snubbr.com

Teleconverters: Does using them stop down apertures at all?
If I were to use a 1.4x teleconverter on a Sigma 70 - 200 2.8 lens, would the usage of the TC stop the lens down to 3.x or 4? Please advise, thank you...

Comments (6)

Yes. A 200mm F2.8 becomes 280mm F4. An F4 lens becomes F5.6, etc. Basically multiply the magnification of the converter by the lens F stop. A 1.4 converter is one full stop, so that halves the amount of light getting to the sensor. A 2.0 converter is 2 full stops so it quarters the light getting to the sensor.Some cool cats that can use your helphttp://www.wildlife-sanctuary.org.

Even if you can't donate, please help spread the word...

Comment #1

A 1.4x teleconverter behind the lens costs you a full stop; f/2.8 is reduced to f/4.0..

Dave..

Comment #2

When the teleconverter is placed between the lens and camera body, it reduces the effective aperture.A 1.4x converter loses one stop, so your f/2.8 lens becomes f/4..

Similarly, a 2x converter loses two stops, making the f/2.8 lens effectively f/5.6.Regards,Peter..

Comment #3

F/2.8 X 1.4 = f/3.92.

F/8 X 1.4 = f/11.2.

F/22 X 1.4 = f/30.8.

Here is image made with lens at f/8 + 2X teleconverter..

Take a look at exif - shows f/16. It was combined by camera from f/8 lens setting and 2X teleconverter http://stan-pustylnik.smugmug.com/gallery/436744#203442258http://www.stan-pustylnik.smugmug.com..

Comment #4

The aperture ratio is the ratio of focal length to effective aperture diameter. When you add a 1.4x TC, it leaves the size (diameter) of the aperture the same, but increases the focal length by 1.4x, so increases the ratio by factor 1.4x..

In practice, aperture ratio measures how bright an image one gets on the sensor (or film) from a subject of a given brightness. Adding a TC spreads the the light over a larger area, so gives a larger but dimmer image, and the higher aperture ratio indicates this dimming...

Comment #5

Stan_P wrote:.

F/2.8 X 1.4 = f/3.92.

Nope, it f/4. 2.8 and 1.4 are both rounded off..

2.8 is really 2^3/2, and 1.4 is really 2^1/2. To multiply just add the exponents....

2^3/2 * 2^1/2 = 2^2 = 4..

F/8 X 1.4 = f/11.2.

Same thing, 1.4 = 2^1/2. Result is typically expressed as f/11..

F/22 X 1.4 = f/30.8.

Ditto, f/32..

Seen in a fortune cookie:Fear is the darkroom where negatives are developed..

Comment #6

Click Here to View All...

Sponsored Amazon Deals:

1. Get big savings on Amazon warehouse deals.
2. Save up to 70% on Amazon Products.


This question was taken from a support group/message board and re-posted here so others can learn from it.

 

Categories: Home | Diet & Weight Management | Vitamins & Supplements | Herbs & Cleansing |

Sexual Health | Medifast Support | Nutrisystem Support | Medifast Questions |

Web Hosting | Web Hosts | Website Hosting | Hosting |

Web Hosting | GoDaddy | Digital Cameras | Best WebHosts |

Web Hosting FAQ | Web Hosts FAQ | Hosting FAQ | Hosting Group |

Hosting Questions | Camera Tips | Best Cameras To Buy | Best Cameras This Year |

Camera Q-A | Digital Cameras Q-A | Camera Forum | Nov 2010 - Cameras |

Oct 2010 - Cameras | Oct 2010 - DSLRs | Oct 2010 - Camera Tips | Sep 2010 - Cameras |

Sep 2010 - DSLRS | Sep 2010 - Camera Tips | Aug 2010 - Cameras | Aug 2010 - DSLR Tips |

Aug 2010 - Camera Tips | July 2010 - Cameras | July 2010 - Nikon Cameras | July 2010 - Canon Cameras |

July 2010 - Pentax Cameras | Medifast Recipes | Medifast Recipes Tips | Medifast Recipes Strategies |

Medifast Recipes Experiences | Medifast Recipes Group | Medifast Recipes Forum | Medifast Support Strategies |

Medifast Support Experiences |

 

(C) Copyright 2010 All rights reserved.