used to change the (technical) impression by an image. Tele lenses compress the depth, a wide angle opens the depth of a scene. Framing is done by your feet.
  • The variation of the focal length can be used to frame the subject out of the scene without changing the location.

The first function of focal length is the "true" photographic approach. The second function of focal length is something between necessity and convenience.

Both are not coupled to primes or zooms but a prime has some educative and didactic function: Changing the focal length is not done by just moving a ring a little bit. Choosing another focal length is a thoughtful action ... should be.

At the moment you have only access to a zoom? Then read the next section ...

Using a zoom like a prime!

In my opinion there is nothing bad with zooms itself, just that I nevere used zooms in the first 20 years of my photographic experience. So I never had a chance to be spoiled by the convenience of zoom lenses. But digital changed it just for me: There is no 4.0/200mm or 3.5/135mm lens in the current canon lens line-up. The choice was the Canon EF 4.0/70 - 200 Zoom which provides an excellent optical image quality straight from the maximum aperture at each focal length in all disciplines.

How to use it as a prime? Before you take a photograph decide what you want. E.g. taking portraits: You want to show the location behind your subject, not to much blurred - choose 70 mm (ca. 110 mm on APC-C). You want to get rid of a background - choose 200 mm (ca. 320 mm on APS-C). Or choose 135 mm (ca. 200 on APS-C) for moderate background visibility. I do the same with my Canon EF-S 10 - 22 - I use just three settings: 16 mm equiv (10 mm on lens), 24 mm equiv. (15 mm on lens) or 36 mm equiv (22 mm on lens). The rest is done by varying the distance between me and the subject.

This combines the flexibility of a zoom with a thoughtful use of focal lengths. Packing my two zoom lenses and two camera bodies gives me the flexibility to use 6 classic focal lengths without changing any lenses (focal lengths in terms of full frame equiv.):

  • 16 mm (3.5) for exaggerated perspectives/near-far-contrast ore if I want to capture impressions
  • 24 mm (4.0) for strong wide angle perspectives
  • 36 mm (4.5) for general photography - I really like the Canon EF2.8/24 (ca. 40 mm equiv)
  • 110 (corresponding classical 100) mm (4.0) for general photography
  • 200 mm (4.0) for moderate tele perspectives
  • 320 (corresponding classical 300) mm (4.0) for stronger tele perspectives

This set is complemented by 3 primes (focal lengths again in full frame equiv):

  • 39 mm (2.8) for general photography, available light, light & compact lens
  • 96 mm (2.8) for macro photography, general photograph, light, compact and due to macro capability very versatile
  • 160 mm (2.0) for moderate tele photography, available light, very compact lens which is unobtrusive

Conclusion

Try to find out what field of photography you want to explore. Understand the meaning of focal length for composition. Understand the limitations of zooms and primes. Than do your choice.

Primes (or fixed focals) have a secret advantage: After using one prime for a longer time you see your photo before you put the camera to your eyes because you know how that lens works! But a zoom can be used like a "set-lens": Try to set your zoom - e.g. the standard zoom17/18-50/55 for crop sensors to 24 mm and you have a classical 38 mm lens - and now use your mind and feet for framing. It's amazing how versatile one focal length can be used - by your mind and with the help of your feet ;-) !

Table with equivalent focal lengths

You can always calculate the 35mm equivalent focal length by multiplying the actual focal length of your lens by the crop factor of your camera. If you want to "simulate" a focal length in 35mm terms, divide that focal length by the crop factor of your camera.

Use the table after the following scheme:

  • STEP 1: Choose the classical focal length unter the 35mm full frame format. If you have a full frame camera, you are ready. Coloured rows show the most common "classical" focal lengths
  • STEP 2: If you have NO full frame camera, check the size of your sensor/its crop factor.
    - 1.3 is the Canon 1DxxX-System
    - 1.5 is Nikon, Sony, etc.
    - 1.6 is Canon, etc.
    - 2.0 stands for all FourThirds systems like Olympus or Panasonic, (etc.)
    Then select the focal length by setting your zoom ring or select the corresponding prime.

Dont try to set exact focal lengths ... do it with a 10% or 5% approximation, that is sufficient. The left column shows roughly the lens category.

Reverse lookups are also possible: You have a Nikon Camera and an 90 mm MACRO Lens. Look in the row for 1.5 APS-C crop sensors and search the line nearest to/with 90mm. The corresponding value in a 35mm environment is 135mm focal length.

  STEP 1: Chose target focal length: STEP 2: Select the focal length on your zoom or a prime with a similar focal length
  35mm Film APS-H APS-C APS-C FourThirds

1.0 1.3 1.5 1.6 2.0
Ultrawide 12,00 9,23 8,00 7,50 6,00
Ultrawide 14,00 10,77 9,33 8,75 7,00
Ultrawide 16,00 12,31 10,67 10,00 8,00
Ultrawide 17,00 13,08 11,33 10,63 8,50

Ultrawide

18,00 13,85 12,00 11,25 9,00
Strong_Wide_Angle 20,00 15,38 13,33 12,50 10,00
Strong_Wide_Angle 21,00 16,15 14,00 13,13 10,50
Strong_Wide_Angle 24,00 18,46 16,00 15,00 12,00
Strong_Wide_Angle 25,00 19,23 16,67 15,63 12,50
Wide Angle 28,00 21,54 18,67 17,50 14,00
Wide Angle 35,00 26,92 23,33 21,88 17,50
Standard 40,00 30,77 26,67 25,00 20,00
Standard 50,00 38,46 33,33 31,25 25,00
Moderate_Tele 70,00 53,85 46,67 43,75 35,00
Moderate_Tele 85,00 65,38 56,67 53,13 42,50
Moderate_Tele 90,00 69,23 60,00 56,25 45,00
Moderate_Tele 100,00 76,92 66,67 62,50 50,00
Moderate_Tele 105,00 80,77 70,00 65,63 52,50
Tele 135,00 103,85 90,00 84,38 67,50
Tele 150,00 115,38 100,00 93,75 75,00
Tele 180,00 138,46 120,00 112,50 90,00
Tele 200,00 153,85 133,33 125,00 100,00
Tele 300,00 230,77 200,00 187,50 150,00
Super_Tele 400,00 307,69 266,67 250,00 200,00
Super_Tele 500,00 384,62 333,33 312,50 250,00
Super_Tele 600,00 461,54 400,00 375,00 300,00
Super_Tele 800,00 615,38 533,33 500,00 400,00
Super_Tele 1000,00 769,23 666,67 625,00 500,00
Super_Tele 1200,00 923,08 800,00 750,00 600,00
Super_Tele 1600,00 1230,77 1066,67 1000,00

800,00

Bottom line

Canon lenses are mentioned here, but the same principles apply for lenses of other brands like Nikon, Leica, Zeiss, Pentax, Sony, Olympus, etc.

History

2010-01-13,mb: Corrections/Refinements, focal length comparison added



 

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