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Although very little (single digit percentages) light is lost to a teleconverter, the ratio of entrance pupil to focal length grows proportional to the magnification of the telecon. For example, if a 100mm f/2 lens has a 2x teleconverter attached to it, the lens will effectively become a 200mm f/4. This is because the lens will always have a 50mm entrance pupil (remember, the name f/number literally means the entrance pupil diameter is focal length/number)

Because the amount of light gathered by the aperture series is based on doubling (f/2.8 gathers twicehalf as much as f/2) the series progresses not linearly but rather along a log-base-2 line. The equation for the increase in f-number as a result of teleconverter is, approximately:

E = 2 x log2(M)

Where

  • E is the (negative) shift in Ev
  • M is the magnification of the teleconverter
  • log2 is the operation logarithm base 2

So if you combine 2 each 2x teleconverter and 1 each 1.4x teleconverters (4.8x total) you would "lose" about 4.5 Ev or stops of light. If you attached that teleconverter to an f/2 lens, it would become a f/9.5 lens.

This equation could be combined with the expression of aperture in Ev to predict new effective aperture based on old effective aperture.

Although very little (single digit percentages) light is lost to a teleconverter, the ratio of entrance pupil to focal length grows proportional to the magnification of the telecon. For example, if a 100mm f/2 lens has a 2x teleconverter attached to it, the lens will effectively become a 200mm f/4. This is because the lens will always have a 50mm entrance pupil (remember, the name f/number literally means the entrance pupil is focal length/number)

Because the amount of light gathered by the aperture series is based on doubling (f/2.8 gathers twice as much as f/2) the series progresses not linearly but rather along a log-base-2 line. The equation for the increase in f-number as a result of teleconverter is, approximately:

E = 2 x log2(M)

Where

  • E is the (negative) shift in Ev
  • M is the magnification of the teleconverter
  • log2 is the operation logarithm base 2

So if you combine 2 each 2x teleconverter and 1 each 1.4x teleconverters (4.8x total) you would "lose" about 4.5 Ev or stops of light. If you attached that teleconverter to an f/2 lens, it would become a f/9.5 lens.

This equation could be combined with the expression of aperture in Ev to predict new effective aperture based on old effective aperture.

Although very little (single digit percentages) light is lost to a teleconverter, the ratio of entrance pupil to focal length grows proportional to the magnification of the telecon. For example, if a 100mm f/2 lens has a 2x teleconverter attached to it, the lens will effectively become a 200mm f/4. This is because the lens will always have a 50mm entrance pupil (remember, the name f/number literally means the entrance pupil diameter is focal length/number)

Because the amount of light gathered by the aperture series is based on doubling (f/2.8 gathers half as much as f/2) the series progresses not linearly but rather along a log-base-2 line. The equation for the increase in f-number as a result of teleconverter is, approximately:

E = 2 x log2(M)

Where

  • E is the (negative) shift in Ev
  • M is the magnification of the teleconverter
  • log2 is the operation logarithm base 2

So if you combine 2 each 2x teleconverter and 1 each 1.4x teleconverters (4.8x total) you would "lose" about 4.5 Ev or stops of light. If you attached that teleconverter to an f/2 lens, it would become a f/9.5 lens.

This equation could be combined with the expression of aperture in Ev to predict new effective aperture based on old effective aperture.

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Although very little (single digit percentages) light is lost to a teleconverter, the rationratio of entrance pupil to focal length is changed bygrows proportional to the magnification of the telecon. For example, if a 100mm f/2 lens has a 2x teleconverter attached to it, the lens will effectively become a 200mm f/4. This is because the lens will always have a 50mm entrance pupil (theremember, the name f/number literally means the entrance pupil is focal length/number)

Because the amount of light gathered by the aperture series is based on doubling (f/2.8 gathers twice as much as f/2) the series progresses not linearly but rather along a log-base-2 line. The equation for the increase in f-number as a result of teleconverter is, thereforeapproximately:

E = 2 x log2(M)

Where

  • E is the (negative) shift in Ev
  • M is the magnification of the teleconverter
  • log2 is the operation logarithm base 2

So if you combine 2 each 2x teleconverter and 1 each 1.4x teleconverters (4.8x total) you would "lose" about 4.5 Ev or stops of light. If you attached that teleconverter to an f/2 lens, it would become a f/9.5 lens.

This equation could be combined with the expression of aperture in Ev to predict new effective aperture based on old effective aperture.

Although very little (single digit percentages) light is lost to a teleconverter, the ration of entrance pupil to focal length is changed by the telecon. For example, if a 100mm f/2 lens has a 2x teleconverter attached to it, the lens will effectively become a 200mm f/4. This is because the lens will always have a 50mm entrance pupil (the name f/number literally means the entrance pupil is focal length/number)

Because the amount of light gathered by the aperture series is based on doubling (f/2.8 gathers twice as much as f/2) the series progresses not linearly but rather along a log-base-2 line. The equation for the increase in f-number is, therefore:

E = 2 x log2(M)

Where

  • E is the (negative) shift in Ev
  • M is the magnification of the teleconverter
  • log2 is the operation logarithm base 2

So if you combine 2 each 2x teleconverter and 1 each 1.4x teleconverters (4.8x total) you would "lose" about 4.5 Ev or stops of light.

This equation could be combined with the expression of aperture in Ev to predict new effective aperture based on old effective aperture.

Although very little (single digit percentages) light is lost to a teleconverter, the ratio of entrance pupil to focal length grows proportional to the magnification of the telecon. For example, if a 100mm f/2 lens has a 2x teleconverter attached to it, the lens will effectively become a 200mm f/4. This is because the lens will always have a 50mm entrance pupil (remember, the name f/number literally means the entrance pupil is focal length/number)

Because the amount of light gathered by the aperture series is based on doubling (f/2.8 gathers twice as much as f/2) the series progresses not linearly but rather along a log-base-2 line. The equation for the increase in f-number as a result of teleconverter is, approximately:

E = 2 x log2(M)

Where

  • E is the (negative) shift in Ev
  • M is the magnification of the teleconverter
  • log2 is the operation logarithm base 2

So if you combine 2 each 2x teleconverter and 1 each 1.4x teleconverters (4.8x total) you would "lose" about 4.5 Ev or stops of light. If you attached that teleconverter to an f/2 lens, it would become a f/9.5 lens.

This equation could be combined with the expression of aperture in Ev to predict new effective aperture based on old effective aperture.

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Although very little (single digit percentages) light is lost to a teleconverter, the ration of entrance pupil to focal length is changed by the telecon. For example, if a 100mm f/2 lens has a 2x teleconverter attached to it, the lens will effectively become a 200mm f/4. This is because the lens will always have a 50mm entrance pupil (the name f/number literally means the entrance pupil is focal length/number)

Because the amount of light gathered by the aperture series is based on doubling (f/2.8 gathers twice as much as f/2) the series progresses not linearly but rather along a log-base-2 line. The equation for the increase in f-number is, therefore:

E = 2 x log2(M)

Where

  • E is the (negative) shift in Ev
  • M is the magnification of the teleconverter
  • log2 is the operation logarithm base 2

So if you combine 2 each 2x teleconverter and 1 each 1.4x teleconverters (4.8x total) you would "lose" about 4.5 Ev or stops of light.

This equation could be combined with the expression of aperture in Ev to predict new effective aperture based on old effective aperture.