Weston Ratings vs ASA/ISO.

[Keith Tapscott.]

I have acquired a Weston Master III meter (UK version). Is the Weston rating the next lower or higher number to obtain the equivalent ASA/ISO number?

 

[desertrat]

Here is a conversion chart:

http://www.westonmeter.org.uk/speeds.htm

ISO 100 is Weston 80. I also use an old Weston meter. I don't bother to make any conversion, because I figure most of my old cameras have shutters that are slightly slow, if anything. So I just pretend my meter is giving me ISO speeds.

 

[Keith Tapscott.]

Here is a conversion chart:

http://www.westonmeter.org.uk/speeds.htm

ISO 100 is Weston 80. I also use an old Weston meter. I don't bother to make any conversion, because I figure most of my old cameras have shutters that are slightly slow, if anything. So I just pretend my meter is giving me ISO speeds.

Thanks for the link desertrat. I had a feeling that it was the next lowest to ASA, but wasn't sure.

It belonged to my late uncle, but my aunt couldn't find an instruction manual. No invercone with it either, so reflected readings only at the moment.

 

[Bill Burk]

Note, the UK version is 1/3 stop different than the US version.

I use 160 Weston for 250 ASA.

When I match f/16 and 1/250 while Weston 160 is indicated, the arrow points at one third mark below 400 on the light scale.

You might find the arrow pointing somewhere else - the UK and US dials are physically different and I believe they differ by 1/3 stop.

 

[David Allen]

I have acquired a Weston Master III meter (UK version). Is the Weston rating the next lower or higher number to obtain the equivalent ASA/ISO number?

You will have to check online whether yours comes from the `US or 'UK'. Generally speaking, from the Weston Master III onwards made in the UK they use ASA ratings and not the previous 1/3 less Weston ratings.

Bests,

David.
www.dsallen.de

 

[Bill Burk]

Just noticed III...

My comment pertains to the II

 

[Keith Tapscott.]

You will have to check online whether yours comes from the `US or 'UK'. Generally speaking, from the Weston Master III onwards made in the UK they use ASA ratings and not the previous 1/3 less Weston ratings.

Bests,

David.
www.dsallen.de

The meter was manufactured by Sangamo Weston Ltd, Enfield, Middlesex, England and distributed by Ilford Ltd.
Model No. S141.3 and the meter number is P1720.

Thanks to everyone who posted and sorry for my very late reply.

 

[chrisaisenbrey]

Here is a conversion chart:

http://www.westonmeter.org.uk/speeds.htm

ISO 100 is Weston 80. I also use an old Weston meter. I don't bother to make any conversion, because I figure most of my old cameras have shutters that are slightly slow, if anything. So I just pretend my meter is giving me ISO speeds.

Something is wrong with this conversion chart: 21 DIN is 100 ASA and not 80 ASA. At least if we talk about modern DIN/ASA.

 

[paul ron]

Here is some interesting reading about these meters..... look at the part about the proper way to hold the meter when taking exposures? Perhaps this may contribute to the errors?

http://www.jollinger.com/photo/meters/other/weston-article.html

 

[Bill Burk]

Something is wrong with this conversion chart: 21 DIN is 100 ASA and not 80 ASA. At least if we talk about modern DIN/ASA.

It does look like you have pointed out an error in that chart.

 

[paul ron]

It does look like you have pointed out an error in that chart.

Something is wrong with this conversion chart: 21 DIN is 100 ASA and not 80 ASA. At least if we talk about modern DIN/ASA.

http://www.westonmeter.org.uk/speeds.htm


which chart says that? im looking at the weston chart linked above n see 21 din=80asa and 22din=100asa.

of course realize the date of those standards... it wasnt an error at the time.

 

[Bill Burk]

http://www.westonmeter.org.uk/speeds.htm


which chart says that? im looking at the weston chart linked above n see 21 din=80asa and 22din=100asa.

Many other references equate 21 DIN to 100 ASA which would mean the chart in the link has an error "off by one". Unless there can be another explanation, it looks like an error.

 

[paul ron]

no its pre revised standards... that was the standard back in 1939.

https://en.m.wikipedia.org/wiki/Film_speed

 

[Bill Burk]

I couldn't find the one step change in your link. My reference book was dated 1942 though.

 

[paul ron]

read the wiki... scroll down to the historic chart... its right after the table notes.

 

[Bill Burk]

Thanks, that makes sense, they point out the possible confusion specifically regarding 80 for 21 in the old chart.

I looked in Mees and found discussion of original DIN of 1931. Tests were developed to achieve maximum film speed. So I can see how the original DIN could easily have been inflated, and it would get pulled back a third stop in an adjusted procedure.

 

[Bill Burk]

I also found an Exacta guide from 1945 which equates DIN 19 DIN with Weston 100 so I can see this would be a fun exercise to try to get the whole story.

Times like these, I just dial in the footcandles for sunny 16 and put f/16 next to the shutter speed for the ISO speed of the film I'm using.

 

[paul ron]

hahahaha i think we've finnally have our standards standardized. it was all new back then and getting the word out wasn't as simple as it is today.

 

[Steve Smith]

Weston is 0.8 x ISO.

So 80 Weston is ISO 100.


Steve.

 

[Sirius Glass]

OR just buy a Minolta, Gossen or Sekonic meter and screw the conversion table.

 

[Chan Tran]

Yeah I wouldn't use a Weston for real. I can see the nostalgia aspect but functionally I would rather guess my exposure than rely on these old Weston meters.

 

[Steve Smith]

Some are very insensitive to light now, but others are good. I have two accurate Master III meters but my Master V hardly moves the needle at all.


Steve.

 

[paul ron]

yeah, my master v is totaly blind but my 715 is as good as any meter.

 

[MartinCrabtree]

I reduce box speed by 1/3 stop on my Master II. It was rebuilt by George Milton of Quality Light Metric and is accurate.