Is exposure index and ISO actually relevant

[Paul Howell]

Using the developer's recommendation Foma Excel or Xtol, the box speed for Foma 400 is of course 400, when using Excel ISO drops to 250. All the film makers say that box speed is just a starting point. Again with Kodak Tmax films using a AF body with Martix metering I do get box speed with most standard developers, with Foma, 400, I shoot at 320.

 

[koraks]

Using the developer's recommendation Foma Excel or Xtol, the box speed for Foma 400 is of course 400, when using Excel ISO drops to 250.

Not quite 400, it seems. Only with Microphen and a high gamma the film just inches over 320, but never quite makes it to 400. With a more modest g-bar of 0.65 or so, it's really a 200-250 film.
As per the datasheet, that is. I assume that's more or less accurate (it does match my experience with this film).

 

[Paul Howell]

I agree, my point is that Foma's Action Pan 400 box speed is 400, 320 is not quite 400 but close and only with Microphen or maybe Acufine. All other develpers 250 to 200. TriX box speed is 400 with microdol X about 200, again using old Kodak data sheets. Box speed is a starting point, nothing more or nothing less. Advising people to shoot at Box Speed with taking into account which developer, which dilution, what temperature, what camera, what meter is not good advice.

 

[koraks]

Advising people to shoot at Box Speed with taking into account which developer

You mean, 'without', right? I agree in that case.

I think there might have been a similar typo (Foma Excel vs. ... Excel!) in your previous post that confused me, and prompted my response

 

[Bill Burk]

It’s crazy that we try to cram everything into one number.

ASA/ISO keeps manufacturers from exaggerating how sensitive their film is.

Camera and light meter manufacturers have corresponding standards so you can use ASA/ISO and get good results.

Or you can choose a number higher or lower than the ASA/ISO speed. Since it’s not ASA/ISO we agree to call it something else. The term is “Exposure Index” or EI.

There are more reasons than people.

In the end you’ll take a picture and the negative will have densities corresponding to different parts of the scene where different amounts of light hit the film.

 

[eli griggs]

I feel that the better you become at the mechanics of handling film, tank, reel, temperature, agitation, taps down to dislodge bubbles, pouring in and out of the tank, including time and angles, as well as, agitation form, and three basic sets if one minute of agitation, first five or ten seconds, tap, tap, rest for the rest of the minute, 30 second agit., taps, rest, repeat or 60 seconds agit., taps, mystery intervals, washes toner, HCA, IF used and Photoflo, hanging and drying, the easier it is to then adjust your films exposure indexs and discover for yourself the desired density for making Grade 3 prints.

Having a set quality of negitive density to strive for, should be the focus of darkroom wet work, regardless of ISO, exposure time and light volume (apature), filters, etc, within your standard and experimental work, for consistent results you are fimiliure with and desire.

This is what I shoot for, no "correct" iso, shutter speed, EI, etc, which add countless subdivisions of unneeded labor.