Negative (film) quality and exposure index used

[Tom Kershaw]

I seem to recall a source either online or in a book (possibly 'Film Developing Cookbook',- haven't found the reference) stating the ILFORD Pan F Plus can give better image quality than ILFORD FP4 Plus at an equivalent Exposure Index (e.g. 64); and that this would also hold true to a comparison of FP4 Plus @ 200 E.I. and HP5 @ 200 E.I. However, these actions would seem to be attempts to accomplish divergent goals. Exposing and developing for 200 E.I; the HP5 Plus film would typically result in lower contrast compared to a "norm", and the FP4 Plus film would result in increased contrast compared to a "norm". Have I missed something?

Tom

 

[rwboyer]

No you did not mis anything at all. Words like quality are really really hard to pin down and in a lot of cases subjective quality and quantitative quality may not match up as well.

I have no idea what you read and what it's point was but...

In SOME circumstances you may be able to achieve more desirable results for a particular scene by using a slower speed film with similar shooting and exposure parameters - let's take your example. Say you need to use a give shutter speed/aperture you could choose to render that scene with a slower speed film shot at ISO X and then developed for a contrast expansion or you could use a higher speed film shot at the same ISO developed for a contrast contraction - The results would be massively different and totally dependent on the scene and how you wanted to render it.

RB

Just my 2¢

 

[Tom Kershaw]

In SOME circumstances you may be able to achieve more desirable results for a particular scene by using a slower speed film with similar shooting and exposure parameters - let's take your example. Say you need to use a give shutter speed/aperture you could choose to render that scene with a slower speed film shot at ISO X and then developed for a contrast expansion or you could use a higher speed film shot at the same ISO developed for a contrast contraction - The results would be massively different and totally dependent on the scene and how you wanted to render it.

RB

Just my 2¢

RB, I agree, you're illustrating a standard usage. Here is the reference:

'Film Developing Cookbook, Focal Press 1998- Bill Troop, Steve Anchhell'

page 54 - 'Avantages of the speed increase'

'This speed increase can be useful in an unforeseen way: A slow film such as Pan F+, with an ISO of 50, can be exposed at EI 100 if it is to be processed in a high acutance developer [surely increasing contrast issues? - TK]. Compare this to a medium speed film like FP4+, processed in D-76 at EI 125. The effective film speed difference between the two films is now only one third of a stop, due to the speed increase of the acutance developer. But despite the slight increase of graininess of Pan F+ processed in an acutance developer, overall image quality will be better than FP4+ processed in a fine grain developer. This is because a slow film almost always produces better image quality than a fast film, even when the slow film’s speed is increased in a speed enhancing high acutance developer.

Likewise, FP4+ or Verichrome developed in FX 1 or FX 2 rated at 200 will give superior results to Tri-X rated at EI 200 and processed in a speed-losing fine grain developer like Microdol-X or Perceptol, even though both films now have the same EI rating.’

 

[rwboyer]

Oh now I have the context -

I personally have never used a developer that gave me a whole stop speed increase in the shadows at the same CI compared to D76 but theoretically you could find two different developers that really did differ by a stop EI in the shadows (zone III is probably the most useful) at a give CI with two different films one being slower than the other - in this case this is just stating something that is obvious but not always true - for instance a slow speed film like PanF in a developer that really gave you an EI of 100 at a CI of say .56 would not always be "better" than say TMX or Delta 100 in another developer that gave you an EI of 100 at the same contrast.

So.... It is just an obvious point that is not always true for any given film/dev combination vs another completely different film/dev combination.

What are you trying to figure out exactly?

RB

 

[Tom Kershaw]

.

What are you trying to figure out exactly?

RB

Just that a developer giving that much speed increase while maintaining reasonable contrast seemed unlikely.

Tom

 

[2F/2F]

I seem to recall a source either online or in a book (possibly 'Film Developing Cookbook',- haven't found the reference) stating the ILFORD Pan F Plus can give better image quality than ILFORD FP4 Plus at an equivalent Exposure Index (e.g. 64); and that this would also hold true to a comparison of FP4 Plus @ 200 E.I. and HP5 @ 200 E.I. However, these actions would seem to be attempts to accomplish divergent goals. Exposing and developing for 200 E.I; the HP5 Plus film would typically result in lower contrast compared to a "norm", and the FP4 Plus film would result in increased contrast compared to a "norm". Have I missed something?

Tom

Nope, that's it. Better "quality", sure.....but contrast would be different.