atlcruiser
Part Yeti
I looked around the web a but i still need some basic explinations and real world situations to get my head around this.
thanks
david
thanks
david
Talk to me about pushing and pulling
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sahe69
Well-known
Pushing= underexposing + overdeveloping. Increase of film speed at the expense of increased contrast.
Pulling= overexposing + underdeveloping. Reduced contrast and improved shadow detail at the expense of drop in film speed.
Pulling= overexposing + underdeveloping. Reduced contrast and improved shadow detail at the expense of drop in film speed.
marcr1230
Well-known
A lot of this was formalized with the zone system as a method to compress or expand the grey scale tones of a photo. The reason you might do this artistic / aesthetic .
Generally you want to stretch a low contrast scene so you have a range of tones from white to black and gradations in between. For a high contrast scene , you want to compress the tones so the photo is not just harshvwhite and jet back.
My biggest obstacle here is that when this was more popular, the artists were using single frames in a view camera. With roll film the entire roll is processed the same way, so you need all the shots to be amenable to the same adjustment.
You can also push film - increase the E.I. To better adapt to low light, and then process accordingly
Generally you want to stretch a low contrast scene so you have a range of tones from white to black and gradations in between. For a high contrast scene , you want to compress the tones so the photo is not just harshvwhite and jet back.
My biggest obstacle here is that when this was more popular, the artists were using single frames in a view camera. With roll film the entire roll is processed the same way, so you need all the shots to be amenable to the same adjustment.
You can also push film - increase the E.I. To better adapt to low light, and then process accordingly
Roger Hicks
Veteran
From http://www.rogerandfrances.com/subscription/ps neg development 1.html
Pushing is no more and no less than over-developing. This gives you more contrast, and more contrast at the thinnest end of the negative (the shadows) corresponds to more speed. As soon as you develop to a different contrast from what is specified by ISO rules, you are no longer talking about ISO speeds but EIs or exposure indices.
The degree of pushing that is possible varies greatly. Some films push more gracefully than others, before becoming too contrasty or too foggy: most 'old technology' films (Ilford's Plus series, Kodak Plus-X and Tri-X) push better than their 'new technology' counterparts (Ilford Delta, Kodak T-Max), though the special 'push' films (Delta 3200, TMZ P 3200) give the ultimate in speed.
Low-contrast scenes can be pushed a lot further than high-contrast ones, because the contrast is low to begin with.
Some developers deliver more speed than others, so you don't have to tolerate as much contrast from overdevelopment. For example, Ilford HP5 Plus in Paterson FX-50 is as close as makes no odds to ISO 800, so EI 1000 is a 1/3 stop or at most a 1/2 stop push, necessitating a very modest increase in development time and a minor penalty in contrast. With Perceptol or another fine-grain developer the true ISO might be 250 so EI 1000 would be a 2-stop push. D-76 is a good push developer but as it gives only about ISO 500, EI 1000 would be a 1-stop push.
Then there is personal preference, and the question of what is acceptable to you. If you are looking only for recognizable faces, as you might be for surveillance photography or at some kinds of rock concert, you could probably rate HP5 in FX-50 at EI 2000 or more -- but you wouldn't have any shadow detail.
As a very general rule, adding 50 per cent to development times doubles effective film speed (+1 stop), while doubling development times quadruples it (+2 stops). This is such a wild generalization that the manufacturers' specific recommendations are far more useful but it gives you an idea of the orders of magnitude involved.
Be wary of the Zone System, because it is in some ways an oversimplification of basic sensitometry (which antedates it by decades) and in some ways an overcomplication. If it works for you, great, but if you don't take to the jargon, just ignore it. A piece on why my wife and I don't use it: http://www.rogerandfrances.com/subscription/ps zone.html
'Pulling' (underdevelopment) rapidly reduces contrast and slowly reduces speed. Personally, if I just want lower speed, I find I get better results from just overexposing and then developing normally, but then, I print in a wet darkroom.
Cheers,
R.
Pushing is no more and no less than over-developing. This gives you more contrast, and more contrast at the thinnest end of the negative (the shadows) corresponds to more speed. As soon as you develop to a different contrast from what is specified by ISO rules, you are no longer talking about ISO speeds but EIs or exposure indices.
The degree of pushing that is possible varies greatly. Some films push more gracefully than others, before becoming too contrasty or too foggy: most 'old technology' films (Ilford's Plus series, Kodak Plus-X and Tri-X) push better than their 'new technology' counterparts (Ilford Delta, Kodak T-Max), though the special 'push' films (Delta 3200, TMZ P 3200) give the ultimate in speed.
Low-contrast scenes can be pushed a lot further than high-contrast ones, because the contrast is low to begin with.
Some developers deliver more speed than others, so you don't have to tolerate as much contrast from overdevelopment. For example, Ilford HP5 Plus in Paterson FX-50 is as close as makes no odds to ISO 800, so EI 1000 is a 1/3 stop or at most a 1/2 stop push, necessitating a very modest increase in development time and a minor penalty in contrast. With Perceptol or another fine-grain developer the true ISO might be 250 so EI 1000 would be a 2-stop push. D-76 is a good push developer but as it gives only about ISO 500, EI 1000 would be a 1-stop push.
Then there is personal preference, and the question of what is acceptable to you. If you are looking only for recognizable faces, as you might be for surveillance photography or at some kinds of rock concert, you could probably rate HP5 in FX-50 at EI 2000 or more -- but you wouldn't have any shadow detail.
As a very general rule, adding 50 per cent to development times doubles effective film speed (+1 stop), while doubling development times quadruples it (+2 stops). This is such a wild generalization that the manufacturers' specific recommendations are far more useful but it gives you an idea of the orders of magnitude involved.
Be wary of the Zone System, because it is in some ways an oversimplification of basic sensitometry (which antedates it by decades) and in some ways an overcomplication. If it works for you, great, but if you don't take to the jargon, just ignore it. A piece on why my wife and I don't use it: http://www.rogerandfrances.com/subscription/ps zone.html
'Pulling' (underdevelopment) rapidly reduces contrast and slowly reduces speed. Personally, if I just want lower speed, I find I get better results from just overexposing and then developing normally, but then, I print in a wet darkroom.
Cheers,
R.
Last edited:
philipp.leser
Established
I would like to note that pushing or pulling does not influence the speed of the film, it only changes the contrast!
In terms of the characteristic curve pushing and pulling changes the slope of the curve but does not (noticeably) move the point where 0.1 log D is reached, i.e. the point that is used to determine the film speed.
Pushing by two stops means that you lose two stops of shadow detail, but you might overall get a more useable contrast for printing the neg, if the scene has a very low contrast.
Regards,
Philipp
In terms of the characteristic curve pushing and pulling changes the slope of the curve but does not (noticeably) move the point where 0.1 log D is reached, i.e. the point that is used to determine the film speed.
Pushing by two stops means that you lose two stops of shadow detail, but you might overall get a more useable contrast for printing the neg, if the scene has a very low contrast.
Regards,
Philipp
atlcruiser
Part Yeti
Chek my math and process here:
If I am shooting 400 tri x and i want to increase a speed.....
I can set the ISO on the camera to 800 to meter
Normally using d 76 at 400 for 8 minutes (400 iso) increase to d 76 for 12 minutes (800 iso,50% increase)
that should give me effictive 800 iso hi contrast negs.
Sound right?
If I am shooting 400 tri x and i want to increase a speed.....
I can set the ISO on the camera to 800 to meter
Normally using d 76 at 400 for 8 minutes (400 iso) increase to d 76 for 12 minutes (800 iso,50% increase)
that should give me effictive 800 iso hi contrast negs.
Sound right?
Roger Hicks
Veteran
Dear Philipp,
You are absolutely right that the effect of pushing/pulling on the ISO speed point is often grossly exaggerated, but with a long-toe film such as Tri-X or HP5 Plus you usually do get more usable speed along with the higher contrast.
Cheers,
R.
not_in_good_order
Well-known
Ilford has a publication about push processing that you may find useful:
http://www.ilfordphoto.com/Webfiles/20062102012331472.pdf
They have some basic info on pull processing as well:
http://www.ilfordphoto.com/aboutus/page.asp?n=89&t=Developing+Black+and+white+film
http://www.ilfordphoto.com/Webfiles/20062102012331472.pdf
They have some basic info on pull processing as well:
http://www.ilfordphoto.com/aboutus/page.asp?n=89&t=Developing+Black+and+white+film
philipp.leser
Established
Dear Roger,
You are right, of course. I just wanted to stress that point, because a lot of times people seem to think pushing is a way to "magically" gain a few stops of film speed (like pushing Tri-X to E.I. 12500 and similar experiments) while in reality the effect is small.
Regads,
Philipp
JohnTF
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Very good posts, I recall a time that I thought my experiments in over developing to shoot in lower light without flash really increased the film speed. Well, it was a long time ago, and I could not afford the right books, so I had to experiment and figure myself.
Then folks would say "Expose for the shadows, develop for the highlights", as if someone who thought the above would understand this, and much less be able to use it with my Gossen Pilot Light Meter. I think a lot of people who said this repeated it perhaps without understanding it.
Perhaps not a perfect explanation, but it did seem to penetrate my skull a bit more, Fred Picker's book on the Zone System explained a lot for me in terms of how film, exposure and development work, in relatively simple terms. I had read Minor White's and Ansel Adams by then, but this was simple, down and dirty, and struck a few chords for me.
The film has a speed, ISO, and there is a threshold below which light effectively does not expose anything you can use. No amount of over developing is going to help. You did not have enough photons to make an image.
If you can meter so that important shadow detail is exposed, that is a good start.
Objects which are highly exposed, are more subject to manipulation by development.
There's more to it all, but hopefully this is a good start.
The zone system is useful to understand how these things work together, and you do not have to swallow it whole to find it of use.
I would like to check my shadows and meter so that the exposure will allow detail to be present in the negative, and not develop so that the highlights are lost.
The choice of film, exposure, developer and development times are your tools.
If you want to do some testing, you can buy some gray scales to shoot to see what kind of results are coming out of what you did. Not a bad use of time, and write down what you do.
Regards, John
Then folks would say "Expose for the shadows, develop for the highlights", as if someone who thought the above would understand this, and much less be able to use it with my Gossen Pilot Light Meter. I think a lot of people who said this repeated it perhaps without understanding it.
Perhaps not a perfect explanation, but it did seem to penetrate my skull a bit more, Fred Picker's book on the Zone System explained a lot for me in terms of how film, exposure and development work, in relatively simple terms. I had read Minor White's and Ansel Adams by then, but this was simple, down and dirty, and struck a few chords for me.
The film has a speed, ISO, and there is a threshold below which light effectively does not expose anything you can use. No amount of over developing is going to help. You did not have enough photons to make an image.
If you can meter so that important shadow detail is exposed, that is a good start.
Objects which are highly exposed, are more subject to manipulation by development.
There's more to it all, but hopefully this is a good start.
The zone system is useful to understand how these things work together, and you do not have to swallow it whole to find it of use.
I would like to check my shadows and meter so that the exposure will allow detail to be present in the negative, and not develop so that the highlights are lost.
The choice of film, exposure, developer and development times are your tools.
If you want to do some testing, you can buy some gray scales to shoot to see what kind of results are coming out of what you did. Not a bad use of time, and write down what you do.
Regards, John
Last edited:
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