It is a useful method for exposing contact sheets. Make a test strip and pick the exposure that just starts to make the edge of the film blend into the black of the space around the negative. Then use this exposure for all your test strips. If you change papers, say from Foma to Ilford, you would find a new 'min time/max black' exposure.
It has much less utility when making enlargements or final contact prints from large format negatives.
First time I did this back in 1975 I wanted really dense blacks in my prints. So I choose a black strip that was very dense. This was a big mistake. It had the same effect as underexposing every negative and over developing; which of course looked horrible (push processing effect).
So, as indicated, don't go too extreme choosing the black strip. In fact there was a good paper out there analyzing many excellent prints and many did not have a maximum black or white density in the image.
First time I did this back in 1975 I wanted really dense blacks in my prints. So I choose a black strip that was very dense. This was a big mistake. It had the same effect as underexposing every negative and over developing; which of course looked horrible (push processing effect).
So, as indicated, don't go too extreme choosing the black strip. In fact there was a good paper out there analyzing many excellent prints and many did not have a maximum black or white density in the image.
Also, it's a good idea to do your black evaluation from a dry print. And, as ic-racer said above, what you're looking for is a convincing black not a "black hole."
Maximum black (D Max) is determined by contrast, Highlights (D_MIN) is determined by print exposure time. Contrast range of a negative is determined by a combination of subject brightness range (SBR) plus development. To obtain the final print YOU want is accomplished by combination of all factors and visualizing the finished product before you click the shutter.
Get a copy of Richard Henry's book "Controls in B&W Photography". You have to run your own tests -- and you have to determine how to develop the paper BEFORE you determine how to best expose it!!!
In alt printing the minimum exposure for black is enough exposure through film's base to match the black of the print where it has been exposed without the negative blocking any light from hitting the paper. This is seen in the rebate -- unexposed portion of negative, such as around (through) sprocket holes or the edge of LF negatives), or the un-printed area of an inkjet negative.
Examining a simple test strip tells one this. Basically, if one does not get as black a black thru the rebate as one does without the rebate, the print will have none of deepest black possible with the material. Then one decides where to go from there.
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