Is exposure index and ISO actually relevant

bluechromis · Apr 3, 2023

grain elevator said:
I feel the opposite is the case - many film beginners and youtubers these days seem to treat EI as another variable along with shutter speed and aperture, which it isn't, or at least seem to vastly overestimate the usefulness of varying it. Maybe that's a misunderstanding coming from digital cameras, people see they can adjust ISO on a film camera as well and think it does the same thing... maybe also the OP's misunderstanding. Of course EI can be varied if light dictates or tweaked a bit to suit other process variables, but sensitivity is baked into the emulsion and straying very far from the ideal exposure (especially towards underexposure, leeway for everexposure is often significant but nothing is gained by giving more exposure beyond a point) will only yield special effects negatives.

I agree that film sensitivity is pretty fixed. As you say, EI can be varied if light dictates. But, for example, there are a lot of places in the world that have dim light, including many indoor spaces. One can easily get into places where even the fastest films will not work at their IS0: 800-1200. If one wants to shoot musicians in dark clubs, skate board parks beneath underpasses, if one wants to do street photography in low light and need a decent shutter speed and DOF, one may be forced to underexpose. For a given photographer, low-light scenes may be their preferred subject matter. I don't think this is a rare niche. If you look at what people find interesting in their social world, there are a lot of low-light subjects. Not everyone wants to take pictures of mountains with a camera on a tripod where there are a lot of options for films and settings. Low light is where digital cameras have an advantage. Yes, shadow detail will be lost with underexposure.

Photography is frequently about tradeoffs. It is believed that Garry Winogrand routinely pushed film because he put on a high value on freezing motion with higher shutter speeds. He was willing to sacrifice some shadow detail because it wasn't as important in his work. My main point is that EI should be taken in the context of what the photographer is trying to do. There are many considerations in this, just as there is a vast variety of subject matter and styles photographers prefer. Doing some tests and actually looking at the results may help someone understand the effect of exposure and development and guide them in choosing what trade-offs to make.

grain elevator · Apr 3, 2023

bluechromis said:
I agree that film sensitivity is pretty fixed. As you say, EI can be varied if light dictates. But, for example, there are a lot of places in the world that have dim light, including many indoor spaces. One can easily get into places where even the fastest films will not work at their IS0: 800-1200. If one wants to shoot musicians in dark clubs, skate board parks beneath underpasses, if one wants to do street photography in low light and need a decent shutter speed and DOF, one may be forced to underexpose. For a given photographer, low-light scenes may be their preferred subject matter. I don't think this is a rare niche. If you look at what people find interesting in their social world, there are a lot of low-light subjects. Not everyone wants to take pictures of mountains with a camera on a tripod where there are a lot of options for films and settings. Low light is where digital cameras have an advantage. Yes, shadow detail will be lost with underexposure.

Photography is frequently about tradeoffs. It is believed that Garry Winogrand routinely pushed film because he put on a high value on freezing motion with higher shutter speeds. He was willing to sacrifice some shadow detail because it wasn't as important in his work. My main point is that EI should be taken in the context of what the photographer is trying to do. There are many considerations in this, just as there is a vast variety of subject matter and styles photographers prefer. Doing some tests and actually looking at the results may help someone understand the effect of exposure and development and guide them in choosing what trade-offs to make.

Agreed! These cases are in the "when lighting dictates it" category. I may have understated how frequently this occurs.
If course, also in these cases EI and ISO matter, to expose consistently, be able to develop accordingly, and get and idea of how much shadow detail one sacrifices. So what is the OP on about?

Alan Edward Klein · Apr 3, 2023

redbandit said:
The triangle so to speak is still important, but with the advant of things... the only portions of the triangle that matter seem to be shutter speed and aperture.

Look at Foma 400 in 134.. box says 400, everybody else says it has to be shot at 320 or less to get reliable images.. Thing is,,, the film does make images at box speed, and depending on the actual PROCESSING done... developer, length of development, agitation pattern when developing it... the results completely negate the actual "specified" EI everyone uses..

Even with other films.. the classic "develop the film 20 percent longer if you were shooting in bright light.." makes a preset ISO / EI as irrelevant.

You have a wider range with digital than what film allows.

Alan Edward Klein · Apr 3, 2023

grain elevator said:
I feel the opposite is the case - many film beginners and youtubers these days seem to treat EI as another variable along with shutter speed and aperture, which it isn't, or at least seem to vastly overestimate the usefulness of varying it. Maybe that's a misunderstanding coming from digital cameras, people see they can adjust ISO on a film camera as well and think it does the same thing... maybe also the OP's misunderstanding. Of course EI can be varied if light dictates or tweaked a bit to suit other process variables, but sensitivity is baked into the emulsion and straying very far from the ideal exposure (especially towards underexposure, leeway for everexposure is often significant but nothing is gained by giving more exposure beyond a point) will only yield special effects negatives.

I've noticed that Portra bracketed will show a difference in colors with a one stop difference. Both shots may be usable. But there is a shift in color.

Alan Edward Klein · Apr 3, 2023

ic-racer said:
With B&W negative, the easy rule of thumb is "the more you enlarge, the less latitude"
Contact prints from B&W negatives have the greatest latitude, but mostly for over-exposure.

So getting the exposure ISO right in film camera is the right approach.

Paul Howell · Apr 3, 2023

I shoot 35mm with my newer AF bodies, Minolta and Pentax with matrix metering at box speed with good results, with roll film 35mm or 120 with calibrated spot meter body I meter shadows at zone III and develop for zone VII, so I do test my development time so as not blow out the highlight's but shoot at box speed with most standard developers. If shooting old MF all mechanical cameras, Nikon, Minolta, Konica, Pentax, and there are others, I test using a ring around of a standard scene, white cloth and black cloth with texture, gray card, light skinned model. in open shade. From that I find the E.I for that camera, I use zone III as my E.I thenI need to test for developer time for zone VII. With sheet film, I again test using a spot meter, same ring around, this time I'm looking for Zone II shadows and highlight for Zone VIII. My older mechanical bodies and lens are all over the map, EI ranges -2 stops to + 2 stops.

Sirius Glass · Apr 3, 2023

Alan Edward Klein said:
You have a wider range with digital than what film allows.

Still not true. That is why digital fakes it with HDR.

Sirius Glass · Apr 3, 2023

Alan Edward Klein said:
I've noticed that Portra bracketed will show a difference in colors with a one stop difference. Both shots may be usable. But there is a shift in color.

Yes, often.

Sirius Glass · Apr 3, 2023

Alan Edward Klein said:
So getting the exposure ISO right in film camera is the right approach.

So using the box speed is a good start. Then learn how to use a calibrated light meter.

bluechromis · Apr 3, 2023

grain elevator said:
I feel the opposite is the case - many film beginners and youtubers these days seem to treat EI as another variable along with shutter speed and aperture, which it isn't, or at least seem to vastly overestimate the usefulness of varying it. Maybe that's a misunderstanding coming from digital cameras, people see they can adjust ISO on a film camera as well and think it does the same thing... maybe also the OP's misunderstanding. Of course EI can be varied if light dictates or tweaked a bit to suit other process variables, but sensitivity is baked into the emulsion and straying very far from the ideal exposure (especially towards underexposure, leeway for everexposure is often significant but nothing is gained by giving more exposure beyond a point) will only yield special effects negatives.

For eight years, I helped out an instructor with a film photography class for general students at a local college. Some students were beginners and some were intermediates that had some experience. I didn't see them rushing out to try different E.I.s. I didn't hear them say they thought that pushing increased film sensitivity. For the most part, it didn't occur to them to use any speed other than what was printed on the box. I am not saying people don't do those things, but I didn't see it in several hundred people that went through those classes.

I am not suggesting that doing exposure/development tests is a priority for a total beginner. But for someone that is further along, that has the basics down, it might be educational even if they only ever use box speed. I think it is easier to see the effect of something when it is extreme than when it is subtle. With tests, one can do that without ruining valuable shots. One can super over-expose and super overdevelop and see what that looks like. One can better see the difference between underexposure and underdevelopment when they are pronounced.

Pieter12 · Apr 3, 2023

Pushing film has been a long-used practice among photojournalists and concert photographers, allowing them to shoot hand-held and without additional lighting. I don't remember when it started, but at some point there was a "speed war" among film manufacturers, and they began marking the box speed at the highest speed they could reasonably eke out of the film with standard developing. Thus films such as Ilford Delta 3200 are really much better rated at 1600.

Alan Edward Klein · Apr 3, 2023

Pieter12 said:
Pushing film has been a long-used practice among photojournalists and concert photographers, allowing them to shoot hand-held and without additional lighting. I don't remember when it started, but at some point there was a "speed war" among film manufacturers, and they began marking the box speed at the highest speed they could reasonably eke out of the film with standard developing. Thus films such as Ilford Delta 3200 are really much better rated at 1600.

It also created a race for big lenses with huge apertures, lots of glass, heavy weight and higher prices. Digital users still buy these but they aren't needed for the most part because of higher ISOs in digital.

Paul Howell · Apr 3, 2023

Pieter12 said:
Pushing film has been a long-used practice among photojournalists and concert photographers, allowing them to shoot hand-held and without additional lighting. I don't remember when it started, but at some point there was a "speed war" among film manufacturers, and they began marking the box speed at the highest speed they could reasonably eke out of the film with standard developing. Thus films such as Ilford Delta 3200 are really much better rated at 1600.

In the 60s and 70 the rage was available light, a reaction to the always flash on in the 50s when 4X5 press cameras with slow lens was the norm. In the 80s newspapers and the wires moved from black and white to color and JP return to always flash. With Af and new shutters that allowed for shutter sync up to 1/350,(Minolta 9) using flash for fill in outdoors at all times was possible.

Pieter12 · Apr 3, 2023

Paul Howell said:
In the 60s and 70 the rage was available light, a reaction to the always flash on in the 50s when 4X5 press cameras with slow lens was the norm. In the 80s newspapers and the wires moved from black and white to color and JP return to always flash. With Af and new shutters that allowed for shutter sync up to 1/350,(Minolta 9) using flash for fill in outdoors at all times was possible.

Still, using flash at a concert was a no-no, even for fill. And higher shutter speeds (therefore higher ISO--of course back then it was ASA) are needed to hand-hold long lenses--though a powerful studio strobe can help with that in certain circumstances. Today's digital cameras with stabilization and insane ISOs have rendered all of that obsolete.

redbandit · Apr 4, 2023

Steven Lee said:
The way I read the OP's question is that exposure index is useless when conveying information about exposure because by itself it's not universal. It depends on one's metering and development. In practice this means that if I take someone's advice of exposing HP5+ at 250 and "copy&paste" it into my workflow, I may end up with a result very different from the person's giving advice.

If that's the case I agree wholeheartedly. I always ignore EI comments for this reason.

Trying to figure out EI discussions on film has always lead me to trouble. It makes no sense...

Without even taking into consideration
-equipment being used
-quality or accuracy of equipment being used

Merely changing the film developer will have such significant impact that it can render running HP5+ at 250 a horridly moot point.

Just running the camera at box iso, and merely a shutter of 1/60 can negate running it at 250... Adding two minutes of development can negate everything done mechanically with the camera.

Hassasin · Apr 4, 2023

The simple answer is it never does if you don't.

It's always the starting point though, then some adjustments are done to match whatever one sees, but messing around with film speed/processing routine based on someone else's experience, instead of trying to find out why yours is not coming out as expected, is not where I would go.

But in general, if film of known quality/storage history does not give you majority of what is expected from given negative in the recommended development routine, the problem is not with film speed used.

Key is not to believe everything that is stated out there. I suppose that might also apply to this post.

Sirius Glass · Apr 4, 2023

redbandit said:
Trying to figure out EI discussions on film has always lead me to trouble. It makes no sense...

Without even taking into consideration
-equipment being used
-quality or accuracy of equipment being used

Merely changing the film developer will have such significant impact that it can render running HP5+ at 250 a horridly moot point.

Just running the camera at box iso, and merely a shutter of 1/60 can negate running it at 250... Adding two minutes of development can negate everything done mechanically with the camera.

If one takes to time to run down all the paths, EI in not needed for modern films, just basic start with the box speed and use a light meters. Then if necessary adjust for getting the shadow details [not all shadow details add to a composition, sometimes basic black is great], and adjust for any filters. Develop normally and life is wonderful.

Paul Howell · Apr 4, 2023

that is not really true at all. It depends on the developer used, looking at Kodak, Foma and ILford datasheets the iso depends on the developer used. Trix and Tmax with Tmax RS developer, D76 and Xtol ISO of 400 is very reasonable, but then Tmax RS vs Tmax developer Tmax developers loses some speed as does Extol at 1:1. Foma 400 is close to 400 with a high energy developers with other developers including Foma's version of Extol loses ISO speed to no better than 200. Old all mechanical cameras, best to test, you are not testing the film but the camera.

xkaes · Apr 4, 2023

Paul Howell said:
that is not really true at all. It depends on the developer used, looking at Kodak, Foma and ILford datasheets the iso depends on the developer used.

And other factors too. Read Richard Henry's book -- CONTROLS IN B&W PHOTOGRAPHY. There is no ONE ISO for a film.

Doremus Scudder · Apr 4, 2023

It takes a given amount of light to produce any density at all on a given film. Less than that and there will be nothing, regardless of the developer you use.

ISO speeds are based on standardized and carefully calibrated exposure and development methods. These methods were decided after extensive testing about which negative characteristics produced the best prints, as determined by thousands of educated print observers.

So, take it for what it's worth. Yes, some developers deliver more, or less, effective film speed because they aren't the standard developer used in the ISO tests. That's great, and the manufacturer's tell you so. Still, I don't know of a developer that makes any film two stops faster; heck, I don't know of one that really makes film a stop faster.

But be aware, underexposing your film means that shadow detail that the standards (and all those print observers) expect won't get recorded on your film. Sure, that pushed and grainy photo of Jimi Hendrix in a dark night club in London with no shadow detail and blocked-up highlights is still a great photograph, but it was a compromise; sacrificing the accepted "ideal" to get some kind of image. Maybe you like that look, so go ahead and underexpose and overdevelop your film, but be aware of what your are doing.

If you want rich portraits with luminous shadows and vibrant but not blocked-up highlights though, you'd better learn how to expose and develop your film. If you're lucky, the manufacturer's recommendations will work just fine for you. If not, you may have to tweak a bit. If you consistently don't have the shadow detail you need, you need to rate your film slower. If your negatives have blocked-up highlights, you need a shorter development time. And vice-versa.

Those are the basics. Sure there is some leeway in the whole process and, sure you can often get a good image from a bad negative, but the laws of physics haven't been repealed, which means there are limits. The whole idea of finding an exposure and development regime that works for you is to first stay within those limits and, only secondarily, to utilize the special characteristics of certain developers and agitation schemes.

Maybe don't bother with the latter till you've mastered the former?

Doremus

Hassasin · Apr 4, 2023

Hm are we're arguing whether film brands have any clue about sensitivity of film they make? Box speed is based on relatively standard testing criteria and then processing data is published. Sure it is purely technical evaluation, often disconnected from real world outcome, or specific scenes. But got to star somewhere, and that is nothing else but the box speed. Doing it any other way is guessing better processing from step one vs. doing it from some later step.

In the end it is going to be likely different from the recommended. But that comes from a lot of factors.

MattKing · Apr 4, 2023

Doremus Scudder said:
So, take it for what it's worth. Yes, some developers deliver more, or less, effective film speed because they aren't the standard developer used in the ISO tests.

As I understand it Doremus, the ISO standard no longer specifies a particular developer, and it is just necessary to specify which developer was used to measure the ISO sensitivity when the film is tested.

xkaes · Apr 4, 2023

Doremus Scudder said:
there is some leeway in the whole process and, sure you can often get a good image from a bad negative, but the laws of physics haven't been repealed, which means there are limits.

Exactly. And since none of us will be exposing and processing our film exactly as to the ISO standard, we need to test our own film and gear and chemicals and paper and likes/dislikes -- and will discover that our personal ISO will be somewhat different than what's on the box.

Maris · Apr 4, 2023

Years ago I'm sitting in the stock room at Star Photographics in Brisbane when a photography sales rep (forget which company) comes in with a box of "magic" developer. He opens the box to show a row of big sealed glass ampoules containing an expensive red liquid called Neofin Rot. He say it delivers a massive increase in film speed. I say "prove it" and hand him a Leica loaded with a short roll of bulk loaded Tri-X. He then whips out a Gossen Lunasix light meter and sets the film speed to 3200 ASA.

Then he declares the film speed gain is genuine and not riding on exposure latitude or forgiving mid tones and highlights. Real shadow detail is the objective and to chase it he takes a meter reading of the darkest thing in the room, a shadow behind a filing cabinet, sets aperture and shutter speed, and makes the exposure. Taking the film away the sales rep has it developed and printed overnight and then comes back the next day with a nice 8x10 showing the stock room with all the tones in place including the dark patch behind the filing cabinet.

Was there a film speed increase? No, not really! The shutter speed and aperture settings obtained by measuring a dark shadow (Zone II) with 3200ASA set on the meter is the same as measuring a grey card (Zone V) with 400ASA set on the meter. Star Photographics did not place a standing order on Neofin Rot for retail sale.

So much of a notional film speed depends on how a light meter is set and used.

Sirius Glass · Apr 4, 2023

Paul Howell said:
that is not really true at all. It depends on the developer used, looking at Kodak, Foma and ILford datasheets the iso depends on the developer used. Trix and Tmax with Tmax RS developer, D76 and Xtol ISO of 400 is very reasonable, but then Tmax RS vs Tmax developer Tmax developers loses some speed as does Extol at 1:1. Foma 400 is close to 400 with a high energy developers with other developers including Foma's version of Extol loses ISO speed to no better than 200. Old all mechanical cameras, best to test, you are not testing the film but the camera.

Sure if only goes off the reservation and ignore the developer's directions, then anything can happen.

Is exposure index and ISO actually relevant

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