This may be a basic question, but I'm having difficulty understanding why you would use N+1 or N-1 processing instead of changing the contrast of the paper. I understand you can use different processing to fit the total exposure range on the negative, but are there other benefits?

-- Eric Burgess (eburg59172@aol.com), February 26, 2001

Answers

I'm sure someone will give you a more complete answer but the quick version is that buy exposing and developing correctly and taking into account the contrast in the scene you photographed vs. how much contrast you want on the finished print, you end up with far more printable information on your negative.

Changing paper grades only gets you so far. If you have thin shadows or blocked highlights, no amount of darkroom trickery is going to change that.

-- David Parmet (david@parmet.net), February 26, 2001.

Eric,

As far as I understood, you assume in your example that your negative is capable of keeping all the brightness range of a given scene perfectly, does not matter will it be developed normally, N-1 or N+1 (a pretty possible situation). If this my guess is correct, then your question rather should be: why people control the contrast via different film development mode, not via using different paper grades? And is there a difference at all between this two means?

My answer is: if the characteristic curves of film and paper were dead straight, there is no difference. But they are not straight: look at technical data sheets from films and paper manufacturers. The straighter is the combined curve (the whole system=film+paper), the closer is the image to the original scene (lets also assume we need a 'literal realty representation', no 'artistic deviations'). The papers grades #4 and #5 have the straightest curves, but 1) they emphasize the grain and scratches 2) to achieve the necessary low contrast in the negative you have to greatly pull the film. Thus the grades #3 and #2 seem to be the best candidates for the title of "normal" paper grade, and the negative contrast is to be matched with that contrast.

If I misunderstood your question, could you please be a bit more specific?

Best wishes. Andrey

-- Andrey Vorobyov (AndreyVorobyov@mail.ru), February 27, 2001.

Eric,

The simple answer is that modifying development is used to match your negative to the contrast range of the subject, not to your paper. The idea is to preserve as much information on the negative as possible. Therefore, minus development is used to stop the highlights from blocking (becoming so dark that they cannot be differentiated on the film) so that you can control them in your print. After minus development, you may still want/need to print your negative on soft, or hard, paper in order to create the image you want.

-- Ed Farmer (photography2k@hotmail.com), February 27, 2001.

Good question! In my experience, changing paper grades tends to have a more pronounced effect on 'local contrast' than does altering development times. (I haven't a clue as to why.)

For example, if you have a high contrast image on film and have to use, say, a grade 1 or grade 0 paper, the mid tones on the print will tend to become muddy and quite unsatisfactory due to the lowering of local contrast. On the other hand, reducing development time to, say, N-, will permit the use of a normal (grade 2-2 1/2) paper grade and far better mid-tones. On the other hand, I find that, for low contrast film images, increasing paper grades to,say, 3 or 4 tends increase local contrast and that, for many subjects, the increased local contrast produces a 'punchier' image which may prove to be quite satisfactory. (Of course, you might not want to do this for a portrait of a lady friend where the increased local contrast of facial skin tones may not be exactly pleasing to your subject. )

Hope this helps.

-- Bill Osterman (boster33@aol.com), March 12, 2001.

Thanks for your help. I need to do a little experimenting, but I understand the basic differences.

-- Eric Burgess (eburg59172@aol.com), March 13, 2001.