Support our Sponsors, they keep FADU free:   AG Photographic   The Imaging Warehouse   Process Supplies   RH Designs   Second-hand Darkroom Supplies  

Notices

Go Back   Film and Darkroom User > Equipment > Equipment miscellaneous

  ***   Click here for the FADU 2015/2014 Yearbooks   ***

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 17th February 2020, 08:27 PM
Nat Polton Nat Polton is offline
Friend
 
Join Date: Oct 2019
Posts: 758
Default Standard Candle.

When I was a schoolboy our science teacher told us about standard candles for physics. He even had the composition and wick specifications to make your own.

I am wondering if there is a standard do it yourself light source to check my light meter against.
All the articles that I have ever read on checking light meter accuracy have told me to check it against a known good meter.
How do you know it's a good meter?

I am looking for something that would tell me to use a certain wattage tungsten light bulb, opal or clear, in a dark room at so many feet or inches.
I figured tungsten to be a bit more standard that the various energy saver bulbs.

Anyone any experience in simple, diy standard light sources. With easily available components.

Cheers .
Reply With Quote
  #2  
Old 18th February 2020, 08:28 AM
Lostlabours Lostlabours is offline
Friend
 
Join Date: Apr 2012
Location: West Midlands/Aegean
Posts: 1,988
Default

When I bought my Elinchom flash heads in the early 1980's they came with a comprehensive instruction sheet and it suggested metering using the modelling lights, These bulbs were non standard so you had to use the correct ones supplied by Elinchrom.

So Elinchrom had standardised on these bulbs knowing their output was consistent, obviously the flash output was much higher so there was an adjustment to make, but in the absence of a flash meter it worked out perfectly.

Light output drops slightly as a bulb ages so you do really need to check against a good reliable meter for reference and accuracy.

Ian
Reply With Quote
  #3  
Old 18th February 2020, 12:02 PM
photomi7ch's Avatar
photomi7ch photomi7ch is offline
Friend
 
Join Date: Jan 2009
Location: East Midlands
Posts: 2,516
Default

A good meter is one you trust. My suggestion would be to use a photograph grey card place it in good light and take a meter reading with two meters and compare the results.
__________________
Mitch

http://photomi7ch.blogspot.com/

If you eliminate the impossible whatever remains no matter how improbable must be the truth.
Reply With Quote
  #4  
Old 9th March 2020, 12:26 AM
M Stewart M Stewart is offline
Friend
 
Join Date: Nov 2016
Location: Milton Keynes, UK
Posts: 72
Default

Is this of any interest?

https://www.ebay.co.uk/itm/VINTAGE-G...wAAOSwKtVeYTHD

I see that there's some instructions included, and they may advise how to use it.

I reckon you'll need dark cloth or similar, so that you aren't affected by stray light. Check using the inverse square rule.

HTH
__________________
Malcolm Stewart
Milton Keynes
Reply With Quote
  #5  
Old 9th March 2020, 07:22 AM
Chrisvclick Chrisvclick is offline
Friend
 
Join Date: Dec 2015
Location: Wales Uk, Gods Garden
Posts: 100
Default

Compare meters, the more you compare the better of course but even 2 out of 3 aint bad (as meatloaf or steinman would say)
__________________
Is there a level below "in the poop" ?
Reply With Quote
  #6  
Old 9th March 2020, 08:29 AM
Barry's Avatar
Barry Barry is offline
Administrator
 
Join Date: Aug 2008
Location: Mendip Hills, Somerset
Posts: 2,365
Default

Malcomb, you may want to check your email as it is not accepting emails as it is full.
__________________
Cheers, Barry
Reply With Quote
  #7  
Old 9th March 2020, 09:03 AM
John King John King is offline
Friend
 
Join Date: Nov 2012
Location: County Durham
Posts: 3,318
Default

If you do not have a standard 37% grey card, the inside of a normal Kellogs Cornflakes box gives the same reading! Bet you didn't know that!
Reply With Quote
  #8  
Old 9th March 2020, 12:59 PM
Terry S Terry S is offline
Friend
 
Join Date: Dec 2011
Location: Southend on Sea, Essex, England, UK
Posts: 3,795
Default

Quote:
Originally Posted by John King View Post
If you do not have a standard 37% grey card, the inside of a normal Kellogs Cornflakes box gives the same reading! Bet you didn't know that!
I always thought that it was an 18% grey card that meters were matched against?

Either way, that's a useful tip there John!

Terry S
Reply With Quote
  #9  
Old 13th March 2020, 11:22 PM
JOReynolds JOReynolds is offline
Friend
 
Join Date: Nov 2012
Location: St Albans UK/Agde France
Posts: 1,074
Default

Wait for a sunny day in mid-June and take readings at midday. This is the reference. Your meter, set at the appropriate film speed, should then indicate the same exposure time and aperture shown in or on the film packing.

Reflection exposure meters calculate exposure on the assumption that the scene you are metering reflects 18% of light incident upon it. The Invercone on Weston Meters and the little dome on others, directed towards the light source, make incident light measurements and simulate the 18% reflectance of typical scenes.

Last edited by JOReynolds; 13th March 2020 at 11:25 PM.
Reply With Quote
Reply
Support our Sponsors, they keep FADU free:   AG Photographic   The Imaging Warehouse   Process Supplies   RH Designs   Second-hand Darkroom Supplies  

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Reversal processing of standard B&W films Rob Archer Chemical formulae 38 6th September 2014 11:28 AM
Cine Film: Standard 8mm or 16mm AlanJones Photography in general 18 20th April 2014 12:10 PM
Rolleiflex Standard update Brock Cameras - medium format 0 23rd July 2012 12:09 PM
macro or standard lens ? Alan Clark Cameras - small format 10 7th April 2010 07:40 PM
Non-Standard Dilutions. Keith Tapscott. Monochrome Film 12 27th January 2010 04:12 PM


All times are GMT. The time now is 10:18 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.