Figuring out my film's true speed

[Moriturii]

So I found the most amazing article, in two parts, that says how you can figure out your film's ISO speed according to a bunch of variables. Stuff all of you already know. Revelation to me though, fantastic.

http://www.halfhill.com/speed1.html
http://www.halfhill.com/speed2.html

My question is, I don't have a darkroom. So I can't do that part. Can I substitute a darkroom in this equation with my scanner and a computer program instead?

 

[tlitody]

There's no such thing as "True Speed". Film speed is variable, within limits, according to developer, dilution, time and temp. I think you are talking about your personal "Exposure Index" abreviated to EI.

Can you do it with a scanner? Probably but I never tried and wouldn't anyway. It would be a lot of farting about when you can judge it by eye from the negatives if you do a film test.

 

[Roger Hicks]

ISO speeds are ISO speeds.

The EI that works best for your metering technique and equipment is easily established.

(1) Do you get detail in the shadow areas where you wanted it? If not, lower the EI in 1/3 stop decrements.

(2) Do you get the tonality you like? If not, change the dev regime.More development (more time, more concentration, more agitation, or warmer) = more contrast. Less development = less contrast.

That's it.

Cheers,

R.

 

[back alley]

ISO speeds are ISO speeds.

The EI that works best for your metering technique and equipment is easily established.

(1) Do you get detail in the shadow areas where you wanted it? If not, lower the EI in 1/3 stop decrements.

(2) Do you get the tonality you like? If not, change the dev regime.More development (more time, more concentration, more agitation, or warmer) = more contrast. Less development = less contrast.

That's it.

Cheers,

R.

very simply put...well done.

 

[Ronald M]

Just photograph a step wedge. The least exposure that gives a printable separation in the two darkest steps is your personel EI

With my materials, I have yet to find one that deviated from box speed.

That said, half box speed and a 20% reduction in development time gives me outstanding negs.

 

[Moriturii]

Yepp! EI is what I had in heart of course! I need to get a step wedge. 🙂

 

[Field]

ISO changes on Fuji Superia 400 when expired... I have a bunch of photos that look way more like daylight then I thought I would get in a dark room with low flash.

 

[tlitody]

ISO changes on Fuji Superia 400 when expired... I have a bunch of photos that look way more like daylight then I thought I would get in a dark room with low flash.

yes that's why they put an expiration date on films so its not surprising is it.