Confused about "Pushing"

[jernejk]

With the recent bad experience "pushing" Tmax 400 to 1600 and getting a negative that's hard to print, I went back to books, trying to understand N+- development and negative contrast.

I think I understand the N+-, but I don't understand how pushing fits in. What I understand happened with my "push" development (guestimates):
- the shadows got a bit more density, maybe zone II is "pushed" to zone II and a half, but probably not more
- the mid tones got pushed from zone IV to say V and zone V to VI
- highlights however, got crazy, zone VI is mapped to VII and VII to IX...
- since I pushed in HC110 with its upswept curve, highlighs maybe got even wilder

Now of course I have a problem, as the skin is in mid tones, but the white background (white towel) is very very dense.
If I expose the print for the highlights, the skin is way too dark. If I expose for the skin, the highlights are virtually non-existant.

So my question is, does "push processing" actually makes sense or even exists at all? Obviously there's no way to change film's inherent ISO. Also no amount of pushing will bring out the underexposed shadows - if something does not exists on the latent image, you can't develop it. All pushing does is create better shadow separation at a huge expense of blown highlights.

Now especially with high contrast scenes, say night photography, pushing makes no sense at all. If anything, with night photos one should "pull" to decrease the negative contrast (street lights usually create high contrast scene). For very very low contrast scenes with virtually no highlights, pushing might actually work.

But with a normal contrast scene, would it be better to underexpose and hope for the best, knowingly sacrifice shadow detail?

 

[Doremus Scudder]

Simple answer:

N+1 (and +2, +3) and N-1 (-1, -3...) are Zone System designations and represent development changes designed to change the contrast of the image on the negative so that it prints well on a normal contrast grade paper. IMPORTANT: the exposure is usually based on keeping shadow detail and is adequate, i.e., the film is exposed properly, so that when developed there is shadow detail.

Pushing is used in low light situations when the film has to be underexposed and shadow detail sacrificed. In pushing two stops, one underexposes the film two stops and sacrifices two stops of shadow detail. The mid-tones of the scene then end up where the shadows would normally have been. The high values are also two stops underexposed and the overall contrast of the negative would be low if developed normally. In order to stretch out the contrast of the negative so that a print made from it will have both dark shadows and black areas (not light grey) and highlights and whiter areas (not light grey), we give the negative more development. This increases the contrast but does not help the underexposure. Detail in the low values is inevitably lost. Photographers that push film either like the look of no shadow detail or are forced to make the best of a low-light situation when hand-holding, etc.

A push-development time may well end up being the same as an N+1 or N+2 time. The difference is the exposure the film got in the first place. In the push-scenario, the film is intentionally underexposed. With the Zone System, exposure is based on shadow detail and is "correctly" exposed.

Hope this helps,

Doremus


www.DoremusScudder.com

 

[markbarendt]

First thing to understand is that a given film and developer's real speed does not change much with changes in development time.

So in your example you are basically giving away 2 stops of shadow detail that simply never reaches a usable threshold. (If you are already using say Tmax or D-76 developer you aren't going to get much more speed with a switch either. If you are using a slow Pyro switching may get you a fair bump.)

If that detail is important to your shot then there are really only two fixes available, 1-more exposure (shoot at 800 or 400) or 2-use a more sensitive film (like Delta 3200).

Development controls contrast, if detail in the highlights isn't usable/printable then reducing development is the fix. IIRC Kodak suggests normal development for film shot at 800.

There is no magic bullet here.

 

[Gerald C Koch]

Three things to remember.

Some films push better than others.
Never push a film unless you absolutely have to.
It is better to use a faster film than to push a slower one.

 

[gone]

You can't get something for nothing, so if you accentuate one level, you're gonna have to give something up on the other end. And, you picked the wrong film for that sort of thing. Shoot some Tri-X at 1600 (or 800, 1200, whatever) and soup it in Diafine. You can even shoot different frames on the same roll at different ISOs.

 

[jp498]

I've had good results with tmax400 and pyro compensating developer for a concert. I used pyrocat hd and when developed with one agitation per minute, it was slightly compensating, thus sparing the scene's highlights from being blown out. Basically, expose for the skin tones or shadows and not worry about the highlights.

 

[ic-racer]

The increased development that is sometimes recommended for underexposed negatives increases the contrast so that you can print the blacks as black. Otherwise the blacks will print as gray. The resulting prints still look like garbage to me so I try to avoid under-exposure at all costs. It is funny (or sad) to read about people that under-expose on purpose.

 

[Gerald C Koch]

Since this is important let me summarize a previous post. It's important not to confuse pushing and pulling with techniques to compress or expand the tonal range of a subject. Pulling and pushing are done to change the films effective speed. Whereas tonal changes (Zone System) are done to fit a subject's contrast range to a particular paper. This is when the concept of N-1, N, and N+1 is applicable. The techniques appear similar but their intent is entirely different.

 

[Tom1956]

Pushing is spoken of as willy-nilly on this site. Film has a proper speed as gauged by a developer such as D-76 and the like. If you push, then switch to Acufine or similar developers, not the standard developers. And you might want to ignore the people who claim Rodinal is their choice developer for pushing.

 

[jernejk]

Pulling and pushing are done to change the films effective speed.

But.. that's exactly the issue. One can not change film's effective speed, only underexpose and hope to compensate with more contrast by overdeveloping. Or am I wrong here?

 

[Tom1956]

No you can't change the speed. You simply take advantage of its built-in latitude and "compensate" for the contrast increase of pushing with a developer like Acufine or Microphen, or somesuch. So effectively speaking you have actually changed the speed and made a "normal" negative.

 

[jim appleyard]

But.. that's exactly the issue. One can not change film's effective speed, only underexpose and hope to compensate with more contrast by overdeveloping. Or am I wrong here?

I think the key word here is effective. No, you cannot change the ISO of a film, but you can change it's EI. You can stretch the latitude, whatever word you want, to give you a printable image where you normally wouldn't get one.

IMO, TX in diafine is about as good as you can get for pushing.

 

[Bill Burk]

A push-development time may well end up being the same as an N+1 or N+2 time. The difference is the exposure the film got in the first place. In the push-scenario, the film is intentionally underexposed. With the Zone System, exposure is based on shadow detail and is "correctly" exposed.

Hope this helps,

Doremus


www.DoremusScudder.com

Doremus points out a clear difference between N+ and Push. With N+ development, there are no highlights that will blow out because by your measurements they aren't there (you might be shooting on a gray overcast day)... You expose the film properly for the shadows... and develop longer than N to bring the higher value, which might fall on Zone VI, up to VII or VIII but there won't be anything higher.

In a recent thread, Raffay shared a photograph that keeps standing out in my mind as a good example of a push processed negative. He has given the photograph a minimal exposure, and developed the proper amount to make up for it. I'd rather give more exposure and develop less to have a normal negative... But whatever he did here - is worth keeping in his "back pocket" as a valid technique to get the contrasty snap that is characteristic of a push.

(there was a url link here which no longer exists)

So to sum up, N+ is different than Push. Times might be the same. But you are doing it for different reasons and you expect different outcomes. A pushed negative will make a graphic, contrasty print. An N+ negative will make a flat subject appear more normal looking.

 

[Gerald C Koch]

But.. that's exactly the issue. One can not change film's effective speed, only underexpose and hope to compensate with more contrast by overdeveloping. Or am I wrong here?

That is why I said effective speed and not actual speed. One, of course, cannot change the actual speed by pushing or pulling. But one can change the effective speed if one is willing to accept the consequences. It's those pesky modifier words.

 

[markbarendt]

The increased development that is sometimes recommended for underexposed negatives increases the contrast so that you can print the blacks as black. Otherwise the blacks will print as gray. The resulting prints still look like garbage to me so I try to avoid under-exposure at all costs. It is funny (or sad) to read about people that under-expose on purpose.

For the OP

What happens with underexposure is simply a matter of compressed or missing tones. As general exposure is reduced (shooting 1600 instead of 400) all subjects end up lower on the film curve, subjects like faces may end up just a bit above the toe of the curve, then when we try to print that face at a "normal brightness on paper we get grey muddiness below rather than nice clean tones and strong blacks because those tones are printing from an area on the curve that has very little contrast.

One reasonable fix here is to print overall much darker and then dodge while printing to lighten the faces and other important parts. You can get strong blacks and sometimes fairly normal looking faces this way and very nice detail in the highlights; but you won't get any more shadow detail.

No you can't change the speed. You simply take advantage of its built-in latitude and "compensate" for the contrast increase of pushing with a developer like Acufine or Microphen, or somesuch. So effectively speaking you have actually changed the speed and made a "normal" negative.

Again to the OP

The effect of a push IMO is not about getting more shadow detail, the "real" film speed/the film's sensitivity to light, doesn't change. Instead a push is about making the film curve steeper to get the mid-tones up away from the blacks far enough to make them easier to print: so that dodging isn't needed. The big problem there is that the whole film curve gets steep and the highlights get too dense to print easily.

The intent of Acufine, Diafine, stand developing in Rodinal, and other "compensation" techniques is to essentially "push" the low tones, get normal mid tones, and "pull" the high tones.

Does compensation work? Yes, sure, the ideas behind the various methods are fairly sound.

The more important question is, is compensation significant? Only you can judge, but when compared to adding exposure or using a faster film, compensating developers are IMO a really poor alternative.

 

[jernejk]

Doremus points out a clear difference between N+ and Push. With N+ development, there are no highlights that will blow out because by your measurements they aren't there (you might be shooting on a gray overcast day)...

I see the point. Yes, N+ is intended to increase contrast in low contrast scenes.

However, push to some degree is the same: "push" would work in dim, low contrast scenes. It can in fact map skin tones higher on the density curve, say if you shoot a portrait in a dim light. *

If photographer knows that push processing by 2 stops will result in very high contrast negative where anything they measure above zone VII (that's really film's native zone V) will be more or less unprintable, or will require burning to get some details in the highlights, that's OK.

Now, the problem is, many sources regard pushing as a technique which in fact increases the film sensitivity. This simply isn't true and can't work on normal to high contrast scenes, unless a compensating developer is used. I misunderstood what pushing really does, and I believe many other film users do, which is unfortunate. To some degree manufacturers even promote the pushing myth, e.g. HP5+ tech information says that: "Best results are obtained at EI 400/27, but good image quality will also be obtained at meter settings from EI 400/27 to EI 3200/36."

Kodak seems to be more clear here: "Push processing allows film to be exposed at higher speeds, however, push processing will not produce optimum quality. There will be some loss in shadow detail, an increase in graininess, and an increase in contrast. The degree of these effects varies from slight to very significant depending on the amount of underexposure and push processing. The results are usually excellent with 1-stop and 2-stop push, and acceptable
with 3-stop push depending on the lighting and the scene contrast."

Interestingly enough, I haven't noticed Ansel Adams writing anything on pushing!


*I wonder however, if comparable result can be printed by simply processing the film normally and use a higher grade paper??

 

[MattKing]

Now, the problem is, many sources regard pushing as a technique which in fact increases the film sensitivity. This simply isn't true and can't work on normal to high contrast scenes, unless a compensating developer is used. I misunderstood what pushing really does, and I believe many other film users do, which is unfortunate. To some degree manufacturers even promote the pushing myth, e.g. HP5+ tech information says that: "Best results are obtained at EI 400/27, but good image quality will also be obtained at meter settings from EI 400/27 to EI 3200/36."

I don't really disagree, but ....

Some films are designed to be better than others when pushed.

The best example is Ilford Delta 3200. It is actually an ISO 1000 film, but it is designed to have a very shallow "curve", which ensures that if you meter at 1600 or 3200, you will get some shadow detail, and if you push process it, the highlights won't block up much.

If you expose and develop it at its ISO speed, you will get good results, but they will be smooth and low in contrast.

The ISO specification for speed is oriented toward concerns of shadow detail and separation at a particular "speed" point. Different films treat the contrast and separation of tones:
a) around the "speed" point of the scene; and
b) in the mid tones and highlights,

in significantly different ways.

Reference has been made in the thread to developers like Diafine. They give you an increase in speed by flattening out the curve - sometimes at the cost of the contrast that gives your subject its effectiveness in the first place.

It is fun and a good idea to experiment with under exposure combined with increased development. That way you can get a feeling for the compromises, and a sense for when it works well.

 

[jernejk]

I don't really disagree, but ....

Some films are designed to be better than others when pushed.

Reference has been made in the thread to developers like Diafine. They give you an increase in speed by flattening out the curve - sometimes at the cost of the contrast that gives your subject its effectiveness in the first place.

Agreed on both points.

The problem is, I used Tmax 400 which already is a high contrast film, and the density can go all the way up to 3 with push processing according to kodak's published charts. To make matters worse, I used HC110, which supposedly has an upswept curve. But it's OK, a lot has been learned in this exercise

 

[Xmas]

Not all films are the same and not all developers either.

So you need to look at datasheets...

http://www.foma.cz/en/catalogue-fomapan-400-action-detail-272

I use Forma 400 a lot and If I look at page 2 of the PDF linked to above

As you increase the time in Microphen the ISO does increase, but then flattens...

The other two developers do not match Mircophen, though the bottom one does hold the gamma and dmin down.

The only rule was don't under expose and over develop.

Ansell sometimes used D25 with a 'post bath' of Borax...

I use Microphen for 9 mins @ 20C with a post bath of Borax and Forma 400, (I set the Weston to 320).

Noel

 

[Tom1956]

So the moral of the story is to use published speed with D-76 or the like, and the Acufine brands if you push. That's pretty simple enough. I'm a Microdol man, but the thread is not about me and mine.

 

[Bill Burk]

Agreed on both points.

The problem is, I used Tmax 400 which already is a high contrast film, and the density can go all the way up to 3 with push processing according to kodak's published charts. To make matters worse, I used HC110, which supposedly has an upswept curve. But it's OK, a lot has been learned in this exercise

Well, yes the density can get up there, but you have to expose and develop it rather extremely to accomplish that.

Try it at 250 and developed to an 0.57 average contrast... Then if you need a little extra kick because the scenery is flat, develop to a little more than 0.62... But pushing just throws out shadow detail, which is something I value so I only grudgingly raise the EI to 400 in extreme cases where I can't use a tripod or add light and I have to take a picture.

 

[markbarendt]

Agreed on both points.

The problem is, I used Tmax 400 which already is a high contrast film, and the density can go all the way up to 3 with push processing according to kodak's published charts. To make matters worse, I used HC110, which supposedly has an upswept curve. But it's OK, a lot has been learned in this exercise

jernejk, contrast is an interesting subject.

The contrast rate of Tmax is normal. A very close match to TriX, Delta 400, blah, blah, blah...

In terms of total contrast, yes Tmax can get very dense, more than it's cousins that I listed above, but that doesn't mean it's any more "contrasty" than any other film (in terms of contrast rate/what actually prints).

What all that density means is that Tmax can record a really long range of tones from the scene. That range makes it a great film for toy cameras or for landscapers with really super long scale subjects who are willing to do a fair amount of burn and dodge when they print.

Just for giggles let's use some real numbers and say Tmax can catch a 14-stop brightness range. (Some say more.)

A normal scene measures about 6 stops, zone III to zone VIII. (That's also about what prints on paper normally.)

Bottom line is that for a normal scene/print you might only use half of Tmax's capacity/density range to make that print. (The percentage of used vs unused will vary but this concept is true of most all negative films.)

All that extra room on Tmax 400 allows for some pretty significant exposure "errors" or "creative use" of the exposure latitude. Lets say Tmax's range is from maybe 1-stop under (EI 800) to 5-stops over (EI 12) for a normal scene. Any exposure in that range can produce a good print and normal contrast. Go outside that range to say EI 1600 or 3200 or EI 6 or 3 and print quality starts falling.

 

[L Gebhardt]

Your description of what happened is correct. By developing more you get slightly more film speed along with more contrast. If you then print with a lower contrast paper/filter you will get an image that has normal contrast and more shadow detail. However given you used a developer that gave you an upswept curve, just lowering the contrast during printing won't exactly undo that (not that it is ever entirely corrected for).

If you used XTOL you would normally get a slightly higher EI. And it also gives more of a straight line contrast curve. So increasing development times will play better with lowered print contrast. Some other developers may be better than XTOL. I just mentioned it since I have experience with it.

 

[markbarendt]

However given you used a developer that gave you an upswept curve,

I actually thought that HC-110 did the same thing, I got corrected by PE and others.

Seems that that info is more of an urban legend than a reality. As I remember the suggestion was that the curve was a near duplicate of D-76.

 

[cliveh]

I sometimes see signs on doors that say push and I pull. I figure this is due to spending too much time looking at negatives and trying to think neg/pos.