general rules for exposure/development parameters

[chris_markiewicz]

Hello. I once again plan to start developing b&w film. I've been

reading various books that I've picked up, and I frequently read this

forum. It's common to see recommendations to, for example, overexpose

and underdevelop, etc etc.

 

I'm wondering if there is a general set of rules for how varying those

parameters affects the developed negative. For example, extending

development time increases/decreases grain. Extending exposure time

increases/decreases contrast. Etc etc.

 

I'm fully aware that things like contrast and grain are VERY dependent

on film choice, developer choice, developer dilution, etc. However it

is my plan to start with a single developer and film (probably tri-x

and hc110). So I'm wondering what I can expect from varying the

exposure and development.

 

thanks for your time

chris

[matt_needham]

Under expose and over develop to increase contrast. Over expose and under develop to decrease contrast.

 

Read: Henry Horenstein's "Black and White Photography", and "Beyond Basic Photography", and then Ansel Adam's trilogy "The Camera", "The Negative", and "The Print".

[stephen gale uk]

You will need to develop your own development times to suit your equipment. For example, if you have a condenser enlarger you will find that it will need less contrasty negatives than a diffuser enlarger.<P>

The previous poster was correct over-developing will increase contrast - I regularly over-develop by around 10-20% to produce negatives that print garde 2-3 on a diffuser enlarger. On my condenser enlarger, prints generally need one full grade less than compared to the same print on a diffuser enlarger.

<P>

In terms of effects, I have deliberately over-exposed Delta 100 at 50asa to produce very flat smooth skin tones for fashion images. I believe that this technique was also used by the Hollywood photographers of the 1940's. In my case, I over exposed by 1 stop and then developed for about 20% less time than for full speed. Here's a <a href="http://www.rightsitewrongplanet.co.uk/display.php?Query_field=Subject&Query_content=fashion&ImageID=81&Update=Yes">link </A>to an example image that is a straight print - there is no PS work on it at all and the skin tones are as they are on the negative. I quite like the effect and think that it is flattering for this kind of fashion work.<P>

Hope this helps. Stephen.

[bruce_watson1]

I can think of two generalities right off. First, expose for the shadows and develop for the highlights. Second, make your negative only as dense as is necessary to get good results.

 

The first one is basically just common sense. If you don't give your negatives enough exposure, you can't get shadow detail. If you negatives have the wrong contrast (controlled by development) then they are hard to work with.

 

The second is somewhat less intuitive. Density is related to graininess in that the more dense the negative, the more graininess it exhibits. How you get there - be it an increase in exposure, longer development time, more agitation, higher temperature, whatever, isn't all that important (they are more similar in effect than dissimilar). The bottom line is that thin negatives have less graininess. So you want no more density than you have to have to get good handling properties, whether you print in the darkroom or scan.

[rick_jones5]

As negative densities increase grain becomes more obvious whether from increased exposure or development. So as you fine tune exposure and development you are trying to expose just enough to get good shadow detail (expose for the shadows) and control highlight densities with an appropriate development time (develop for the highlights). As the highlights become denser the result is increased contrast because as development times increase the shadow areas pick up very little density while the highlights increase in density very rapidly and can become too dense if time and temperature are not carefully controlled. But talking about what you can expect can never replace what you can learn from controlled exposure/development tests you perform. Densitometers and plotter programs can provide this information but so can 3 or 4 rolls of film exposed to the same scene varying the base exposure and development times.

[roger_hicks1]

More development (whether achieved by stronger dev, longer time, higher temperature or more agitation) means:

 

More contrast/

Bigger grain/

Less sharpness/

 

Less development therefore means:

 

Less contrast/

Smaller grain/

More sharpness/

 

More exposure means:

 

More density/

Bigger grain (except with chromogenics)/

Less sharpness/

 

Less exposure therefore means:

 

Less density/

Smaller grain (except with chromogenics)/

More sharpness/

 

ALL exposures and dev times are therefore a compromise. Which compromise is best for you is a personal choice.

 

My own compromise leans towards slightly generous exposure (I find I get better tonality this way, but tonality is hard to quantify -- I give 1/3 to 2/3 stop extra) and, as compared with the manufacturers' recommendations, about 10 per cent extra deverlopment so my negs print on grade 2 to 3 using Meograde heads on Magnifax 4 enlargers.

 

Note also that true ISO (ISO contrast and speed point) varies widely according to the developer. Ilford HP5 ranges from 250 or less in fine-grain developers to 650 or better in speed-increasing developers such as Microphen and DDX. A lot depends on metering technique, too. Spot meter the shadows (the only way to guarantee adequate shadow exposure -- I use the IRE 1 index) and you can use the full ISO; use an incident meter on a sunny day and you might need an extra stop or more.

 

You might want to take a look at The Photo School at www.rogerandfrances.com.

 

Cheers

 

Roger