Please explain push processing to me...

Trying to figure out what push processing is and what advantage is it

to me?

 

Do I take some ISO 100 film, shoot it as it were ISO 400 (exposure,

etc) and then "push" it up to 400 when I develop it?

 

In other words, over expose the film and compensate when developing?

 

Or, do you purposely under expose the film and then push it up to a

400?

 

And what's the benefit over just buying some ISO 400 film? Grain?

Tone?

When you shoot ISO 100 film at 400, you are underexposing the film by two stops. To compensate, you increase the development time or "push" the film by two stops. The development time for a two-stop push is something you or someone else determines by experimentation and testing.

 

When you push you increase contrast and grain. Sometimes you might want to do that, say if the lighting is flat, and you've decided that good contrast is more important to the image than fine grain.

 

The advantage of using a faster film when you need it is that you usually will get normal contrast and finer grain than you will by pushing a slow film.

David is right on. Rating a 100 film at 400 is UNDERexposing by 2 stops. In addition to over-processing by increasine the time, there are developers specifically designed for pushing, such as Acufine. This does not apply to color work. It is nearly always better to use a faster film, and much depends on the desired effect. Pushing (and pulling) is often used in emergencies, or when mistakes are made.

You underexpose the film, then overdevelop it. This is in an attempt to make negs that print on "normal" paper; the pushed film doesn't really gain any speed, it's just developed for higher contrast. It'll also be grainier and less sharp.

Push processing is the biggest myth in photography, and the subject that is most misunderstood by beginning (and sometimes experienced) photographers. If you want photographs with a normal range of tones, then you should use the appropriate film near its rated speed (per film speed tests conducted on Zone I density). Don't even think about pushing film just to compensate for low light conditions unless you are already using the fastest film available (TMAX or Delta 3200, both of which are bit speed overrated by the manufacturers).

 

This is not to be confused with increasing the film speed as a result of N+ (normal plus) processing, a procedure that is used to increase negative contrast. In N+ processing the film speed may increase (and negative development time increased beyond the normal time), but it is not to compensate for low levels of light, but to compensate for low contrast lighting conditions or whenever you want to increase the contrast of the scene as part of your artistic vision.

Push processing is normally thought of as: "Increasing development time or temperature to compensate for under exposure"

Unfortunately sensitivity increase does NOT in fact occur.

 

Push processing will increase the density of the exposed negative in the following fashion:

 

Where the negative was exposed to a lot of light (Capturing the high lights) the negative will turn a lot darker than it normally would.

Where the negative was exposed to medium light (Say grey) the negative will turn a bit darker than it normally would.

Where the negative was exposed to low light, (Capturing the shadow area) the negative will hardly increase its density.

 

You could argue that the film seems more sensitive in the grey and highlight areas, but this is NOT USUALLY the reason for push processing. In MOST cases push processing is done because the film was shot as a more sensitive film, in this example the camera measured (18%) grey 2 stops too bright thus exposing anything under grey in the "under exposed range" of the film.

 

So the end result is that areas in photo which were grey and LIGHTER will be lighter still, and areas in the photo which were darker will REMAIN DARK.

 

THUS: Push processing has as a result to INCREASE CONTRAST, not sensitivity of the film.

 

If you want to improve your grain, try a longer exposure time and a tripod, or a 2 part developer.

It's not just a matter of overdeveloping to compensate for underexposure.

 

B&W films are very sensitive to chemistry. Film "speed" - whether we're talking strict ISO definition or our personal preference (EI or exposure index) - is greatly affected by choice of developer and how we use it.

 

For example, Ilford HP5+ exposed as an 800 film and processed in Rodinal 1:25 delivers better tonality and finer grain than HP5+ at 400 processed in Ilfosol S 1:14. And the same film in Ilford ID-11 or Kodak D-76 (pretty much the same chemistry) will deliver even different results.

 

So, is HP5+ exposed at 800 and processed in Rodinal 1:25 really "pushed"? Or is it simply the *correct* processing for the lighting conditions and subject matter at hand? In my case - photographing people outdoors under open shade - I don't consider it push processing. I consider it the correct exposure and processing for my tastes since it delivers the gradation of skin tones I happen to like.

 

As the EPA and we cyber-wafflers like to say, YMMV.

Yes, the developer may affect film speed. That's why a Zone I density test should be conducted. Here are some selected examples from "The Film Developing Cookbook," Anchell and Troop, Focal Press 1998, page 5: "Speed decreasing": Microdol-X, "Speed maintaining": D-76, "Speed increasing": XTOL.

 

If you are photographing in open shade, the inherent contrast range of the scene may be low (as metered by the difference between the darkest area and brightest area). Therefore N+ processing may be desired which includes a bit more development and higher film speed to increase the contrast. Normal processing (N) is usually defined as a scene with some sun lit areas and some shade, and where some shadow detail is required.

 

The actual processing and film speed can vary by each photographer because there are many factors that affect the final print contrast other than scene contrast and negative development time. These include enlarger light source, film agitation techniques, brand of photo paper, brand of VC filters, paper developer, toning technique, etc.

Oh, pooey, Mark. All that Zoniespeek just confuses things. If Jim is just now trying to grasp that "push processing" involves *under*exposure and compensation in development, the last thing he needs to worry about now is N+bullshit. Save it for sheet film users.

 

Jim, all you need concern yourself with at this point - especially if you're shooting 35mm or rollfilm - is getting acceptable, printable negatives. Later, hopefully much later, when you become self important, you can fret over all 11 Zones.

hehe, I like Lex's answer.

 

Thanks for the help guys!

The Zone system is not just for sheet film users. Many 35mm and MF photographers shoot the whole roll in the same lighting conditions. N+ simply means extra development and more contrast. It's not that complicated. The point is that there is a difference between needing more light (in which case you are better off switching to a faster film) and needing more contrast (in which case just increase the film speed and increase the development).

I agree with Mark. That's why I have 3 backs for my 6x6 SLR and 4 Spotmatic bodies. Each roll is exposed as N , N+1, or N-1 as needed.

 

(4th body is for color).

 

You can not push film. Period. Each film & developer has one and only "speed" rating. A Zone 1 test will show you what that speed is. And it is valid only for your camera, lens, light meter, thermometer, water supply, ect.

 

If you really need more speed than say Delta 3200 (which is really an 800 speed range film) provides, buy faster lenses.

 

I chased that rainbow for years until I did my own OBJECTIVE tests and realized that by "pushing film" all I really got were crappy negatives that are a pain to print.

Whatever works for you, Anthony, but I can't imagine a better way to kill the spontaneity afforded by the 35mm format than having to lug several bodies around just for the purpose of worshipping at the Zone Shrine.

 

Of course, I'm really no better. I usually lug at least two bodies with motor drives. But the important difference is I'm "spontaneous". ;) (I hope you realize I'm pulling your leg here.)

 

Also, in my experiments with the Zone System in school I found I could get pretty much the same results by bracketing and processing appropriately to conditions later. Horrors! Bracketing with b&w film? Yeh, but if it works and no one can see the difference on paper, what's the diff?

I think that Lex should apologize for calling my comments bullshit in this thread. It's not bullshit, it is accepted by many well known and knowledgeable photographers.

 

Lex deleted my comments when I said used the term "BS" in another thread, which I don't know of anyone that finds the abbreviation offensive.

 

Is there some kind of double standard here?

1. 'Pushing' comprises two parts:

 

A. Deliberate underexposure

B. Deliberate lengthening of development as a compensation for 'A'.

 

'B' actually does not compensate for 'A' in the way most people believe. 'B' actually merely increases the contrast of the negative. In low-contrast scenes, an _apparent_ speed increase is obtained. In high-contrast secenes, shadow detail is simply lost, and no _apparent_ speed increase is obtained.

 

2. Ansel Adamds does not recommend extending development for 35mm film to get N+ scale. See page 92 of 'The Negative'.

 

"When working with individual exposures we may develop our film in relation to the exposures. When working with roll film we should plan our exposures in relation to Normal [and Normal-l] development." [Later edition]

 

In all cases, extending development increases grain and fog.

Gimme a break, Mark. You're just now getting around to taking offense at a comment I made more than one year ago? You must have easily raised hackles and a lotta time on your hands.

 

Anyway, read my comment carefully and in context. It speaks for itself. You have no cause to take offense.

 

Regarding the double standard you perceive, that's your opinion. As I explained via e-mail, it is a moderator's unfortunate duty to occasionally exercise personal judgement in what to edit/delete/censor, whatever term you prefer. I believe my judgement is fairly liberal and appropriate for the B&W Forums. I'm surprised you find it necessary, for a second time, to take up this issue publicly on the forum rather than discussing the issue with me via e-mail. Frankly, I'm not interested in discussing it further at this point. Take up the issue with photo.net administration if you're dissatisfied. Or cuss up a storm if you believe that superfluous obscenities will add credibility or spice to your contributions.

Hans, my results don't show that push processing, in all cases, results in fog. Perhaps differences in film, developers and other variables matter significantly.

 

No matter how often this subject arises, we never seem to bridge the gulf between those of us who rely on push processing as an occasionally useful tool and those of us who find the practice abhorrent regardless of justifications or circumstances.

Lex, my only concern is that you apply your editing on a consistent basis. There was no need for you to edit my "BS" comment in another thread, and then try to defend it, especially when others (including yourself) use the phrase completely spelled out. I never try to spice up my responses, they are almost always very technical and very boring.

Lex:

 

Fog and grain increse linearly with development time. Whether the increase is objectionable is of course another matter.

It amazes me that a principle as simple as "areas of the

negative which have received more exposure will develop more

quickly than areas which have received less exposure" could

develop into such complex systems of adversarial beliefs and

fanatical attitudes. Thank goodness I figured out the basics

before photo.net ever came into existence--it's frightening the

amount of dogma I've been able to recklessly (and sometimes

maliciously) violate and still end up with easily-printable

negatives.

The phrase "will develop more quickly" seems somewhat ambiguous to me, and I suspect to many others. In fact, it is not just a matter of the speed of the development, but the maximum increase in density that can <b>ever</b> be achieved.</p>

 

Those parts of the negative exposed for shadow detail do not increase as much in density because of increased development as do areas exposed for highlight detail. That is, the maximum <b>increase</b> in density that can achieved for highlight exposure is <b>always</b> more than the increase that can be achieved shadow exposure. This is why increased development causes more contrast (a bigger <b>difference</b> between shadow density and highlight density).

Jacobsen on the topic of the last few posts

Again, Jacobsen.