Pushing the film: not a good thing for picture quality, you will get more grain, extreme contrast, and might get blocked high-lights or undefined shadows, or both at the same time... Why do we do it anyway? Well, sometimes there is simply not enough light to expose a film at it's real speed, and sometimes a tripod adn long exposure times are not the solution (e.g. when shooting people - movement would be visible).
Pushing is mainly used in for taking pictures of people in low light, when the subject matter is more important than the picture quality...
Pulling film: This is used to reduce negative contrast in scenes with very contrasty lights (e.g. bright sun at noon).
Lowering the exposure index of your film (i.e. shooting 400 ASA film at EI 250) is not always pulling film - most manufacturers are simply a bit overenthusiastic when it comes to rating their films' speeds...
Shooting at the 'real' film speed (which, depending on the whole chain of shooting a picture - camera shutter, lightmeter, development - different developers give different film speeds with the same film type, type of light source of the enlarger, contrast range of the printing paper, print developer used) will give you more easily printable negatives with more open shadows that will show finer detail.
There are methods to establish the 'real' film speed using a densitometer and a lot of math, or you could one of the two following methods:
go to <htttp://www.barrythornton.com> and click 'Unzone';
or go here:
<http://www.halfhill.com/speed1.html> and
<http://www.halfhill.com/speed2.html>
.. or you simply rate your film a bit lower than what is printed on the box (64 to 80 for a 100 film, 250 to 320 for 400), and reduce your development times for about 15%.
Roman
Pushing is mainly used in for taking pictures of people in low light, when the subject matter is more important than the picture quality...
Pulling film: This is used to reduce negative contrast in scenes with very contrasty lights (e.g. bright sun at noon).
Lowering the exposure index of your film (i.e. shooting 400 ASA film at EI 250) is not always pulling film - most manufacturers are simply a bit overenthusiastic when it comes to rating their films' speeds...
Shooting at the 'real' film speed (which, depending on the whole chain of shooting a picture - camera shutter, lightmeter, development - different developers give different film speeds with the same film type, type of light source of the enlarger, contrast range of the printing paper, print developer used) will give you more easily printable negatives with more open shadows that will show finer detail.
There are methods to establish the 'real' film speed using a densitometer and a lot of math, or you could one of the two following methods:
go to <htttp://www.barrythornton.com> and click 'Unzone';
or go here:
<http://www.halfhill.com/speed1.html> and
<http://www.halfhill.com/speed2.html>
.. or you simply rate your film a bit lower than what is printed on the box (64 to 80 for a 100 film, 250 to 320 for 400), and reduce your development times for about 15%.
Roman
