Box ISO rate and Real ISO

marciofs · Apr 28, 2014

Hi,

So, I shot and develop a roll of 35mm Fomapan 400 with Rodinal following the data in digitaltrhth.com.
But later on I founded out the real ISO of fomapan 400 is 250 with Rodinal.
So I wonder of the data in digitaltruth.com, dispite it says ISO 400, is indicating the development time for its real ISO which is 250?

I god a good result from development but I usually over expose a bit.

AgX · Apr 28, 2014

The "real" ISO speed with Rodinal would mean applying ISO standards on estimating the film speed of this combo.

Ian Grant · Apr 28, 2014

You really mean your personal EI (exposure index). I don't use the 400 but do use the 100 & 200 both at half the box speed with great results.

Ian

markbarendt · Apr 28, 2014

The ISO rating of a film is done per ISO specs by the manufacturer. Probably not done with Rodinal.

If you follow the manufacture's instructions and use the same developer, agitation, temperature.... then you should find the speed very close to what the manufacturer found.

If you do anything else it's no longer going to match the ISO and the new number is better referred to as EI or exposure index.

Your EI is "personal" and reflects your processes, biases, metering practices, your equipment's vaugarities, the quality of water used, and more.

Finding an EI other than box speed and different than others find, that works good for you for any given combo of equipment and materials, is perfectly normal.

Alex Muir · Apr 28, 2014

I have also wondered about whether or not to use the 'box speed' development time quoted in guides like Digital Truth for the EI I have calculated. I have normally done that and then adjusted the development time, if necessary, for future films. I think the quoted time for a particular film/dev combination at 'box speed' generally comes from the manufacturer of the film or developer.
If you got good results with the method you tried, I would stick with that speed and time.
Alex

Gerald C Koch · Apr 28, 2014

Usually a film manufacturer will give developing times and film speeds for a variety of developers. The more common developer information is usually included as an insert or printed on the box. Don't use Foma film so this may not be the case for them. Developer manufacturers provide similar information. I usually take information given by third-party sites with a certain amount of scepticism.

marciofs · Apr 28, 2014

I am saying that because wherever review I find in the internet they say Fomapan 400 is actually ISO (or better perfomaced) at 250 to 320 depending on the developer (250 for Rodinal). And I have read many posts complaining about issues with this film exposure and replies explaining it is because 400 is not the real ISO.

After reading that (in different pages) I was surprised I got a good exposure. And I was wondering if the data in digital truth is actually adapted to develop it at ISO 250, or if it was because I am used to over expose a bit so I just got luck.

This is a example of what I got: http://www.marciofaustino.com/uploads/1/6/4/6/16464874/9508865_orig.jpg

Bill Burk · Apr 28, 2014

Possibly your shutter is "slow" which allows you to get good results using EI 400 settings, even if processing in Rodinal might give you an actual film speed closer to 250.

marciofs · Apr 28, 2014

I will try with an other camera then..

Xmas · Apr 28, 2014

marciofs said:
I am saying that because wherever review I find in the internet they say Fomapan 400 is actually ISO (or better perfomaced) at 250 to 320 depending on the developer (250 for Rodinal). And I have read many posts complaining about issues with this film exposure and replies explaining it is because 400 is not the real ISO.

After reading that (in different pages) I was surprised I got a good exposure. And I was wondering if the data in digital truth is actually adapted to develop it at ISO 250, or if it was because I am used to over expose a bit so I just got luck.

This is a example of what I got: http://www.marciofaustino.com/uploads/1/6/4/6/16464874/9508865_orig.jpg

The real ISO is in the manufacturers data sheet for Formapan 400, the box speed in marketing hype to a degree.
The Formapan 100 data sheet also seems accurate, not tried Formapan 200 much.

Forma have provided the contrast, fog and ISO dependency for time and temp for three developers.

google
formapan 400 datasheet

Then you need an adjustment for your developer, meter/shutter and metering technique.
Digital truth is closer to 'Analogue Porkies'

Rodinal @ 20C 1+100 stand will be in the 250-320 range with low contrast, but you may not like the rendering, I set my Weston to 250. Pour in the Rodinal invert a few times and set the kitchen timer for 60 minutes. Id also temper the following solutions to 1C, cause the Forma is not as prehardened as Kodak or Ilford film.

Most of my shooting is high contrast.

Noel

TimFox · Apr 28, 2014

The actual ISO speed (formerly ASA) is a property of the film only. If you go to the actual ISO specification document, the number is based on exposure at the "toe" of a negative film, where it first starts to show density above the base level. The development details will affect strongly the slope of the curve above the toe, and therefore the exposure required to reach the standard 18% density grey level. Still the best description of how to rate film speed for specific applications can be found in Ansel Adams works on the Zone System.

gone · Apr 28, 2014

With that film, anything is possible. I was shooting Arista EDU 100 at the box speed and getting terrible results. Found out later that the film is actually Fomapan, and that I needed to shoot it at ISO 50. When I did that it looked much, much better. Tri-X is another film that seems to not be rated correctly by the maker, as pretty much everyone will tell you that it is really a 200-250 ISO film, and my tests say just that. Of course, it being Tri-X, you can shoot it all over the place and get great results.

The maker of the film gives you what they consider to be the correct ISO, but what developer you use, how you meter the shots, how you print the negs, etc will determine YOUR optimal ISO. There really is no other way to do it except to shoot a test roll. What I consider to be the optimal ISO is not what someone else agrees with, nor should it be.

I shot a roll of Tri-X yesterday w/ my FT QL using a yellow filter, and metered it w/ a hand held meter at ISO 125. Then developed it normally. The shots came out perfect. On my NiKon N8008s and using the same yellow filter, I set the camera's TTL meter to ISO 320. These values came about by shooting test rolls and noting the results, and they differ from one camera to another. A dull, cloudy day will also require something different from a bright sunny day. Sometimes I shoot Tri-X at ISO 50 w/ a yellow filter because I personally like that sort of look sometimes. So it just depends on what you want on the finished end. Everything is done to suit my eyes, not anyone else.

gone · Apr 28, 2014

Well, too many angels on the point of this pin. Just shoot a test roll or two under controlled conditions using different ISO settings, take careful notes, develop consistently, and you're there.

marciofs · Apr 28, 2014

momus said:
Well, too many angels on the point of this pin. Just shoot a test roll or two under controlled conditions using different ISO settings, take careful notes, develop consistently, and you're there.

Yeah I will do that just for curiosity, because I like what I got anyway.

c6h6o3 · Apr 29, 2014

momus said:
Well, too many angels on the point of this pin. Just shoot a test roll or two under controlled conditions using different ISO settings, take careful notes, develop consistently, and you're there.

Amen. The correct film speed is what gives you sufficient shadow detail. I rate my HP5+ at 100.

cliveh · Apr 29, 2014

Shoot at box speed and develop to your own requirements.

markbarendt · Apr 29, 2014

c6h6o3 said:
Amen. The correct film speed is what gives you sufficient shadow detail. I rate my HP5+ at 100.

Just for giggles can we have some context for that rating.

Developer?
In comparison to manufacture's specs are you using minus development, stand...?
Are you "zoning"? If so details?
Subject matter?
Spot meter or incident?
Are you using old Petzvals or newish multicoated lenses?
Is part of that rating a safety factor?

My intent here is not to put you on the spot c6h6o3, but to help marciofs understand how you made your choice and at least some of considerations that go into the decision.

markbarendt · Apr 29, 2014

Michael R 1974 said:
His handle is the molecular formula for Pyrogallol. I'm gonna guess ABC. That's one stop. Zones, that's another 2/3 stop. Close enough.

Sirius Glass · Apr 29, 2014

cliveh said:
Shoot at box speed and develop to your own requirements.

+1

Doremus Scudder · Apr 30, 2014

Some here still haven't figured out that ISO testing is based on one particular development regime using a standard developer and a contrast index that likely does not relate to either of those things for most of us. ISO speed is similar to EPA mileage estimates for new cars: a good basis of comparison but your mileage may vary.

The issue is further clouded by the practice of some manufacturers to label the film at a different "Box Speed" than the ISO speed. I find this deceptive and poor marketing in the long-term, since many will simply have poor results since their expectations have been falsely raised.

Personal EI is based on the amount of shadow detail that each individual photographer finds necessary/acceptable for the kind of work s/he is doing. This includes personal and artistic decisions regarding developer, contrast, etc., etc. This includes all kinds of "pushing" and Zone Systems, etc., etc.

Kodak's old recommendations still hold: If your negatives have too little shadow detail, increase the effective film speed. Too much shadow detail (i.e., more than you need)? You are overexposing and can get away with less, thus giving you faster shutter speeds/smaller apertures.

Overall contrast is similar: Consistently too contrasty? Reduce development time. To flat? Increase. Plus, learn to base development on scene contrast.

Best,

Doremus

Ian Grant · Apr 30, 2014

Doremus Scudder said:
Kodak's old recommendations still hold: If your negatives have too little shadow detail, increase the effective film speed. Too much shadow detail (i.e., more than you need)? You are overexposing and can get away with less, thus giving you faster shutter speeds/smaller apertures.

Overall contrast is similar: Consistently too contrasty? Reduce development time. To flat? Increase. Plus, learn to base development on scene contrast.

Best,

Doremus

Other way round you mean increase the exposure by decreasing the Effective film speed (EI - exposure index) - to give better shadow detail.

Ian

Rick Jones · Apr 30, 2014

The ISO for many films are calculated at a contrast index in the 60's. I print with a condenser enlarger and prefer a negative with a much lower CI. As development times are shortened shadow detail can disappear very quickly which I offset with a lower EI. Testing for ISO at a CI of .45 would make film manufacturers very unhappy. The ISO 400 calculated at a CI of .62 would not hold up at the lower CI. Would you prefer to market the same film at 400 or 250 if you were a manufacturer?

Jaf-Photo · Apr 30, 2014

The digital truth timings should take account of the film/developer combo to get a normal exposure for the nominal ISO setting.

I haven't used Rodinal in a while but supposedly, you can lose up to a stop of film speed with limited pushability. Therefore some people overexpose the film to compensate.

personally, i rely more on manufacturer data sheets, to set a starting point for times. Then you have to dial it in to your shooting style and preferences.

markbarendt · Apr 30, 2014

Rick Jones said:
The ISO for many films are calculated at a contrast index in the 60's. I print with a condenser enlarger and prefer a negative with a much lower CI. As development times are shortened shadow detail can disappear very quickly which I offset with a lower EI. Testing for ISO at a CI of .45 would make film manufacturers very unhappy. The ISO 400 calculated at a CI of .62 would not hold up at the lower CI. Would you prefer to market the same film at 400 or 250 if you were a manufacturer?

Being able to choose a personal CI and EI is a wonderful thing. I develop and shoot for the specific CI and EI I like too.

The ISO number though is different. The ISO standard is a very specific and measurable and manufactures have to disclose it. Marketing and using a film in the real world is a different animal yet again.

For example this from the Ilford Delta 3200 data sheet:

DELTA 3200 Professional has an ISO speed rating of ISO 1000/31º (1000ASA, 31DIN) to daylight. The ISO speed rating was measured using ILFORD ID-11 developer at 20°C/68ºF with intermittent agitation in a spiral tank.

It should be noted that the exposure index (EI) range recommended for DELTA 3200 Professional is based on a practical evaluation of film speed and is not based on foot speed, as is the ISO standard.

markbarendt · Apr 30, 2014

I should have mentioned that my normal/target EI is typically the ISO speed.

I do agree Michael. Several of the biggest leaps forward in my skills and understanding came from settling on using box speed to shoot, standardizing on a "normal" development regime, and using incident metering as my gold standard.

Various things drove me this direction; the standardization and latitude C-41 brought to the table, using roll film for most everything, learning that the ISO standard had it's roots in 1,000's of people judging real printed results, figuring out that Kodak, Ilford, and Fuji have really done their homework...

When I started experimenting with the practical aspects of shooting and standardizing my B&W process based on principles C-41 taught me, I was amazed. Chasing off Ansel's ghost and unlearning the "need" to adjust development for every EI change was another major step forward. Long live VC paper.

Box ISO rate and Real ISO

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