# Ok, noobiest question ever - can't figure out film speed



## DocFrankenstein (Jun 12, 2005)

What's APX? What's ISO? Are they related? How does one measure them?

I was told I got ISO 100 BW film... now I figure out it's ISO 400?

Minor details like that can really make my day.

The actual roll looks like this:
http://andrew4137.fotopic.net/p16217715.html

On the box it says Agfapan APX 135-36

So, what's the ISO speed of my film?


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## terri (Jun 12, 2005)

Who told you this was 100 speed film?  :scratch:  It has 400 in very large print.   It's 400 speed film.  

Agfa is the manufacturer, don't know what the APX designation is supposed to mean.  Matt probably knows what it is, I've not used it personally.


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## DocFrankenstein (Jun 12, 2005)

terri said:
			
		

> Who told you this was 100 speed film?  :scratch:


The salesman at henrys. :lmao:


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## Kent Frost (Jun 12, 2005)

135=35mm (don't know why they refer to it as 135)
36=how many exposures are in that roll.

A lot of times, you'll see that on the roll. 135-36 or 135-24.


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## Mumfandc (Jun 12, 2005)

Kent Frost said:
			
		

> 135=35mm (don't know why they refer to it as 135)
> A lot of times, you'll see that on the roll. 135-36 or 135-24.


The "135" is the product number Kodak originally listed these films as.


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## ksmattfish (Jun 12, 2005)

DocFrankenstein said:
			
		

> What's APX? What's ISO? Are they related? How does one measure them?



APX is just a name for the label like Tri-X, Delta, Tmax, Acros, etc...  In some cases the label does not indicate ISO, and in others it does.  Tmax and Delta come in several speeds, while HP5 and Pan-X are labels for specific ISO films.  It's just up to the manufacturer, and how they want to market the product.  

ISO is a number that represents the manufacturers' recommendation of the film's sensitivity to light.  I don't know what ISO 400 film has 400 of, but I know that every doubling or halving of the ISO number equals a stop:  25, 50, 100, 200, 400, 800, 1600, 3200....


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## Kent Frost (Jun 12, 2005)

ISO used to be called ASA. 

ASA=American Standards Association
ISO=Internation Standards Organization.

You can see why they switched.


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