Useful and Cheap: The Johnson Exposure Calculator

[Jocko]

I realise that many people pride themselves on using "Sunny 16", but the rest of us often need a little help!

I've come across something which I think is genuinely useful - the Johnson Exposure Calculator, made in the 1950s-60s. The two most commonly encountered versions are respectively for negative and reversal films. Both frequently appear on British E-Bay and sell for pennies.

The calculators are the final form of the late-19th century Wellcome Calculator, thus in effect encapsulate the wisdom of 70 years of photographers. It shows.

I bought mine a few days ago for 50p ($1) each. I am astonished by the level of accuracy they offer. The negative version is invariably well within half a stop of a meter reading and usually spot on. The Reversal Calculator is yet more precise. Because they take time of day and latitude/longitude into account, they are much more accurate than the simple calculators available online. At the very least they force one to think about the light and would come into their own when batteries fail or meters are forgotten.

The Calculators have usually lost their original documents, so I attach the instructions and alternative tables, which should be used outside Northern Europe. I hope this proves useful to someone!

Cheers, Ian

 

[dmr]

Hmmmm ... kind of like Sunny 16 but taking into account other significant variables.

Thanks. 🙂

 

[Kent]

"Clouds in sky and sun shines bright,
1, 25 and f is 8."

Does not really rhyme but often works.
(1, 25 is supposed to mean 1/125 sec)

Interesting attachments. Thanks.

 

[Xmas]

Ian

In '61 I had a Periflex and a exposure calculator this was a circular slide rule which fitted into a leatherette pouch, you dialled in the film speed and looked up the exposure in a table.

This replaced the tables that Kodak did for each film type.

Probably the circular calculator is a collecors piece today, I can remember giving it away but I dont recall who I gave it to. I was given the calculator by a friend of my fathers, nostalgia...

Noel

 

[Ash]

I think within 10 minutes of your post, all ebay sellers have added a digit to their prices 😀

 

[Jocko]

I think within 10 minutes of your post, all ebay sellers have added a digit to their prices 😀

OK chums! Lets wait a week or two before pouncing! Seriously, these things really are pretty common!

But - the same calculator, in a slightly less convenient, bound into the book form, was also included in Wellcome's Photographic Exposure Record & Diary and The Johnson Photographic Yearbook. The latter was very populatr in the 1950s and 60s as an "ideal Christmas stocking-filler" for photographic dads...). Copies are still widely available (on E-Bay or here for example - http://www.vintagecameras.co.uk/books.htm ) - so there's no shortage!

Cheers! Ian


Noel - would this be your calculator?

http://cgi.ebay.co.uk/ws/eBayISAPI....MEWA:IT&viewitem=&item=130079430154&rd=1&rd=1

 

[Xmas]

Ash

You wont be able to work out what 4/6 was, and my slide rule was similar to Ian's but nicer.

But I dont want to replace the calculator, I know I found a deserving home for it, my problem is I dont remember who it was. I did the same with the Watson daylight loader. But when I needed a replacement I got three from my friendly photo dealer, two at £3, one at £5, a lot cheaper then origional cost.

In '61 I was like you broke.

Noel

 

[Xmas]

Ian

Yes, and it seems like yesterday.

Noel

 

[Xmas]

Ash
In '61 they reduced the safety factor in the film speeds from 2.5 stops to 1.2 stops, 'because most people were using meters', I knew I was poor I was using a 2nd hand circular slide rule.
Noel
P.S. an origional one came in a brown leatherette slip case

 

[ChrisPlatt]

Great! Most here have a hard enough time with their distance glasses and squinty little RF viewfinders,
now you want them to carry their reading glasses too?

I can just see them switching back and forth now. It'll take them all day to take one "candid" photo! 😉

Chris

 

[Xmas]

Chris

You are having a stressful day like Ash?

The slide rule was no worse (better) than the Weston Master or Kiev top plate calculators. And I dont have bifocals.

Noel