Understanding Deviation from Box Speed

[MattKing]

George Milton was pleasant to deal with on the telephone as well.

 

[russell_w_b]

Hope this helps,

Doremus: it certainly does. Many thanks for a useful and interesting post - and thanks to everyone else who replied too; appreciated.

I know about pushing and pulling; that a film manufacturer specifies the range of EV over which a film may produce acceptable results, given compromise to grain, etc..., and that developing time is adjusted accordingly; that some film may be pushed and pulled further than others.

But hitherto I've tended to take 'box speed' as gospel and exposed accordingly. Lately I've been paying more attention to what is effectively a deliberate overexposure giving to me, more dynamic pictures and this chimes with my experience of images shot on a camera with a sluggish shutter speed against one which is near enough right: a sort of 'auto-compensation' as it were. I shall bear all this in mind when shooting with my different cameras.

Since starting te develop film I have standardised on my agitation (four in the first ten seconds then four in the first ten seconds of every minute, the 'Ilford' way. I've done maybe three or four stand-developed films and one or two 'Rodinal'-suggested agitations of a minute followed by one every thirty secs, but I can't really see a difference with this as I'm a 'gentle agitator'. I use HC-110 B or E and shall keep on with this during the lockdown but I generally use ID-11, of which I've five litres to make up. I'll wait until I'm in a position to use it all first! I've used Rodinal too and I like them all: HC110 is convenient and I think it works great with Ilford film. But it's all subjective.
--

R.

 

[Bill Burk]

I just read some of Zamia-White-Lorenz New Zone System Manual. I used to hate it and still have a hard time unpacking it. But there are gems in there (bi-directional exposure and developing). What I just saw clearly shows that the ISO/ASA speed is effectively N+1 in Zone System terms.

How does that boil down? Most people develop for N normal in Zone System terms.

The shorter development time doesn’t reach ASA parameters, so they are not getting the film’s full speed.

If you don’t think you are getting the film’s full speed try to develop longer.

I calibrate my entire system on the assumption that fresh Kodak TMAX-400 actually is 400 when developed to the ASA parameters in D-76 1:1

Then I shoot it at 250 because I like to.

 

[Doremus Scudder]

... If you don’t think you are getting the film’s full speed try to develop longer. ...

...or expose more fully if you like the contrast your getting from your present development time.

Doremus

 

[ic-racer]

Anyone with a local pond can duplicate the work of Loyd and Jones on their own Film speed is all based on "first acceptable print" and anyone with a darkroom can figure that out with some trial and error. (of course if you don't have years of darkroom experience making excellent prints, you won't be able to do this).

 

[john_s]

......... What I just saw clearly shows that the ISO/ASA speed is effectively N+1 in Zone System terms.

How does that boil down? Most people develop for N normal in Zone System terms.

The shorter development time doesn’t reach ASA parameters, so they are not getting the film’s full speed.

.......

This is expressed brilliantly clearly.

 

[grat]

I realize this is supposed to be the analog only forum, but as someone who scans their negatives instead of printing them, I find that "Arista EDU Ultra 400", aka "Fomapan 400 Action", works best for me at box speed. So does 400H.

My light meter has not been calibrated per se, but it has been tested against my (presumably) calibrated DSLR, and produces equivalent readings, so all three seem to be in agreement on what "ISO 400" means.

 

[Vaughn]

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.

When I first started to photograph in the redwoods with the 4x5, I metered with a Luna Pro at box speed (not that I knew the term in '77) and exposed one sheet there and gave a second sheet one more stop exposure. Most of the time the second negative was the good one, so I always gave an extra stop after that...did not know I was cutting the box speed in half. I was still was having trouble with some shadow detail and eventually learned about reciprosity failure...and perhaps someday I'll learn how to spell it.

But for most uncomplicated photographic work, landscapes, for examples, expose a few sheets of film (or a roll), keep notes, and it should be obvious to one's eye on the light table and in the print what the proper exposure was...and from that, one's actual film speed, or bloody close enough for general work. Not rocket science unless one wants it to be.

 

[voceumana]

When I ran speed tests on Kodak Tri-X Pro (ISO 320) I got a speed of 320; for Verichrome Pan (ISO 125), I got 160. For Ilford FP4+, I got 100. My meter was a Pentax Digital spot modified by Zone VI, and my shutters were modern. Running your own film speed tests adjusts for your meter variances (and any calibration factor built into the meter's design--i.e., what "average grey" the manufacturer thought was average), shutter speed variations, and developing process.

FYI, Kodak never has claimed TMax P3200 was an ISO 3200 film--the "P" in its name indicates it is pushed to get to 3200.

As always, and thus the whole purpose of this thread, "your results may vary". ISO standards are designed for repeatable results, and thus use a developer and developing techniques that don't fit what photographers use--but the results are repeatable and reliable, and that is essential for any standard.

 

[Sirius Glass]

I shoot box speed without problems. If I want more shadow details, I use a spot meter and put the target into the appropriate Zone.

 

[Maris]

I work backwards by doing stepped exposures of a fairly complex "standard scene" in sunny weather just outside my door. Then I go immediately to the darkroom and develop that film. Ten minutes later I know for sure the exposure I need to give to get the negative I want.

Then I go back to that scene before the light changes and deploy my light meter in the usual way. I adjust the meter's ISO setting so that the meter now tells me the exposure I already know is correct. Meter calibration is complete for that meter, that scene, that light, that film, and that filter (if any).

Most black and white negative films seem to run 2/3 to 1 stop slower than box speed. The "backwards" method also works well where there is no ISO information; infrared films behind odd filters, orthochromatic behind cyan, etc, etc

 

[RalphLambrecht]

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

+1;this is really all one needs tp know and do.

 

[Adrian Bacon]

Adrian Bacon confirmed this for Fomapan 200 in replenished Xtol.

IiRC I posted my Foma times and graphs in the resources section

 

[Anon Ymous]

IiRC I posted my Foma times and graphs in the resources section

https://www.photrio.com/forum/resou...plenished-xtol-for-8-45-at-24c-in-a-jobo.423/

While we are at it, have you tried Delta 100 in Xtol?

 

[Adrian Bacon]

https://www.photrio.com/forum/resou...plenished-xtol-for-8-45-at-24c-in-a-jobo.423/

While we are at it, have you tried Delta 100 in Xtol?

yes. 7:30 at 24C, EI 100. Zone 5 came out to 0.86, zone 1 was 0.12. Replenished xtol, JOBO agitation.

 

[Anon Ymous]

yes. 7:30 at 24C, EI 100. Zone 5 came out to 0.86, zone 1 was 0.12.

Thanks!

 

[Adrian Bacon]

Thanks!

I thought I posted in the resources. I might have brain farted getting it posted.

 

[Anon Ymous]

I thought I posted in the resources. I might have brain farted getting it posted.

Very likely so.

 

[Adrian Bacon]

Very likely so.

that what happens when you start getting old. I’m not *that* old, but I’m def. not a young spring chicken anymore.

 

[Craig75]

Anyone with a local pond can duplicate the work of Loyd and Jones on their own Film speed is all based on "first acceptable print" and anyone with a darkroom can figure that out with some trial and error. (of course if you don't have years of darkroom experience making excellent prints, you won't be able to do this).

This is the key.

 

[alanrockwood]

Anyone with a local pond can duplicate the work of Loyd and Jones on their own Film speed is all based on "first acceptable print" and anyone with a darkroom can figure that out with some trial and error. (of course if you don't have years of darkroom experience making excellent prints, you won't be able to do this).

If I'm not mistaken I think that conceptually film speed was based on "first excellent print" rather than "first acceptable print." It's a bit of a fine point, but I think those are slightly different criteria with the second being a higher standard than the first.

Another standard could be "best possible print" which would be a higher standard still.

Even defining the "best possible" standard might be problematical. For example, given two identical films in different formats, a large format negative may give the best possible print under different exposure/development conditions than a 35mm negative. The large format film is less grain-sensitive in the print state and might give its best possible print for a denser negative, i.e. higher exposure, i.e. lower film speed rating, whereas a 35mm negative, which is more grain-sensitive in the print stage, could do better with a thinner negative, i.e. lower exposure, i.e. higher film speed rating.

One could also make the argument that the best possible exposure would occur near the midpoint of the characteristic curve, which could be defined either as the midpoint of the (more or less) straight-line portion of the curve or alternatively at a density about near the midpoint of the density range for the film.

 

[Juan Valdenebro]

Deviation from box speed just doesn't exist... Film works the way it works: different EIs and different development times should be used for different scenes' contrast.
Box speed is a compromise, just a middle point that doesn't really matter for all types of light.

 

[Bill Burk]

This is expressed brilliantly clearly.

Thanks. This amounts to 1/3 stop, significant but not dramatic.

 

[john_s]

Thanks. This amounts to 1/3 stop, significant but not dramatic.

It seems a bit more than 1/3 of a stop for me, but there are all sorts of confounding variables (metering technique, enlarger light sources, etc).

 

[Bill Burk]

It seems a bit more than 1/3 of a stop for me, but there are all sorts of confounding variables (metering technique, enlarger light sources, etc).

The other 2/3 stop are accounted for in the difference between Zone System’s “stop down four stops from V to I” versus the standard “10x” (1.0 Log E, 3 1/3 stops) from metered point to 0.1 above B+F.