development of films

I have a couple of questions. First, I am new to medium format, and have only developed one roll which was quite contrasty (it was a very very bright day). I am using D-76, 1:1. I have two different types of films, Neopan 400 which I shot at 400, and Agfapan apx 100 where I shot a few at 100 asa and the others I shot at 50 asa. When developing 35mm I was told to decrease the development time by 15-20% for every stop change (from 100asadown to 50 asa). Now I am ready to move onto the medium format films I am unsure what to do. Also, I was reading In The film developing cookbook by Anchell & Troop that when you are developing 120/220 roll film that you should increase the develoment time by 20-30%. Sooooo, do I increase my time by 20-30% if I haven't changed the asa? and then if I have changed the asa (i.e. from 100 to 50) what do I do?

generally speaking, shooting the film at a slower asa will give you more shadow detail but minimal effect in development. Altering the development alters the contrast, and by the sounds of it, your 1st roll was contrasty enough although you recognised the light would have been contrasty. If other rolls are also in contrasty light, I'd be inclined to decease developemt a bit (10-15%) and see if that is better, then fine tune some more if required (of course you could hold off developing these rolls and do some tests 1st) I've never heard of increasing development for MF films, but if it's in that book, they would have some basis for it (Steve's on this forum, so email him for an answer from the horses mouth!).

You should get some nore knowledgable replies

Shelly, I dont know but I seriously doubt Steve recommends adding 20 to 30% development time just because you switched to 120 film from 35 mm. I see no reason to do this nor have I heard anybody recommend this before. Perhaps you misunderstood?

But anyway, since you shot some at asa 100 and some at asa 50, I would recommend to develop as if all the roll was shot at 100, is better to have some overdeveloped negs than underdeveloped.

The 15 to 20% rule of thumb is ok, but given the vagaries of film developing and all the other factors that affect expsoure perhaps 50 asa is the correct EI for you, if so then your negatives shot at 100 would be underexposed and underdeveloped. Not a good thing! You can always give your negatives more printing time, but you cannot get info that is not in the neg.

So to answer your question, I see no reason to give 20 to 30% more development time just because you moved up to 120. If you are developing with single reel tanks and you fill it so that it covers the reel, the developer there should have enough strength to develop your film in the same time as 35 mm. For the case of the apx film I would say develop it just like all was shot at 100 asa and see what are the results before you go making changes in your usual development routine.

The reason exposure and development adjustments are sometimes advocated when switching between the same emulsion in 35mm and medium format is because of minor differences in film base thickness.

(Medium format film bases are sometimes thinner than their 35mm counterparts. Kodak specifies this on their website; dunno if Ilford and others do. This is not a reference to emulsion thickness, an entirely separate matter, one which film manufacturers don't seem to specifically address.)

Only experimentation and experience will determine whether any adjustments are necessary for you and, if so, how much.

You can check the Massive Development Chart website as a reference, and go from there depending on what you want to do. Everyone has their own favorite film/chemicals/times, but this gives you a starting point. Any search engine will find it.

Steve

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This is applicable to you based on your experience Les. The other side of the coin I develop 400 tmy with exactly the same times for 8x10 and 120, even though I beleive the emulsions are different, the results seem to be the same.

You know the factors influencing developement are too numerous to make blanket statements like this and IMO they just as likely to produce overdeveloped negatives as not.

I guess like most anecdotal experience, it seems to work for some and not for others.

35mm is often developed minimally to control grain. In larger sizes, you can get better separation by developing more than you might 35mm.

I don't see how the base thickness of itself would make a difference to dev time, but the emulsion might well be slightly different in different film sizes

I've never given 120 longer than 35mm, but generally do give maybe 20% more when doing 5x4 (in a tank). Emulsions may vary from format to format but this is only one of many variables.