Do you expose the film accurately or overexpose?

[hasan_ali]

When you use B&W film, are you as obsessive with exposure as with a slide film. or do you expose a bit extra over the meter reading? I have read in Photo Technic that it may be Ok to overexpose even by a couple of stops!!

I would appreciate any helpful suggestions.

Hasan

[jeff_white1]

Exposing any negative film is different than exposing a positive

film. Positive films subtract density with exposure, so too much

exposure or not enough exposure will leave you with an unacceptable

image. Negative films build density with increased exposure, so the

important thing here is to make sure the needed detail makes it to

the film. "Accurate exposure" is an industry developed standard for

comparing films and getting a generally good result. If more exposure

gives you a better negative or finished image, is it really

overexposing?

[andy_laycock1]

I usually hear this sort of comment from slide shooters; that for print film your exposure can be off by X number of stops because you can make up for it during printing. I have always found this advice to be flawed since it encourages sloppy exposure. It is true that you can compensate somewhat to give 'acceptable' results but an accurately exposed negative will produce an exceptional print. There is no replacement for proper exposure no matter what the medium.

[alan_gibson6]

This topic keeps coming up, in various forums. I agree with Andy: the

correct exposure is the best exposure.

 

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For merely "ok" results, people talk about B&W negative latitude. If

you meter a grey card, you will get good detail in shadows about 2

stops below that reading, and highlights about 6 stops above.

(Speaking very loosely, the film has more latitude to overexposure

than underexposure.) The exact numbers depend on the film and

development. On that basis, if your subject has a contrast range of 8

stops, AND you meter shadows and highlights, AND you calculate the

mid-point, AND you set your camera to that reading, you will capture

all the tones. Depending on your meter, you *might* get the same

result by setting the meter 1 or 2 stops slower than your film's ISO,

and taking an average reading.

[jeff_white1]

It seems the question is "What is correct exposure?" Now if you

follow Alan's analogy that your film will show detail for 2 stops

below your exposure setting and maybe 6 stops above your exposure

setting but to get a good exposure read the highlight and shadow and

expose for the mid-point. Lets put some numbers in and see what

happens: 100 ISO film, gray card reads EV 15, 2 stops below is EV 13

and 6 stops above is EV 21, that would give an exposure of 1/125 at

F/16. If we find the mid-point that would be EV 17 with an exposure

of 1/125 at F/32. If only 2 stops of exposure are held on the film

below our exposure setting that would equate to EV 15 and everything

that lived in the EV 13 & 14 range would be lost on the negative and

never make it to the print. In a less contrasty photo this approach

would work, in this situation it didn't. I think to sum up what most

of the "Masters" have felt since the beginning of photography, those

using the zone system and those using other exposure methods is DON'T

underexpose and DON'T overdevelop.

[alan_gibson6]

Jeff, thanks for pointing out that error. I was trying to give an

example when people might legitimately "overexpose", but my brain was

going faster than my fingers, and I left out some important words.

That paragraph should have read:

 

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On that basis, if your subject has a contrast range of 8 stops, AND

you set your meter to 2 stops slower than your film's ISO, AND you

meter shadows and highlights, AND you calculate the mid-point, AND

you set your camera to that reading, you will capture all the tones.

Depending on your meter, you *might* get the same result by setting

the meter 1 or 2 stops slower than your film's ISO, and taking an

average reading.

 

<p>

 

Jeff also says: "DON'T underexpose and DON'T overdevelop." I only

partly agree with this. I do believe that developing for more than

normal is OK, when the intention is to increase contrast. In these

circumstances, the film might neeed a slighty increased EI to

compensate, at the shadow end of the characteristic curve. Adams

calls this "N+1", or whatever. But overdeveloping in order to

underexpose is only OK if we remember that we will also increase

contrast.

[jeff_white1]

I agree with what Andy and Alan are saying that you should make the

best exposure that you can. The point that I am trying to make is

that exposure and development are relative. In a low contrast

situation I would develop more than normal and probably expose less

than normal if using sheet film or it is correct for the whole roll.

For a high contrast subject I would expose more than normal and

develop less than normal. When I suggest overexposing as a normal

course of action, I am talking 1/3, 1/2 or maybe even 1 stop. Many

people in my experience would be doing well if the could expose that

accurately. The idea of "don't under expose and don't over develop"

was written recently by David Vestal about discussions that occurred

between Ansel Adams and Ralph Steiner also in an article by Howard

Bond talking about the truths he has learned in B&W up til now. The

idea is that if yout negative is too thin from under exposure or too

thick from over development it will be difficult to get a good print,

not impossible but difficult. An exposure that makes the best

negative to make the best print should be all our goals. That

information may not come on the side of a box or data sheet though.

[alan_gibson6]

I agree with Jeff, and here's an anecdote about "DON'T underexpose

and DON'T overdevelop". My apologies if it is drifting somewhat from

the topic.

 

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When I was even younger than I am now, I used to believe that I could

increase the effective speed of my film by stewing it for a long time

in developer. What I didn't fully appreciate was that the major

effect was to increase contrast. This raised the density of mid-tones

appreciably, and I used to judge "correct" exposure as that which

reproduced a grey card as grey on the negative. For some styles of

photograhy, this is not a terribly bad definition of EI (Effective

Index), although it is not the standard definition. However, I now

normally judge "correct" exposure (and development) to be that which

gives me good detail in whatever shadows I am interested.

 

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Incidentally, the (dubious) definition of correct EI being defined as

reproducing a grey card as mid-grey on the negative seems to be

adopted by some manufacturers. Watch out for phrases like "you can

expose at EI 3200 if you don't care what happens to the shadows".

[john_sibold]

I have been a proffesional photographer for 18 years. I shoot tons

of B&W film and still do all my own processing by hand. i have found

that your exposure depends a little on how you process. My personal

findings are: tri x 120 or tri x 35mm should be shot at about 320

ISO and tmax100 120 or 35mm should be shot at an ISO of 80. These

both open up the shadows a little and still gives wonderful blacks.

 

<p>

 

I am a B&W lover and I think you should try a few combinations of

exposures and processing procedures until you find a gray scale and

density you like.....

[_ted__johnson]

The 'true' answer is, as in all things photographic, find a system, by experimentation, that suits your style of photography and, gives you the results you want. The only 'rule' in photography is...there are no rules!

[shreepad_joglekar]

Above----Very true I think There in NO correct exposure also, one

just cannot mathch any scene to real sight of human eye, b'cos the

eye can dynamically adjust to a large spectrum of intensities. the

Correct expoure as you call it I think, should be decided so as to

suit the Mood of the situation you want to portray.

Ansel adams zone system helps a lot for visualizing the final mood

of the print

 

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thanks

shreepad