Overexposing and pushing the film

[fatihayoglu]

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Hi all,

 

I am experimenting shooting film, using TX400 with my MP. I have read a lot for film, it is good to overexpose. One of the ways to do it is adjusting the ISO to the half of the film speed. I also would like to push the film to 1600 as I’m going to use if during evening, night.

So if I adjust my ISO dial to 800 and ask the lab to push the film to 1600, do I effectively overexpose 1 stop and push the film 2 stops?

 

Thanks,

 

Fatih

 

 

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[spydrxx]

Rethink your math. The nominal speed of TX 400 is 400. If you expose for ISO 800 you will be underexposing by 1 f stop. If you then push process for iso 1600 you will be underexposing by another 2 f stops. There is no overexposure here, merely underexposure.

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[fatihayoglu]

Rethink your math. The nominal speed of TX 400 is 400. If you expose for ISO 800 you will be underexposing by 1 f stop. If you then push process for iso 1600 you will be underexposing by another 2 f stops. There is no overexposure here, merely underexposure.

If I expose for 200 and process for 400, does it mean I overexpose 1 stop? I am very confused with this math

[avatar230]

If I expose for 200 and process for 400, does it mean I overexpose 1 stop? I am very confused with this math

 

If you rate Tri-X at 200 and then process normal, you should get negatives that are overexposed 1 stop.

 

If you rate the Tri-X at 800 and then process with a 2-stop push (telling the lab it was rated at 1600), you should also get negatives that are overexposed by 1 stop.

 

These two scenarios, however, will not produce identical negatives. The first scenario, because of the normal processing time, will produce a dense but normally-grained neg.

 

The latter, because of the true push-processing going on (meaning, leaving the negs in the developer longer than standard) will produce grainier negs that, even with the "overexposure," may suffer from thin shadow areas.

Edited November 23, 2017 by avatar230

[fatihayoglu]

If you rate Tri-X at 200 and then process normal, you should get negatives that are overexposed 1 stop.

 

If you rate the Tri-X at 800 and then process with a 2-stop push (telling the lab it was rated at 1600), you should also get negatives that are overexposed by 1 stop.

 

These two scenarios, however, will not produce identical negatives. The first scenario, because of the normal processing time, will produce a dense but normally-grained neg.

 

The latter, because of the true push-processing going on (meaning, leaving the negs in the developer longer than standard) will produce grainier negs that, even with the "overexposure" may suffer from thin shadow areas.

Yes the negatives will be different I appreciate that. I am trying to experiment overexposing. Sure I can do it for every image checking exposure meter of the camera but I might forget it. But if I’d adjust the ISO dial at 200 but process it for 400, then without thinking too much I’ll overexpose each picture 1 stop.

And I can do the same for 800/1600 version. For my learning curve I guess it might be interesting I guess. This way I can see how much grain the film produces as well, hopefully

 

 

 

 

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[Frase]

Will that not mean you are exposing for 400 but developing for 800, so all you are doing is over developing?

[Tom R]

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Why are you doing this? Is this a matter of curiosity or are you trying to achieve some effect by adjusting exposure?

 

Perhaps you should get to a library and check out some texts on the "zone system," which might give you some grounding in the fundamentals of exposure. If you decide to do this, remember that 135 (35mm) is a smaller format than the films that were used by many of the commonly found authors on these topics (such as Ansel Adams), and may not give you the expected results.

[pico]

Don't put to much emphasis on Ansel Adams' Zone System. He was using early films and film has changed remarkably since, and he used large format and excruciating manipulation to make his prints.

 

You are using modern films but miniature format. It makes a difference.

 

I rate Tri-X at 320, under-develop by 15% in D76 1:1 and print in a condenser enlarger. Work from 320 as normal for starters. Pushing film development usually increases contrast for better or worse. Some developers use solvents that mush grain, causing grain to be somewhat less apparent, at a loss of accutance (AKA apparent sharpness.)

Edited November 24, 2017 by pico

[250swb]

Rethink your math. The nominal speed of TX 400 is 400. If you expose for ISO 800 you will be underexposing by 1 f stop. If you then push process for iso 1600 you will be underexposing by another 2 f stops. There is no overexposure here, merely underexposure.

Push processing compensates for under exposing the negative. You would understand it better if you thought in terms of increasing the density of an underexposed negative as the goal. The more it is pushed (over developed) the denser it gets, so developing a negative shot at 800 ISO as if it were 1600 ISO increases the density by one stop over normal exposure. Of course nothing is a straight line and films and developers each have their own characteristic curves, but most photographers would understand that it is development that is the 'push' part of the process just as it can be the 'pull' part of the process in achieving the required density. 

[fatihayoglu]

Why are you doing this? Is this a matter of curiosity or are you trying to achieve some effect by adjusting exposure?

 

 

I have read many times, people are saying you should almost always overexpose while shooting with film. So by exposing to 200, and developing to 400, technically I will be overexposing.

 

The reason why I am trying the same for 400/800 and 800/1600 combo is, I will be traveling to Paris for a short trip and while walking at night or evening, I would like shoot some film as well. As 400ISO might not be enough, I would like to see how the film will response to pushed value.

 

Do you think I am doing something wrong?

[michaelwj]

I think there's a lot going on here.

Firstly, the "perfect" exposure captures sufficient detail in both the highland shadows. Film (negative film) has a high tolerance for overexposure but little tolerance for under exposure, so it's best to wet on the side of overexposure - hence people exposing 400 film at 250 or 320, it just covers a bit more shadow.

Now, when you push your film to 800, you simply don't get enough light in the shadows, so you develop it a bit longer to try to bring out any shadow detail you can while maintaining some decent mid and high tones. But the shadows will not have the detail and will start to look grainy from the extra development.

You're proposing the shoot at 800 but develop even more. There won't be any more detail in the deep shadows and you'll start to clip highlights. I wouldn't. Err on the side of overexposure but when you push you're pushing because you don't have the light. If you can give it more light, best not push.

 

One thing to remember is that the shadows are largely controlled at exposure. If not enough light hits the film then you can't fix it later.

The highlights are controlled in development. Longer development leads to brighter highlights but not much brighter shadows.

(The overall mid tones are somewhat corrected by pushing an underexposed negative, but you overdevelop the highlights and the shadows still lag - therefore increased contrast.)

 

Would I do it? Sure. I'd go to 1600, expose for the subject and let the shadows go to black and the highlights go to white. That's what night looks like anyway, dark shadows and bright lights. Don't overthink it and have fun.

Edited November 24, 2017 by michaelwj

[Tom R]

I have read many times, people are saying you should almost always overexpose while shooting with film. So by exposing to 200, and developing to 400, technically I will be overexposing.

 

The reason why I am trying the same for 400/800 and 800/1600 combo is, I will be traveling to Paris for a short trip and while walking at night or evening, I would like shoot some film as well. As 400ISO might not be enough, I would like to see how the film will response to pushed value.

 

Do you think I am doing something wrong?

 

I am not making any statements about "right" or "wrong" so much as asking you to examine your assumptions. I'm not sure what anyone means by the "perfect" exposure--other than perfect by some objective measure. If that degree of accuracy is relevant to the image(s) you are attempting to create, then maybe I would reconsider my choice of 35mm film ...

 

It is true that most 35mm films have a greater tolerance for overexposure than for under exposure. But, I'd also be willing to wager that a great many "timeless" and so-called "essential" images were created with "less than perfect" exposure. 

 

I think it's good to question the "fundamentals"--such as exposure. But I think that it's also important to keep things in context. I use the word "fundamental" to mean a concept that is sufficiently abstract and coherent so as to be applicable to a great number of specific applications. So, understanding exposure means that you have a working mental model of "exposure" that works in a great number of applications, such as film, digital, different formats, etc. And, more importantly, having that conceptual understanding is only helpful if it fits into a larger context---which, in this case, is what it is you're hoping to produce.

Edited November 24, 2017 by Tom R

[mikemgb]

Reading through this thread I seem to see a lot of overthinking. If I want to push 400 ISO film to 1600 I simply expose it at 1600, which is 2 stops under, then push development by 2 stops to compensate. HP5 is very good for this.

 

 

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[Ko.Fe.]

I have read many times, people are saying you should almost always overexpose while shooting with film. ...

Do you think I am doing something wrong?

 

I can't blame you, but where you were able to find it so wrong many times? I never read anywhere "you should almost always overexpose while shooting with film". It is so wrong, because it doesn't tells you where to measure.

 

I develop film as I measure it. This is it. The way I measure it is always for areas closer to shadows, not where it is brightest part. It is not overexposing, because then I print I get all parts visible. Shadows and bright sky. 

Edited November 24, 2017 by Ko.Fe.

[DickieT]

I agree, the question does not seem to be if the film is properly rated @ 400 (or something else) or if it requires some compensation. I think Fatihayoglu is simple looking for some more shutter time in the dark and the suggestion from mikemgb does just that. Have fun !

[Steve Ricoh]

To the OP, it's probably worth reading this: http://emulsive.org/reviews/film-reviews/ilford-film-reviews/ilford-hp5-plus-in-35mm-120-and-sheet-formats

[fatihayoglu]

I can't blame you, but where you were able to find it so wrong many times? I never read anywhere "you should almost always overexpose while shooting with film". It is so wrong, because it doesn't tells you where to measure.

 

I develop film as I measure it. This is it. The way I measure it is always for areas closer to shadows, not where it is brightest part. It is not overexposing, because then I print I get all parts visible. Shadows and bright sky. 

 

My research on this subject says, I need to expose to the shadows and then by rating for 200 but developing for 400 should give me 2-3 stops overexposing.

[fatihayoglu]

I agree, the question does not seem to be if the film is properly rated @ 400 (or something else) or if it requires some compensation. I think Fatihayoglu is simple looking for some more shutter time in the dark and the suggestion from mikemgb does just that. Have fun !

Exactly, when I am shooting at night, I need some more shutter speed so I want to rate the film for 800 and then process it for 1600. I am hoping to get a stop faster shutter speed and 1 stop overexposing.

[adan]

You are mixing up two things.

 

The moment you make the choice to shoot Tri-X at 800 or 1600 or any ISO higher than 400, you have already thrown out the window any possibility of exposing for the shadows or overexposing. Shooting Tri-X at 800 means underexposing it - no matter how you develop it.

 

If you expose at 800, and develop for 1600 - you will get more contrast (heavy dense highlights) and more grain, but no significant increase in shadow detail.

 

You quote the idea of "expose for the shadows" - but miss the second part of that concept, which correctly and completely stated is, "Expose for the shadows, and develop for the highlights." Which only applies for normal correct-ISO picture-making.

 

Developing film chemically is essentially a process of amplification or multiplication - extra developing produces more silver from a given amount of exposure. It is like turning up the volume knob on a sound system - turn it all the way up (push-process the film with more development) and you may be able to hear very faint sounds in the original recording (or get more detail in marginally exposed shadows), but only at the expense of making the normal sounds far too loud and painful to listen to.

 

Additionally, at the shadow end of the exposure range, film always has a minimum exposure  - a floor - and if the shadows are not exposed at least that much, they don't respond to development at all.

 

Normally exposed TX may have a range (arbitrary units) of 1 to 1000 units of light. If you underexpose one stop, you give the film only 0.5 to 500 units. But if the floor is 1, then 0.5 = zero, as far as triggering a response. No effective exposure. When you then develop the film for a 1 stop push, you multiply everything, chemically, by 2.

 

So your shadows will be 2 x 0 = 0 (zero additional density and detail). Your highlights will be 500 x 2 = 1000 (normal highlight density).

 

If you underexpose one stop (800) and develop for two stops (1600), the equations will be: shadows 4 x 0 = 0 (still no shadow detail developed) and 4 x 500 = 2000 (double the highlight density - very dense, "blocked" highlights).

 

Here are Kodak's own "characteristic curves" for Tri-X - showing the contrast (steepness) and density (maximum height) that comes with additional development (more time in the developer).

 

http://theonlinephotographer.typepad.com/.a/6a00df351e888f88340162ff921628970d-800wi

 

Notice that in the shadows (left end of the curves) - there is virtually no change - no increase in shadow detail. No amount of development will restore shadows that did not get enough light to begin with. And TX at ISO 800 or higher automatically means "not enough light."

 

It is inherent in pushing film that one gets less and less shadow detail, just pure blacks, and starker and starker contrast and highlights - the classic "charcoal and chalk" appearance

 

http://theonlinephotographer.typepad.com/.a/6a00df351e888f8834016760da0f3c970b-600wi

 

"Shadow detail" and "pushed film" are mutually exclusive concepts.

_______________

 

Additionally, the idea that films always benefit from more exposure mostly applies to chromogenic films - films where the final image is produced by dye clouds, and not physical chunks/grains of metal (silver). Color negative films, and "B&W" films like Ilford XP2 that use the color negative process for convenience.

 

Pure silver films tend to get more grainy and less sharp with extra exposure (although 200 for TX is usually safe). This just has to do with the physical differences between clouds of dye and metallic silver grains. Imagine filling your back yard with more and larger cotton balls vs. filling it with more and larger rocks. Which will be smoother? (yes, I know - the analogy is a bit of a stretch )

 

In fact, back in the days of the early Leicas and photographers workign with the small negative and the films of the time (1930-1955 or so) - the minimum possible exposure that ensured shadow detail was the preferred exposure - any excess density would immediately result in excessive grain and halation and other flaws, which could not take the enlargement the small 35mm negative needed.

Edited November 24, 2017 by adan

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[fatihayoglu]

You are mixing up two things.

 

The moment you make the choice to shoot Tri-X at 800 or 1600 or any ISO higher than 400, you have already thrown out the window any possibility of exposing for the shadows or overexposing. Shooting Tri-X at 800 means underexposing it - no matter how you develop it.

 

If you expose at 800, and develop for 1600 - you will get more contrast (heavy dense highlights) and more grain, but no significant increase in shadow detail.

 

You quote the idea of "expose for the shadows" - but miss the second part of that concept, which correctly and completely stated is, "Expose for the shadows, and develop for the highlights." Which only applies for normal correct-ISO picture-making.

 

Developing film chemically is essentially a process of amplification or multiplication - extra developing produces more silver from a given amount of exposure. It is like turning up the volume knob on a sound system - turn it all the way up (push-process the film with more development) and you may be able to hear very faint sounds in the original recording (or get more detail in marginally exposed shadows), but only at the expense of making the normal sounds far too loud and painful to listen to.

 

Additionally, at the shadow end of the exposure range, film always has a minimum exposure  - a floor - and if the shadows are not exposed at least that much, they don't respond to development at all.

 

Normally exposed TX may have a range (arbitrary units) of 1 to 1000 units of light. If you underexpose one stop, you give the film only 0.5 to 500 units. But if the floor is 1, then 0.5 = zero, as far as triggering a response. No effective exposure. When you then develop the film for a 1 stop push, you multiply everything, chemically, by 2.

 

So your shadows will be 2 x 0 = 0 (zero additional density and detail). Your highlights will be 500 x 2 = 1000 (normal highlight density).

 

If you underexpose one stop (800) and develop for two stops (1600), the equations will be: shadows 4 x 0 = 0 (still no shadow detail developed) and 4 x 500 = 2000 (double the highlight density - very dense, "blocked" highlights).

 

Here are Kodak's own "characteristic curves" for Tri-X - showing the contrast (steepness) and density (maximum height) that comes with additional development (more time in the developer).

 

http://theonlinephotographer.typepad.com/.a/6a00df351e888f88340162ff921628970d-800wi

 

Notice that in the shadows (left end of the curves) - there is virtually no change - no increase in shadow detail. No amount of development will restore shadows that did not get enough light to begin with. And TX at ISO 800 or higher automatically means "not enough light."

 

It is inherent in pushing film that one gets less and less shadow detail, just pure blacks, and starker and starker contrast and highlights - the classic "charcoal and chalk" appearance

 

http://theonlinephotographer.typepad.com/.a/6a00df351e888f8834016760da0f3c970b-600wi

 

"Shadow detail" and "pushed film" are mutually exclusive concepts.

_______________

 

Additionally, the idea that films always benefit from more exposure mostly applies to chromogenic films - films where the final image is produced by dye clouds, and not physical chunks/grains of metal (silver). Color negative films, and "B&W" films like Ilford XP2 that use the color negative process for convenience.

 

Pure silver films tend to get more grainy and less sharp with extra exposure (although 200 for TX is usually safe). This just has to do with the physical differences between clouds of dye and metallic silver grains. Imagine filling your back yard with more and larger cotton balls vs. filling it with more and larger rocks. Which will be smoother? (yes, I know - the analogy is a bit of a stretch )

 

In fact, back in the days of the early Leicas and photographers workign with the small negative and the films of the time (1930-1955 or so) - the minimum possible exposure that ensured shadow detail was the preferred exposure - any excess density would immediately result in excessive grain and halation and other flaws, which could not take the enlargement the small 35mm negative needed.

 

So how can I gain an extra stop of shutter speed from a TX400 film during night? If I set the ISO wheel at 800 and develop for 800 or develop for 400? I am getting really confused now, even more than before

 

Also how about setting ISO wheel to 200 and developing as standard 400. It does mean everything will be 1 stop overexposed right?