Reciprocity of Foma 200 and Multigrade IV

[EASmithV]

I've heard that Foma 200 has awful reciprocity characteristics. I'll just give an extra stop for anything over 1 second?

And does Multigrade IV even have a reciprocity failure? It seems fairly linear.

Am I making any sense? It's quite likely my brain is frieed today...

 

[Freakscene]

The technical data sheet at: http://www.foma.cz/upload/foma/prilohy/F_pan_200_en.pdf has a table for reciprocity "Schwarzchild effect". At 1s indicated, you need to open up 1.5 stops, at 10s you need to open 3 stops and at 100s you need to open 4 stops.

B&W papers have reciprocity failure (all silver based photo materials do) but you rarely use exposures long enough to see its effects. It is a problem with Ilfochrome/Cibachrome because it causes colour crossovers.

Marty

 

[EASmithV]

Good lord, Is the reciprocity for the Foma 200 really that bad? I heard tell that the manufacturers recommendations for reciprocity were a bit overzealous.

 

[Ian Grant]

I did some practical test and found the reciprocity was nothing like as bad as the datasheet. This is what I wrote in a previous post

"At 1 second it only only needed around half a stop (recommendation is 1.5 stops) and at lower light levels 10 seconds it was about a stop (not the 3 stops recommended). These test were made in poor daylight 1 second @ f8 100 EI and very low interior lighting 10 seconds @ f8. These are the conditions the film will be used in.

Still need to test how the film behaves with nigh shots, but it seems to be only a little worse than HP5 / Tri-X for reciprocity failure."


Since then I've shot some low light scenes using those factors with no problems, but it's best to do your own tests. Just bracket & make good notes.

Ian

 

[Philippe Grunchec]

Ian, did you also test the Foma 100?

 

[Ian Grant]

I haven't Philippe, but I guess I could take a couple of shots in the evening, today or tomorrow and see if it's similar as I have Fomapan 100 in my Yashicamat at the moment.

So I'll tell you in a day or so.

Ian

 

[Philippe Grunchec]

Great! Thank you so much.

 

[EASmithV]

Questions about Foma 200 reciprocity

I looked at the Foma datasheet, and to be honest, It really makes no sense to me.

Can someone tell me some more detailed information? Does anyone know the equation which describes the rate of reciprocity for this film?

 

[Nikanon]

it basically means anything between 1/2 second and 1/1000 dosent need correcting, its factorial in the way it is corrected, like 1 second has 3x factor, so you take the equation 2 to the power of x = your factor, so a factor of 3 equals 2 to the power of 1.5 roughly, or like 2 to the power of 2 is 4, so a factor of 4x is corrected by 2 stops, so when your exposure is about 100 seconds your stop change is about 4.2 stops because 2 to the power of 4.2 is roughly 18 or 18x

 

[Ian Grant]

Philippe. I haven't forgotten, there was only one frame left in the camera and I didn't want to use a complete roll of film doing some quick tests.

Ian

 

[EASmithV]

Maybe (probably) I'm just thick tonight, but I fail to see how that last one made any sense.
Can you put that into a simple equation?

 

[EASmithV]

In another thread I mentioned doing some basic practical tests, EASmith you started that thread too !!!

Ian

Jeez, I must really be thick tonight... Let me see if I can dig it up...

 

[David A. Goldfarb]

Threads merged.

 

[EASmithV]

Thanks for correcting my snafu David... :rolleyes:

Ian, assuming that the reciprocity is in fact as bad as the manufacturer says when using tungsten lighting, I'm trying to get an equation that I can easily chart on something like a graphing calculator for a quick reference. What is really driving me up the wall is the fact that I can't seem to wrap my brain around any of the numbers.

In your earlier post you said you were rating the film at EI 100. Was that with adjusted dev time, or were you already overexposing a stop?

 

[Ian Grant]

You need to go out and use a roll or two of film doing you're own tests, films will behave differently under different low light conditions.

No film manufacturer offers anything more than a very basic guide, usually erring on over cautious and worse case scenario. You also need to bare in mind that most people find Fomapan 200 only has an effective EI of 100for normal use.

Ian

 

[EASmithV]

You need to go out and use a roll or two of film doing you're own tests, films will behave differently under different low light conditions.

No film manufacturer offers anything more than a very basic guide, usually erring on over cautious and worse case scenario. You also need to bare in mind that most people find Fomapan 200 only has an effective EI of 100for normal use.

Ian

I only have it in 8x10 sheets

I guess I'll just start by multiplying the final time by two to correct for reciprocity. I'm stopping down pretty far, so it should be longish. We'll see, hopefully the film's latitude will take the inaccuracies in exposure.

I'm going to go try it now, back in a bit.

 

[Ian Grant]

You're best option is to do some tests with 120 film, preferably with a roll film back and a 5x4 camera using similar apertures or as close as possible to those you'd use with the 10x8 camera.

Unfortunately it's a bit hit & miss with too many variable shooting 1ox8 blind.

Ian

 

[EASmithV]

You convinced me to just trash the data and shoot some to test. The results are encouraging.

I'm tempted to just ignore any and all fancy reciprocity calculations except to simply double the exposure for anything over 1 second.

Meter reading was 30 seconds @ f64.3, doubled for reciprocity.
Final exposure was 1 minute at f64 using ISO 200.
Dev in stock D76 in a Beseler drum for 6 minutes.

Sorry for the poor quality of these preview shots, I had to crank my Dig**al to a high ISO...

 

[Ian Grant]

So not really a very low light level, that's equivalent to the 1 second @ f8 that I tested, and considering you shot at 1 minute is still very close to the half stop I found rather than the nearly 4 stops that Foma recommend.

One problem is reciprocity is not just related to the length of Exposure but also to the intensity of the light, which is very different at 1 minute @ f64 with a 10x8 camera compared to say 1 minute at f8 with a 35mm or 120 camera, there's a 6 stop difference.

The way you were asking I was expecting very much lower light levels

Ian

 

[EASmithV]

So not really a very low light level, that's equivalent to the 1 second @ f8 that I tested, and considering you shot at 1 minute is still very close to the half stop I found rather than the nearly 4 stops that Foma recommend.

One problem is reciprocity is not just related to the length of Exposure but also to the intensity of the light, which is very different at 1 minute @ f64 with a 10x8 camera compared to say 1 minute at f8 with a 35mm or 120 camera, there's a 6 stop difference.

The way you were asking I was expecting very much lower light levels

Ian

Well, it was low light for me...
I did have it fairly diffused.

 

[RalphLambrecht]

I've heard that Foma 200 has awful reciprocity characteristics. I'll just give an extra stop for anything over 1 second?

And does Multigrade IV even have a reciprocity failure? It seems fairly linear.

Am I making any sense? It's quite likely my brain is frieed today...

EA

You can safely assume the reciprocity of Ilford Multigrade IV to be around 1/16 of a stop for every doubling in exposure. In other words, when extending the exposure from a verified 16s to a new 32s, add 1/16 stop and make it 33.4s.

new time = =10^(log(old time)+log(2)*(1/16))

 

[Uncle Goose]

I wondered about reciprocity of Fomapan 100 too, I took a test on a subject that my lightmeter judged at 4sec on f11, I took the shot and after that one I took the same shot at 8sec on f11. The stuff is now in the developing tank hopefully I have them developed tomorrow. Then I can scan them and post the unaltered result here so we can see a side by side comparison.

 

[Uncle Goose]

So, I developed the Fomapan 100 roll with the test on reciprocity on it and here is the result. First one is taken with the readings the lightmeter gave me without adding any time for reciprocity failure, photo taken at 4seconds on f11. In the second one I doubled the time to 8seconds on f11.

4 seconds on f11

8 seconds on f11​

I must say there isn't that much change, the second one is a little bit lighter but it's not that serious. I think the latitude of the film makes up the little errors you can make. Of course I didn't take the test on really long exposures but it give more or less the idea that the reciprocity failure is not that bad. To be honest, I like the first more since it has a darker mood in it.

I didn't do any post-process besides making the photographs a little smaller.

Photographs taken at an old abandoned Cokes factory with a Bronica ETRSI 50mm on Fomapan 100 rollfilm. Negatives scanned with an Epson Perfection 4990 Photo.

 

[RalphLambrecht]

I see a big difference! The second image has much better shadow detail. The shadows in the front are dead in the first image but show detail in the second.

 

[Ian Grant]

The second image mirrors what I've found with Fomapan 200, and confirms that the Foma reciprocity figures with these film aren't a useful guide, in fact they are rather alarmist.

There's a big visual difference between the two, and as Ralph says the second has a far better tonal range, I'd be happy with that andI shoot a lot of images under similar conditions.

Ian