Pulling Tri-X 400

[Oltremare]

Thank-you Roger

so you suggest longer developing time ..... together with an overexposure, say 200 or 320, OR keeping the label ISo??
Thanks again

 

[Photo_Smith]

Rule of thumb contrast increases with development time, it doesn't really increase the speed as the intertia (speed point) remains the same or similar relative to fog and density increases more in the upper values compared to the shadows.

Another rule of thumb is rating higher than box speed increases contrast when developed accordingly and shooting lower than box will decrease contrast when given slightly less development.

Tri-x is an ISO 400 film when developed and exposed correctly to give film base plus fog plus 0.1 and 1.3 DLog E units (which is a 32:1 scene brightness recording capability)

Rating it at anything else is an EI value that deviates from ISO standards.

 

[alfredian]

First half, second half equation

First half, second half equation

I read this in a darkroom manual somewhere. As a good "first approximation" to developing a film shot at "non-standard" speed, take your "usual" developing time for whatever you're using and..
Divide the time by two. The "first half" of the new development will be half of the usual minutes.
Take the second "half" of your traditional time and modify it by multiplying it by this ratio:
("shot" speed/"proper" speed) -- in your case = 100/400 = 0.25.
So, half your usual time plus one-quarter of the other half (one-eighth of the old total) will be the one to use. Five-eighths of the original time. The underlying logic is that the first "half" of the time provides a "useable image" - after that you're going for suitable highlights/shadows. "Too much" light (your case) is compensated by "too little" development in the back-half. Same concept for pushing (exposing your roll at 1600 would be two stops over, = 1600/400 = four times the back half). Hope this helps. --alfredian

 

[Roger Hicks]

Thank-you Roger

so you suggest longer developing time ..... together with an overexposure, say 200 or 320, OR keeping the label ISo??
Thanks again

Stick with the nominal ISO. With a little extra development, it should be fine. I'd certainly not go below EI 320.

Photo Smith is of course absolutely right that the shadow speed will increase very little, if at all, because of the ingenious way in which the ISO standard is written, but equally, unless shadow detail is important, the apparent speed will increase with over-development.

Cheers,

R.