# Thread: Plus and Minus Development Percentages

1. ## Plus and Minus Development Percentages

Stimulated by a couple of recent threads on APUG (I'm posting here as well, as I know some don't venture there) and some testing I've been doing, I'm just wondering what people are finding *in general* for N+1 N+2 N-1 and N-2 development, given as percentages of Normal. Do you find it depends highly on the developer, or do the percentages stay pretty much the same?

Tim

2. ## Re: Plus and Minus Development Percentages

Speaking in general terms, I find the following to be a good system:

N+1=N*1.4
N+2=(N+1)*1.4

N-1=N*.7
N-2-N*.6

YMMV

Best,
Randy

3. ## Re: Plus and Minus Development Percentages

How about general guidelines for exposure as well? I know I saw a helpful web page that summarized all of this neatly in a table, but now I can't find it anymore. Thanks.

4. ## Re: Plus and Minus Development Percentages

Test. Really. If you use 1.4X normal for TMAX 100 to get a +1 you are in big trouble. 0.15 is more like it, but you should test.

5. ## Re: Plus and Minus Development Percentages

Originally Posted by Kevin Crisp
Test. Really. If you use 1.4X normal for TMAX 100 to get a +1 you are in big trouble. 0.15 is more like it, but you should test.
So you find that the percentages vary quite a bit from film to film? This is all assuming temp/aggitation, etc remains constant.

Like I said in my post, I do test. I'm just curious to see if the percentages stay relatively constant from person to person, developer to developer, and as you suggest, film to film. I've read a couple "general rules"- I'd like to know how accurate they are to the "general photographer".

Thanks,
Tim

6. ## Re: Plus and Minus Development Percentages

Yes, it will vary from film to film. Tri-X is a great film to minus in my experience but will only go to plus 1 or so. FP4+ is a better film for plussing but I did not like the way it minussed.

As a place to start +10-15&#37; for +1, +20-25% for +2, -10-15% for -1, -15-20% for -2

For -2 I would add 3/4 to one stop of exposure, for +2 you could try cutting 1/2 stop from your exposure

again. different films will need to be treated differently.

steve simmons

7. ## Re: Plus and Minus Development Percentages

It does vary with film and developer. For example with Tri-x in HC110, I'd go more like 125% to get to a plus one. That would be too much for Tmax 100, where adding just a minute makes a big difference. I'm processing in trays.

8. ## Re: Plus and Minus Development Percentages

Originally Posted by steve simmons
Yes, it will vary from film to film. Tri-X is a great film to minus in my experience but will only go to plus 1 or so.
it also varies from developer to developer. i've shot TriX at EI 25,600 for example, with surprisingly nice results.

9. ## Re: Plus and Minus Development Percentages

Originally Posted by steve simmons
Yes, it will vary from film to film. Tri-X is a great film to minus in my experience but will only go to plus 1 or so. FP4+ is a better film for plussing but I did not like the way it minussed.

As a place to start +10-15% for +1, +20-25% for +2, -10-15% for -1, -15-20% for -2

For -2 I would add 3/4 to one stop of exposure, for +2 you could try cutting 1/2 stop from your exposure

again. different films will need to be treated differently.

steve simmons
Thanks Steve-

So would this be the general rule for a traditional grained film like FP4+, HP5+? Someone else has mentioned (on APUG) T-grained films are different (I know Delta and Tmax are T-grained, but not sure about Tri-X).

I'm also curious how one would judge "development to completion". This is mentioned by Schaeffer in the AA guide book 2. Is it also quite different from film to film and developer to developer? Would 2x normal length generally be sufficient? At what point is base fog going to become such a problem that contrast starts to decline, or can this even happen? I ask because I had some FP4+ negs of a very low contrast subject (rock face) where I wanted to really separate highs and lows. I gave (IIRC) about 30-50% more dev time (HC-110 dil H) and I still had poor contrast in the contact print. Schaeffer mentions AA used to develop some of his negs to completion to do what I was attempting. Did I fail in development or in the printing?

Tim

10. ## Re: Plus and Minus Development Percentages

It wasn't a failure. You just found out what your materials would give you. Films were different in Adams' day. Tri-X is a "traditional" film; the T-Max and Delta films respond to process changes more quickly, so require less dev time changes to achieve the same changes in contrast, compared to "traditional" films like Tri-X or FP4+. Test using Mr. Simmons' guidelines (on a full-scale subject), print, and go from there.

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