snubbr.com

What is the diffrence between the Flash Guide No & the flash range?
I was browsing the specifications of a konica minolta camera and on their official site I read that the flash guide no. is 12meters and flash range is 5 meters?So, What is the real effective range of the flash?and what is the other no.?Thank you very much..

Comments (10)

Moataz wrote:.

I was browsing the specifications of a konica minolta camera and ontheir official site I read that the flash guide no. is 12meters andflash range is 5 meters?So, What is the real effective range of the flash?and what is the other no.?.

Guide numbers are a way of indicating the power or range of a flash but they're not expressed directly in meters since the number of meters would depend on other factors like f-stop, ISO, etc..

Instead the Guide Number is calculated by multiplying a given f-stop by the flash to subject distance at a given ISO (usually ISO 100). The resulting Guide number is expressed as a single numeric value depending on whether it's being used to calculate distance in meters or in feet. ie; a Guide Number of 38/125 would indicate a GN of 38 for calculating distance in meters or 125 for calculating distance in feet..

For example with a flash that has a Guide number of 125 (feet) , we can determine the effective range of the flash for any available f-stop or what f-stop will be required to obtain an exposure at a given distance in the following ways....

To determine the required f-stop, divide the GN by the distance between the flash and the subject, ie; 125/20(feet) = 6.25 which gives you an f-stop between f/5.6 and f/8.0 for a subject 20 feet away at ISO 100..

To determine the distance the flash can reach at a given f-stop, divide the GN by the f-stop value, ie; 125/5.6 = 22.3 which tells us our flash can reach 22.3 feet at f/5.6 using ISO 100 (but we already new that)..

So, assuming the numbers on that page you were looking at were accurate (if not slightly misrepresented), a GN of 12 in meters would give you a shooting distance of 5 meters if you were using f/2.4 at ISO 100. That range would be reduced at smaller apertures or increased at higher ISO settings. Shutter speed will have little or no impact on the flash range but it will impact the balance between the light from the flash and the ambient light already available at the scene..

Tom Younghttp://www.pbase.com/tyoung/..

Comment #1

Thank you very much, You are always the first one who explains the problem I submit each timeThanks for your efforts..

Comment #2

Tyoung wrote:.

Guide numbers are a way of indicating the power or range of a flashbut they're not expressed directly in meters since the number ofmeters would depend on other factors like f-stop, ISO, etc......

Great explanation - thanks from me too ..

Comment #3

So what would something like.

4.2m (13.7ft) 2m mean - as shown in DPR side by side for comparisons?.

Madhabi..

Comment #4

To add to that great answer by tyoung, each time you double the ISO speed (i.e., from ISO 100 to ISO 200), your flash range increases by approximately 1.4x.

For example, if the flash had a GN of 140 feet at ISO 100, and you are shooting with an aperture of f/5.6, you can expect a properly illuminated subject at maximum range of around 25 feet (GN of 140 feet divided by 5.6 = 25 feet)..

But, if you increased your ISO speed from ISO 100 to ISO 200, you can expect a properly illuminated subject at around 35 feet (25 feet x 1.4 = 35 feet)..

JimChttp://www.pbase.com/jcockfield..

Comment #5

Madhabi Roy wrote:.

So what would something like.

4.2m (13.7ft) 2m mean - as shown in DPR side by side for comparisons?.

Could you please state which camera you are referring to.Here is a possible related example:http://www.dpreview.com/reviews/compare_post.asp?sortby=36The Canon A620 section lists this:Flash guide no. 4.2 m (13.7 ft) 2 m.

Note: I think this is probably incorrect, what is being described is the maximum flash range, which is not the same thing as the guide number..

However, in the review of the same camera, the specifications state:Max flash range 4.2m (W), 3.0m (T), ISO 100That is a slightly different (and presumably more accurate) version.The meaning is,at ISO 100, lens at wide-angle setting, maximum range is 4.2 metres (13.8 feet).At ISO 100, lens at telephoto setting, maximum range is 3.0 metres (9.8 feet)..

The reason for the variation is the lens maximum aperture changes from f/2.8 to f/4.1 when zooming from wide to tele.Hope this helps,Peter..

Comment #6

Sherwoodpete wrote:.

Madhabi Roy wrote:.

So what would something like.

4.2m (13.7ft) 2m mean - as shown in DPR side by side for comparisons?.

Could you please state which camera you are referring to.Here is a possible related example:http://www.dpreview.com/reviews/compare_post.asp?sortby=36The Canon A620 section lists this:Flash guide no. 4.2 m (13.7 ft) 2 mNote: I think this is probably incorrect, what is being described isthe maximum flash range, which is not the same thing as the guidenumber..

However, in the review of the same camera, the specifications state:Max flash range 4.2m (W), 3.0m (T), ISO 100That is a slightly different (and presumably more accurate) version.The meaning is,at ISO 100, lens at wide-angle setting, maximum range is 4.2 metres(13.8 feet).At ISO 100, lens at telephoto setting, maximum range is 3.0 metres(9.8 feet).The reason for the variation is the lens maximum aperture changesfrom f/2.8 to f/4.1 when zooming from wide to tele.Hope this helps,Peter.

I was referring to the Panny TZ3, but all the others also had nos. in a similar format ( I was comparing the TZ3 with FZ18, FZ8, Canon SD800IS etc).

Madhabi..

Comment #7

Also note that GN depends on ISO and meters/feet. The usual figure is ISO 100 and feet. But not always since some cameras don't offer ISO 100 and most of the rest of the world uses meters..

And note that many external flashes have a zoom head which zooms along with your lens. In this case, the GN is also dependent on the flashes zoom setting..

One last note: the GN is usually overstated by one stop (1.4). So, while your GN 100 flash should correctly expose at 25 feet and f/4, you're more likely to get a correct exposure at f/2.8. With autoexposure, all you need to do is stay within 70% of the theoretical maximum distance...

Comment #8

Greg Nut wrote:.

Also note that GN depends on ISO and meters/feet. The usual figureis ISO 100 and feet. But not always since some cameras don't offerISO 100 and most of the rest of the world uses meters..

Yes.. .

Many of the flashguns from Europe, Metz ones for instance, incorporate the guide number in metres into the model name of the unit..

The famous Metz CL-45 range of hammerhead guns have GN of 45 ......

... resulting in an aperture of f/4.5 at a distance 10 metres (ISO 100 assumed).

..... 10 metres = 34 feet (close enough.)Regards,Baz..

Comment #9

Madhabi Roy wrote:.

I was referring to the Panny TZ3, but all the others also had nos. ina similar format ( I was comparing the TZ3 with FZ18, FZ8, CanonSD800IS etc).

A bit like this:.

Http://www.dpreview.com/...cameras=canon_a620%2Cpanasonic_dmctz3&show=allSeems like the flash information may be inaccurate.The review here gives better details:http://www.dpreview.com/reviews/panasonictz3/Flash" Range: 0.6 - 4.2m (wide) 1.0 - 2.8m (tele)..

Comment #10

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.