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kennethcooke
12th March 2009, 03:30 AM
I am interested to know the finding of other members regarding personal ISO ratings for different Monochrome film ie I read that most photographers don't work with manufacturers ISO settings. This issue came to light recently regarding Kodachrome 64 asa which most photographers, myself included tend to rate it at 80 asa. Regarding Monochrome I have read that Kodak Tri-X 400 asa is one of the few film stocks that people shoot at manufacturers rating

Argentum
12th March 2009, 04:37 AM
ISO speed is just the standard manufacturers use. The film characteristic curve is not fixed. Different developers will give different film speeds and different development times will also give different film speeds. So which is the one to use. Well that depends on purpose, lighting conditions, subject contrast range, intended print size, aesthetic required etc etc. Too many variables to say any film should be used at one specific speed.
For example, your typical landscape in the middle of the day may have 10 stops of range whilst at dusk it may only have 5 stops of range. So taking one film such as HP5, you would want to reduce development to contain that 10 stop range and the result of that is that you also need to give more exposure or you will loose shadow detail. The extra exposure is achieved by using a slower film speed. But when you come to photograph the dusk scene, you need to give extra development to expand that 5 stop range and that also means you need less exposure so you use a faster film speed. Film speed is not fixed.
What is normal? Well around a 7 stop range should be normal for a literal translation from subject to paper as paper holds 7 stops. But does the literal translation give you the aesthetic you require? I can't answer that but I might decide that I'm not interested in the literal translation because I favour harder or softer contrast than normal and I might use a different film speed accordingly.

Steve Smith
12th March 2009, 08:12 AM
If you search for it, you can find some very good and detailed tests to do to work out your own personal EI for a film.

I didn't bother. Instead, I took the lazy route.

I noticed that in 90% of all cases I read about, the conclusion was to rate the film at half its ISO and reduce the development time. e.g. HP5+ ISO 400, rated at EI 200 and develop for 75% of the ISO 400 time.

This was good enough for me so I started doing just that and I found that I liked the results.

I don't do it all the time, usually just when there is good light. In dull conditions I rate it at EI 400.

This ties in with the point made above in that dull light is usually accompanied by low contrast so it's not so important to boost the shadow detail. Actually, you are doing it automatically without thinking about it by increasing the overall exposure to compensate for the dull ambient conditions.



Steve.

Monoman
13th March 2009, 09:07 AM
Excellent advice on establishing personal film speeds here:
http://www.barrythornton.com/
Click on the 'Technique' section of the menu.
Hope this helps.

kennethcooke
13th March 2009, 09:55 AM
Excellent advice on establishing personal film speeds here:
http://www.barrythornton.com/
Click on the 'Technique' section of the menu.
Hope this helps.
Funny you should mention Barry Thornton see my thread in "Photography Art and Aesthetics". I personally find his work clinical and uninteresting, and wheres the grain?

Argentum
13th March 2009, 10:24 AM
How much film speed do you want?
If you like a little coarseness in your prints, then I would stay away from T-grain films. HP5 deved in dilute Perceptol is pretty good. Nice and sharp but not as smooth as some of the T-grain films. I use it at EI 160 1+2 dilution for around 12 mins at 20 degC. But if you want more speed (and grain) try it with ID11 or Microphen at Ilfords recomended times and dilutions.