Film Exposure And Film Density

[ian barber]

I have recently returned to a project I started in 2020 which is learning more about sensitometry. My reference material is an excellent book by Phil Davis.
I wanted to pickup where I left off which is all about film exposure and film density.

My first experiment was to put into practice the theory behind under exposure will yield better tone separation in the high values.

Here are three exposures I made of a church door on HP5 and developed in D23 for 8 minutes.
One is Normal exposure, one is 1 stop under and one is 1 stop over.



On the light table, the one which was under exposed by a full stop showed to have more separation in the highlights at the expense of less density in the shadow areas resulting in flatter, less separated low tones which corresponds to what the book described.

 

[Alan Clark]

Ian, I think exposure is only one half of the story here. The amount of development you give the film also plays its part.

Alan

 

[ian barber]

Ian, I think exposure is only one half of the story here. The amount of development you give the film also plays its part.

Alan

I haven't got to the developer section yet. What's your experience with this Alan

 

[Alan Clark]

My experience is that bright contrasty light causes the most potential problems. In these conditions I give reduced development to stop the highlights on the negative getting too dense and lacking in separation. This can also bring the midtones down and make the print look rather dull. I counteract this by giving an extra stop of exposure when taking the picture. This puts the midtones nice and bright, where I want them. Reduced development controls the highlights and keeps them open, and the extra exposure gives plenty of shadow detail. The best of all worlds....Not my idea of course. Ansel Adams gets the credit.

Alan