Can film really be pushed?

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waileong

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I've heard that Ilford 3200 and Kodak 3200 films aren't really 3200 ISO, the true ISO is only about 1000-1200, so shooting them at 3200, one basically ends up with "empty" shadows, ie no shadow detail.

I understand that a film's sensitivity is already determined at manufacture by the size of the crystals/grains, the type of technology used, etc.

So my question is, can films really be pushed?

Can one really shoot Tri-X at 1600 and expect full shadow detail?

Do speed-increasing developers really increase the sensitivity of the film so that it can record more detail in the shadows?

Or is pushing merely increasing contrast at the expense of shadow detail, ie one may get proper highlights with a 2 or 3-stop push, but no or little increase in shadow detail?
 
Films can be pushed a little, sometimes more with more complex methods.

Increasing development time with an ordinary developer like Xtol or D-76 or T-max will usually increase contrast at a greater rate than it will increase speed, so this method doesn't really give you more speed, but it might give you a look that you like, particularly if the light is both dim and low contrast, which it might be.

Speed developers like Acufine or Microphen will get you an honest 1 to 1.5 stops in general--speed measured as shadow detail.

Some low contrast or compensating developers can get you around two stops, but might only be advisable in certain lighting conditions. I found I could get two stops with a version of the Perfection XR-1 formula (see article at unblinkingeye.com on the subject), but the resulting neg was very low in contrast, so it would be useful for, say, urban night photography, which tends to be high contrast lighting, but not necessarily for shooting in ordinary light just to get a higher shutter speed or smaller aperture.

Then there are more exotic methods like "hypering" involving techniques like exposing film to ammonia vapors before exposure. These methods work and have been used quite a bit in astrophotography, but aren't very convenient for many purposes.
 
ISO depends on a lot of factors. But B&W film has a lot of exposure latitude, which means that there is some wiggle room.

Because of that wide latitude, it can be shot at a lot of ISO settings, with varying results. Pushing is basically using up the latitude of the film and using a developer and/or time and temperature to compensate. There are always compromises when you move away from the optimum, but the extent of those compromises depends on the scene to a great extent. A low contrast scene will push better than a high contrast scene, for example. That's why shooting 400 ISO film in broad daylight on an overcast day at ISO 3200 produces a much different result than one shot at midnight under street lights.

So, you can "Push" film, depending on your definitions. But it will blow out shadows and highlights if the scene is contrasty.
 
There's two issues:

Yes, film can be pushed. People have been doing that for ages.

The ISO is often decided by the marketing rather than the technology people. So a film which is really ISO320 (technology) can be sold as ISO400 (marketing).
 
There are a few factors here:
- type of film
- if the film is pre or post sensitized
- type of developer
- development dilution/time

I am not a specialist in chemistry, so I will limit myself to the practical aspects:

- I find that my limit appetite for grain sits with TX, so I dislike the "fast films".
- Tri-X in Diafine will give you a true 1250-1600 speed and normal contrast
- you can push it almost as much in very dilute compensating developers, but you have to overcome problems like fogging, uneven development, midtone compression, etc, so it is a more experimental path, although many do it with success

TX in Diafine @ 1600
2842338036_9e1b7eedfd.jpg


TX in Diafine @ 6400 (underexposed 2 stops)
2847896856_a21b49b5b1.jpg
 
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note that pushing film, which is a 2 part process of underexposure and overdevelopment, is about bringing the midtones up to the right level, at the sacrifice of highlights. It doesn't actually have anything to do with shadow detail. So you can push any film, to any EI. You just might get terrible results if it's in the wrong combination with developer.

most speed increasing developers will give a true boost of about .66 stops, IMO, from box. I don't think I've ever gotten what seemed to be 1 stop, though perhaps very close with scanning,w here I find film to be about .33 stops faster than silver prints and densitometers.
 
'Pushing' means different things to different people; the only common denominator is 'rating it faster than the box ISO speed'. Note that Delta 3200 and TMZ are NOT marked as ISO speeds, but as EIs or exposure indices.

There is no film on the market today which will not reach or exceed its box ISO speed in at least some developers, except perhaps Neopan 1600 where (unless they have changed it) they actually claim ISO 1600. Many films will exceed their box speed by up to almost 1 stop in the right developer -- typically Ilford Microphen or Ilford DDX.

These are true ISO speeds: speed point 0.10 above film base plus fog, ISO contrast.

A very few films will only deliver their true ISO speed in speed increasing developer. The most egregious example I know is Fomapan T200, which is about ISO 180-190 in Microphen. ISO standards allow speed variations of +/- 1/3 stop, so anything above 160 can legitimately be claimed as ISO 100. Thus, for example, in the same developer, at ISO contrast, Acros 100 is likely to be 1/3 stop slower than Delta 100 -- but in (say) Microphen, Acros could legitimately be claimed (just) as an ISO 125 film.

By the same token, many films are much slower than their box speed in fine-grain or otherwise unsuitable developers. An ISO 400 film might be close enough to ISO 800 in Microphen, but ISO 250 or less in Perceptol: less than one-third of the speed.

Next, you need to know about long-toe and short-toe films. The easiest place to find out about these is probably:
http://www.rogerandfrances.com/photoschool/ps neg density.html (density and d/log e curves)

With a 'short toe' film, contrast builds very quickly with increasing development; with a 'long toe' film such as Delta 3200 or TMZ, contrast builds more slowly, so you can often get acceptable contrast even with extended development times. True maximum ISO speeds of popular long-toe films in typical speed-increasing developers are approximately 650-800 (Ilford HP5+, Neopan 1600, probably Tri-X but I don't know), 800-1000 (TMZ), 1000-1200 (Delta 3200).

So: true ISO speed depends on crystal habit, coating weight, type of sensitization and choice of developer. Acceptable 'push' speeds depend on subject matter, the contrast of your camera lens and enlarger lens, and personal taste. Remember, 0.10 over fb+f does not represent the minimum printable density: that can be as little as 0.03.

As a general rule, a stop or at most a stop and a half over true ISO speed can be surprisingly acceptable, but sooner or later you run out of shadow detail and contrast becomes too high.

In other words, yes, film can be 'pushed' to a higher true ISO than the box speed, though I regard this as a true speed increase rather than a push. You can then underexpose to varying degrees, and overdevelop to varying degrees, which I regard as true 'pushing', i.e. with increasing loss of shadow detail. At first the loss of shadow detail may be irrelevant, but sooner or later -- half a stop or at most a stop -- you have to kiss more and more shadow detail goodbye.

If only the mid-tones are important, as already noted, you can rate films incredibly fast -- Delta 3200 at EI 10,000 and more - but you will have no shadow detail at all.

You may also find the following useful on the subject of ISO speeds:

http://www.rogerandfrances.com/photoschool/ps iso speeds.html

Cheers,

Roger
 
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A speed gain might be possible by using a different developer but gaining speed by pushing (extended developement) will only increase contrast.
 
Roger Hicks said:
A very few films will only deliver their true ISO speed in speed increasing developer. The most egregious example I know is Fomapan T200, which is about ISO 180-190 in Microphen.
Click to expand...

I get about the same in Acufine.

True maximum ISO speeds of popular long-toe films in typical speed-increasing developers are approximately 650-800 (Ilford HP5+, Neopan 1600, probably Tri-X but I don't know)
Click to expand...

I can get a reliable EI 800 with fresh TX in Acufine. Lately I'm actually using Paul Farber's Acufine substitute formula that appeared I think in _Camera and Darkroom_ some years ago, which seems to give a bit better grain than Acufine. The formula is posted on APUG.org.

As a general observation, if one is trying to maximize speed, it's important to use fresh film.
 
David Goldfarb said:
II can get a reliable EI 800 with fresh TX in Acufine.

As a general observation, if one is trying to maximize speed, it's important to use fresh film.
Click to expand...

Dear David,

Probably not quite ISO 800 for the TX (as with HP5) but close enough that it doesn't matter: as you say, a reliable EI 800. Thanks for the voice of experience there.

As for the second observation, generally, very true indeed -- though I have seen reliable reports of anomalies. I've a friend staying at the moment, an ex-member of the ISO film speed standards committee, so when he gets back (he's out for the afternoon) I'll ask him about this too.

Cheers,

Roger
 
Interesting thread. David, could you put up a link to the APUG formula you noted? I did a search and didn't find it. Perhaps I'm missing something. Alternatively could you do a cut and paste into this thread for everyone or send me a PM.

thx Jan
 
It is helpful to not think of film speed as an absolute measurement, but as a relative indicator. In absolute terms, film speed should indicate how sensitive a given light-sensitive medium is to light. But in reality, speed is determined by averages as tested with reference developers, in a controlled environment. It is determined by giving the film exposure to a known light source and then developing it in a controlled environment, meaning that chemistry, temperature, time, and every other factor that can be controlled, is - and the result is a reference.

The aim is to create a 'best result' when the film is used in a specified (and hopefully typical) manner.

When you expose or develop the film in other than the specified manner, it reacts to those changes. Some of those changes have been tracked and many people agree with them - the result being commonly-accepted 'push' and 'pull' developers, times, and methods, (as well as things like reciprocity adjustments, etc).

There is no easy way to say how far a film can be pushed or pulled, because it is dependent upon so many variables, including how you want the finished product to look. There are just general assessments.

It's like saying your car is a 30 MPG vehicle or a 15 MPG vehicle, or some other specific number. Is it? That depends, doesn't it? It probably averages some MPG figure, based on how you drive it, where you drive it, and so on. But it could change if someone else drove it, or you changed your typical destination, etc. So many variables can affect the MPG - so too with film speed. And like MPG, film speed has an upper and a lower limit that you can't easily get past, or not without a lot of compromises. The question is what compromises you can live with.
 
Thanks David, I just went thru your NYC BW images again. I always enjoy them. I've got a Crown Graphic and some grafmatic holders. I really should get this stuff out and shoot it.
 
My experience with pushed film--such as HP5 in Microphen--is that you get perfectly acceptable pictures with a good black and highlights but half the graduation of tones is missing. For me the Microphen / HP5 combo was very smooth and snappy, but sort of empty.

Also I've been working on the premise that longer development does not increase contrast but increases density. It's the agitation with longer development that increases contrast--so if you let the film stand inverting the canister every two or three minutes you get detailed highlights and shadow detail when shooting under severe conditions at night. I don't know if this helps with speed but it does yield a bit more richness.
 
summaron said:
Also I've been working on the premise that longer development does not increase contrast but increases density.
Click to expand...

A false premise, unfortunately.

For anything resembling normal conditions (i.e until gamma infinity), more development always means more contrast, whether you achieve it by longer times, more agitation, higher temperature or stronger developer.

Extra agitation will actually boost toe speed more, which means increased true ISO speed at the ISO contrast.

You can verify this with a densitometer. Your negs may well please you more, and print better, and please you better, so you're not doing anything wrong: anything that gives you pics you like better is right. But your theory about density and contrast is simply not true.

Cheers,

Roger
 
Very interesting discussion. I hope Lynn Miller chimes in here as he is currently getting some very good results (tonally) from pushing films with stand development in Rodinal.
 
I think the case where low agitation could be used to improve speed would be stand development, with no agitation except at the beginning of the development cycle, the principle being that the developer adjacent to the highlights would be quickly exhausted, while the developer adjacent to the shadows would continue to work, and this also produces some interesting edge effects.

I haven't tested this as a way of increasing speed, so I don't know how much you can get by this approach.
 
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