I have finally made the plunge into medium format. Over the last 2 years or so, I have noticed some references in this forum in developing MF films. That is, assuming all things are equal (eg. film, exposure, developer, etc) I recall that there was some suggestion that if a given 35mm film is exposed and developed a certain way, it does not necessarily follow that the same parameters apply when developing the equivilant 120 film; I recall some suggestion that the development time for the MF film needs to be adjusted somewhat.

Is this so? If yes, is there a starting point at which one can begin the testing process (eg. If I have certain combination in 35mm that works well for me, do you vary any factor in the MF process, eg. increase the MF development by say 10%?). And importantly, if there is such an adjustment required, can someone explin the basis of this necessity please.

Many thanks in advance!

-- Frank (fa@alvaroedwards.com.au), November 25, 2001

Answers

As far as I know, there are at least two reasons. One is that despite the same name, a manufacturer might put a slightly different emulsion on the 120 for technical or manufacuring reasons, so the resulting development time might be different.

A second reason is that to minimise grain, 35mm is generally slightly under developed. Because enlarging ratios are smaller, MF doesn't need that so much, and can be developed to a slightly higher contrast. This presumably has some benefit in tonality. Sheet film negatives tend to be developed to a higher contrast again.

You could start with the same dev time as 35mm. Or maybe a tad more. There is a huge table of dev times on

http://www.digitaltruth.com/

but they come fom different sources, so might not be directly comparable.

Someone with more experience in MF than I will probably elaborate on the above.

Regards.........john stockdale

-- john stockdale (jo.sto@bigpond.com), November 25, 2001.

Some films do have slightly a different emulsion and/or film base between formats. You can tell whether this affects the development by checking the data sheets on the manufacturer web site for their recommended development times to see if they differ between formats. Even if your developer is not listed, you can usually tell whether the emulsion and film base are the same or differ in some manner.

Whether or not you need to develop to different contrast levels due to different format sizes (or even enlarger light sources) is obviously a separate question.

-- Michael Feldman (mfeldman@qwest.net), November 25, 2001.