Understanding Deviation from Box Speed

Hello all,

Am I correct in thinking that when someone says the likes of 'Fomapan 400 Action is really at best a 200 ISO film' and Kodak says 'Developing TMax 400 in HC-110 the film should be rated at 320 ISO', what they are really saying equates to 'shoot at box speed but overexpose by a stop or so and develop at box-speed figures'?

As opposed to pulling or pushing a film under or over box-speed and developing shorter / longer according to the amount of push / pull required?

I've never consciously adjusted my light-meter setting and always shot at box-speed (apart from pushing Tri-X once or twice and developing accordingly) but I've found that on my Baldix folding cameras I get better dynamic range on Foma 400 than I do on my Yashica D, and I suspect it's because the folder shutter speeds are slower than they say, effectively over-exposing the film. Which leads me to the original question.
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Kind Regds,

R.

First, a few words about "box speed". When explicitly stating ISO at the box speed, the manufacturer declares that film X was found that it conforms to the ISO criteria for film speed with a developer that isn't disclosed. It could be any developer out there. This also implies that it won't necessarily reach this ISO speed in any developer, for some it will be lower. If the manufacturer doesn't use the "ISO" word, then it means that you'll get ok to ok-ish results at this exposure index. Real film speed, by ISO criteria, would be lower. TMax P3200 and Delta 3200 are not true 3200 film, but ISO 1000 to 1250 or thereabouts.

Fomapan 400 is not a 400 ISO film in any developer. It's a 200 to perhaps 250 ISO film, depending on developer used. Likewise, if Kodak say that TMax 400 should be rated at 320 if developed in HC110 they mean that it really is an ISO 320 film in HC110.

Pushing and pulling have nothing to do with up/downrating film. It is push/pull processing. You push processed your Tri-X, because you uprated it (and underexposed it). If you hadn't push processed it, then you'd get hopelessly thin negatives. So yes, if you shoot Fomapan 400 at EI 400, then you basically underexpose it and perhaps the slow shutter of your folder improves things.

Anon Ymous said:

Pushing and pulling have nothing to do with up/downrating film. It is push/pull processing. You push processed your Tri-X, because you uprated it (and underexposed it). If you hadn't push processed it, then you'd get hopelessly thin negatives. So yes, if you shoot Fomapan 400 at EI 400, then you basically underexpose it and perhaps the slow shutter of your folder improves things.

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Thanks for that, Anon Ymous. Yes, the likes of Ilford film datasheets suggest a range of processing times depending on what speed you choose your film to be rated (It just happens to be labelled as ISO400, say, but is capable of push-pull processing to the degree stipulated on the datasheet) So what advantage is there in marketing Foma as ISO400 when it patently isn't? Might it be that acceptable, but not the best results are obtainable if treated as found using the developer recommendations as written inside the box, so it can be sold as 'action' film? And is there a difference between Foma 200 and Foma 400 in that case?

russell_w_b said:

And is there a difference between Foma 200 and Foma 400 in that case?

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Foma 200 is more like ISO50-100.. so they just bumped up the rating for the entire range.

eatfrog said:

Foma 200 is more like ISO50-100.. so they just bumped up the rating for the entire range.

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It's also a different kind of film ("hexagonal core/shell tabular silver halide grains", to quote Foma's website).

@russell_w_b As others have said, none of their films reach their box speed in ISO terms, they're half to a full stop slower. It's simply a matter of competing in a market and making your products look better. Their films may otherwise be ok and their prices are certainly nice, so it's up to you to decide...

The reaction of the emulsion with the development chemicals varies with the make of the emulsion (film) and the chemicals used. The true speed in a certain developer is the one that will give you a density over base and fog of .03 to .06 for 35mm and .1 to .15 for roll film. So, you test your film in the developer of your preference and decide how much exposure is needed along with standard development times to get that. That will give you the true speed of your film in your developer.
Push and pull are different and apply to your preferences to get to the desired properties (negative, tonality, etc) of the final image on the negative.

russell_w_b said:

Hello all,

Am I correct in thinking that when someone says the likes of 'Fomapan 400 Action is really at best a 200 ISO film' and Kodak says 'Developing TMax 400 in HC-110 the film should be rated at 320 ISO', what they are really saying equates to 'shoot at box speed but overexpose by a stop or so and develop at box-speed figures'?

As opposed to pulling or pushing a film under or over box-speed and developing shorter / longer according to the amount of push / pull required?

I've never consciously adjusted my light-meter setting and always shot at box-speed (apart from pushing Tri-X once or twice and developing accordingly) but I've found that on my Baldix folding cameras I get better dynamic range on Foma 400 than I do on my Yashica D, and I suspect it's because the folder shutter speeds are slower than they say, effectively over-exposing the film. Which leads me to the original question.
--

Kind Regds,

R.

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hey russell
box speed is determined in a lab. and from what i understand is, like development times, a starting point.
when i shoot i do not have the same camera and meter and situation as the lab that determined the film speed, and when i process my film i do not have the same development situation as the lab that determined the times ...
so i do a simple test ( shoot a couple of rolls and bracket expose, and bracket develop and pick what my speed and development situation will be ).. people get so hung up on this stuff. what they should actually put
on the box is ISO 400, process in HC110 dilution B 7.75mins. YMMV... and if 400 and 7.75 works that's great, if 100 and 8 minutes works, great cause it really is a personal taste thing

have fun!
john

I determine the speed and appropriate development time of a film with a densitometer, but you don't have to get that technical with it. As John said, shoot a typical scene bracketing your exposure for different film speeds, then develop for time listed in the MDC. Print/scan the negs and see which you prefer. Adjust from there.

This comes from back in the day when photographers had densitometers and measured the amount of exposure it took to achieve minimum useable density. In Zone system terms it is called Zone 1. Every film I have ever tested needed to be rated a stop slower than the box said in order to achieve zone 1.

jnantz said:

'... process in HC110 dilution B 7.75mins. YMMV... and if 400 and 7.75 works that's great, if 100 and 8 minutes works, great cause it really is a personal taste thing...'

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Thanks, jnantz. Seems like advertised 'box speeds' are of the same validity as advertised womens' clothes sizes. I've seen various people rate FP4+ at 80 ISO instead of 125 ISO, etc... It is very subjective and so far I have been happy with my results. If it wasn't for the discrepancy in shutter speeds I would probably have not noticed a difference and accepted the 'thinner' Foma 400 negatives as shot on my Yashica D (with its more accurate shutter) as the norm.

I get it being subjective, and I daresay there are scientific ways of establishing values with densitometers, etc... But I don't have any of that. I tend to put the neg on a sheet of newsprint and if I can just see the newsprint through the darkest bit of the neg, I reckon it's OK. I don't have a means of wet printing - yet (I've done this in the past but thirty years ago) - but I scan (or digitise with a camera) and adjust white and black points according to the histogram I get. The slightly over-exposed 'juicier' negs give me a greater histogram range. I have 15 working film cameras and I'll bet all the shutter speeds are slightly different!

jnantz said:

have fun!

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Oh, I do...

zanxion72 said:

The true speed in a certain developer is the one that will give you a density over base and fog of .03 to .06 for 35mm and .1 to .15 for roll film.

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While this is a reasonably useful approach to rating the film speed, it is closer to a Zone system approach than an ISO speed standard approach.
The current ISO speed standard is as much related to contrast as it is density. Historically, the ASA/ISO speed standard was pegged to a particular developer. Now it is pegged to a particular contrast.
My sense is that the Foma films achieve less Zone 1 density when they reach the ISO contrast, so those who use Zone system approaches to measuring speed find them slower.
If you focus on shadow details - as a lot of darkroom printers do - choose an EI that gives you the shadow detail you want, and a development time that gives you good mid-tone and highlight contrast and detail. That is essentially a Zone system approach. For most films, because of the difference in the definitions themselves, expect an EI that is about 2/3 of a stop less than the ISO speed of the film.
If you are most interested on how straight prints (like machine prints from a commercial lab) will appear to a viewer, metering using the ISO speed and developing to a standard contrast will tend to give you the best looking prints. That is because ISO speed plus standard development has been designed to maximize the quality of mid-tone and highlight rendition, and that is what viewers (other than some darkroom printers) value most highly.

Anon Ymous said:

@russell_w_b As others have said, none of their films reach their box speed in ISO terms, they're half to a full stop slower. It's simply a matter of competing in a market and making your products look better. ...

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True but you could of course ascribe similar motives to Kodak and Ilford with their 3200 films

pentaxuser

pentaxuser said:

True but you could of course ascribe similar motives to Kodak and Ilford with their 3200 films

pentaxuser

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Yes, although one would argue that these films were specifically formulated to be push processed. Anyway, to be fair to Foma, it is Fomapan 400 that is the most iffy when it comes to film speed. Their datasheets are also very good and give information about what their actual speed is in different developers. According to them, Fomadon Excel (Xtol clone) and Microphen are the best choices. Fomapan 100 actually reaches ISO100 in them, while the 200 variant gets about a third less. IIRC, user Adrian Bacon confirmed this for Fomapan 200 in replenished Xtol.

russell_w_b said:

Oh, I do...

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good cause if you don't ( to me at least ) its a waste of effort and time..

I shoot at EI usually 2/3rds to a stop slower depending on which film I'm using. That gives better shadow separation. The only time I ever used actual ISO of a film was when I was first starting out and had no clue about sensitometry.

Another film speed thread.

Two points of merit.

1) As one can see in this table (only half of the info shown) there are many film speed rating systems. Each with a different goal

2) The ISO system's goal is thinnest negative which produces the first excellent print.
a) ISO is based on ASA
b) ASA is based on fractional gradient
c) fractional gradient is based on a panel of observes rating negatives obtained by photographing some 8x10 transparencies of some 'pictorial' scenes.
d) A photograph of Willow Pond, Rochester, NY was one of the transparencies.
e) So ISO speeds are good for pictures of ponds.

The key is manufactures recommended starting point. Meters may or not be accurate, shutters may or not be accurate, and film speed is also dependent on the developer, temperature, and time, method of agitation or lack there of. Second, most makers posted the ISO at the somewhat forgiving side , on over exposure end. The thinking was although the thinness negative that yields printable shadows and highlights is the ideal, the thought that a somewhat overexposed negative is more desirable than a negative that is too thin, if it's there it is not there. Verichrome (sp?) pan was rated at ASA/ISO 100, but as a film marketed to folks who used box and other simple cameras, when I tested Verichrome I found that I could shoot at 200 to 400 depending on the camera. With a modern camera, late model SLR with matrix metering, electronic shutter I've found that box speed is pretty close, the exception is Foma 400 which I shoot at 320. But with older (some cameras now going on 50 years) the ISO is all over the place, I put tape of the back of each body with my personal E.I for that camera to keep track. Not having a densitometers I use a ring around to figure what ISO works best for each camera and developer. When thinking about Zone I generally look for shadow detail in Zone III. Maybe I should get a densitometer.

Russell,

As you can see, you can get as technical as you want with measuring and quantifying all this stuff about film speed and development time. The manufacturers rate film and determine processing times using precision equipment and following strict procedures, which aren't likely to match what we have. We simply need to be aware that our equipment and processing will be different from those used by the manufacturers and be ready to make adjustments accordingly.

A more practical approach, IM-HO, is to simply follow Kodak's advice from years past:

If you consistently have too little shadow detail, rate your film slower. When in doubt, err on the side of overexposure. (It's rare that we have too much shadow detail at box speed.)
If your negatives are consistently too contrasty, develop for a shorter time, and vice-versa.

Also, be aware that how you rate your film speed (E.I. = Exposure Index, which is personal as opposed to ISO, which is determined according to international norms) affects the amount of shadow detail you end up with. Development time, which is a separate thing, affects the overall contrast of the negative; i.e., how much separation there will be between tones of different exposures. Less development time = less separation and vice-versa. (I mention this because you seem to be conflating film speed and development.)

"Pushing" is a vague term that basically means underexposing on purpose (for whatever reason; low light, etc.) and then overdeveloping to compensate somewhat. The resulting negatives lack shadow detail but have the highlights in the right place.

"Pulling" is overexposing and underdeveloping in comparison to the manufacturers recommendations. It is often just a compensation; many of us find that "box speed" is too optimistic (or we like more shadow detail) and that most recommended development times are too long.

If you've followed this thinking this far, you can see that, ideally, there's a best exposure and development time for every situation. Indeed, systems like the Zone System have been developed so that photographers can expose an individual negative based on how they want shadows rendered in any particular scene and then develop it based on how much overall contrast they want, based on what the lighting range was in that particular scene. This works well with sheet film and a spot meter, but not so well with roll film and an in-camera averaging meter. With the latter, we usually find a general E.I. and development time that gives us results that allow scenes of extreme low contrast or high contrast to still be printed well.

Hope this helps,

Doremus

pentaxuser said:

True but you could of course ascribe similar motives to Kodak and Ilford with their 3200 films

pentaxuser

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They never claim those films are ISO 3200. Their datasheets clearly state the real ISO speed.

Recently started shooting color, so I shot two rolls of Fuji 400H at box speed. Much to my amazement both rolls came back from processing by a pro lab 1-stop underexposed. I was shooting in strong daylight using my normal metering. Very disappointing. This has not happened with Portra 400. On further study I see that over exposing one stop for 400H is widely suggested , so I'll try that next.

Arthurwg said:

Recently started shooting color, so I shot two rolls of Fuji 400H at box speed. Much to my amazement both rolls came back from processing by a pro lab 1-stop underexposed. I was shooting in strong daylight using my normal metering. Very disappointing. This has not happened with Portra 400. On further study I see that over exposing one stop for 400H is widely suggested , so I'll try that next.

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First step: Get your light meter calibrated. Do not wing it.

Good idea to get the meter calibrated. Been meaning to do that. . Who is that guy in CA that specializes in meter calibration?

Quality Light Metric.

Arthurwg said:

Good idea to get the meter calibrated. Been meaning to do that. . Who is that guy in CA that specializes in meter calibration?

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Send the camera or meter in. He will call you with his estimate. He typically charged me $88US per sensor plus shipping. He is the go to guy for Hollywood Studios. My Hasselblad PME had to go to Hasselblad New Jersey.

George had calibrated my Pentax Digital Spot Meter and he told me that it was accurate down to a certain point. Below that point the drift was ... . A year later I could not find my notes so I called him and asked him to look up the information. He told me to just bring it over [a 15 minute drive]. The next day he called me to pick it up. He had recalibrated it to be accurate for the whole range and by the way ====> no charge.

George Milton
Quality Light Metric
7095 Hollywood Blvd
Los Angeles, CA 90028

(323) 467-2265
9 AM to 6 PM Monday through Friday